[Gach]

If it retarded it’ll seem like a dog.

[Cliff R]

Three things need to happen here.

First, you need to verify the intake open point to make sure the cam isn't retarded. A little to late now (without a LOT of work) to set it all up with a degree wheel and piston stop to find TDC. Just remove the drivers side valve cover and slowly rotate the engine until the #1 intake valve starts to open. If you have the means put a dial indicator on it and stop at .050" tappet lift. Glance down and see where the timing mark is on the harmonic balancer. Reference the cam card and see if it's close to the listed specs. Of course this assumes that the balancer was checked during the build and hasn't slipped some.

Next, rebuild the carb with high performance parts and tune it for the added power, I can help with that. A stock carb is WAY too lean with the huge DB rods in it to make any power with the cam upgrade.

Remove the distibutor, drive out the roll pin, remove the gear, pull the shaft out of it and clean, polish and lubricate all the parts in the mechanical advance mechanism. I would also weld in a positive stop for the advance in case you install lighter springs to get the timing curve in a little sooner.

A larger cam without a corresponding increase in static compression is going to loose some vacuum at idle, power right off idle, and shift power up in the RPM range. Typically when this happens the engine will want more idle fuel, and more timing, and all in a tad earlier than it did with the stock cam.

I did see any mention of what head gasket was used but hopefully it was a Felpro at .039" thick and not something in the .050-.060" range which would just take more power out of it.

I'd also add here that I've used that cam in quite a few low compression 400 builds and it acts like a pretty "big" cam in them. It will make great power as well. The first engine in my Ventura was a low compression 400 with 6X-8 heads and it ran high 13's over 100 mph with that cam against a stock converter and 2.73 gears. It would rip the tires right off the rims on a full throttle blast from a standing start and took some work to get it to hook at the track on street tires.

If your nearly identical engine is a big "turd" you are missing a few things and need to figure them out. I doubt if it's how deep the pushrods are in the lifters. I ran the stock bottleneck studs on my heads but simply added adjustable 3/8" locknuts to them......hope this helps some......

[Jay S]

Originally Posted by Shockwave78

What do you think would cause that only at WOT?

Are you still running the stock spark plugs?
What plug is in it now?

I have done a couple engines that had cam swaps that as soon as the engine went to WOT it would nearly die or gag. Needed a colder spark plug, made a huge difference. I had one low compression engine once that would only idle, open the carb at all it would bog. Took 2 heat ranges lower to make that one run. Does that sound like what it is doing? More throttle, the worse it runs?

[Gary H]

My bet on this is that the camshaft is retarded due to the timing chain gears being installed incorrectly. Over the years I have had multiple customers bring their cars in here with the same symptoms as your engine, very poor performance after a cam change and new multi- keyway timing chain install. In each case, the timing chain was installed incorrectly by lining up the mark on the keyway on the crank gear sprocket rather than the correct one. If it was my car, I would pull the timing cover and check to see that I had the timing chain installed properly.

[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

[Shockwave78]

Originally Posted by Cliff R

Three things need to happen here.

First, you need to verify the intake open point to make sure the cam isn't retarded. A little to late now (without a LOT of work) to set it all up with a degree wheel and piston stop to find TDC. Just remove the drivers side valve cover and slowly rotate the engine until the #1 intake valve starts to open. If you have the means put a dial indicator on it and stop at .050" tappet lift. Glance down and see where the timing mark is on the harmonic balancer. Reference the cam card and see if it's close to the listed specs. Of course this assumes that the balancer was checked during the build and hasn't slipped some.

Next, rebuild the carb with high performance parts and tune it for the added power, I can help with that. A stock carb is WAY too lean with the huge DB rods in it to make any power with the cam upgrade.

Remove the distibutor, drive out the roll pin, remove the gear, pull the shaft out of it and clean, polish and lubricate all the parts in the mechanical advance mechanism. I would also weld in a positive stop for the advance in case you install lighter springs to get the timing curve in a little sooner.

A larger cam without a corresponding increase in static compression is going to loose some vacuum at idle, power right off idle, and shift power up in the RPM range. Typically when this happens the engine will want more idle fuel, and more timing, and all in a tad earlier than it did with the stock cam.

I did see any mention of what head gasket was used but hopefully it was a Felpro at .039" thick and not something in the .050-.060" range which would just take more power out of it.

I'd also add here that I've used that cam in quite a few low compression 400 builds and it acts like a pretty "big" cam in them. It will make great power as well. The first engine in my Ventura was a low compression 400 with 6X-8 heads and it ran high 13's over 100 mph with that cam against a stock converter and 2.73 gears. It would rip the tires right off the rims on a full throttle blast from a standing start and took some work to get it to hook at the track on street tires.

If your nearly identical engine is a big "turd" you are missing a few things and need to figure them out. I doubt if it's how deep the pushrods are in the lifters. I ran the stock bottleneck studs on my heads but simply added adjustable 3/8" locknuts to them......hope this helps some......

I will check the valve timing today, and the head gasket used has a compressed thickness of .045

[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.

[slowbird]

Originally Posted by Shockwave78

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)

Can you clarify this statement?? You saying the secondary air valve is only opening about a quarter? If so have you verified that the secondary butterflies are opening fully? Have you pulled all the plugs to see what they look like?

[Shockwave78]

Originally Posted by 78w72

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.

I did not do the rocker arm adjustment exactly like in the link, I rotated the engine over to each cylinder in firing order and adjusted each on tdc of the compression stroke, which should have the same result. I have not done a full engine teardown/rebuild before this, but have done basically everything else there is to do on a stock engine, I've been working on cars/engines similar to this one for about 7 years. As far as the gas droplets and vapor out of the top of the carb, it is only at WOT and it has enough velocity to curve back and hit the middle/top of the windshield. I will be checking the timing today with the method as Cliff said, I will look into renting a leak-down tester and doing the warm compression test as well. The more tests I do the more it looks like a cam timing issue as many have said, but if nothing else it is a learning experience.

