Ping, but only when hot, still need help

JeepsAndGuns · #1 11-27-2006, 07:01 PM

So I am getting some ping in my 401, but I notice that it only does it when the engine is warmed up. No ping when its cold. I have been running mid grade for the past few months to help it some, but I only drive it a little bit on the weekends. I am wondering if it doesnt have something to do with the large open element air filter thats on it. I am thinking that when its cold, sucks cold air = no ping. But once warm, it sucks in the warm air = ping. I dont have the stock air cleaner to put on it, but I am thinking about getting one to try, mabey makeing one of those nifty dual inlet ones like I have seen on here (or mabey the idea I have been haveing on my own custom intake

)
Will the stock air filter housing fit on a holley truck avenger?

sveperformance · #2 11-27-2006, 07:06 PM

If you do not have your EGR valve conected and working you will have to take some timing advance out of it .Bill

JeepsAndGuns · #3 11-27-2006, 08:29 PM

No EGR on this engine. It has the edl non egr intake on it. Timing is only set at 10*, any less than that and it runs like CRAP.

byson1 · #4 11-28-2006, 08:32 AM

Have you had the dist. recurved to reduce total advance? I have seen lots of threads on that. The ping is obviously caused by fuel preigniting before the piston is at top dead center. High octane (which is slower burning) gas will cure it. Reducing the air flow, which in effect makes for a richer air fuel mixture may cure it as well but I would consider that somewhat of a bandaid fix. I'm not sure about the air cleaners fitting. I would look into recurving the ditributor. You'll be suprised as to what it will do for power and eceonomy.

JeepsAndGuns · #5 11-28-2006, 09:18 PM

The choke is electric and I have it adjusted to come off pretty quick. So it doesnt run very long before it comes off. So it probably doeant have mutch to do with the choke. It seems like it doesnt start doing it untill it gets to around 180-195. Thats when it will start doing it. Seems like it only does it when lugging just a little, pushing the gas harder makes it get worse, mabey not worse, but no better. If I let off the gas and take it easy it does alright. On flat road it seems like it doesnt really do it too mutch, mabey just accelareing on a small incline (like from a stop) or mabey after slowing down a but then speeding back up without down shifting (but I'm really not lugging it that hard) It is kinda slow to warm up (I think my t-stat might be stuck open) But its been a while since I have driven it enough to get it warmed up. I only drive it on the weekends, and the past few I havent driven it enough to warm it up all the way. I need to get it back out and drive it.

JeepsAndGuns · #6 11-29-2006, 04:51 PM

No fuel leaks on the outside, didnt see and wetness on the inside (except for what squirted in there from the accel pump)

Eugene 1 · #7 11-29-2006, 05:43 PM

I I had the same problem with a 401 the solution: TFI Dizzy and ran a colder plug it did wonders even in the heat of summer.I have since upgraded to HEI and its even better..If you can... chuck the EGR

JeepsAndGuns · #8 11-30-2006, 05:01 PM

No EGR on this engine. The ignition is the TFI. Coil, cap/rotor, and accel wires. Plugs are champinions gaped to 45.

JeepsAndGuns · #9 12-10-2006, 05:10 PM

Been driveing it all weekend and the ping is still there. It only does it once it all the way warmed up. (guage at 195 for a min or two) It only does it when the engine is pulling. I noticed today that it only seems to do it in 3rd and 4th gears. Seems like it doesnt do it at all in 2nd (T18) I pull out in 2nd, accelerate, no problems, shift to 3rd and push the gas and I can hear it, let up and accel slower and it stops. Shift to 4th and it will do it is I am still pulling. Cruseing is fine, if I push the gas down just a little, like to pass a slower car (not passing fast like you would on the highway) or going up a small hill it will do it, push a little harder and it gets louder, push even harder (kicking in the secondairys) and it goes away. So I pretty mutch have to get on it pretty hard when I pass or go up small hills to keep it from pinging. I got out the timing light today and messed with the timing a little. I had it set at 10*. I started out droping it to about 9*, no change, so I droped it down to about halfway between the 10* mark and the 5* mark. Still didnt really change.

So what are my options?

When the secondairys open it goes away. they open= more fuel. Do I need to up the main jets one size and leave the secondairys alone??

Hot engine air being sucked in by open paper filter? Change to a stock type filter?

Right now I am running mid grade gas, do I need to step up tp premo? I used stock compression pistons in this engine so I dont think I should have high enough compression to need the premo stuff.

Any other ideas?

**Ristow** · #10 12-10-2006, 05:21 PM

you need to limit the amount of advance the vacuum advance gives.it stops pinging when you floor it because the vacuum drops low enough to remove the advance given by the vacuum unit.

if you have the vacuum unit with the big hex shape behind the nipple,put the biggest sae allen wrench that'll fit inside the nipple,you may need to turn a wiggle it to get it to engage the hex inside.turn it counter-clockwise to stiffen it up,which it needs,so it drops out earlier.

you can also limit its' range by putting a pin through the housing in the correct location.

