Inliners International Forums General Discussion Engines New to inlines, critic my build plan!

You have the wrong crank or wrong pistons.

Just confirmed it again, 175 thousandths. He is going to check the stroke of the crank to see if I was sold the wrong crank.

So the compression height of the 307 pistons are 1.655, the compression height of 230 pistons are 1.780. Am I mistaken to believe I would have been better off with 230 pistons? That would bring my deck height from .175 to .050 which would be much better.

Currently
Block - 230
Crank - 250
Rods - 230
Pistons 307

I show compression height of the 250 piston at 1.655, same as the 307 piston. So that would put your deck at .030"

Actually I have 1.675 for some 307 & 327 pistons, that would bring it even closer to .010" deck.

Either way, if your deck is .175" something is wrong, that would jive with using a 230 crank and 307 or 250 pistons. Should be easy enough to measure the stroke and find out!

Just wondering who is going to bore to 4.0" & use 327 pistons?

MBHD

So... my fault, sort of. The engine being sold as a 250 was, apparantly, not a 250. The machinist checked the numbers and it is a 230 crank. This sucks to say the least. I should have checked myself, but I was in a rush to get it apart and up to the machinist... that's what I get for trusting someone!

New (re-manufactured) crank is ordered and on the way to the machinist. Not a good day...

Actually I have wondered about this -
Since the six and SBC are the same bore spacing, and the SBC comes at 4.000 bore and goes to 4.030 or even 4.040 if youre lucky, why cant the sixes in general take a 4.000 bore? Are the walls deliberately thinner? I guess so, I will have to recheck my drill-bit data but I know the space between cylinders on a 350sbc is pretty small.

Maybe if you did a sonic and lucked out, will any of the sixes take a 4.000 bore and still have .100 wall left?

People have done it.

My friend Douglas has in Brazil, but the engine let go & his was just for racing only.
He also was using a low percentage of nitro methane fuel.

The walls are too thin to go that much of an overbore.
I would not recommend it for street use.

You could hard block fill the whole block might work for racing?

MBHD

Hank,
Yup now I remember. The drill bit for a 350 Chev is about 1/8", so a perfect 350 block with no core shift would have a cylinder wall thickess of
(4.400-4.000-.125)/2 = .137" - .020" roughness = .117"
So at 30-over your 350 walls would be .102" thick, maybe even .082" if you had some core shift.

The 230 six I measured had a 13/64 drill slip in between cylinders thru the freeze plugs. So at 4" bore, the wall thickness would be
(4.400-4.000-13/64)/2 = .100" - .020" roughness = .080"
So a Six bored to 4.000" would have walls of .080" in a PERFECT block with no core shift, and as thin as .060" in a more typical core shifted block. That's too thin.

So the 230 cylinders ARE cast thinner than 350v8 cylinders.
Not sure on the 292, I will see if I measured any.

Not that any of this affects Mitch, he just needs a 250 crank!

I enjoy reading your posts, don't worry about a little wander of the thread especially when it's thinking of trying something new or different.

That being said, I will probably have a freshly ground .010 over 230 crankshaft for sale in the future along with a set of main bearings for it. Still angry about the whole deal, money is already tight since summer time is when I catch up on house renovations. Just shingled part of the house and the whole garage, along with new aluminum soffit and fascia. Grrr....

Just received word from my machinist, it is at .055 deck height with no deck work being done so far. I told him to deck it as low as he is comfortable with.

According to my calculations, if it stayed at .055 and I did no head machining, it would be 8.5:1 compression.

If he decks it to .035 deck height and I take 2cc's out of the combustion chamber, it'll be 9.02:1 compression, which would be pretty good in my book.

I'll know more once he gets done, for now I'm just hoping he isn't overzealous and I'm not mis-calculating!

.055 DH is huge. I like to keep the DH as strong as possible. That is why my pistons offered on my site have taller compression height.
What piston are you using? The .055 seems like a bunch.

Yeah, the thickness between the cylinders is thin, but more importantly is how thick it is on the cylinders thrust side. Because of core shift and the shape of the cylinder barrel is often cam shaped, the cylinder walls are often between .150"-.180" thick on a non-Mexican block, but i've seen then way thinner before boring also. The Mexican blocks are often as thick as .230" or more(depending on core shift on the thrust side). So after an overbore, as long as you are still above .125" thick on the thrust side, this will be acceptable for a performance or race application. Filling is also better if your toward the low side of thickness.

The pistons are Sealed Power cast units for a 307. The 250 pistons from Sealed Power actually had a lower compression height!

