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after my performance update, the 442 runs very poor. With the update, i replaced the j heads to fresh rebuilt ka heads, the valvetrain changed to a comp cams high energy 268./268. kit and i replaced the rocker arm to comp rocker arm with 1.6 ratio.
before the update, the car runs very well for several years.
i checked the compression and the cylinder leckage, also i replaced sparks and spark plug wires. Without effort.
then i replaced the intake manifold gasket, also without effort. After that, i surfaced the used performer intake. Today i tested the engine and it runs still poor.
The timing of the GM Hei dist (its the old that runs good before) is at 4* by 1100rpm , i know it should be at 8* by 1100rpm, but when i give it more early ignition the engine begins with shaking an want to stall.
after my performance update, the 442 runs very poor. With the update, i replaced the j heads to fresh rebuilt ka heads, the valvetrain changed to a comp cams high energy 268./268. kit and i replaced the rocker arm to comp rocker arm with 1.6 ratio.
1. Was the camshaft degreed? Or just installed "Dot to dot"? Any chance you have a cam designed for the "old" lifter-bank angle? (A 45 degree cam instead of a 39 degree cam)
2. Did you verify that the damper mark aligned with the "0" of the timing pointer when the #1 piston is at TDC?
3. Did you verify that the pushrods have clearance in the heads when switching to 1.6 rockers? I had to grind the livin' bejezzus out of my "C" heads to get clearance.
4. Do you have retainer-to-rocker clearance through the full range of motion? Retainer-to-valve stem seal clearance at full lift?
5. IS THE LIFTER PRELOAD ADJUSTABLE? Any chance they're too tight? (This should show up on a cylinder leakdown test as "leaky valve(s)".)
Originally Posted by Bastler
before the update, the car runs very well for several years.
So it's probably NOT something in the short-block except maybe cam timing.
Originally Posted by Bastler
i checked the compression and the cylinder leckage, also i replaced sparks and spark plug wires.
What is the cranking compression for all eight? What was the leakdown percentage for all eight? Any chance the plug wires were mis-routed, or #5 and #7 plug wires run too close together?
Originally Posted by Bastler
The timing of the GM Hei dist (its the old that runs good before) is at 4* by 1100rpm , i know it should be at 8* by 1100rpm, but when i give it more early ignition the engine begins with shaking an want to stall.
Makes me suspect that the damper ring has moved on the hub. Timing mark is no longer accurate.
Originally Posted by Bastler
I also rechecked the timing marks on the cam, with my afr gauge i can check the fuel mix, everything seems fine.
The "dot-to-dot" timing marks on the timing sprockets means very little. Degree the cam.
What is the AFR at idle?
Originally Posted by Bastler
i really have no idea why the engine didn‘t run good, i have spark, fuel and compression.
You need:
Air/fuel mixed in the right proportions; Adequate compression;
A spark across the plug gap at the right time; and Non-restrictive exhaust.
Have you tried a cylinder-balance test to see if the problem is specific to one or more cylinders? For example, with a dual-plane intake manifold, if every-other cylinder is weak at idle, you almost certainly have an idle circuit that's not feeding fuel properly--or a vacuum leak into one of the two planes.
1. Was the camshaft degreed? Or just installed "Dot to dot"? Any chance you have a cam designed for the "old" lifter-bank angle? (A 45 degree cam instead of a 39 degree cam)
//The cam comes out of a comp cams kit K42-229-4, the cam design is without a degree option. There is only one hole in gear for the cam pin.
2. Did you verify that the damper mark aligned with the "0" of the timing pointer when the #1 piston is at TDC?
//i will check this this, could happen that the damper isn‘t straight anymore
3. Did you verify that the pushrods have clearance in the heads when switching to 1.6 rockers? I had to grind the livin' bejezzus out of my "C" heads to get clearance.
//it‘s all clear, this is the 1442-kit from comp cams
4. Do you have retainer-to-rocker clearance through the full range of motion? Retainer-to-valve stem seal clearance at full lift?
//i will check this
5. IS THE LIFTER PRELOAD ADJUSTABLE? Any chance they're too tight? (This should show up on a cylinder leakdown test as "leaky valve(s)".)
