mixing early/late BBC parts

[Rich Biebel]

That is definately no problem. I built a 502 for a bracket/street driven car and used a GenVI block with early oval port, closed chamber heads. I can't recall what head gasket I used but I belive it was a GM gasket. That engine is still going. It never had any problem and has run in the 9's after it was transplanted from a street car into a racecar. I got the info for what I needed and bought some parts from one of the GM Performance parts dealers thru their catalog. Pace Chevrolet. Scoggin Dickey is another good source. Lots of good info in those catalogs..........

[Ken Haase]

Thanks for the help guys. I'm trying to come up with a viable engine for my dually. My grand experiment with Rectangle port heads was a bust, even with revs of 3 grand plus. I should have known better; just gettin' stupider with old age. I now realize why the diesels are the engine of choice. I just can't afford one.

[Alan Roehrich]

Ken, the hot setup is the old closed chamber oval port heads, or the Vortec heads. About 96 to 100cc chamber, and 2.19 intake valves with 1.88 exhaust valves. If you can get 10:1 compression it will work fine. My old 454 had about 9.5:1 and it really wasn't enough, even though I went down in cam to a 218/.520. An all steel flat bed truck, with steel wheels and no overdrive it would get 12-14 loaded or not, and pull 20K pounds with ease. With the air on. Of course, with Camaro headers, 3" pipes, and huge mufflers, it sounded a lot like a stock car on the Interstate. I think with 10:1 compression, overdrive, and fuel injection I could do better.

[Ken Haase]

Alan, thanks for the additional info. You've prompted a new batch of question's, if you don't mind answering them.
What gear ratio was your truck? My dually has 4.10's.
Did you use a 'stock' converter, or one for towing?
Your thoughts on stroking to 496. That would boost the compression ratio a little.
Best header tube size?
Did you stay with a Q-jet? Manifold?

This is an '86 C-30, so no OD. The engine is a low miles 454/425 crate. The Vortec heads you mentioned came out in '96 I believe, so they should be a direct bolt-on. I know the smart play would be to buy a late model diesel. But, since my wife recently lost her job (30+ years as an RN with the same hospital), the bucks just aren't there. Realistically, probably not for these engine mods either. We'll see.

I appreciate everybody's help.

[Adger Smith]

I think the gasket is a 1047 Fel Pro. Better check.. it's late & I'm at home, far away from any cataloges.... & my memory is getting, well just say a bunch of birthdays :~)

[bobby]

I have a set of 215 oval port closed chamber heads for sale. I think the date code is in 67 sometime.

[Alan Roehrich]

Ken, the truck had 3.73 gears. You don't need 4.10 gears if you build enough torque.

I had a converted Allison AT545 converter, a big cooler, and a Derale extra deep cooler pan. I built my own 400TH. The stock one would not hold the torque.

Have you considered a bolt on overdrive unit? I think Strange still makes one.

I had a Weiand dual plane, a 2" spacer, and an 800CFM Q-Jet on it. If I weren't going with fuel injection, I'd probably use a Performer RPM Air Gap.

The Vortec heads are probably your best bet, if you use the old heads like I did, you'll need to put a full set of hardened seats in them. I think we're getting close to $300 to put 16 seats in. Another thought is a new set of the 100cc Edelbrock heads.

In order to run high compression (up to 10.5:1 is good) you need to have it at zero deck, quench and squish is critical to killing detonation, it won't work if you don't do it. You'll need forged pistons, if you were to get in a bind with a tank of bad gas you could easily kill any cast piston.

The trick here is you won't be running much timing, maybe 12 initial at 800 RPM, and 34 total at around 3200, with a limiter on the vacuum advance,(I had an MSD system on mine) keeping the vacuum advance from pulling in more than 10-12 degrees. If you have plenty of compression, you do not need, and cannot use, timing to make cylinder pressure. You'll have to tune the timing.

I also had an oil cooler, and a fully tricked out cooling system so that my coolant temp stayed around 160-180 degrees. With no hot oil flowing through the radiator from the engine or transmission, a good water pump, a 7 blade clutch fan, and a good radiator, I had no problems.

I don't think I'd stroke it with that gear (if you had an overdrive on it I might), unless the trailer is massive. More displacement will hurt mileage, and you should have incredible power.

I had Hedman 1 3/4" headers on it, 3" collectors, and 3" pipes, with massive Flowmaster mufflers.

The engine made 450HP and 450 foot pounds of torque, peak HP was around 5300-5500, peak torque was around 3700. It ran for about 200K miles, most of it towing various trailers, before Dad wrecked the truck. The engine had very little wear in it, the block is going in the race car in a week or so.

Were I doing this again, I'd likely build a 496, use two TBI units on an Edelbrock intake (either that or I'd actually prefer a 1000cfm throttle body for a tuned port on an oval port tunnel ram and port injection) and Edelbrock heads, and back it with a 4L80E.