In the middle of a rebuild for my 59 270 GMC does anyone still make rods and pistons?

You can have the rods reconditioned and Egge may be a source on pistons...

I am most worried about the pistons right now, no idea what I need for a size yet.

I also can not find any on the Egge website.

The 3.78" bore is not that unusual.
The problems:
Which combustion chamber do you have (head casting number will help), some need a special dome config.
The compression distance is very tall, not modern, no way to fix this.

As CNC stated, the rods can be rebuilt. Cheap pistons may be hard to find as all the old ones are consumed. New pistons can be made custom order. Much pricier but overall a much better option for weight of piston and better rings. 12Bolt is a dealer for Ross pistons and can get them made. Usually 5-6 weeks wait.

I heard nearly $1,000 including shipping

I doubt it would be 1 K, but would bet them to be 7-800. Price depend on lots of things. Flat top, dome, valve recess's, availability of rings ect.

I can not remember if it was here or on the HAMB that someone used longer rods and off the shelf pistons. Also save 1.25 lbs per cylinder. It may have been for a 302 but 270 I think. All GMC rods are te same except some have a bigger pin and there is a difference in the width of the tab that holds the insert on the crank end on some of the newer engines. 8" Hudson rods will work using a Mopar bearing. 270s can go out safely to almost 4" bore and some have gone all the way to 4". My 270 is a '57 and has the newer style small port head. Just fine for the street. Anyway there might be a rod that opens up piston choice.

Indeed, they were all domed and different shapes. I got these photos from the old Patrick's site:

Ron Golden from here on Inliners. He used a shelf 400 Small Block Chevy piston on Hudson rods....

Here's the thread - images are in tact. Inliners Hi Performance post circa '13

Thanks for the responses guys, the head casting number is: 2194819
Im not going for a super hot build maybe a little hopped up with a intake and cam but nothing crazy. And with the gas prices needs to use 91 octane

400 Small Block Chevy piston: 4.125"

I guess my next problem would be finding bearings for the crank and rod now. I saw someone still makes cam bearings
Any recommendations for a cam?

W/r/t cam
What does it weigh
Transmission
If AT, what stall speed
If manual, what 1st gear
Axle ratio
How much slow traffic
What static CR

Ron was using a 302 bored to 4.125", so the 400 SBC piston worked out for the 308 Hudson rod length.....

Just a stock 59 GMC 100, not a ton of slow traffic but I do not want to effect drivability to much. I plan on taking it on day road trips at about 55MPH, I plan on a SM319 overdrive but right now it has the stock Sm318

The real problem that has plagued the Stovebolt's and GMC's for a long time has been replacement lifters. There was a period of time not terribly long ago, there was none available. As for the camshaft, you may end up having to have yours reground. Some cam companies such as Oregon Cams can also reface your lifters provided they aren't worn too badly.

Here is Ron's post from 2008 describing his GMC 302 build......Also, Hudson rods, not Packard!




Beater,

321" GMC (+0.125")Block is filled with HardBloc to water outlet.
308 Hudson rod (8.115" C-C)
0.880" Pontiac pins, 84 grams lighter than GMC.
JE 11.5:1 piston (400 grams lighter than GMC)
Stock main brgs.
CR90P rod brgs ( 1940-1950"s Chrysler)
2.02/1.60 SB Chevy valves
#983 cylinder head, ported. 264 cfm @ 0.600" lift
Dema Elgin did the cam based on everything else in the engine.
I wouldn't consider anyone else grinding a cam for this engine. Pulls like a freight train above 3500 rpm.
Aluminum roller rockers we made. (1.85:1 ratio on a 1.00" shaft)
I saved 1.25 POUNDS per cylinder with the piston/pin/rod.
Bearings look good after 20 pulls on the dyno and 6 runs down the strip.
Smith Brothers Pushrods, Bend, Oregon. 5/16, 0.125" wall. Beautiful work and delivered on THE day promised.

