[Shockwave78]

Originally Posted by Stan Weiss

175 psi sounds very high for that cam and 8.0:1 CR. Was this test hot or cold?

Stan

I did the test cold, I don't know how it could be higher than 8:1 because I didn't have any machining done, and I am using the stock pistons, crank and heads

[PunchT37]

Well, at least you found your problem. Stock Pontiac cams have 390 ish to 400 lift on a non adjustable system. So, when you put a cam with more lift, especially with the same length pushrods, you`re pressing on that cam too hard. Hope you didn`t round it off.

[Gach]

When Crower design that cam, over what ever cam it replaced 068 ? Don’t know….why do you think it made more power over a stock 068. I’m just using the specs as an example, so don’t hold me to them. Lets say 068 was on a 112 what ever. The Crower cam on a 109. What 3-4 degrees advanced plus the added more lift. Plus the opening and closing changes. Which increases cranking compression. Better cylinder filling more power.

[Shockwave78]

Originally Posted by PunchT37

Well, at least you found your problem. Stock Pontiac cams have 390 ish to 400 lift on a non adjustable system. So, when you put a cam with more lift, especially with the same length pushrods, you`re pressing on that cam too hard. Hope you didn`t round it off.

the cam looked ok after break in, no scoring or abnormal wear

[Sirrotica]

As long as the base circle on the cam is close to the same as the OEM camshaft you could use the non adjustable OEM nuts. The lift is probably okay with OEM springs.

The way the OP description sounds like the cam timing is off. He's not going to have 15 Lbs of vacuum, or 150-175 Lbs of compression with the valves are off the seat. Just because the cam and timing chain, and gears are new doesn't mean that the keyways are all cut exactly where they should be, or there wasn't some error in the assembly. If the valves weren't seating you'd likely have a miss, or very possibly a backfire when trying to accelerate.

I have had a Comp cam ground for an oldsmobile that ran like crap because half of the cam lobes were on center where they should be, and half of the lobes were off center. Machining mistakes happen. Nothing we did would make that car run well because the cam was ground incorrectly.

The hydraulic lifters are very forgiving to adjust the valvetrain even if all the specs aren't dead on. There are a good many of domestic engines that have no provisions to have adjustable valve trains. Those engines have mild hydraulic cams installed all the time without going to an expensive conversion to make the valvetrain adjustable.

While I'm not against making a Pontiac valvetrain adjustable, I don't belive that this is the OPs problem, rather that it's a cam timing issue. I have installed more than a few mild performance cams into Pontiac engines without making the valvetrain adjustable, the lifter travel made up the difference to make sure all the valves were seating. If the new cam has a base circle close to the OEM cam, it should work satisfactorily with a non adjustable valve train.

Years ago I worked on a 66 Catalina that ate the nylon timing gear teeth, when it was replaced it inadvertantly was one tooth off. The car idled just fine, but was about as gutless as a 6 cylinder full size car. After resetting the cam timing it would fry the RR tire off. Cam timing has a huge effect on performance.

I'm curious also of what carb, and intake the engine has on it, the wrong intake, with improper gearing can make a car gutless as hell because of the runner velocity is wrong for the combination. All the parts have to be in harmony to gain performance. Transmission, gearing, intake, and carb, and exhaust system, would all be helpful to know before condemming the non adjustable valve train.

[Jay S]

Hot can add 5 to 10 lbs on a compression test. 150 was in the low end of what it should have been, but still ok. Going from 150 to 175 isn’t that unusual after a lifter adjustment, a sign it was running too tight. Sometimes the lifters bleed off and don’t recover as fast as you might expect also, more true these days when lifter bleed rates vary quite a bit. it It may not stay at 175lbs if you tested it right after adjusting the lifters. Altitude and atmosphere conditions effect the pumping compression too. Hopefully it runs better for you.

If your not running all the emission controls I think you will want to back off the timing from 18. The emission controls shut the vacuum advance off until the engine reaches a minimum temp. I think that was why they ran so much initial. If the emission equipment is all hook up yet it probably needs to be at 18 like it says.