[Shockwave78]

Just checked the rocker nuts, and when they are torqued down per the manual, I can watch the valve open. I backed the nuts off to adjust them like you normally would with an adjustable valvetrain, did a compression test and it returned 175 psi, a bit more than I was expecting, given the whole engine is stock except the cam. Regardless I am definitely switching the nuts out today! I had to swap the valley pan after break in and had a chance to check the cam and there were no wiped lobes or abnormal wear, thank god. I have also been using the car as a daily for the past year or so, which narrows down other potential problems it might have, but this is a really good starting point (hopefully the only problem)!

Thanks for all the input and ill report back with updates after the new rocker nuts.

[Gach]

Originally Posted by Shockwave78

Just checked the rocker nuts, and when they are torqued down per the manual, I can watch the valve open. I backed the nuts off to adjust them like you normally would with an adjustable valvetrain, did a compression test and it returned 175 psi, a bit more than I was expecting, given the whole engine is stock except the cam. Regardless I am definitely switching the nuts out today! I had to swap the valley pan after break in and had a chance to check the cam and there were no wiped lobes or abnormal wear, thank god. I have also been using the car as a daily for the past year or so, which narrows down other potential problems it might have, but this is a really good starting point (hopefully the only problem)!

Thanks for all the input and ill report back with updates after the new rocker nuts.

Bingo ! Yeah I knew 150 compression was really low ! good glad you found the issue

[Gach]

PS: 175 will be fine..no worries

[Gach]

Originally Posted by Stan Weiss

4.12" bore, 3.75" stroke, 6.625" rod, 8.0:1 CR, 270 intake duration 109 ICL (26/64), should at sea level should produce about 148 psi cranking compression.

Stan

Is that one of you Calculator programs simulators, maybe should adjust it, because he really ended up with 175 compression…. oops.

[Stan Weiss]

Originally Posted by Shockwave78

Just checked the rocker nuts, and when they are torqued down per the manual, I can watch the valve open. I backed the nuts off to adjust them like you normally would with an adjustable valvetrain, did a compression test and it returned 175 psi, a bit more than I was expecting, given the whole engine is stock except the cam. Regardless I am definitely switching the nuts out today! I had to swap the valley pan after break in and had a chance to check the cam and there were no wiped lobes or abnormal wear, thank god. I have also been using the car as a daily for the past year or so, which narrows down other potential problems it might have, but this is a really good starting point (hopefully the only problem)!

Thanks for all the input and ill report back with updates after the new rocker nuts.

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

Stan

[Gach]

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

Why ?

[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.

[Shockwave78]

Installed the new rocker nuts and....... still no power. Might be a bit better but not by much. On the highway at WOT it cant get past 60. Also on the highway cruising at part throttle it missed or coughed 3 or 4 times, on the 30 minute test drive, that was the only time. The last thing I noticed is, at WOT when the top flap of the secondaries open as much as they can (which isn't much, maybe a quarter open) there is white fuel vapor being blown out of the top of the carb, enough to hit the windshield and cover it in gas droplets. I cant tell if it is out of the primaries or secondaries.

And to add insult to injury, my oil pressure gauge stopped working and is stuck at 60 psi

[PunchT37]

Hmmm. Reversion?

[Shockwave78]

I do not have the tools to perform leak down testing.

[Sirrotica]

Revision in the intake manifold is causing the mist to come out of the carb. Revision is caused by the cam timing being off, or the firing order being wrong. I would first check the firing order, if it's okay I'd be looking at pulling the timing cover, and rechecking your timing marks.

The bouncing vacuum gauge could be caused by incorrect firing order, it's the easiest thing to check, verify it's correct first.

From the description I would say the cam is retarded, causing the intake valve to still be open as the piston is on it's upstroke. Doing a cam change in chassis, it is fairly easy to think you have the marks aligned, and they are off. To add to this you have 3 adjustments to choose from with the timing gears.

Reread the directions on your variable keyway timing set, and double check your work.

I've been called many times over the last 50 years to fix situations such as this, and usually it's something overlooked when reassembling the engine. If it ran fine before the work was done, it a distict possibility it's in the reassembly process.

There is a slight possibility of defective machining, or parts, but 99 times out of 100 it's an oversight, it happens to everyone at one time, or another. All the guesses that the valve adjustment was causing the problem were incorrect. From my own real life experience, I'm telling you the obvious order of troubleshooting your symptoms.

