Major pinging problem, and now something new!

[Docmacs'77]

A friend, who's "supposed" to know a lot about building engines, and I, pulled my old tired 350 out of my '77 and commenced to build a 383 stroker and dropped it in. Anyway, the car has been idling great and sounds good, and I can cruise around normally, but if I step on it, it pings. I initially had the base timing at 12* and dropped it down 2* at a time in between test runs and took it all the way down to 2* btdc and it still pings. I have the heavy springs in the distributor and when I did the "all in" timing method described by Lars, I got a total of 32* for the centrifugal and base (with the base timing of 12*), so that should be fine. I left the dist vacuum disconnected and plugged the line. I just don't get it. I was thinking that maybe my cam wasn't degreed correctly by this friend, because actually, he didn't use a degree wheel at all. He was like "nah, don't need it. I'll just get the dots lined up on the crank and the cam and it'll be there". Now I'm really wondering what's up. At TDC on the compression stroke of #1 the rotors pointing at #1 plug wire. I was told by somebody that knew how to figure it out, that I had 10.67 CR. I'm using 93 octane. Do you think I'll need to add some racing fuel to stop the pinging, or maybe it's something else? Anyway, after taking it all the way down to 2* I took it for a test ride and it still pinged when I goosed it. So I just cruised it and it ran great and sounded fine. Actually went to Bestbuy and then drove around for probably 45 minutes before pulling into Sonic. I killed it there for about 20 minutes and when I started it up it was sputtering and just generally running crappy. I drove it back home and when I killed it, it ran on for like a half a second. This afternoon I pulled the plugs and they were really fouled out black. I replaced them thinking that's why it was sputtering and started it up and it didn't sound like it was running real smooth. I backed it out and took it for a test drive and it's still running crappy and spitting and sputtering. When I pulled it back in the garage and killed it, it backfired out the carb. I remember somebody saying that if it backfires out the exhaust, it's running lean, and if out the carb, it's running rich, which would account for the black plugs. Right? When it's idling it kind of sounds like it's surging on and off. Any ideas why all of a sudden last night it would just start running so bad? I mean it was purring nicely for almost an hour before I stopped at Sonic. Sure appreciate any advice on the pinging and the new stumbling problem. Marc.

 

[Pa Goose]

Sounds like the carb to me. Mine, an 81, has the 'Electronic Quadrajet' and did the same things as you described above. Rebuilding the carb solved the problems. I do not recomend rebuilding a quadrajet if you have not done it before. I actually had the help of a local Vette owner to do mine. Now runs great, just got to find the electrical problems it has recently developed.

 

[BarryK]

first of all, don't adjust and reset the timing based on initial timing, do it by setting total timing.

i'd first set the timing at 36º total with the vacuum advance can disconnected and the vacuum line plugged.
set for 36º and see how it does. if it pings than drop 2º at a time until it stops and see where you are.
After you get a setting that doesn't ping than read your initial timing and see what it is.
Substract your initial timing # from your total timing # and you will see how much centrifugal advance your distributor is giving you.
also, it would be a good idea to also remove the cap off the distributor, put a rubberband around the weights prevent the centrifugal advance from coming in and again check the initial timing at idle. compare both the initial timing readings now and if it's higher before you put the rubberband on the weights it's telling you that your centrifugal advance is starting to come in at idle speed which is too soon and you want to change out your springs to prevent this.
Also check to see at what point the centrifugal advance is all in at on your total timing - you want it to be all in by around 2800-3000rpm. some people prefer all in by 2500 but I prefer 2800-3000 to be a little safer - the sooner it's all in the more risk of detonation.

After all this, reconnect the vacuum advance and check initial and total again and calculate the amount your vacuum advance can is adding in - it should be 15º or 16º.

Oh..........you are hooked up to full manifold vacuum rather than ported vacuum, correct?