*shimniok* · #11 12-10-2006, 05:38 PM

Retarding timing should help. Someone else posted this.

The symptoms you describe are classic symptoms of timing being too far advanced such that the total advance for base timing and vacuum timing is too much.

Either you have too much vac advance, or too much mechanical advance, or too much base timing advance. I'd start by retarding timing. I think there are shops that can check your mechanical and vacuum advance for you.

Vac advance comes into play most under heavy engine load part throttle, and least under light throttle or WOT.

Michael

JeepsAndGuns · #12 12-11-2006, 06:08 PM

I did retard the timing some. (was at 10*, now its at more like 7 or 8) And it didnt really change. I guess I will try messing with the vac advance. It has that hex shape to it. When I start adjusting on this, how mutch do I adjust it at a time? 1/2 a turn, 1 turn, 1/4 turn? Probably wont have enough spare (daylight) time this week to work on it so it might have to wait untill this weekend.

FSJ Thing · #13 12-11-2006, 06:19 PM

Quote:

Originally Posted by JeepsAndGuns

I did retard the timing some. (was at 10*, now its at more like 7 or 8) And it didnt really change. I guess I will try messing with the vac advance. It has that hex shape to it. When I start adjusting on this, how mutch do I adjust it at a time? 1/2 a turn, 1 turn, 1/4 turn? Probably wont have enough spare (daylight) time this week to work on it so it might have to wait untill this weekend.

I say carbon in your combustion chambers. It gets glowing red-hot and detonates the fuel/air mixture before the sparkplug fires.

Lots of snake oils for this, seafoam, Berrymans Chem-tool (my favorite), BG44K, etc.

Berrymans Chem-tool is only like $4 a can, what do you have to lose?

JeepsAndGuns · #14 12-11-2006, 06:36 PM

Carbon build up already? I just built this engine and put it in some time last year (done forgot) I never wrote down the mileage because I am pretty sure my speedo is way off. With the ammount I drive it, there is no way this thing has any more than 10,000 miles on it.

*shimniok* · #15 12-11-2006, 07:03 PM

Before you start changing anything, what happens if you remove the vac hose to vacuum advance entirely??? If it goes away, you can try to change that adjustment or maybe better yet look up shops that can help you test the distributor and its curve profile both mechanical and vacuum. It could be that even if getting rid of vacuum makes it go away the mechanical advance causes advance too early which is exacerbated by vacuum under load. I have heard there are crappy distributors out there that are way off where they should be.

Since you said you recently built the motor... though this is a last resort thing to check into, I understand there are some tricks around getting quench set up right on AMC. Lots of details on this on http://www.bulltear.com Hopefully this is just a simple timing adjustment issue.

Michael

FSJ Thing · #16 12-11-2006, 07:22 PM

Quote:

Originally Posted by JeepsAndGuns

Carbon build up already? I just built this engine and put it in some time last year (done forgot) I never wrote down the mileage because I am pretty sure my speedo is way off. With the ammount I drive it, there is no way this thing has any more than 10,000 miles on it.

Still a definite possibility, though it would mean something else is wrong, i.e. incomplete combustion, oil leaking in through intake valve seal, using real dirty fuel with ineffective fuel filtration, etc.

Quick question I shoulda asked first, how do your spark plugs look?

JeepsAndGuns · #17 12-12-2006, 04:59 PM

Havent checked the plugs in a month or two (heck, mabey more) but when I did they looked great, nice brownish color to them. If it wasnt pouring down rain right now I would go pull a couple.

As for the dizzy, its a reman thats not but a month old. I recently had to exchange it because the vac advance blew on the old one (lucky it was still under warrenty) I will add dis connecting the vac advance line to my list of things to try this weekend.

*shimniok* · #18 12-12-2006, 05:09 PM

Quote:

Originally Posted by JeepsAndGuns

As for the dizzy, its a reman thats not but a month old. I recently had to exchange it because the vac advance blew on the old one (lucky it was still under warrenty) I will add dis connecting the vac advance line to my list of things to try this weekend.

I've heard aftermarket reman distributors can vary widely in terms of spark curve. Keep us posted, hopefully we can get thing fixed...

Michael

dngrs1 · #19 12-13-2006, 02:13 AM

Sounds to me like he's got the vaccuum advance hose connected to manifold vaccuum port on the carb. With an edelbrock carb this is an easy mistake. Are you running an edelbrock carb?

GWChris · #20 12-13-2006, 04:51 AM

Once the throttle is open, there's not any real difference between ported and manifold vacuum. There's a bit of a transition regaion between the two just off idle. Anyway, if the ping happens when the throttle is well off idle, that wouldn't be it. If it happens with real light throtle, it could be.

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