327 build advice

Hi guys. Rebuilding my 327. Currently it has TRW forged .030 over .125 domed pistons with 492 angle plug heads. Don't know what cam. It had a low RPM roughness from about 1300-2200 RPM that drove me NUTS. I could never get rid of it fully, only reduce it no matter what I did. (New plugs, new wires, new distributor, new carb, etc., etc.) The roughness was worse when cold and lessened when warm, but never went away. It was almost as if it was on 7 cylinders or out of balance. Hard to describe. It did run really well above 3000 RPM. I ran 93 octane.

I wonder if this was detonation?

Anyway, I got a hair up my a55 and pulled the motor last week, tore it down (I didn't notice anything obvious wrong during the tear down) and am ready to start ordering parts. I already ordered the RHS vortec 64 cc heads with the 2.02 valves.

I haven't ordered pistons yet but was looking for advice on this area.
I was thinking Voodoo cam as well, but not sure which one.
I have a Holley 600cfm with vac secondaries (I can change this if necessary)
I'll get a new intake also
patriot 3/4 length headers with 1 5/8 primaries
No vacuum or power accessories
muncie 4 speed
3.70 gears in the rear, posi.
and it's in my 1957 chevy which is an occaisonional weekend hotrod.

Any ideas, advice on this combo? Thanks for any info.

Mike


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Not knowing how familiar you are w/how an engine feels cammed w/a lot of overlap, so I'll ask if you're sure the engine was not running right or if the cam was possibly the cause of it running rough.

Was the idle also rough or did the rough running start at 1300 RPM and quit at 2200 RPM? If that was the case it could have been several things like the engine balance, accessories/brackets vibrating, worn motor mounts, problem w/the torque converter/transmission or further back in the drive line if it was only doing it while moving.

I mention this so hopefully you don't end up w/the same symptoms after rebuilding the engine.

if your looking for a good set of pistons what you should really do is take it to a respected mashine shop they can help you find exacly what you need, but i would recomend JE pistons, get those (sets normally run in the $1k range) the mashine shop will tell you exacly what needs to be ordered ie bob weight, height, pin di ect and have it balanced when you put it back together check all your work twice and look evrything over real good

I haver no idea on what type of cam it had as it was last rebuilt in the mid 80's by my uncle and his memory lasts about 2 weeks! But it completely came alive at 3K RPM.

The rear motor mounts (bell housing mounts) were actually broken, not completely through, but not solid. I thought this might be the case too, but for whatever reason the roughness lessened as the motor warmed. And it idled fine as well.

Looking forward to getting this engine rebuilt. The compression wasn't all that great for the domed pistons, 140-ish psi. I think that's low, but I could be wrong.

That's something else the cam timing can have an effect on- the cranking psi. A better test for ring seal is to use a leak down tester, but if it's going to be rebuilt anyway, it's kind of a moot point.

Are you planning on taking advantage of the development that has been done in cams since the engine was last built, and install a modern grind into it?

There`s two signs the cam was on the large side, the low cranking compression and since the power didn`t come in until 3000 RPM. I`m surprised you were able to skate by very long as it had too much compression for 93 octane gas. Going with Vortec heads is a big step in the right direction. Since this is a weekend hot rod as you say, then I`m guessing that means street machine.
I would also have the block decked .010 and use a .028 thickness
head gasket with forged flat top pistons. With the RHS heads, flat top
pistons and decked, the compression ratio should land in the 9.5:1 range
with a decent quench distance.
While the voodoo cams are nice cams you don`t need a dual pattern cam,
if it were me I would use a single pattern. However which ever you chose
I would stay around the .224 duration @.050 range.
What I outlined is a combo that matches fairly well as that`s the name of the game, the combo must match to make max power.
I would also use a larger carb. If it were me, a Quadrajet. However if you want a holley then a 670 street avenger.