This might get kinda long, but PLEASE help me out here. I'm running out of ideas. I have a pinging problem at heavy part throttle, like right where it's about to shift down if I give it any more gas. It's usually around 2000 - 3000rpm. And only when the engine is FULLY warmed up. Here are the specs on it: 383 cid, 87+ block, Keith Black pistons, 10.25:1 compression, Edelbrock Performer RPM heads (70cc straight plug), roller cam (specs below), Edelbrock RPM intake, Holley 650 vac carb, HEI with MSD6AL, TH700r4, 4.11 rear.
Here's what I've tried already: Turn ignition timing back to 30* total, unhook vac advance, rejet carb (up 3 jet sizes from optimum on Dyno), took distributor to local "professional" to recurve, none of this helped at all. Did some research, found out cam was too small, not enough duration causing too high compression. Was TPIS ZZ9 (282/287 dur, 212/226 dur @ .050, .483/.520 lift, 112 lobe sep). Compression checked, sure enough, 200+ psi. Changed cam to Crane (296/304 dur, 234/242 dur @ .050, .539/.558 lift, 112 lobe sep). Now compression tests to 175 psi. Still pings!!! Re-tried everything with timing & carb, adjustable vac advance, new power valves, tried 4 sets of colder NGK plugs (up to #9 heat range now, any colder and I'll be running top fuel plugs). Nothing even seems to help. Engine is out now. I'm going to try brand new distributor with no MSD6 next. Everyone says it shouldn't be pinging at this compression with aluminum heads. Never runs hot, 190 max. My engine builder's next idea is new pistons to drop compression. Anyone have any other ideas/input? I'm running out! Please help!!!!

 

Heck I am running way more compression than you and doing ok. For a temporary set, unhook the vacuum advance canister and plug it off the carb.
You can set the timing to like 18 degrees initial and 36 total.
What is your timing at idle with the canister un-hooked? Should be ablout 8, then add the can, which you only want it to pull 8-10. Then you have 18 degrees. If you have too much advance in the canister, it sometimes will pull way to much, too fast.
If you have low gears like you do, you can get by setting it up to run of mechanical. Set the distributor to the highest you can without problems starting the motor. then stop it at either 36-38, all before 3000. And do without the vacuum advance.
Just a thought....I am and know of quit a few guys doing it on higher compression motors.
Give 'er a try and let me know.

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350 4 bolt main, Speed-O-Motive 383 stroker kit, re-sized rods ground for clearance,TRW Forged pistons,10.7:1 compression,HPC Coated RPM intake, Speed Demon 750 cfm carb,World Products Sportsman II heads,2.02/1.60 valves, Comp Cam 1.6 roller rockers, Comp Xtreme 284 cam,240/246@.050 with .540 lift,Crane pushrods,ATI damper,Proform HEI and MSD6A box,HPC coated 1 5/8 headers, 2.5" exhaust with 40 series mufflers,TH350 with B&M 3000 stall, Powertrax NoSlip Locker, 4.11 gears.

 

You didn't say what gas you're running.

What gas are you running?

Have you checked your balancer mark/tab against TDC? If it's slipped backwards 10 degrees, at 30 indicated you're running 40. Do you have the correct balancer/tab combo?

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/LB9 block, ZZ3 cam and intake, TBD heads, Hooker headers & y-pipe, 3" Catco cat).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

yea what octane gas? I use 94

 

That's another really crazy thing. I usually run good Amoco 92 octane, which is the highest easily available around here. Very early in my troubleshooting I tried half a tank of 104 octane (gas, not booster) and it didn't even seem to help. I haven't tried 104 since the cam change, but I always use 92.

As far as the balancer and timing, I degreed the cam in and also double checked the timing on the balancer and tab. I'm using a Fluidamper, so I know it hasn't "shifted".
As for distributor timing, I normally run the timing at 8-10 degrees at idle with no vac canister, but I tried going all the way back to 4 while I was messing with it. For the total timing I've tried everything from about 30 to 38 degrees. I don't remember exactly how much my vac canister pulls. Mine only adjusts the rate, but I was going to try one of the better vac canisters where you can adjust the rate and limit the pull. I can't really try any of this right now, as the engine is out, but I'm looking for ideas to try when I get it back in, in a couple weeks, as well as stuff I may be able to look at while the engine is out. Thanks for the ideas guys, and keep them coming if you have any more.

 

It sounds to me like your distributor has either too heavy weights or too light springs, either of which will make the mech advance come in too soon. Like if it's all in a 2200 RPM but the engine would prefer that it not be all in until 2750.

Get a curve kit and experiment with the springs & weights.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Thanks guys. I guess I never really messed with the mech curve much cuz I took it to a "distributor guy" who recurved it and said it was good. Locally he's a very trusted guy, but I guess you can't trust anyone like yourself. Any other suggestions?