Yes Scott, That is the one I was thinking of. I wonder if Ron is still running it? I bought 2 sets of Hudson rods after that for a 302 I may build someday. I wonder if there is a piston that would work in a 270 with the Hudson rods?

The Hudson rod needs a piston more or less 1.115" shorter than OEM. That CD length may exist, but not be something with a life expectancy.
Deck height (to .000") = 50% of stroke + rod C-C length + piston compression distance.
Piston to head .035" including compressed head gasket thickness.
In a quench chamber "work with" is critical to no less than .035" and no more than .060" P-H. below that crashes the head when hot, above that has minimal knock suppression.
I can't imagine how much a high compression dome for a 400" SBC does not resemble a GMC chamber.

I believe he sold that engine. Talked with him at a swapmeet. Also think at that time he was working with a turbo 4200.

I brought this up at our chapter meeting today. One member may be able to chase down what you need when you know what over bore you need. He had a good supply when he sold his shop but thinks they went to Salt Lake City.

Thank you! It will be going to the machine shop today or tomorrow, my next problem is bearings, is there .10/.20/.30 available? I belive cam bearings are the same as Chevy.

Welll Im not sure the block is saveable I�ll attach pictures of crank caps and the block crank surface. https://imgur.com/a/SPSo04b

OK, It spun a couple of mains? That can be fixed but may not be cheap enough. What we do on these old engines doesn't always make sense. Sometimes it is just the challenge/fun.

It may e time to make some choices.What do you want for your '59 to be? Do you want it to have it's original class or be a modernized cookie cutter driver? Opps, I may have let my bias creep out. I wish you were closer.

I really want to keep it original as a 59 GMC Ive also thought about tracking down a 336 GMC to put in. The truck actually has a pretty good running 62 235 that needs some carb work and a rear main seal pretty bad. Is there a way to put a rear main in without pulling the engine?

Yes, you can do that. I evolves a puller like Chinese handcuffs.

Well I guess I have decisions to make I can get a good running 336 GMC motor for 1300, or a Fresh block with pistons and crank for my 270 for 1000$
The 336 would be cool but technically not "correct" for my truck.

As far as I know there was not a 336, A 236? 236& 256 were limited production short deck engines. While a 248 would not be a bad choice. A rebuilt 270 Shortblock for $1000 isn't a bad rice if done well. I doubt if you could redo yours for that + time.That's where I'd go.

The 336 is a specific GMC v8 made by Pontiac base on the 370/389 was only used in 58/59.
From what I understand the block is not assembled on the 270 but it has all the parts to be and I could slap my head on it.

Well heck, the 336 wouldn't fit here. If you would be OK with a V8 a brand new crate motor is hard to beat. Not a classy though.

Is the 270 close enough that you could give it a good inspection before you buy it? Is the price negotiable?
It would give you a chance to make the most beneficial modifications while you assemble it. #1 better intake, #2 better exhaust, #3 a cam more suited to your use. A totally stock 270 may be best suited.

I went to another machine shop today and he says he thinks its repairable but I might need a new crank. So looks like Im going 270 after all, im sure someone on here could locate a crank if I need one, I will for sure need a 1 rod cap. And 2 rod nuts, a cam, lifters and the hard parts bearings and pistons.

I helped a young guy here who was planning to put a GMC in his '49 Chevy pickup. I helped him locate a 302 & a nice 270 along with intake, carbs, headers & cam from a friend's stash. He was a military guy and put in for a transfer to Texas. He took all the Jimmy stuff and sold it back there and put a 350/350 in his pickup. You can't trust young guys.

The only cranks I have are the 4 bolt flywheel style.

I am sorry to hear that, not all young people are like that but a lot can be. Ill update this thread when I know more from the machine shop.

It was said in jest. He was a good guy bit in over his head. He liked my pickup. I let him drive it so he could compare it to the 216 in his '49. It would have been fine if had stuck around but once he left here he he fell under the influence of regular car guys. He really did not understand what treasures had been nearly gifted. That has happened to me a few times but it has worked out just as often and I still have more than enough junk.

