HitTheHole

I have a 1970 Olds 350 with #6 heads. I'm having it bored 0.30 over and using I-beam 4340 racing rods with Probe 14475-030 pistons, 3cc dish, 1.625" compression height. The heads combustion chamber volumes are 64cc, bore 4.087", stroke 3.385", probably use a 0.040 head gasket. The heads are being completely reworked with 2.0"/1.65" valves, ported & polished. The variable here is deck clearance. Is there any way to figure out what that might be before any milling? I'm actually worried about compression being TOO HIGH for pump gas. Using a number of .025" for deck clearance, I come up with 9.98:1 compression but that number is a "guesstimate". Can anyone provide me with a more accurate estimate for deck clearance or advise me on the compression? Thanks!

coppercutlass

sounds similar to my current running gear. also make sure you have true 64 cc's. Use this. At zero deck you are at 10.62 to 1 compression . at .025 you are at 9.98 to 1. That's where I am on my current 355 and im good on pump gas 93 im at .025 in the cylinders with my speed pros. Currently building a 355 with probe pistons as well that block is at zero deck but the heads are closer to 70 cc's they are also #6 heads.


This the calculator I use.


http://www.rbracing-rsr.com/compstaticcalc.html

cutlassefi

What octane do you have available? 91? 93?

When you have the heads done just have them polish the chambers as well.
That'll minimize the chance of detonation in two ways, a smooth surface and lowering compression ratio by having a larger chamber.

Cam selection will be important as well. Make sure you enough cam in it to bleed of some pressure at low rpms but not too much to make it a pig.

Best of luck in your build.

HitTheHole

So did you get "closer to 70cc" combustion chamber in your heads as a result of having the heads reworked? With a deck clearance of 0.10" that would give me 9.7:1 which is where I'd like to be.

cutlassefi

Which rods are you using? Who makes them?

HitTheHole

Chevron Supreme is 92 octane. Does that work for a 9.7:1 compression engine without experiencing detonation? I'll be running an HEI distributor with the option of using an advance curve kit, if needed.

coppercutlass

Hit the hole cutlassefi brings up a good point before you deck the surface makes sure how far you are in after the new pistons and rods. I have ran mine on 91 92 93 no issue. #6 heads are realisticly closer to 68 cc's . If you have the chambers polished before than that will gain you some cc volume but the oversized valves will also take up some chamber volume. The only way to figure it out is to cc the head and pre assembly steps to get you your measurements to make sure you beck the surface the correct amount.

HitTheHole

OldsRocketParts.com Small Block I-Beam Racing Rods
http://www.oldsrocketparts.com/produ...eam-race-rods/

coppercutlass

From what I have heard mondello is behind those and the sale of them. For your hp needs and goals you may be better off reconditioning your stock rods if they check out and avoid the scammers.

HitTheHole

Stock Olds rods are the "weak link" of the engine. I got the new set of rods for $299 which, in my opinion, was a great price. Stronger, lighter, no cost for reconditioning.

coppercutlass

I have spun them up but pretty high with no issues Lots of guys have. I belive these rods are also pretty new and made by procomp overseas. Take that with a grain of salt. Maybe chebby rod and piston combo will be better with a well known rod brand like scat.

HitTheHole

Of course, everything will be balanced and tolerances measured. I considered using Chevy rods and reworking the crank but in the end, decided against it. Decided not to go with the Speed-Pro/TRW pistons because of issues with quality, tolerances and piston rattle. Considered going with custom 6cc JE or Diamond pistons but at $1,000 and a wait time of 3-4 weeks, decided against it. I've already purchased the rods and Probe pistons so I'll let you know how it turns out.

coppercutlass

Good luck let us know how it goes. Im currently running speed pro's on stock rods with 9.9x to 1 compression . It gets beat hard no issues yet knock on wood lol.

cutlassefi

If you got them for $299.00 then go for it, just have them checked.
9.7:1 on 92 should be fine. What cam did you go with?
And the Probes are lighter and have a better ring pack than the Speed Pros.
However they will need at least as much clearance as the Speed Pros. If you can keep the compression ratio in check that should prove to be a good combination.

HitTheHole

Thanks, Cutlassefi. I haven't chosen a cam yet. I don't know enough to make an educated choice. So many to choose from. I'm going to rely on my builder to help out with that choice. Using Edelbrock Performer 2711 manifold with Edelbrock Thunder Series AVS Carb, 650cm, electric choke, Thornton exhaust manifolds, 2.5" MagnaFlow exhaust, TH350 and posi 3.23 rear end. I'd prefer not to have a rough idle. Suggestions? Keep in mind the heads are completely reworked with 2.0"/1.65" valves, ported & polished.

Octania

SCAT parts are "the Shyt"

ha ha ha

http://dictionary.reference.com/browse/scat?s=t

"scat3 [skat]
noun
the excrement of an animal."

Avoid "C.A.T." brand main girdles I guess:

http://www.ebay.com/itm/151173321106...84.m1555.l2649

cutlassefi

With your mods you need the 7111 intake and a cam with some decent lift to take advantage of the ported heads. And lift has little to no effect on drivability. Duration and overlap effect that.

Let me know if I can help.

coppercutlass

Im running a howards 512/512 227/234 duration @.050 cam and it has a nice lopey idle but it is very smooth idles in the 700 rpm range . Pulls very strong .Don't know what you mean by rough as far as sound or idle consistency . Im sure mark can set ya up with a cam.

HitTheHole

Too late now to turn back on the manifold. It's going to be the 2711 (fully polished).

coppercutlass

That intake is going to act like cork on your combo.

HitTheHole

If I need to, I can always put a spacer on it for more air flow. I just don't anticipate running RPM's that high.

cutlassefi

That won't help it, those runners are teenie tiny.
Wrong intake. If you keep it then you may as well just put stock heads on it along with a stock cam.
Wrong intake.

HitTheHole

Is anyone aware of any problems with hood clearance on a '70 cutlass if I used the RPM manifold on my 350 with an Edelbrock Pro-Flo Series air cleaner (net height from carb flange 3.75")?

cutlassefi

RPM will fit fine under your hood, with just about any air filter. Some need drop bases but most will fit.

Fun71

Agreed. I have the RPM on my '71 with a generic 14" air cleaner and I actually put a slightly taller air filter on it with no clearance issues.

HitTheHole

Thanks Fun71. Good to know. I ordered the RPM today. Was just hoping to avoid any surprise clearance issues. Since I'm using fully polished, it takes a while to get them. Didn't want to hold up the build if it interfered with the hood.