#5 heads on late Olds 350 (1977)

[BigGeorge]

I'm going to keep my question short and to the point. I have a 1977 Oldsmobile vin R 350 with 3a heads. If I replace those heads with the early #5 heads (port, polished, divider weld, new valves, springs, etc) what would happen performance wise? I know about enlarging the head bolt holes. Also, would I need a different head gasket from stock and if so, what thickness?

I have had these heads collecting dust for years. Now I have a few pennies to spend. I have no intentions of not keeping my Olds all Olds powered but when you start looking at performance to value ($$$), it just hard not to go another route with GM performance.

 

[88hurstolds]

Essentially you're increasing compression and flow.
I'm assuming you're also going with a new cam as well?
www.realoldspower.com is where you need to visit for accurate advice.
Lunati Voodoo cam would be a good cam choice...

 

[DROLDS84]

Will cost more than a few pennies to do everything you mentioned to those heads.#5's are great SB heads,imo they are the best flowing stock heads.Had a set stashed and let myself get talked out of them.Wish I still had them.

 

[olds307 and 403]

Mill them at least .020", add 2.07/1.625 valves with bowls opened up. Add matching springs to a better cam, definitely needed and maybe machine the guides for positive seals. Use the Rocket Racing .028" head gaskets with the milling you will be right around 9 to 1, a good upgrade allowing a cam in the 215 to 220 range.

 

[Gozer442]

Those are the best flowing iron heads! Port match the heads to the intake, get an adjustable valvetrain, block off the EGR crossover passage to cool down the intake, and that will give you a huge power increase over the stock heads. Being a later year block, you may have to open up the head bolt holes on the head to match the block. I know that had to be done when putting #5 heads on a 403 SBO. Anyone else want to chime in on that?

 

[L92 OLDS]

I spent $1,200 on my #5 heads and did all the tricks with stainless BBO valves and put them on an Olds 403. In retrospect I should have gone bigger with the cam because I still had more low end than I needed. Along with a cam swap and comp valve train it put my 442 in the high 12's. It sounds like the original poster has already done his homework. This is a popular, cost effective swap for SBO's if you want to keep your car all Olds. I was looking for more performance and have moved on to modern LS technology. So far I am very happy with the results. Keep your car all GM.

 

[Kennybill]

I did a similar build on a 1976 Olds 350 that had #8 heads. I've done a 403 and the 350 diesel had 1/2 head bolts. 4-5-6-7 are all good heads. I use stock small valved but I did grind the A.I.R. bumps off the roof of the exhaust ports. Single angle valve job with 100# seat pressure springs. I put the Comp Cam 256H, I think, 0.456/0.456. Edelbrock performer, 3:73 posi. You don't want to go to big on the cam because of your compression. You'll be around 9 to 1, jmo.

 

[BigGeorge]

Thanks guys. I should mention that my pistons and cam are stock. I have no intentions of replacing the pistons but I would change out the cam if necessary. I'm really trying not to go too deep into the motor at this time. I have an Edelbrock RPM intake, 3.42 gears with posi (7.5 rear though), Sanderson Shorties, 2.25" duals and that is mostly all I have done. It feels strong but by my estimates I'm probably only making about 200hp.

Someone mentioned it costing more than a few pennies...I hope that if I put $1200 bucks into the heads it better run out of a coat of paint!!!

My goals are simply wanting more power because it is only natural to want more. I have no plans to race other than a little stop light action here and there.

 

[BigGeorge]

Teaser pic...

 

[Gozer442]

With a stock cam/valvetrain, you won't get much performance from the swap, and you'll run the risk of hurting something on the motor. Swapping the heads will effect your rocker geometry...putting more stress on stressed out stock rockers/pushrods/bridges/lifters/camshaft/valves/guides. Get a cam/lifter kit that will accept a stock valvetrain (under 480 lift max). At the bare minimum, replace the seats and retainers for the springs, and get some properly sized pushrods. I'd hate to see all the work you put into your motor, just to see a valve drop out, \or a pushrod bending and causing damage to the lifter/cam/valvetrain/head.