Bluerocket76

Hello everyone, got 1984 5.0 307 5a heads for 100 dollars off craigslist tore it down.I also have a 1976 350 with number 8 heads.my parts are speed pro flat top pistons edlebrock intake 1 stage above stock melling cam high volume melling oil pump with bolt on oil pick up new lifters new distributor new wires new water pump new engine mounts new oil pump drive shaft new gasket set new headers new 5 quart oil pan new rocker arms sbi going in a 1978 chevy pick up short bed found it with the oldsmobile engine installed and running pulled it out guy who i bought it from said it was a 260 up by mexia tx dallas fort worth area by Arlington oldsmobile plant is where the numbers said it came from block has that 358999 something like that with that 2 off to the side numers say 1976 my question is what should i tell machine shop about the heads as far as decking and what piston to wall clearence i should have I have number 8 heads disassembled and new 2.00 stainless steel intake valves and 1.63 exhaust valves from the number 8 heads for the 5a heads am ready am ready for the machine shop???????ordered arp studs and connecting rod bolts cross over blocking plates for heads neoprene rear main gasket for crankshaft crankshaft was turned 0.010 on mains and rod journals block was lined honed just need machine shop clearences for good piston to wall clearence where my oil clearence should fall for my mains and rods and any assembly tips would greatly be appreciated thank you

cutlassefi

When you ramble on with no punctuation most won’t read it. Just an FYI.

Bluerocket76

Well it's not Chinese

joe_padavano

It's not English, either.

Look, you want people to help you. You MIGHT get a better response if you make it easy for them to understand your question. Just sayin'.

Bluerocket76

I apologize we all cant afford the the likes of a Harvard Alumnus Education, or go to a prestigious High school ,am just trying get some advice on this engine. If you cant drop some knowledge dont worry about it then. oh you have some unknown knowledge i cant reach oh unlock the mysteries of the universe to me

joe_padavano

We're talking high school education, not Harvard. And FYI, cutlassefi is probably one of the most skilled Olds engine builders on this site. You'd be wise to solicit advise from him.

olds 307 and 403

With flat top pistons, run your #8 heads. I ran 5A heads in a 78 1/2 ton and 94 Z71 but used the factory 14cc pistons in a 76 350, worked well 8.5 to 1 with a 204/214 cam. The #8 heads have fairly small runners and a much better exhaust port, once a bowl hog cutter is used vs the 5A. Also 2" intake valves won't fit 5A heads, the factory 1.875" #8 intake valves will. Do you really want a 10 to 1 350 with crappy flowing 5A heads? Pretty sure a 9 to 1 350 with a better than stock cam will work great.

Bluerocket76

Thank you. I just read so were that 5a heads would yield better compression because of the smaller chamber.

Bluerocket76

Skeletore ,I call upon you to relinquish thy knowledge of thy oldsmobile. Tell your minions to diverge or they to shall know thy wrath of thy serpents tongue

Bubba68CS

Would likely be better if it was. Google translate can handle that - it doesn't do anything with this.

Your snide comments have been in response to the guys who could probably help you the best. No one is asking for perfect grammar, but something resembling a sentence would go a long way...

Toss the 5a heads, use the #8s.

Fun71

Yeah, higher compression but smaller ports so overall lower performance. As said, use the #8 heads with the flat top pistons. Probably a good idea to cc the combustion chambers and measure how deep "in the hole" the pistons are so you KNOW what the compression ratio is and not just guess and hope for the best.

olds 307 and 403

Good idea for sure. My #8 heads, two sets measured 77 to 78cc on untouched 76 350's. With .030" oversized pistons that supposedly sit .025" in the hole and a .041" standard replacement head gasket will give you 8.9 to 1, not bad. With that cam, stay below 9.5 to 1, with a clean up mill on the heads and deck should put you at 9 to 1 or slightly better. This will run fine on 87 even with fairly agressive part throttle timing, which you want. Get the bowls opened on both sides with a cutter and a 2" intake valve, keep the 1.625" factory exhaust valve. Get the quality Cloyes billet timing set and degree the cam as well. What trans and gearing are going with this? Towing or a fun toy?

Bluerocket76

Dear Oldsmobile forum, I first would like to apologize for my comments ,and bad grammar its not the kind of person I am. Just the situation am in isnt so great and grammar and punctuation is the last thing on my mind. Thank you for all your help and in the future I will take my time .Thank you and God speed.

Kyle's77cutlass

Check my 350 build I did this summer.

https://classicoldsmobile.com/forums...-build-134492/

Kyle's77cutlass

Just a quick ramble of my build.
350 punched 30 over
Flat top pistions
Deck zeroed
Ported and polished #8's with 2"intake
450 HP 490 TQ with just under 9.5 to 1
Would of used 7a's, but would of raised compression a bit too much.

ragz442

This sounds about exactly what my 350 build was, been over 10 years now, but it runs good. I never had it dyno'd or ran it down the track yet, it's definitely faster than my low 14 sec. 77 442 I sold though. The guy that did the machine work talked me into keeping the number 8's to keep CR at/near 9.5 to 1, he was familiar with Olds motors. The crank just needed to be polished and standard bearings were used. I believe he milled the heads 0.030 and I used Felpro head gaskets. I assembled it, brazed the center dividers, blocked off the cross overs with a Holley SD intake, headers and Ebrock 750 manual choke carb wired wide open. I don't drive it in the Winter. What cam are you running? I can't remember mine off hand but have the card somewhere (Lunati).

Kyle's77cutlass

Mark helped me with the build, did an amazing job. Lunati roller cam and lifters 276 intake 277 exhaust at advertised duration My risers are filled too, 7111 intake port matched and 750 brawler

ragz442

Nice, that explains the 450 HP. I was gestimating mine at 350. Everyone rags on the #8 heads, but with the right pistons and machine work they perform well. I usually run mid grade fuel, never had any detonation problems.

Kyle's77cutlass

My #8's on the left and #7a's on the right. Did a comparison between the 2, fair difference in the bowls. If you are going to port and polish, not much difference in flow between any heads I think. #8's shave the heads to bring up compression and you are golden. To me, the only gain from #7a's and under is the smaller chamber to raise compression.