Block is good! He says go for 40 over pistons if Im having them custom made what should I go for like 60? He said anything 30 over or above. He thinks crank will clean up also. When Im buying pistons is there a way I could bump compression up a little to make some power? I will call eggy tomorrow after I see what you guys think.

If 30 over will do it right. Do 30 it will leave you more in the long run If you ever needed to do it again. But if you never plan to rebuild again Take the 40.
Just my2cents

I agree with twisted6 if it will clean up at 30 do it. 30 years from now you may want to do it again. By then you'll be able to print pistons at home.

If it were me I would pin the machinist down to where it will clean up. I would have the pistons made and hand them to the machinist before he bores the cylinders or at least do a cleanup bore to fit the pistons. With the '59 270 head flat top pistons are best. Shaving the head & decking the block can add compression. Do your homework and check to see if this has already been done to your head & block. Best Gasket makes a very good gasket set & the best rear main seal I have ever used. Bearings should not be a problem.

Yep that all makes sense, he said he would like to have the pistons before he bores it to get it exact. From what he can tell he said nothing has ever been machined on the block its probably never even been rebuilt. Would eggy know what pistons I could run like flat tops? My next question was getting a rear main seal that works well, I assume the Best gasket has a updated design that works better?

Many of the GMC engines required dome pistons because of their large combustion chambers to obtain their factory compression ratios. Just look at the pistons that came out of it to make sure you get the correct ones.

Ok so I called Tom Landon and he was very helpful told me to magnflux the head and some other good info will be looking for some pistons here first now. Need some 30-80 over pistons for a 59 GMC with small port head will try and find some NOS Zollners, also looking for a 302 intake and exhuast.

Why 302 intake & exhaust? Are you going with a 302 head? The small ports heads are plenty for the street. The small ports are not small rather the big ports are enormous. You may have a hard time sealing big port manifolds on a small port head. The gasket surface is pretty thin.

Small port it is then, I already have adapters for the big port to small port intake and thought the 302 2bbl would hop it up some and keep the stock look. Any good places to look for NOS pistons didnt see any on ebay.

If you can get to a counterperson who cares you may get lucky. AutoZone started by buying NOS parts from dealers & parts stores going out of business. There is still some stuff buried there. O'Reilly bought CSK (who bought dozens of smaller parts brands) and if you can get someone to get in touch with the Home base in Missouri they can do a lot. When I worked for CarQuest the computer searched the stock of every CarQuest store & warehouse in the country. A good counterperson at Napa can do the same thing. None of these places teaches their people to do this anymore. You might find some old guy that has been doing it a long time or some young person who likes to play with his computer. You machinist might have better luck because he will get to the commercial parts guy.

The folks on the Stovebolt website specialize in old GM trucks. Someone there might be able to help.
LINK TO STOVEBOLT

I will run around to the part stores and see what they have and post a couple WTB adds on the inline 6 websites.

Good luck to you. I hope you can find them. I know there is a set out there somewhere. What bore size are the one with the $1000 270?

Im not sure I can call and ask him. Same with the bearings he has.

Are the cam bearings in a 270 GMC the same as the chevy inline?

I think so. I'm headed out to the shop for a while and I'll check my old books.

That would be great thank you! Lifters look good I found 1 bent pushrod but other then that all seems to be going well.

OK, I found them in two catalogs and it's kind of interesting. I learned something. The Chevy 216 from '37-53, the early 235 '49-'54 (not the full pressure 235) & all the GMCs 228-302use the same cam bearings. The 235 & 261 from '54-'62 use a different set because the cam had larger journals.

I found this from both a Perfect Circle & Dura-Bond. PC # SH209S DB # CH-2

I wish you were closer. We will be touring the Dura-Bond plant in Carson City after our Chapter meeting next month. The guy who runs it is a member. Dura-Bond makes almost all of the cam bearings used in the US no matter what label is on the box they come in. It is an interesting process. I'll see if I can take some pictures.

Photo's Or even some Tech Info would be good to maybe post over in the tech.