[Gach]

That was one of first things I suggested cam timing, but when he found valve adjustment was off, and then it pick up compression once that was changed seem possible that could’ve been the issue, but let him do compression test tomorrow on all 8, and check valve adjustment. Then if that doesn’t change much then most likely its cam timing, thats what I’m thinking. Cams retarded.

[Jay S]

Originally Posted by Shockwave78

Installed the new rocker nuts and....... still no power. Might be a bit better but not by much. On the highway at WOT it cant get past 60. Also on the highway cruising at part throttle it missed or coughed 3 or 4 times, on the 30 minute test drive, that was the only time. The last thing I noticed is, at WOT when the top flap of the secondaries open as much as they can (which isn't much, maybe a quarter open) there is white fuel vapor being blown out of the top of the carb, enough to hit the windshield and cover it in gas droplets. I cant tell if it is out of the primaries or secondaries.

And to add insult to injury, my oil pressure gauge stopped working and is stuck at 60 psi

With too hot of a spark plug the HEI will compensate at lower RPMs buy reducing the dwell at lower RPMs. It will run fine at lower RPMs with too hot of a plug. Once you get above 2500 RPM an overly hot spark plug will fame out and do what you are describing on the secondary air door.

If you happened to retard the cam timing the colder spark plug will help some, but wouldn’t correct it. The pumping compression reported does not describe a cam timing problem. Double checking the cam timing is probably the next step I would do after trying a little colder spark plug.

[Stan Weiss]

Originally Posted by Jay S

With too hot of a spark plug the HEI will compensate at lower RPMs buy reducing the dwell at lower RPMs. It will run fine at lower RPMs with too hot of a plug. Once you get above 2500 RPM an overly hot spark plug will fame out and do what you are describing on the secondary air door.

If you happened to retard the cam timing the colder spark plug will help some, but wouldn’t correct it. The pumping compression reported does not describe a cam timing problem. Double checking the cam timing is probably the next step I would do after trying a little colder spark plug.

Jay,
This is my feeling also. But since he only did a cranking test on 4 cylinders that is why I think he needs to do all 8. There is always the chance that in manufacturing some lobes got mis-machined.

Stan

[78w72]

Originally Posted by Shockwave78

Installed the new rocker nuts and....... still no power. Might be a bit better but not by much. On the highway at WOT it cant get past 60. Also on the highway cruising at part throttle it missed or coughed 3 or 4 times, on the 30 minute test drive, that was the only time. The last thing I noticed is, at WOT when the top flap of the secondaries open as much as they can (which isn't much, maybe a quarter open) there is white fuel vapor being blown out of the top of the carb, enough to hit the windshield and cover it in gas droplets. I cant tell if it is out of the primaries or secondaries.

And to add insult to injury, my oil pressure gauge stopped working and is stuck at 60 psi

Did you do the adjustment right with the new nuts? Positive the engine was a TDC of compression stroke and you adjusted the correct lifters based on that link? Just asking since I/we dont know how much mechanical experience you have. I recently tried to help a guy from another country adjust his rockers and even after sending the link & a couple youtube videos... he just tightened all the rockers to "zero lash" then added 1/2 turn to all the rockers at one time, didnt work out to well and took him a few tries to get it right, engine is running good for him now.

Also, if the crower lifters say 1/2 turn, thats what they should be set to... 1/2 turn past zero lash is not a lot, most HFT lifters recommend that unless they are the type that say 1/4 turn.

Leak down tester- Check with local auto part stores, they may offer a free rental for this. or get the warm cranking compression numbers to help others on here diagnose the issue.

Gas droplets on the windshield- I have had that happen on a couple engines that ran great when I would remove the shaker scoop & add a velocity stack to look cool would very get small amounts of gas droplets from holley & q-jet carbs when driving at normal speeds... reverberation or not, the engine ran great with or without the air cleaner removed so i dont think thats part of the issue your having.

After trying some of the tests mentioned above to identify the issue, you may need to pull the timing cover to check cam timing & timing chain alignment... but if you are sure the chain/gears were installed right, i dont think not degreeing the cam is causing the problems, i have installed cams straight up that run great. its easy to get the timing chain off a tooth or even installed 180 off if following chevy manuals.