 

[Docmacs'77]

first of all, don't adjust and reset the timing based on initial timing, do it by setting total timing.

i'd first set the timing at 36º total with the vacuum advance can disconnected and the vacuum line plugged.
set for 36º and see how it does. if it pings than drop 2º at a time until it stops and see where you are.
After you get a setting that doesn't ping than read your initial timing and see what it is.
Substract your initial timing # from your total timing # and you will see how much centrifugal advance your distributor is giving you.
also, it would be a good idea to also remove the cap off the distributor, put a rubberband around the weights prevent the centrifugal advance from coming in and again check the initial timing at idle. compare both the initial timing readings now and if it's higher before you put the rubberband on the weights it's telling you that your centrifugal advance is starting to come in at idle speed which is too soon and you want to change out your springs to prevent this.
Also check to see at what point the centrifugal advance is all in at on your total timing - you want it to be all in by around 2800-3000rpm. some people prefer all in by 2500 but I prefer 2800-3000 to be a little safer - the sooner it's all in the more risk of detonation.

After all this, reconnect the vacuum advance and check initial and total again and calculate the amount your vacuum advance can is adding in - it should be 15º or 16º.

Oh..........you are hooked up to full manifold vacuum rather than ported vacuum, correct?

Yes, I did that already. Hopefully correctly. Actually the vacuum hose is connected to ported vacuum I think, except I've had it unplugged anyway and it still pinged. Anyway, the way I checked the timing was I took it down 2* at a time (in between test runs) and it pinged all the way down to 2 degrees before TDC. I also wrapped rubber bands around the counterweights - let me back up: I initially wrapped the rubber bands around the counterweights and took the idle as far down as it would go and still idle, and then checked the timing (it was at 12*), I then took the rubber bands off and took the idle back up to the normal idle RPM and rechecked the timing again - it didn't change so I knew the centrifugal advance wasn't coming in during idle. After this I dropped the base timing 2* at a time between test runs but it pinged all the way down to 2* BTDC. Should I continue - like take it down to 0, -2, -4 etc. just in case my cam wasn't degreed properly (heck, I know this guy didn't use a degree wheel anyway)? Any ideas? Since I'm definitely not a pro on timing, I'd like to ask another question. I have a Stinger timing light which has the up and down advance arrow buttons (I guess it's considered a dial back?). This is how I used it when I checked the total timing. After plugging off the vacuum line to the vacuum canister, I checked the base timing with the light and it was set at 12*. I then slowly increased the RPM on the carb throttle and watched the white timing line on the balancer move downward (clockwise) until it stopped moving, which was about 3000 RPM. While holding the RPM there, I began tapping on the up arrow on the light until the white line lined up with the 0 mark on the index marker and then look at the reading on the timing light and it read 32*. Is that considered my total timing? Did I do it correctly? Thanks a lot, Marc.

 

[MoeJr]

First off if you truly have 10.67:1 CR you are gonna have a seriously hard time running on straight 93 octane.

Sounds like your buddy installed the cam straight up which is fine as most modern cams have a few degrees of advance built in.

If you are using flat top pistons and 64CC heads I don't think you are gonna be able to run this thing on pump 93.

When my Dad and I build any HP motors we always ask what is the intended use and if they are gonna want to run on 93 octane or use some race fuel mixed or straight. With pump 93 and iron heads max CR u want is 9.5:1 and with aluminum heads you can add a point.

Just my .02

 

[BarryK]

sounds like you did the timing correctly.
may be the cam is not degreed correctly, the ring on the balancer slipped, or you are running higher compression than you think.
My motor in my '65 L76 is 11:1 compression and I have no problem running on 93 octane pump gas.......

always the possibility that your timing light is off also. You may want to borrow another light from a friend and check through your timing readings again. It's happened before that you are chasing a problem that doesn't exist because of a faulty diagnostic tool........