Maybe tracked down some NOS pistons, but not sure if they are the correct ones, https://www.ebay.com/itm/284423525763 someone also said Federal Mogul 9845CP. A slightly narrower 1905CP fits some engines, 248, 270, and 302. Main bearings: F-M 697M but Im also not sure those are correct can anyone cross reference the part numbers?

Those may be a high compression version. I'm not sure. The pistons in my '57 270 are flattops. I don't know if that if stock? I built it in the late '70s. I think those will work for you and I'd grab them before someone else does. These and the ones with the other engine seem to be your choice right now.

I'll try to look up some some rod & main bearing numbers this afternoon.

I am worried about it not working correctly with my head, are you sure they will work?

I'm not sure but here are some links to pictures. And pictures of mine with what appears to be flattops. The dome pistons for the older heads are not like these.

LINK

LINK

Mine were also flat tops, I wonder if you could still run the domed ones and up the compression

I think they are a high compression set. The raised part goes up into the combustion chamber. I have no idea how much they would raise it but within reason more compression is better.

My Perfect Circle catalog shows these bearing numbers. A counterperson should be able to cross reference them if needed. Rod Bearings # CB427P Undersize P10 P20 P30 P40 Main bearing # MS428P Undersize P10 P20 P30 P40

Figured it out it�s for the 30-53 heads.

The other option is to use the old style head. The only dome pistons I have ever seen for the old style head had a full dome.

I wish I could find a 1959 part number reference searched the internet nothing, and my repair book for 1959.

Priced a set today with modern ring pack, domed version with .990 pin. Bore 3.915 cost delivered is 900. Also pricing for a bore in the 3.821 area is the same with a modern ring pack.

There were (3)different production changes involving connecting rods in the 270 engines. Knowing which version of connecting rod you have greatly affects rod bearing selection because of the tang width of the bearing needed and piston selection due to wrist pin diameter changes. You need to know which you have before you order any parts to verify you get the correct parts.

Those books are on the bottom of the pile I'll try to get to them tomorrow.

The rods are all the same length. The big piston pin were only 302 I think. Pretty sure the wide tang was only the later engines which is the number I posted. I'll see if I can find a Perfect Circle or Federal Mogal piston maybe TRW number.

Here is a Link to a thread on the HAMB . LINK It shows the full dome piston used with the Old open chamber head & the H head. Below in the thread there are drawings of the dome piston in the old chamber and two flat top pistons with the 302 head, D chamber. The late 270 head is more like the 302 head than the open chamber but not the same. The pistons you found will not work with the old head or the 302 head. I believe they are late 270 aftermarket high compression pistons.

Jim Carter used to sell them on special order. He may be able to help. LINK

I can get the rod number to your guys tomorrow, I am learning a lot thank you guys so much! ! push rod is bent but lifters look good still. I will probably end up ordering custom pistons. Who still makes them Ross?

Patrick's used to sell Venolia forged pistons and still may. The Venolia pistons have domes specific for the GMC heads and you can buy direct from them also. Verify your forging numbers on the rods to make sure all rods are the same and don't assume they are original to the engine. After 80 years of existence, anything could have ended up swapped and changed in it from mechanics just trying to get the vehicle back on the road. My Sealed Power book shows the evolution of the changes in connecting rods and the big pin was common to both the 270 and 302, since those two engines were the only ones remaining at the end of the production years. There are several different forging numbers for each style of rods produced, so if you're still in doubt, just get your machine shop to confirm the ones you have.

I did not know that about the big pin. Pin size is a problem when trying to find off the shelf pistons.

There is nothing wrong with good used pistons. These long pistons tended to wear on the skirts and knurling was used to improve the fit. Old techniques work on old engines.

If you order custom pistons you will likely reduce the rotating weight a lOT.

Venolia is out of business about 2 years. As said before. I can order them direct thru Ross. Have some ordered now. Priced a set today with modern ring pack, domed version with .990 pin. Bore 3.915 cost delivered is 900. Also pricing for a bore in the 3.821 area is the same with a modern ring pack.

