[steve25]

So your saying your 350 Olds fitted with a 670 cfm avenger flattend out above 4800 due to lack of CFM / being too small for that motor?

I would like to refer you to a dyno test done on a factory Tripower built up 421 that made 475 hp, yet still made 350 hp up at 5500 running on just its center 2BBl !!

A gotta say for sure you had something going on with that 350 Olds that was cutting into power above 4500 ( like jetting ) but it sure was not CFM.

The poorer idle of that 770 was likely due to the idle air bleeds needing to be changed I would say .

[HWYSTR455]

Originally Posted by steve25

So your saying your 350 Olds fitted with a 670 cfm avenger flattend out above 4800 due to lack of CFM / being too small for that motor?

I would like to refer you to a dyno test done on a factory Tripower built up 421 that made 475 hp, yet still made 350 hp up at 5500 running on just its center 2BBl !!

A gotta say for sure you had something going on with that 350 Olds that was cutting into power above 4500 ( like jetting ) but it sure was not CFM.

The poorer idle of that 770 was likely due to the idle air bleeds needing to be changed I would say .

I drove that car on the Power Tour, and when going over some mountains it was overheating. The Holley crew stopped and we jetted it up by 4 sizes to control it, but once I came out of the elevation it was pig rich.

I juggled jets in that car well before going on the Power Tour, and no matter what I did it was never 'right'. Even the Holley guys made comments and suggested going to the 770.

It may not have been due to CFM, but the Holley guys recommending the 770 made me think it was.

My 1/2" fuel line thread was based on that car, so delivery was not an issue, for sure.

It had #5 69 heads on it that were ported.

The tbi setup allowed me to tune it all out, wasn't going to waste time with elaborate tuning of an off the shelf 'budget' VS Holley.



.

[ericwoo]

Originally Posted by chiphead

Do not pass go, do not waste time on a leakdown, pull both heads and CC the chambers. A leakdown may help confirm condition of bottom end, but I don't think it's the root cause of what's going on here. It would appear that one head got milled and one didn't. Where did these heads come from?

Originally Posted by PontiacHO

Run thru the valve adjustment first just for eliminating the valves too tight on one side. Run a compression check again on that weak side. If that doesn’t reveal anything (and it probably won’t) you’re on your way to removing the heads anyway.

Originally Posted by Schurkey

Pumping compressed air into the cylinders without a leakdown tester is ABSOLUTELY FINE for testing valves, head gaskets, and looking for cracked castings. Because the only acceptable result is ZERO leakage past the valves, into an adjoining cylinder, or into the cooling system.
.

Ok this is what I found out with the leak down test. Air is coming out of the valve cover breather on the Driver side but not the Passenger side. From what I am reading, that would be worn piston rings, correct?

A while back, I do remember seeing surface rust on steel components when I took off the valve cover. I was thinking a little bit of water must have seeped through the valve cover gasket when I degreased the engine compartment. I wonder if surface rust developed on the piston rings and cylinder, ruining it. However, I do not remember the engine producing much more power before washing the engine either.

I will never understand the engineering of Pontiacs poor valve cover design with the 4 bolts. I always had issues with sealing them to prevent oil coming out.

Originally Posted by tom s

Are both heads 6500?Tom

Yes, I just confirmed both sides say 6500

[Schurkey]

Originally Posted by ericwoo

Ok this is what I found out with the leak down test. Air is coming out of the valve cover breather on the Driver side but not the Passenger side. From what I am reading, that would be worn piston rings, correct?

Maybe. I don't understand why one side of the engine would have blowby pressure but the other side doesn't. However, "air coming out the valve cover" could be TOTALLY NORMAL. Kinda depends on the volume of blowby--there's always going to be some.

What are the gauges on the leakdown tester showing? Do you have a Master Orifice to provide some feedback on what is acceptable? If not, you need to test some known-good cylinders of about the same bore diameter.

You don't have "breathers" on BOTH valve covers...right? Is there a properly-functioning PCV system on this engine?

Originally Posted by ericwoo

A while back, I do remember seeing surface rust on steel components when I took off the valve cover. I was thinking a little bit of water must have seeped through the valve cover gasket when I degreased the engine compartment. I wonder if surface rust developed on the piston rings and cylinder, ruining it. However, I do not remember the engine producing much more power before washing the engine either.

One of the main byproducts of combustion is water vapor. Blowby puts that water vapor into the crankcase.

If the engine is running, there's no "surface rust" on the cylinder walls.

Originally Posted by ericwoo

I will never understand the engineering of Pontiacs poor valve cover design with the 4 bolts. I always had issues with sealing them to prevent oil coming out.

Bolts cost money. So do drilled and tapped holes. You want GM big-shots to give up their bonuses so you don't have oil leaks?