I realize this is an inliner site, but to be brutally honest if I wanted to build a incredibly powerful engine I would go with a LS-style of engine. I actually have a 6.0 LS style engine that would push over 400 HP just by putting a regular carburetor on it, stock everything else! I am building this as "budget" as possible, except for certain areas where I can have a drastic (IMO) effect by spending a slight bit more, like roller rockers, multi-angle valve job, lump port, etc. Things that will directly affect efficiency. If I can get 9:1 compression with the cheap pistons (under $20 a piece) it isn't worth me spending bigger dollars to get it to 10:1, which is probably my limit on pump gas. I'm sure some will disagree with me, but that's just my thinking!

If you install a decked 194 cyl head you can have 9:1. But that will cost you more money towards your build.

I do not think anyone is suggesting for you to build an incredibly powerful engine, & they are not suggesting any incredibly powerful engine parts for you to purchase.

You can build this engine anyway you like to.

We are just giving you suggestions so you would glad about your engine build choices.

Anyone can throw in an LS, or SBC engine & be just like everyone else.
It is even standard practice to put an LS engine into a Mustang.
Nobody will notice your LS or SBC there are just too many of those out there IMO.
As far as making an engine efficient, compression ratio has a lot to do w/that, you might save some $$ by using cheap pistons, but by doing so you have to do other machining processes or purchase a 194 cyl head to bring the compression up to where you are going to have a more efficient engine, in the end, IMO, you are not going to be saving a lot by using the wrong pistons.

Good luck w/the rest of your build.

I don't feel like anyone is pressuring me, I just don't want people to feel like I'm ignoring their opinion either! There is just a certain path I'm going with this engine, and certain things are just not in my budget for this. I'm learning quite a bit from this site, and I don't want to offend people and bring my learning to halt.
This build is, as you pointed out, to be a little different. Yes, the '50 3600 it is going in would have had an inline 6 cylinder, so it will look, to most, like it's just a prettied up stock pickup. However, underneath the shiny engine paint and maybe a few shiny pieces on it, haven't decided yet, there will be a updated version (250 instead of 216/235) and upgraded with as new of technology that can be used. The TBI I am planning will be hidden and look like a carb to most, the roller rockers will be concealed, and the electronic ignition will look stock from the exterior. Lump ports will not be seen, the 5 speed will not be seen (aside from new shifter location) and the IRS will be hidden as well, although the bed floor may be raised. The whole concept of my build is new technology that will not be seen or noticed by most. I'm going to keep steelies on it with white walls, it'll hurt the handling but I'm more concerned with keeping the vintage look. People will know it's modified, but will almost always underestimate the severity.

Well, all that being said, I hope it's clear. I never intend to offend!

I really am just guessing for now, until the engine comes home (the machinist said it's ready to be picked up) I won't know my final dimensions. However, once I do get them, I'll be sure to pass along the info. Hell, once it's done (a long ways down the road, I have another pickup ahead of it) I even have a friend with a dyno so I can give out some final numbers. I'm not building it for power, but it'll still be fun to know.

Just to make sure I have it right. With the 295+.060 307 piston in the block with a correct 250 crank you are .055 down in the hole at TDC without anything removed from the block. Is this right? I wonder if they took a little off the top of the piston because it is .060 over. Enginetech says that they do this on their pistons. Too bad we can't know what height the pistons that came out were. Jay 6155

You are correct, at least that's what my machinist told me! In theory, you could check the 295 piston with no overbore and compare compression height to the 295 with .060 and see if it's different.

Does anyone know what the stock compression is on a 250? Going by a replacement piston with no dish or dome and my deck height, it would be around 8:1, as a guesstimate. 9:1 or more would be quite the improvement by itself.

Worse case scenario, I will still have more compression than factory which falls under my goal of updating the original engine. It'll be light years ahead of the 216/235 that was originally in it.

Thanks Mitch, Enginetech says that they cut about .010 off the top of the piston. Jay 6155

Yes, they do it intentionally to retain the stock compression when you bore an engine. Since boring an engine increases its compression, they compensate for it by a shorter compression height piston for overbores.

That's exactly the advertised static compression ratio for my '78 Camaro 250cid. I haven't cracked it open to check it yet.

Sweet, good guess me!

According to Summit Racing's website & specs, the 295 pistons have the same compression height. I suppose it's possible that there isn't a chamfer or something on the smaller pistons, but that's pure speculation.

