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Overhaul talk
machine shop wants to know how extreme I want to go and he figured out by my body language that my son and I had different thoughts. Engine has 30 over forged pistons, mild cam upgrade, Edelbrock Performer intake with same 600cfm 4v. Heads are ok but want to "expand pistons" after honing block to keep clearance in range .005 or less. Either that or replace pistons to 40 over.. TALK ENGLISH TO ME.
He also said if I though it ran ok before losing pressure It should scream once together and running right.

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Alan L
What specifically do you need to know? 40 over means an overbore of .040 inches beyond the standard bore, I.E. 4.000" bore 40 over is 4.040" diameter.

A "mild upgrade" cam could be anything from a torque style RV cam to a solid lifter performance grind. You'll want to find out the lift (how far the valve is opened), duration (how long, in degrees of crankshaft rotation, the valve stays open) and lobe separation angle which has to do with overlap (when both the intake and exhaust valves are open near the top of the exhaust stroke). When you find out what the cam specs are check back here and have some of the guys here give feedback.

"Expanding the pistons" is a way to knurl the skirts of the pistons to reduce the clearance between the piston and cylinder wall. This has been used for years on stock style rebuilds.

I hope this is what your'e looking for and I have not offended you by being too simplistic. JT

Jeff T.

Low buck, touring style, '73 Convertible "rolling restoration", 351c, 2v heads with a shave and a haircut, Performer intake, Holley 650(ish), roller rockers, screw in studs, guideplates, stainless valves, Duraspark / Motorsports MSD, T-5 conversion. 1-1/8" front, 3/4" rear swaybars KYB shocks and some home brewed subframe connectors. Future plans; JGC steering box, Cobra brakes and... paint, interior, etc.

When I die I want to die like grandpa, peacefully in my sleep... not screaming, like his passenger.

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As usual, Jeff is "on the money" with his response.

I agree with the individual from the Machine Shop in that if you were satisfied with the performance before the loss of pressure, you should be even more so upon the completion of the procedure.

Remember, the camshaft is the key piece in the puzzle as to how the engine will respond and the performance level that will be provided. Sounds as if you were happy with the performance.

Were they able to determine what caused the loss of pressure and the failure?

I second...or is it third...the cam as the key piece. My son and I had differing thoughts on how to cam the small block chevy in our jeep wrangler. He was intent on the performance, and general attitude, of a performance cam. After we installed it, the jeep screamed, but it was just too lopey for me to enjoy at idle and low speeds. We compromised and replaced it with a milder cam that still gives great performance, but with less outward attitude.

Once you narrow your options, definitely seek thoughts from folks who are running what you're considering.

I agree with all of the above.But also as a new guy to the hobby I also know what it is to see specs on a cam and have no clue what they mean.Try telling your engine builder what you are looking for in your own words. EX: you want a car that is drivable on the street but still has a mean sound or you would like a street strip setup witch would be alright around town but not really for the highway but can hold it's own at the strip.If your engine builder knows his stuff he should be able to find the perfect setup for your needs.

If not bring it to CTongueanada my guys will treat you right hahaha

Also if he wants to go .40 over it might be because your block is a little worn out and they want to clean it up.He will have to check the cfm's in the heads to pick your pistons.If you want to run on pump gas try not to go over 10:1 compression or close to that.{At least that is what my engine guy told me hahaha}


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