//yes, it‘s adjustable. I preload it like comp cams write it in the instructions. No ticking noises
So it's probably NOT something in the short-block except maybe cam timing.
//I also think so
What is the cranking compression for all eight? What was the leakdown percentage for all eight? Any chance the plug wires were mis-routed, or #5 and #7 plug wires run too close together?
//I have about 130psi +- 10 psi, Leakdown test shows about 17-20%. I rechecked the plug wires several times.
Makes me suspect that the damper ring has moved on the hub. Timing mark is no longer accurate.
The "dot-to-dot" timing marks on the timing sprockets means very little. Degree the cam.
What is the AFR at idle?
// afr at idle is about 13
You need:
Air/fuel mixed in the right proportions; //i will test it with another carb Adequate compression; // checked it several times, with warm and cold motor
A spark across the plug gap at the right time; and // tried 0.035 and 0.08 gap Non-restrictive exhaust. // headers
Have you tried a cylinder-balance test to see if the problem is specific to one or more cylinders? For example, with a dual-plane intake manifold, if every-other cylinder is weak at idle, you almost certainly have an idle circuit that's not feeding fuel properly--or a vacuum leak into one of the two planes.
// the third cylinder doesn‘t run, i checked the exhaust manifold temp, and it increase only slow, not like the other
// vac leak is also a thing, i often read that the performer intake doens‘t seal right, i will build a tool to test it
130 psi cranking compression is on the low side of acceptable. Cranking compression varies due to about two dozen variables, among them altitude and cranking speed, and whether the throttle was open during the test. Around here, 150-ish is pretty normal. Have you ever tested your compression gauge to see if it's accurate? I connect mine to "shop air" now and then, if the compression gauge reads about the same as the gauge on the compressed-air regulator, I figure it's close enough.
Having a dead #3 cylinder is certainly going to make a difference. Any vacuum hoses on the intake manifold runner for that cylinder? Fouled spark plug? Failed carb gasket?
Don't test for vacuum leaks with aerosol BRAKE cleaner. Two reasons:
1. Not all BRAKE cleaner is flammable. If it won't burn, it gives no indication of rich or lean.
I use aerosol CARBURETOR cleaner, or a propane tank and a hose to direct it where I want it.
Just to ask the question...have you adjusted the idle mixture screws?
I'm still concerned about how the engine runs bad when the timing is advanced to what I'd consider a "reasonable" level. Do you have the vacuum advance connected? How many degrees of vacuum advance does the canister provide? And, absolutely, you need to find TDC #1, and verify that the timing marks align.
Last edited by Schurkey; June 22nd, 2020 at 08:03 PM.
130 psi cranking compression is on the low side of acceptable. Cranking compression varies due to about two dozen variables, among them altitude and cranking speed, and whether the throttle was open during the test. Around here, 150-ish is pretty normal. Have you ever tested your compression gauge to see if it's accurate? I connect mine to "shop air" now and then, if the compression gauge reads about the same as the gauge on the compressed-air regulator, I figure it's close enough.
// it’s a low comp short block, i think the compression is Not the best, but ok
Having a dead #3 cylinder is certainly going to make a difference. Any vacuum hoses on the intake manifold runner for that cylinder? Fouled spark plug? Failed carb gasket?
// i checked the hoses and plugs and wires. The gasket is new. I think the engine has one big problem and the third cylinder effect it the most
Don't test for vacuum leaks with aerosol BRAKE cleaner. Two reasons:
1. Not all BRAKE cleaner is flammable. If it won't burn, it gives no indication of rich or lean.
I use aerosol CARBURETOR cleaner, or a propane tank and a hose to direct it where I want it.
// good trick, next time i use propane
Just to ask the question...have you adjusted the idle mixture screws?
// i have a afr about 13, i can regulate the mixture with the manual choke. Till now i didn‘t set the screws
I'm still concerned about how the engine runs bad when the timing is advanced to what I'd consider a "reasonable" level. Do you have the vacuum advance connected? How many degrees of vacuum advance does the canister provide? And, absolutely, you need to find TDC #1, and verify that the timing marks align.
// i connected the dist to the ported and manifold vac for testing, slightly different
thank you for the help.
my next step is to check the timing mark on the balancer, i orderd some measuring tools for a exact mesurment. Then i will check the timing of the crank at the rockers.
till the tools are delivered, i have a 600cfm carb for testing, i know, a little small but for a test should be ok.