He's trying to determine which rods he has, either the big pin or small pin. Small pin is .990 same as BBC....

Looks like Patrick's may have withered away as well...where does the time go?

Correct, then it is just a matter of tear down and measure. If he has big pin, the rods could be rebushed to the .990 pin.

If you're referring to Patrick's in AZ, he's been gone for a while and Mother Trucker Trucks in AZ (JoeM) pretty much picked up after him but not sure exactly what he carries. If anyone would like JoeM's email, ping me in a PM and I'll provide it to you. This is also something I would probably call Jim Carter and speak with either Jim or John, either of them will most likely know and possibly where you can get parts if they can't get them for you.

JoeM is a standup person, in my experience. I purchased a ring/pinion from him for my '46 to convert the torque tube over to 355:1, and was sitting on those for about a year when I switched plans and decided to use a '55 Series 2 rear axle so I could swap the trans to an open driveshaft. He exchanged them for me to a 3.38:1 set for the Series 2 and didn't charge me. And some irony in how me and Joe met, we were both run off from the VCCA Forums for discussing swapping a ring/pinion in my '46, they told us that was supposed to go in the forum where "Hot Rods" would post. Both of us banned without even a PM from the moderator, no warning, nothing...Joe was actually more furious about it than I was, if that is even possible...

I would give JoeM a call first, to see if he could help, and Jim Carter after that. Joe might have the rods you need. Short of those suggestions, I'd go to the H.A.M.B. as that's where you find the guys that would be doing this type of stuff to their 270. I could be off there though...But the few folks here that tried to help you are some of the others that would know, so the H.A.M.B. may not be of any more help.

Yeah I knew Mother Trucker is on the HAMB. I thought for sure that Phillip was going to take the reins from Patrick and carry the torch....

Phillip really got wound up when Speedway screwed with Patrick over the Fenton brand. That took a lot out of Patrick too. Not the first to get bulldozed by Speedway. I did quite bit of business with Patrick & Phillip and never had a problem, other that getting off the phone. These days $900 is a reasonable price for custom pistons.

Yeah, Patrick was very proud to have the Fenton line, he knew Fenton personally and had an agreement to use his name. Speedy Bill was a snake and like you say, bulldozed them out of it. I also witnessed Vic Edelbrock almost break Speedy in half at the Hot Rod and Restoratuon Show in Indy one year over Speedy knocking off the original Slingshot Flathead intake Vic's dad designed. I wished he would have, for Vic Jr to have been in his 70's at that time, he was 6'4 and Speedy was built like Pee Wee Herman, he deserved it....

I still haven't looked at the rod number yet, but was searching forms and found out you can do a "full flow" is it worth doing? Also is it possible to do a one piece seal by some machine work? Just thinking if im redoing the engine I should do all the modern upgrades I can.

There also used to be a link on here to an internet article, I think it was Webrodder, about how to do a one piece rear main seal conversion on a Stovebolt. Provided you can find a seal that has the correct ID dimensions for the GMC crank, and the block and rear main cap has adequate material around the seal area to allow machining for that, then it could be done.

I had to di the full flow filter conversion on my 270.



I have heard of using a Chrysler one piece seal but was never able to find the details. It does involve quite a bit of machine work. Best Gasket makes the best rear main seal I have ever used. It comes with a template for trimming to make sure you get the right amount of squish on the seal.

Ok I think I�ll just keep the rope seal if they make a good one. Any specs on the full flow conversion?

This explains the GMC full flow conversion. It's also here on the Tech Tips page if the link doesn't work.


https://www.inliners.org/tech/full_flo_GMC.html

That link didn't work for me. Try this one. It is straight from the Tech Tips in the side bar at the left of this page. Good clear instructions use care and you'll be fine. It is simple.

Fill Flow

Wow that is pretty simple actually, should have been that way factory. Now I got to figure out what I want to do build wise with the engine Factory output is 130hp and 240TQ which is pretty decent actually, so im thinking stock cam and maybe bump up the compression a little?