[400 Lemans]

https://forums.maxperformanceinc.com...ower+degreeing See Cliffs post #6. The 60240 is the same deal.

[78w72]

Originally Posted by Shockwave78

I did not do the rocker arm adjustment exactly like in the link, I rotated the engine over to each cylinder in firing order and adjusted each on tdc of the compression stroke, which should have the same result. I have not done a full engine teardown/rebuild before this, but have done basically everything else there is to do on a stock engine, I've been working on cars/engines similar to this one for about 7 years. As far as the gas droplets and vapor out of the top of the carb, it is only at WOT and it has enough velocity to curve back and hit the middle/top of the windshield. I will be checking the timing today with the method as Cliff said, I will look into renting a leak-down tester and doing the warm compression test as well. The more tests I do the more it looks like a cam timing issue as many have said, but if nothing else it is a learning experience.

I will let others chime in on the adjustment... but I dont think thats the correct way to adjust them. Doing each piston at TDC does not get the lifter on the base of the cam lobe. If you can rotate the engine & know how to find TDC of COMPRESSION stroke (TDC can be on exhaust stroke too) then I would suggest you follow the procedure in the link I posted, its very important to do this adjustment the right way.

Just wanted to mention carbs can spit fuel droplets when exposed to the wind while driving, mine would do it at WOT too but also at lower speeds & less throttle, especially on the holley double pumper carb i had on a 455, could watch the droplets arch up onto the windshield just like you describe.

Learning experiences are good, that how we all learn, but this may be a time to learn how to adjust rockers correctly, the way i understand how you described it is not the correct way.

Hope you can figure it out.

[Sirrotica]

One other thing that I thought of that can cause revision, a clogged exhaust, or catalytic convertor. I have no idea if your cat is still in place, or not, but there is a slight possibility that you have a clogged catalytic convertor. Likely not that it would happen all at once just after a cam change, but a remote possibility.

If you suspect this, loosening the crossover pipe at the exhaust manifolds will confirm your suspicion. You don't need to remove the pipes, just lower them until they leak, and test it.

I just wanted to cover that possibility, even though it's not high up on the things I would check. I have found a handful of times that somehow the exhaust gets restricted internally, causing this same symptom.

[Gach]

Yeah he’s doing valve adjustment wrong.

[Shockwave78]

Originally Posted by Gach

Yeah he’s doing valve adjustment wrong.

why would it be different if the cylinder that was being adjusted was on tdc of the compression stroke? Wouldnt the lifters have to be on the base of the lobe? Im not trying to be stubborn, just genuinely confused as to what difference it would make.

[Shockwave78]

Originally Posted by Sirrotica

One other thing that I thought of that can cause revision, a clogged exhaust, or catalytic convertor. I have no idea if your cat is still in place, or not, but there is a slight possibility that you have a clogged catalytic convertor. Likely not that it would happen all at once just after a cam change, but a remote possibility.

If you suspect this, loosening the crossover pipe at the exhaust manifolds will confirm your suspicion. You don't need to remove the pipes, just lower them until they leak, and test it.

I just wanted to cover that possibility, even though it's not high up on the things I would check. I have found a handful of times that somehow the exhaust gets restricted internally, causing this same symptom.

The car has side pipes on it without cats, about as simple as it gets

[78w72]

Originally Posted by Shockwave78

why would it be different if the cylinder that was being adjusted was on tdc of the compression stroke? Wouldnt the lifters have to be on the base of the lobe? Im not trying to be stubborn, just genuinely confused as to what difference it would make.

I will let others explain why its different, but basically the cam isnt on the base circle for both valves when a given cylinder is at TDC... but for now just trust it is different and readjust everything following the link I posted. Loosen all the nuts & get the engine on #1 TDC compression stroke and adjust the valves shown in the link... engine has to be on TDC of the compression stroke. If youre not sure how to verify compression stroke just ask, its very simple to do. Then you rotate it as described and do the other valves shown.

This is very important, understand it later but readjust correctly before running it any more.

[Gach]

You don’t have to do in the firing order either. When exhaust starts to open adjust intake when intake starts to close adjust exhaust. That way your on heel of the cam in both events.

[steve25]

Any time I have seen that condition you describe from someone’s carb the firing order was wrong.

[Sirrotica]

Originally Posted by Shockwave78

The car has side pipes on it without cats, about as simple as it gets

As I said, I have no knowledge of what you've done to the car, but it did come with a cat on it, so I wanted to cover that remote possibility.

If you adjust the valves running, like the chevy procedure, back them off until they clatter, turn them down until quiet, than add 1/4 turn you'll be in the ball park, and can eliminate valve adjustment as the cause. Yes it's messy, but it is effective, and very simple, and quick. You can then go back and adjust the valves any way you feel is the best way, but it quickly gets valve adjustment out of the way as being a problem. Getting stuck on how is the very best method of adjsting valves is incosequential when you're troubleshooting an engine problem, do it the simplest way, and move on.

Getting stuck of turning the pushrod between your fingers, while making sure the lifter is on the heel of the cam is a little involved for troubleshooting a problem. You can go back, and redo the valves later if you feel the need to.

Make sure the secondary metering rod/rods haven't fallen out of the hanger too, another easy to check problem that I've seen happen. Also when stripping an engine down, and disturbing a Q jet, if it has sediment in the bowls, you can redistribute the sediment to clog an orifice(s) and screw up part of the circuits in the carb.

Then you're back to firing order, or cam timing.