 

That's the only thing that will cure it. It's not hard, just get a curve kit and experiment, it takes like 32 seconds to re-curve the mechanical part of it. So easy I can even do it.

I think your distributor guy just guessed a little too aggressively, which is easy to do; it's always just a guess anyway. Basically he did what I would do to my own car, which is go for broke and then scale it back as necessary. This is like carburetor calibration; every combination of CID, pistons, heads, cam, gasoline, driver, car weight, gears, converter, transmission, altitude, temperature, etc. etc. will require a different setup.

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"So many Mustangs, so little time..."
ICON Motorsports

 

when something seems to not make any sense, then maybe it doesn't.

maybe it's not spark-knock at all. Maybe your pistons are rattling. Have you checked the condition of your pistons? ring lands, skirts, and wrist-pins? you may find the source of the noise.


if it is spark knock, then maybe it's not on all cylinders. have you tried swapping carbs to eliminate a malfunction on one of the corner circuits?

have you checked in your distributor cap, or your plug-wire arrangement for evidence of crossfires? the #5 & #7 wires crossing is a common cause of pinging on smallblock chevies.

 

by the way, your camshaft was not too small.

what are you running for exhaust?

 

I guess I've started to wonder if it's really pinging too. Could it be something else if it only does it under those conditions?
- Has to be completely warmed up.
- Only under heavy part-throttle.
- If it kicks down it won't do it, full throttle won't do it.
- Only about 2000-3000 rpm.

Since I have the engine out now anyways, maybe I should just pull it apart again and check those things just to make sure. When I did the cam swap, I never pulled the heads or took a good look at the pistons or any of that, which I guess I probably should have done.

For the cam, I guess I'm just going off what I've heard other places. On the Crane website (among other sources) it states that anything over 175 psi on a compression test is too much. So when I tested mine at 200 psi, everyone I talked to said I needed a bigger cam to bring that cylinder pressure down. But as I said, it didn't help the pinging (or whatever it is) anyways, so who knows?

The exhaust is full length headers, 1 5/8" primaries, to 2 1/2" dual pipes with crossover, Dynomax Super Turbo mufflers, and 2 1/2" duals out the back. But I've switched to Flowmasters over the winter.

I've tried 3 carbs. Started with a Holley 650 vac, tried a Holley 600 vac I had around, and tried a buddies Holley 750 vac also. No noticeable difference with any of them. I haven't looked closely at the plug wires or cap, which I definitely will do asap. The wires are Accel 300+ 8.8mm wires, nobody's had bad experience with those I hope? Thanks again for all the ideas guys!! this site rocks as far as technical knowledge goes. And by all means, keep them coming if you have more ideas for me to look into.

 

Still sounds like pinging to me, based on your description of what it does and when it does it. Still sounds like an overly aggresive mechanical advance.

Tried the curve kit yet?

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"So many Mustangs, so little time..."
ICON Motorsports

 

No I haven't tried the curve kit yet. The engine is out right now, but it should be back in and running in 2 weeks. I will definitely do the curve kit first.

 

I would take it to a shop that has the distributor machine. that way it will take all the guess work out of it. Now's the time with it all torn out, and for about $40, you can't go wrong.

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350 4 bolt main, Speed-O-Motive 383 stroker kit, re-sized rods ground for clearance,TRW Forged pistons,10.7:1 compression,HPC Coated RPM intake, Speed Demon 750 cfm carb,World Products Sportsman II heads,2.02/1.60 valves, Comp Cam 1.6 roller rockers, Comp Xtreme 284 cam,240/246@.050 with .540 lift,Crane pushrods,ATI damper,Proform HEI and MSD6A box,HPC coated 1 5/8 headers, 2.5" exhaust with 40 series mufflers,TH350 with B&M 3000 stall, Powertrax NoSlip Locker, 4.11 gears.

 

Have you tested the fuel pressure during the hard acceleration? What kind of fuel pump are you using?

[This message has been edited by TunedPort350 (edited March 21, 2001).]

 

Supposedly the guy I took the distributor to last year recurved it with a distributor machine. Who really knows, I don't trust other people to work on my stuff much, but he has a good reputation around here.

No I never checked the fuel press. That's a good idea though. I also thought about getting an air/fuel ratio guage. I'm running a Carter street/strip electric pump mounted back by the axle.

 

Bowite- read the artilce in the tech articles section of this website about tuning the HEI distributor for performance. Make sure the curve described in the article is close to how your distributor is set up.

I'm 90% sure from what I've read that you just have too damned much vacuum advance coming in at too low a vacuum level. Also, make sure the vacuum advance can is hooked up to a PORTED vacuum source on the carb- that's one that only supplies vacuum once you are above idle speeds.