Engine still popping...

I got the engine back together, 16 new lifter's and re broke everything in, everything is moving and looks good, engine holds 60psi oil pressure cold and 35-40 warm. Still had a slight popping, changed plugs and wires, it got better but still has a slight "pop" pulled the plugs and #5 was real dirty looking, all the others were a ashy grey color. so did a compression check on all 8 clyinder's

1. 120
2. 109
3. 115
4. 116
5. 115
6. 123
7. 120
8. 118

It has a Stealth intake on it, and there is a threaded hole, and plug over the #5 intake runner, it wasnt real tight, sso i un screwed it, als had no thread tape or anything on it, so i just put a small dab of pipe dope around the top of the threads so to not get it in the intake and letting that setup now, also re tightened, probably 2-3 turns farther than it previously was. So correct me if Im wrong, but if that was sucking any air it would of made that one cylinder lean correct? causing some of my popping and slight flame out the exhaust?

Have you done a leakdown on it?

No leaks at the header flanges?

Barney wrote:Have you done a leakdown on it?

Negative, not sure what or how to do it?

maverick wrote:No leaks at the header flanges?

Not that im aware of, that plug in the intake runner didnt do anything to help it. Ill have to listen in the video's but dont think it popped while running tonight, but does while setting still clearing it out in the 3000rpm range...

My old engine had a slight pop like what your describing mine ended up being my ignition box. Might be worth looking into.

When I first got the Fresh 557 A headed deal together w/new block i could tell it wasn't right by the sound of it.(light popping). The heads were fresh from (so called) great machine shop. So I did a leak down and sure enough. I pulled the heads and poured raw gas into the ports and all but a couple cyl. leaked. So I did a hand LAP job on them. The car dropped FROM 9.40et,to 8.90 on first pass.

I also had a problem with popping, in my case it was from the exhaust on acceleration. I tried new fuel pumps, ignition boxes, ignition timing, spark plugs, carb adjustments and carb changes nothing worked. I finally made the decision to open the engine up and take a look at the cam timing, found the cam was installed 5 degrees retarded even though the crankshaft sprocket showed it was in the 4 degree advanced position . I degreed the camshaft in at 0' using a new Cloyes 9-3122 timing set, put everything back together and no more popping. A side benefit was a better running engine with increased vacuum and running less rich @ idle. Hope this helps. Todd

dfree383 wrote:Refresh our memories, what all have your done to it?

New lifter's since i had the one that collapsed, new plugs and wire's new distributor gear, as it was all but gone. when i dropped it back in and re checked the "slack" in timing chain threw the fuel pump hole and it seemed tight so i didnt change it, just have 1 dirty plug...

So, it "pops" all the time (accelerating and idling, including 3000 rpm in neutral)? Was the cam degreed? How about the ign. timing, where is it at? No vacuum advance?

No it Idle's fine, I didnt notice it poping last night at the race, just when i was clearing it out just before the pass, which was in N in the 3000 RPM range...

pull the plugs for clues

could be ignition this involves many items. an off colour plug would be a starting place like your #5 was see if the new plug looks the same.

could be a worn cam lobe

Already did....



#5 plug on left, #6 plug on right

do the other plugs look like #6?
if so find out why #5 isn't firing properly

also here is a video from it from the last race, havent had time to get last nights loaded yet, but it was popping when i cleared it out on this run to

Yes all 7 other plugs look like #6, I have tried swapping plugs from 5 to 6, when i do the dirty plug that was swapped from 5 to 6 cleans up, and the clean one from 6 that was swapped to 5 was dirtied up and it doesnt really take long to do it, do one Launch and go threw the gears, 1-2-3 and shut it off and it turns dark like that, I have put in new wire's, even tried swapping the new wires around to see if one of the new wires were bad but no change, that is why i did the compression test. but according to the compression test it looked okay..

I'm a rookie but it definitely wouldn't hurt to leak down the bad cylinder?

Have you checked the valve adjustment on that cylinder ?,

no, they are D3 head's not sure how or if they can be adjusted?

Old blue Racin Team wrote:no, they are D3 head's not sure how or if they can be adjusted?

OK, I now see the photo of your plugs,you could try jetting your carb down 2 #s on the driverside primarys to see if that cleans the plug up. What intake are you running,and what carb?,

The Stealth and a Holley 750 vac secondary, if it was jetted to high wouldn't it mess up more than just the front cylinder? then again it seems the secondary's could be coming in and over fueling when it is reved that high since it run's great at idle...

also i asked before with no response, what is and how do you do a leak down test?

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also i asked before with no response, what is and how do you do a leak down test?

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Here is a link to one at Summit, you can get them about anywhere. http://www.summitracing.com/parts/sum-900010/overview/

A leak down test determines if there is a leakage of compression past the rings or thru one of the valves, or possibly the head gasket. The amount of leakage is measured in percentage of air loss by the gauges on the tester.

First you calibrate/set the leak down tester to your air compressor as per instructions, roll the engine over to TDC on the cyl your checking. Make sure both valves are closed, or better yet back off the rocker arms, and block your carb wide open. Then connect the tester hose to the adapter in the spark plug hole and read the percentage of leakage on the gauges. Then if excessive leakage, listen to see where the leakage is coming from, from the carb, (intake valve), headers, (exhaust valve), or out of the crankcase (rings).

If you don't have it exactly at TDC, when you apply air to it, it might push the piston down, you might have to keep the engine from rolling over.
Some say to do this when engine is at operating temp, but some say you can do it cold. Either way you do it, just do it the same every time to get a good comparison.

Ive had a bad ground on my msd box before that had me scratchin my head. Im not sure if thats what you've got goin on here but its worth mentioning.