 

[Docmacs'77]

sounds like you did the timing correctly.
may be the cam is not degreed correctly, the ring on the balancer slipped, or you are running higher compression than you think.
My motor in my '65 L76 is 11:1 compression and I have no problem running on 93 octane pump gas.......

always the possibility that your timing light is off also. You may want to borrow another light from a friend and check through your timing readings again. It's happened before that you are chasing a problem that doesn't exist because of a faulty diagnostic tool........

Thanks Barry, I'll try checking it out with another timing light.

 

[kingkeith427]

You should try some octane boost or better gas because I've always heard 9.5 to 1 compression is max for pump gas. Good luck.

 

[BarryK]

You should try some octane boost or better gas because I've always heard 9.5 to 1 compression is max for pump gas. Good luck.

octane boost stuff that you find at the auto parts stores is nothing but a waste of money! at most I believe it may boost your actual octane a FRACTION of a point.
The only one that benefits from you buying and using the stuff is the manufacturer of the products.

My car is running 11:1 compression I believe (a stock rebuilt '65 L76 motor) and I run regular 93 octane pump gas with no problem.

 

[MoeJr]

Barry did you have the engine rebuilt in your car? If not then I would bet it was rebuilt with dished pistons and such to lower the CR. 11:1 is not gonna run on 93 octane without either major pinging or having the timing retarded quite a bit.

 

[BarryK]

Moe

I was told that the motor was rebuilt sometime in the past but I can't say for sure one way or the other. IF it was rebuilt everything else is very stock and original on it and it was never decked (thank god) and the original (or original type) 30-30 cam is still in the car and honestly if you are going to rebuild this motor no one in their right mind would really keep a 30-30 cam in here, it's too radical a cam for the street and sucks below the powerband which doesn't start until 3500rpm.
Is it possible that it was rebuilt with a lower compression? Sure, since I don't know the history of the motor before I bought it, but if it was there weren't many signs or clues to it.
The timing is dead on perfect to what factory specs call for - it is not retarded at all.
BTW, I do know other guys with cars that have 11:1 compression running 93 octane with no problem........

 

[glen242]

First off if you truly have 10.67:1 CR you are gonna have a seriously hard time running on straight 93 octane.

Sounds like your buddy installed the cam straight up which is fine as most modern cams have a few degrees of advance built in.

If you are using flat top pistons and 64CC heads I don't think you are gonna be able to run this thing on pump 93.

When my Dad and I build any HP motors we always ask what is the intended use and if they are gonna want to run on 93 octane or use some race fuel mixed or straight. With pump 93 and iron heads max CR u want is 9.5:1 and with aluminum heads you can add a point.

Just my .02

Built a 383. Speed Pro 12cc dish pistons, 5.7 rods, '0' deck or as close as possible (I checked @ 0.001), 64 cc TF 23* aluminum heads, FelPro 0.039 1010 head gasket, 36* total timing all in by 2600 rpm, 15* vacuum advance, rejetted rebuilt Q-Jet, CC XE274 cam, PermaCool 16" electric fan - engine temp never exceeds 200*, stock rad recored to 4 tube big block specs.

I run mid grade, 89 octane, without a problem. Don't believe the CR numbers, run them on any good CR program, like the one on the KB site.

CR number, I have calculated, is 10.30.

 

[BarryK]

I run mid grade, 98 octane, without a problem.

is that a typo??
98 octane is "mid grade"?

well, maybe it is if you are comparing between something like 93 premium pump gas and something like 100 octane or 110 octane racing fuel.......

 

[Jack]

is that a typo??
98 octane is "mid grade"?

well, maybe it is if you are comparing between something like 93 premium pump gas and something like 100 octane or 110 octane racing fuel.......

Around here ... mid grade is 89 ... that's probably a typo. Moreover, mid grade 89 should work in alum head 10.3CR 383 w/XE274 ... that cam's 230* @ 0.050" duration is bleeding-off some static CR.

