Inliners International Forums General Discussion Engines GMC stock head 302 build recommendations

Does anyone know the stainless valves that were mentioned a while back?

How about recommendations on pistons, cam, etc? I am aiming for 9.5:1 CR, 3/4 cam, nonleaded valve seats. I have a Clifford intake w/ a Quadrajet and Fenton CI headers. Someday port fuel injection and a turbo w/ intercooler.

The application is a '46 GMC pickup w/ a 5 speed, street use with occasional heavy hauling, 5,000. to 12,000. feet elevation.

Thanks

Ed, They were 1.94 Intake and 1.6 Exhaust used by Don Haymes(Don1450) in a 302 punched to 320.
The are Chevy V8 valves readily available.
Go into search and type in 302 Valves in High Performance forum. It'll pop up and maybe you can contact Don.

Thanks,

Ed

Ed I've been planing a simular engine for myself. The only source for overbore forged pistons that I could find is Patrick's. I think they are a bit pricy but they are Vinoloas and I am still stuck in the 60,s. I,m not sure you need unleaded seats these engines were designed to run on low on no lead gas I'm not sure about the cam, I would talk to a good cam grinder about my plans.I suggest DELTA Camshafts of Tacoma Wa ,or Colt Cams of Langley BC Canada. Good Luck If a little is good more is better and too much is just right

While we are talking about vthing valves does anybody know if 2.02's will fit?

Vic Holley, who built my 320 cid GMC, found the stainless (1.94 and 1.6) valves. i believe they are a widely available replacement for small-block Chevrolet v-things. They are a fairly close fit in the 302 combustion chamber; i don't think i should try the 2.02 intake.

The pistons are Patrick's "Venolia"-style, with Total Seal molyndheum rings--not "cheap" in any way, but well made. Compression ratio is 9:1.

The cam is a "Howard" that Donnie Johansen ground on a NOS military core (228 @ .050).

With two Holley Webers on an Ellis manifold this engine makes 362 foot-pounds of torque at 3065 rpm and 265 hp at 4390 rpm. i think that this engine demonstrates the value of Vic's head work.

i hope to have the car up and running by December 2005. More carburetion--another Holley Weber or three Webers--might open up the top end some more. We may try that, once everything else is in order, if i can find the right pieces.

God's Peace to you.

d

I just completed a 302 as we speak.I used Chevy V-8 1.94 intakes and 1.60 exhaust valves,Manley hi po street valves,springs with a damper,again V-8 item.Comp cams makes a lower spring cup that fits perfect and gives a 1.700 installed spring height,perfect.The small block valves have a slightly shorter stem,ya need to correct the rocker arm geometry,easy to do.I got a cam ground of my own specifications,I highly recomend Colt Cams in BC Canada.My cam is 215 degrees duration at .050 lift,lift at the valve is .430.Remember this,the actual GMC rocker arm ratio measured by me is 1.4 not 1.5 listed by all cam makers.So, all the cams you see are short on actual valve lift by about .035 and short on duration by a few degrees.
I'm running an actual 9.3 compression ratio,Venolia pistons,I sent them a mold of the combustion chamber to design the piston.Using 1/16 compression rings,3/16 oil rings.I measured the stock 302 head combustion chambers at 121 cc's,had the head milled .040 to get the chambers to 112 cc's to keep a small 25 cc pistom dome.The pistons are installed at zero deck clearance.The rod small ends were rebushed for Chevy big block V-8 wrist pins so I wouldn't have to have custom pins made.
I searched around quite awhile to find Clevite 77 bearings,the mains have been out of production for 20 years.I didn't want to use the currently available Federal Mogul made in Mexico bearings.
Got a 390 Holley 4 bbl on a Patrick's intake and a home made set of short tube tri-y headers.
I modified the the oil pump pick up tube by using a larger diameter tube from a V-8 with a home made pick up enclosure and screen.And of course the full flow oil filter.
Should make 230 HP at 4500 rpm.
302 in basement
More 302

for the street and haulling stay with the 1.94 intake valves. dont waste money on the seats bronze wall the guides that will take care of the unleaded gas problem.

Wow, Tony, you've really come a long way on that thing since we schlepped it down into the basement. Nice job.

Four,thanks,it goes down the steps in pieces easier that up the steps in one piece,lol.
Building the GMC was interesting cause of all the bogus information there is about these engines.

Tony, please share what you have learned in the buildup. I've been thinking about doing something similar and would hate to reinvent the wheel.

