350/255HP Help please

[Kevin Panzino]

Are you saying the leakdown is 8 to 9%????

[jamie2370]

Not trying to be ugly but that combo should make north of 430. How "new" are pistons? Most likely the problem is the ring package. Having said that I am not an engine builder nor do I build my own motors but I have been around stock for all my life and fairly up to date with what it takes to make them run.

[HP HUNTER]

Originally Posted by jamie2370

Not trying to be ugly but that combo should make north of 430. How "new" are pistons? Most likely the problem is the ring package. Having said that I am not an engine builder nor do I build my own motors but I have been around stock for all my life and fairly up to date with what it takes to make them run.

Yes 430 + with much higher peak than 5600 RPM. 119 MPH @ 3350 = 440 HP

[Alan Roehrich]

You're down 35HP or more, and your peak is maybe 600RPM or more low.

If you're really leaking close to 10% on an engine that is up to 160 degrees, you're not sealed up.

I seriously doubt that either Total Seal or CP has missed the mark on the rings or pistons, especially if you had them work together. I've used their stuff successfully many times.

[Adger Smith]

He said "Cold" Leak. That never has told me anything. I don't race Cold Engines... Could have bad ex seats and when it gets hot they go away..... Just Saying...

[Alan Roehrich]

Originally Posted by Adger Smith

He said "Cold" Leak. That never has told me anything. I don't race Cold Engines... Could have bad ex seats and when it gets hot they go away..... Just Saying...

Agreed. Cold leak down is useless. Honestly, on these engines, you need to be using a Dwyer gauge, or something, to test blow by on the dyno. Leakdown, even hot, can be misleading. Measuring blow by eliminates all of that.

[Jim Hanig]

If its a junkyard block 384 is not that bad,if its leaking more than 6% you got problems, Call Greg at race rings get his ringpack give him the grove dept,and he will fix you up get it honed with a plate . Cam should be in at 103-104 with a three speed.spring pressure around 145 -385 with reg lifters. Bowtie should pick you up 20. good luck.Not all dynos are the same.

[Chipper Chapman]

I'll get it up to temperature and do another leakdown. Don't have access to a Dwyer guage. Cam is in at 103. What you guys are saying about 35-40 and 600rpm down is exactly what I have been figuring but can't find why. Engine is a factory block but fresh at .065 with plate. Pistons are a couple years old, Manley rods, (light piston heavy Rod)

[Mark Ugrich]

Originally Posted by Alan Roehrich

Agreed. Cold leak down is useless. Honestly, on these engines, you need to be using a Dwyer gauge, or something, to test blow by on the dyno. Leakdown, even hot, can be misleading. Measuring blow by eliminates all of that.

Alan, could you describe how the Dwyer gauge works?Is it basically installed like a vacuum gauge? I've never heard of one.Looks like there are several different calibrations.Which is correct to use to measure ring seal as you described? Thanks,Mark

[Alan Roehrich]

Originally Posted by Mark Ugrich

Alan, could you describe how the Dwyer gauge works?Is it basically installed like a vacuum gauge? I've never heard of one.Looks like there are several different calibrations.Which is correct to use to measure ring seal as you described? Thanks,Mark

Mark, if memory serves correct, you want one that reads 0-10 scfm. The 12" tall model is probably the best.

What you do is connect the gauge to the only outlet where any crankcase pressure can escape from the engine, everything else must be completely sealed. The easiest way is to connect the gauge to a breather with a tube outlet, such as the one used in a crank case evac kit. The gauge must be mounted perfectly vertical.

You then make dyno pulls as you normally would. We normally use our vacuum and or evac system for a while to seal the engine up, then after we've got it where we want it and tuned, we make a couple of pulls with the Dwyer gauge on it to make sure it is sealed up.