Ordered my camshaft, I went with the MPG Performance cam. For $50 new, I couldn't turn it down. It fits with my plan of increased efficiency with a little more kick as well. If anyone else wants one, there is one more on Rock Auto. They are discontinued otherwise.

Just curious what the specs are on the camshaft?

$50 Bucks, great price. Score!

MBHD

Is this the Cleavite cam talked about on page 2? If so that is the cam I have for my build. Part # CS1033R ? Jay 6155

That looks like a decent cam,
if these are the specs.

Very mild.
Intake Duration: 194 Deg.194 Deg
Intake Lift (inches): .265"
Intake Lift (mm): 6.731 Mm
Intake Valve Lift 1 (inches): .464"
Intake Valve Lift 1 (mm): 11.786 Mm
Lobe Centerline (exhaust): 115 Deg115 Deg.
Lobe Centerline (intake): 105 Deg105 Deg.
Lope Separation: 110 Deg.110 Deg
Overlap: 45 Deg45 Deg.

Cam Type: Hydraulic
Exhaust Duration: 204 Deg204 Deg.
Exhaust Lift (inches): .280"
Exhaust Lift (mm): 7.112 Mm
Exhaust Valve Lift 1 (inches): .490"
Exhaust Valve Lift 1 (mm): 12.446 Mm

Looks like normal price is $120 & up, great score , again!


MBHD

Thats what I have. Just a little more than the Comp 240 but not as much as the comp 252. Except for lift it's really close to the "929" sbc cam. For $50 I may get a spare. Jay 6155

Y'up, it's definitely mild. If I go larger and larger, I'll lose my MPG aspect of my build and driveability! I could have stayed with a stock cam even, but I had to give her a lil more grunt...

Engine is back from the machine shop!
Clean Block - $40
Bore Block - $85
Surface Block/Check Piston Height - $100
Check Line Bore - $35
Grind Crank - $50 (Unfortunately was done before we found out it was a 230 crank)
(2)Check Rods - $10
(4)Recondition Rods - $48
Balance Engine - $110
Total Labor - $478

Haven't had the chance to tear everything open yet, currently putting the finishing touches on my garage redo. Glad to have it all back, hopefully start piecing it together in the next few weeks.

Checked main bearing clearances, all right at 0.00175. Washed block all out to make sure there wasn't any shavings from the machining process. I love assembling engines, something calming about it.

Crank and rods are in. All top rings were around .013, all second rings were around .018, all oil rings were around .019, give or take .001 here and there.

I didn't check my rod bearing clearance, didn't think about it until I had all my rods lubed up and put in. It would have been easy (and smart) to do it when I had all the parts laying there. As close as all the mains were, I'm hoping the rods were similar.

Installed the pistons on the rods using a electric rod heater, all went well except pistons 1, 4, and 5 didn't seem as loose on the pistons as the other cylinders. They do move, and after they were installed the entire rotating assembly moves easily enough, but it's just sticking in my head.

Next up, cam, water pump, and freeze plugs. After that I'm out of parts to install until funds come in.

Forgot to add, deck height came out to be around .025. According to my calculations, this brings compressing to 9.45:1 assuming a 72 CC head. I won't know my head's specs for a while, that'll be a fund raising project of it's own since it seems to be an area where great improvements can be made. Lump ports, roller rockers, larger valves, etc etc.

Is there any certain areas that these heads were known for having cracks? Something I can keep an eye out for before I send it to be magnafluxed and the like?

You should have put the cam in right after you installed the crank. The cam will hit the rods all the way in and make it much more difficult to install it after the rods are installed.

Live and learn!

Cam is in, timing set is installed, oil pump is installed, and water pump is installed. Also finally got some pictures for everyone. First a few of my engine, next is my other inline pickup with a 3.5 inline 5 in it. Sadly, it's going out to a friends farm to be packed in a barn since I am too busy with my side business, which was ironically started to earn extra money for the pickup. It'll keep it out of the rain and be covered up for a few years until I finish my other restorations.

That's a lowrider for sure! Looks good.

Thanks. It has air ride, when fully aired up it's pretty close to a stock 2wd, maybe a couple inches lower. I have heavily modified the stock frame, but after a certain point it was just polishing a turd. I am going to step away from it, get my other work done, then come back and build a frame from scratch.

Small engine update, freeze plugs are in!

Very cool truck. Is it the picture or is the i5 on a slant like a Dodge slant 6? It,s very nice to see the engine come together.i am very curious to see how that cam runs. Jay 6155

It's level, it's probably the front of the valve cover that makes it look slanted. The pickup is on a slight pitch, but I took the pic level.