Jason,I may have overstated using "bogus",lol.Here's what I found,like I mentioned,the actual rocker arm ratio is 1.4 not 1.5,so keep that in mind when choosing a cam cause all the cam grinders think it's 1.5.I measured the lift at the lobe and at the valve with corrected rocker arm geometry.So I had a cam ground with more lobe lift to make up for it.
I also noticed the stock oil pick up tube is a smaller diameter than the pressure feed tube of the pump.Just about every other engine design has a larger pick up tube than the feed side of the oil pump.I modified a small block Chevy pick up tube,it's larger than the stock GMC item.The 90 degree fitting on the feed side of the pump is restrictive,I bored out the diameter as much as I dared, better yet would be to throw away the sharp 90 degree fitting,and use a larger radius fitting.Same goes for oil lines on a full flow filter,avoid any fittings with sharp turns.Each sharp angle fitting reduces oil pressure by a few PSI, add em all up and you loose 10 psi.You can jack up the pump relief valve spring,but that just takes more power,and may overload the drive gear and heat up the oil.
Quality bearings were another problem,I searched quite a while to find genuine Clevite 77 main sets.The only readily available bearings are Federal Mogul CP's made in Mexico.The are supposed to be a good bearing, but I wasn't satisfied with the bearing crush,the Clevites were much better.
The factory machining on this standard bore block was horrible,the bores weren't straight,the block deck wasn't parallel to the crank,but the crank bores were right on.The machinist had to mill the block at a angle to get it straight,The bore problem was solved by properly boring the cylinders on true centers.
The Crankshaft was standard and smooth,but the throws were off and the factory had cut the crank slightly undersize.I didn't want to cut the crank at all cause you loose the hardening,but I compromised with a .010 cut, and trued up the crank throw indexing as much as possible.The connecting rod bores were off as much as .010.Took care of that by rebushing the small ends for .990 Chevy big block V-8 wrist pins,offsetting the bushing bores to get all the rods the same length.
I'm not vendor bashing here, but both Arias and Ross didn't seem interested in making me pistons.Venolia was interested and asked for a head combustion chamber mold so they could build a piston to fit my specs.And they were cheaper by 100 bucks.
All these little items do add up ,makes no sense to throw money at a performance engine unless you check every item and correct any problems.I mocked up the block,crank,rods and pistons several times at the machine shop to check clearances along the way.My machinist is careful,but it's my engine,I do my own assembly,it pays to be involved during the machining process.
I did these steps on the 261 I built for the truck 7 years ago and it had excellent power and was smooth,hopefully the GMC will run as well and the 3500 bucks I spent for machining and parts will be worth it.
And the long motor myth,in my case,the GMC 302 was the same lenght from the bellhousing mounts to the front of the fan as the Chevy 261 engine that was in the truck.The motor mount holes in the front crossmember will be moved forawd only 3/4 of an inch with a slight trimming of the corssmenber for oil pan clearance.

TonyP do you still have the number for Venolia.

Thank You }[oooooo]

You mean the piston number or their phone number?Here's their address and number Venolia
The piston quality was excellent,they'll build anything ya want, any ring size,any pin location.I still have the combustion chamber plaster mold I made of an unmilled 302 GMC head with Chevy small block V-8 1.94 and 1.60 valves.Venolia should also have a record of the piston they built for me.If you need it,give me an email.
Another note,the 302 connecting rod is kinda short,the piston pin is fairly low on the piston.A half inch longer rod would add more torque and locate the pin into a more favorable location.

Tony, it will be good to hear how your engine runs. I agree about the longer rods, then we could use some standard pistons with a more normal compression height. Unfortunately I don't see any longer rods available. Do you think they would fit in the block?

Ed Pruss
Longmont, CO

Ed,There are custom rods available,cost too much for my wallet,especially on a street engine.

Today's "Blast from the Past" There is excellent info here on GMC 302 head builds from 2005. The Venoila link link still works! This is an example of what is here and likely nowhere else. It is later than what is in California Bill's book. Very interesting info on valves, springs, guides, rocker ratio, hardened seats..........
I found this using a tip from stock 49. I did a Google search: "inlines.org GMC 302 head"

Strange to have put this up this morning because an old Inliner friend called about a problem with the head on his 302 this afternoon. He had just gotten it back together and was heading to last weeks meeting and it started missing. One of the hardened seats he had installed came out and blocked the valve open. the pushrod came out of the rocker and made a lot of noise. Luckily no serious damage but he's looking for a new machine shop. This guy has a two diligent Inliner member number and has been building these for years. Just shows it can happen to any of us.