 

[JohnZ]

Barry did you have the engine rebuilt in your car? If not then I would bet it was rebuilt with dished pistons and such to lower the CR. 11:1 is not gonna run on 93 octane without either major pinging or having the timing retarded quite a bit.

Not true - static compression isn't the only factor determining sensitivity to detonation - the other factor is actual dynamic compression, which is a function of cam timing (intake valve closing point). I've had several 11:1 327/365's, and still have my all-original 11:1 '69 Z/28 (all of which have the "30-30" cam), and all run just fine on 93 octane pump premium, without a hint of detonation (8* initial, 26* in the distributor, 34* total, all in by 2800, with 15* of manifold-vacuum-connected vacuum advance that's fully-deployed at 8" Hg.). Swap out the "30-30" for a 300hp hydraulic cam, and it'd detonate like a coffee can full of ball bearings due to the earlier-closing intake valve increasing the dynamic compression ratio.

 

[MoeJr]

Good Point John. I didn't take into account that with a bigger cam like a 30-30 you can run more CR.

Doc what did you use for a cam in your 383?

 

[glen242]

is that a typo??
98 octane is "mid grade"?

well, maybe it is if you are comparing between something like 93 premium pump gas and something like 100 octane or 110 octane racing fuel.......

Yes, a typo, should be 89. Corrected

 

[RUSS O'BLENES]

PINGING PROBLEM

THE TWO MAIN THINGS THAT CONTROL PINGING ARE CYLINDER PRESSURE AND CAM TIMING. CHECK THE CRANKING COMPRESSION. IF IT IS UNDER 180 YOU SHOULD BE ALRIGHT. THE CAM DURATION @ .050 SHOULD BE 225 OR MORE WITH THE SET UP YOU HAVE. IF THE CARB IS RUNNING LEAN THAT COULD CAUSE PINGING UNDER A LOAD. GOOD LUCK RUSS

 

[Docmacs'77]

Major screw up = major $$$

Well, don't have to worry about that pinging anymore. I kept having a miss (inconsistent spark from plug wires) and I took it to a professional engine builder to check it out. While I was there, I told him I was also concerned about the smell of oil on the drive over and the fact that it just didn't seem to have the power that it should, as well as the pinging. He pulled the intake off the next day and found some metal shavings in the lifter valley. He told me some other interesting news. Mr. "Mechanic" friend doesn't really know crap. I found out from the engine builder that this guy who helped me put the motor together installed the pistons upside down, i.e. they were turned 180 degrees off when he installed them on the rods. Therefore, the valve reliefs were positioned on the wrong side so that the valves were hitting the flat side of the pistons (mine are flat tops) instead of matching up and going into the reliefs. This cause the intake valves to all be bent and of course some nice nicking and gouging on the pistons. He also told me the block (which I'd bought from this "friend" for $175 had been sleeved in #7 cylinder and the sleeve had actually been shoved up about 1/16". All in all, this know-it-all friend just cost me new intake valves, new pistons - oh yeah, I almost forgot. 2 of the rod bolts were finger loose and a 3rd one had already fallen off into the oil pan. This guy does some nice work, eh? 3 of the rods had some flat spots on them. Also, he never broke in the cam (2000 RPM for 20 minutes), so this flat tappet cam was worn down on alot of the lobes. Sooooooo, now I'm springing for a new cam, rods and pistons. I told the builder the heck with it. I'm going with a roller cam, roller lifters, forged pistons and forged rods. At least this way, I know it'll be done right and I won't have to worry about it. This builder has a good reputation in town and guarantees his work. My only regret is that I didn't know about him before I let this "friend" screw with my engine. Should get the car back in a few weeks. Will let y'all know whats up and stick a few pictures in here. Thanks for all your input. Marc.

 

[MoeJr]

Wow sounds like a major mess. At least it wasn't the matching numbers block. Do you have the original engine for the car?

Hope the new guy builds a killer for you. Let us know how it is progressing.

:bar