350 Engine mix and match

[56Roadmaster]

Hi,

I have the following questions for the engine guys

My engine: 1977 350 2bbl, 74cc combustion chambers, dish pistons. (Engine is in a '67 cutlass)

1.) Are all 68-77 350 cranks the same? or will interchange?

2.) Will earlier 350 (i.e. higher compression) heads work on the later block?

3.) If the heads work do I need to change the intake?

4.) Are there pistons available to boost comp to 9-9.5:1 using the 74 cc heads?

5.) For dual exhaust do I need both manifolds or just passenger side?

Thanks,

Scott

[joe_padavano]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 56Roadmaster</div><div class="ubbcode-body">Hi,

I have the following questions for the engine guys

My engine: 1977 350 2bbl, 74cc combustion chambers, dish pistons. (Engine is in a '67 cutlass)

1.) Are all 68-77 350 cranks the same? or will interchange?</div></div>

Yes. The only difference is that engines originally bolted to manual transmissions have the recess for the pilot bearing drilled. Most that came with automatics do not have it drilled. Also, every single small block Olds (260, 307, 330, 350, 403) use exactly the same stroke. Except for the balancing (and the crank flange bolt pattern on the 64-67 motors), the cranks interchange.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">2.) Will earlier 350 (i.e. higher compression) heads work on the later block?</div></div>

Yes, though you need to calculate the real compression ratio based on piston dish, head volume, and gasket compressed thickness.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">3.) If the heads work do I need to change the intake?</div></div>

It's not mandatory but desirable.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">4.) Are there pistons available to boost comp to 9-9.5:1 using the 74 cc heads?</div></div>

See answer to #2. You can get flat top pistons, 6 cc dish, and larger dish pistons.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">5.) For dual exhaust do I need both manifolds or just passenger side? </div></div>

Neither. Olds never made "dual exhaust" manifolds for the small block. All small blocks used the same manifolds. When dual exhaust was used, there was a factory cap on the second opening on the RH manifold.

There is now an aftermarket vendor selling supposed dual exhaust manifolds for the small block Olds, but I got a chance to inspect them at Carlisle and they don't look like they flow any better than stock, so it's not clear they're worth the money.

[56Roadmaster]

Joe,

Thanks a lot for that information. That makes things easier. This car is a project I picked up and my 16 year old step son is learning on it. Some one either wound the - out of this engine, or got some dirt in it or both and then ran for it a while. Two rod journals were visibly 0.125" under size from wear. luckily it did not come apart.

Interesting about the exhaust manifolds have the cross over port capped.

You have helped us out.

thanks again.

Scott

[OldsDoug]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: joe_padavano</div><div class="ubbcode-body">When dual exhaust was used, there was a factory cap on the second opening on the RH manifold.</div></div>

Hey Joe, do you have any idea if anyone's reproducing that cap? I just used my last NOS one... have tried to convince a couple of welders I know to make some for me out of flanges and flat stock but they all go "foo, just use a flat piece" - not really satisfactory because asbestos is no longer available to make a gasket! Thanks-

Regards,

Doug

[joe_padavano]

The Parts Place (www.thepartsplaceinc.com) sells one for $39.00. It doesn't look like an exact replica, but it will work. Year One also sells something they call a blockoff plate, but the picture is of a section of flared pipe with a welded-on piece of plate and a separate flange. You could do that yourself for free.