Not hard at all. The ticket part is drilling the hole in a thin part of the block and being able to thread it.

A lot has been learned about cams since 1959. Check some of the milage grinds as they are perform in your normal driving range, off idle to 35000 or so. With a good mild build and the right gearing you'll be happy.

My cam looks pretty rough anyone who still makes cams for these? Called eggy they do not make pistons for 270's gonna have to go for ross or maybe some NOS

Finding a cam company that has cores to make a new cam for you may be tough, you'll just have to start calling A to Z to find one. If your old one still has good teeth for the distributor , you can always consider having it reground....there is also a bunch of GMC guys over on the HAMB and Stovebolt forums that might give you a better core if yours isn't salvageable.

Your old cam and lifters can be sent out for regrind. 12Bolt can help with this. There are many cam companies that still offer this service. Not all can do lifters.

Found some NOS zollner .40 over flat tops! paid up for em but hey they are hard to find and came with some good rods even.
Now to find some .40 over rings.

Does anyone know how to tell if a oil pump is good? I found a rebuild kit but am curious if it needs it or not.

You would have had to seen the engine in running condition to know for sure. If the gears look scared up and rough then its probably best to replace them. Since the condition is unknown, replace them to be on the safe side....

I�ll take it apart and tell you what I see with it, my next question is, is it worth mulling the head to up the compression? Not trying to build a race motor but want a good running engine I could take on the highway to 65 but mostly in town. Same with the cam selection don�t need nothing crazy but maybe a little hop up?

If it's not broke, don't fix it.

On the GMC, the top row of bolts for the side cover bolt into the cylinder head. The more you mill the block and/or head creates misalignment in the side cover. Easily fixed, just be aware it affects things the more you cut off....

Yeah no milling it is then, to keep the stock look and hop it up some a small cam, and 2bbl 302 intake and exhuast. I think factory it had 130hp and 250tq so not a slouch stock.

Better plan: tell people you have a cam, and don't.

If you are going to put a big port intake on a small port head there will be a sharp reduction in size at the head. Some fitting can be done but you may need a special gasket to seal it. I have that and you really have to pay attention. The GMC has 3 rings that help align the intake & head. I made a set that fits the big port on one side and the small port on the other. The ID is tapered to help reduce the restriction. I think it actually helps increase velocity.

I just want to make sure, that the linkage would be the same so I don�t have to mess with that. Should I try and find a 302 exhuast and intake so then I don�t need the adapted gasket or would you still need it.

It will be easy and straight forward if you just stick to your 270 parts. You do not need anything 302 and you will gain no drivability by using them. If you want more carbonation do it with a 270 manifold. There is power to be had with better intake & better exhaust but you can add that later if you want.

Yeah I probably should just leave it alone for a while.
Anyone know if someone makes a GMC engine paint?

So the rods I got with the pistons I bought are 2135419, the ones that came out of the engine were 2341204. Worried about them working with the crank now.

Double check the forging number on the one's that came out of you engine, there is a 2342204, but I don't see a 2341204. They only difference you'll need to worry about with the crank is to make sure you get the rod bearings with the correct tang to fit the rods properly.

I double checked casting number is 2341204

That could be a less common forging number then, but the bearing tang width and wrist pin size will dictate what parts are to be used.

Just got to the carburetor on the engine, it�s a carter YF which I believe is not factory and the throttle shaft seems to be broken off.

Pictures?

https://imgur.com/a/VVWYe6T

I can't really tell. I don't think it is stock. Over the years lots of carbs have been replaced with whatever would bolt on. It does look broken.

I did this simple search and you may find some info here. STOCK 270 Carb

Yep Not the correct carb, I might go raid a 270/302 GMC at the local junk yard to get the carb and the correct linkage.
Anyone know of a place that would be willing to make me some pistons rings if I can not find any for my .040 over pistons?

Keep looking on eBay rings show up.

There is a set of 0.050 over that could be sized of that fit your pistons.

