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#81
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If it retarded it’ll seem like a dog.
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#82
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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......
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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
#83
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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? |
#84
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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.
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62' Lemans, Nostalgia Super Stock, 541 CI, IA2 block, billet 4.5" crank, Ross, Wide port Edelbrocks, Gustram intake, 2 4150 style BLP carbs, 2.10 Turbo 400, 9" w/4:30 gears, 8.76 @153, 3100lbs |
#85
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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. Last edited by Jay S; 08-09-2023 at 08:27 AM. |
#86
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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
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Stan Weiss/World Wide Enterprises Offering Performance Software Since 1987 http://www.magneticlynx.com/carfor/carfor.htm David Vizard & Stan Weiss' IOP / Flow / Induction Optimization - Cam Selection Software http://www.magneticlynx.com/DV Download FREE 14 Trial IOP / Flow Software http://www.magneticlynx.com/DV/Flow_..._Day_Trial.php Pontiac Pump Gas List http://www.magneticlynx.com/carfor/pont_gas.htm Using PMD Block and Heads List http://www.magneticlynx.com/carfor/pont_pmd.htm |
#87
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#88
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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. |
#89
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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?
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#90
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#91
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https://forums.maxperformanceinc.com...ower+degreeing See Cliffs post #6. The 60240 is the same deal.
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#92
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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. |
#93
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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. |
#94
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Yeah he’s doing valve adjustment wrong.
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#95
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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.
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#96
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#97
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This is very important, understand it later but readjust correctly before running it any more. |
#98
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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.
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#99
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Any time I have seen that condition you describe from someone’s carb the firing order was wrong.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#100
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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. |
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