The dead #3 cylinder is the critical part here. Focus on that.
You may have additional problems--with the ignition timing, for example--but that's going to affect ALL cylinders. You need to figure out what's wrong with #3 specifically.
Spark across the gap? Plug not fouled, distributor cap not carbon-tracked?
Fuel/Air ratio? Vacuum leak into #3 making for a lean misfire? Intake not sealing on the #3 runner? Vacuum accessory leaking air into #3 runner?
You've tested compression, that should be OK.
I wouldn't expect an exhaust restriction only on #3 unless it's a valve not opening.
Have you pulled the valve cover to see if the rockers are moving like they should on #3? No broken valve spring?
The dead #3 cylinder is the critical part here. Focus on that.
You may have additional problems--with the ignition timing, for example--but that's going to affect ALL cylinders. You need to figure out what's wrong with #3 specifically.
Spark across the gap? Plug not fouled, distributor cap not carbon-tracked?
Fuel/Air ratio? Vacuum leak into #3 making for a lean misfire? Intake not sealing on the #3 runner? Vacuum accessory leaking air into #3 runner?
You've tested compression, that should be OK.
I wouldn't expect an exhaust restriction only on #3 unless it's a valve not opening.
Have you pulled the valve cover to see if the rockers are moving like they should on #3? No broken valve spring?
today i checked the tdc to the mark on the damper, it‘s ok.
Also checked the timing from openening the intake valve to the mark on on the damper. The valve opens at appr. 24 degree, comp cams say it‘s right.
i checked the vac lines also, like the plugs. I turned the distr about 1/8 but the error stays at cyl 3.
i read about a guy who replaced his intake gasket about three times, he had the same problem.
tomorrow i will build an plate for the intake carb side and give some pressure air in, i will loose the rockers so i can hear where a leak could be and measure out how much air i loose.
after that i will take off the intake and look after the cam. and measure it.
then i install the intake again and make a pressure test with the same condition. I hope to see a difference.
i tested also a another carb today, same rough idle and missing cylinder.
till now i used a edelbrock intake gasket and a thicker flat out gasket. I think next time i will take the composite fel pro or edelbrock gasket.
FIRST thing I'd do is to pinch-off or remove all the vacuum hoses from that vacuum tee on #3 runner. Any one of them--or a non-sealing pipe thread on the tee--could be affecting the mixture to #3 and causing the misfire.
5. IS THE LIFTER PRELOAD ADJUSTABLE? Any chance they're too tight? (This should show up on a cylinder leakdown test as "leaky valve(s)".)
//yes, it‘s adjustable. I preload it like comp cams write it in the instructions. No ticking noises
COMP CAMS instructions include "Through various testing we have discovered that the recommended lifter pre-load should be set .045" or 1 turn of the wrench past zero lash for optimal performance.
EVERY cam I have installed has ran like **** using those instructions. Most camshaft instructions say to use 3/4 to 1 full turn of the adjusting nut after zero lash. Try backing the pre-load to 1/4 turn and try again. I am not the most experienced when it comes to camshafts, but my limited experience shows a common theme of using less preload than the instructions call for to get best performance.
COMP CAMS instructions include "Through various testing we have discovered that the recommended lifter pre-load should be set .045" or 1 turn of the wrench past zero lash for optimal performance.
EVERY cam I have installed has ran like **** using those instructions. Most camshaft instructions say to use 3/4 to 1 full turn of the adjusting nut after zero lash. Try backing the pre-load to 1/4 turn and try again. I am not the most experienced when it comes to camshafts, but my limited experience shows a common theme of using less preload than the instructions call for to get best performance.
I tested your suggestion, you are right.
thanks a lot, now the cylinder is running. The engine runs now better but rough. I will check all the rocker arms and set them new
thanks a lot, now the cylinder is running. The engine runs now better but rough. I will check all the rocker arms and set them new
Glad that worked for you. I still don't understand why cam manufacturers insist on using those same instructions that always run the valves too tight. There are a lot of engines on the road that would run a lot better if the rockers were loosened up just a little bit.
June 21st, 2020, 07:33 PM