Is that the CCKW ring set? I�m not sure if the earlier rings would fit, but I can�t imagine they would change it.

I am not an expert on rings & fitting rings. You should do some study before you jump into it. Here is a link to the 0.050 set I saw. Thee is al the so an expensive 0.040 set from Australia.

0.050 Rings

I found these not sure what .040 over is in fractions.
https://www.performancenowdirect.com/piston-ring-set-1956-62-gmc-truck-6-cyl-270/

That works out to 3.78125 or standard bore.

Well new problem, the bell housing is a Chevy bell housing, will that fit my 270 or will I have problems? Casting number 3837001im debating switching to a 4speed now.

If you can give them the dimensions, Total Seal can make you whatever ring you need! Good people and grat products!!

Update: Got to get a dimensions for total seal and they will make me some rings, block is getting line bored and should be done this week or next with the full flow conversion as well, I will be a 20 overs on rods and mains. Will be sending in the cam and lifters next. Now I am worried about the oil pump and if it works or not.

Be a good idea to still consider getting a 302 intake manifold. The reason Tom Langdon suggested it is because it takes a 2 barrel carburetor and you need a carburetor anyway. The larger carb will help performance, the manifold bolt pattern is common to the small Rochester and Carter bbd 2 barrels. I run one of these on my 270 I have in a 47 Chevy 2 ton:

https://www.ebay.com/itm/125234014726?hash=item1d28876a06:g:92gAAOSw2X5iRb4Z&amdata=enc%3AAQAHAAAAoOfoQnbwV7u0V%2BjrhYahTsyQePShI2qYmm%2FkPvKpsIQG2cGx3T0VFyVWHgasR8Nxn84yMtq%2BXwzpy4kIlLb%2BZV078wtKxnGYmW9TyToVeOA52I%2F%2F2YrfhD2ykBEmfrPVmM%2BKuMFaVQQjI6uKuDTQvuSRiQ1pPqvLgyOa%2FuSm%2BqhLU9PJB3upn7KN090CohDa3Uc%2FoY1G97wWx5jUDUym0yA%3D%7Ctkp%3ABk9SR8aj2_nfYA

https://www.ebay.com/itm/125234014726?hash=item1d28876a06:g:92gAAOSw2X5iRb4Z&amdata=enc%3AAQAHAAAAoOfoQnbwV7u0V%2BjrhYahTsyQePShI2qYmm%2FkPvKpsIQG2cGx3T0VFyVWHgasR8Nxn84yMtq%2BXwzpy4kIlLb%2BZV078wtKxnGYmW9TyToVeOA52I%2F%2F2YrfhD2ykBEmfrPVmM%2BKuMFaVQQjI6uKuDTQvuSRiQ1pPqvLgyOa%2FuSm%2BqhLU9PJB3upn7KN090CohDa3Uc%2FoY1G97wWx5jUDUym0yA%3D%7Ctkp%3ABk9SR8aj2_nfYA

Tom Langdon can help you find adapter rings to make the large port manifold fit the small port head.

Little update here, got busy machine shop was backed up thing came up, but I�m back at the rebuild now, turns out the rods are 302 rods that came out the 270, but I do have a set of good 2135419 rods just wondering if those will work my crank it says both the 302 rods and that casting number rods use narrow bearings so it should be alright?

I think you keep missing what is being said to describe the connecting rods. All GMC rods, regardless of what cubic inch they came out of will fit onto any GMC crankshaft. The width of the bearing tang, the bent portion of the bearing that fits into the notches in the rod and rod cap are what is different. There are numerous rods that have the same forging numbers but can have either size of bearing tang widths and also different wrist pin sizes, so you have to measure both the tang widths and wrist pin size on the rods you have to get the correct pistons and correct bearings. So when it comes to GMC and their forging numbers, the forging numbers are almost irrelevant because so many of them can have both style of bearing tangs and either size wrist pins....Hope that helps!

Okay understood, I kept the old bearings and they fit into the new connecting rod notch correctly and fits well.