Major pinging problem, and now something new!

[Docmacs'77]

Sorry if you've seen this post twice, but I accidentally placed it originally in the "General" forum instead of Technical. Since I don't know how to "transfer" it to the technical forum, I just copied and pasted it. Thanks for your indulgence.

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.

 

[fine69]

Docmac,

This sounds alot like the problems I recently had after my rebuild (sputtering, missing, etc). I believe mine was attributed to installing the incorrect cam (Edelbrock Performer RPM), and also poor break-in procedures without using an oil with a high zinc content.... so I might have wiped that cam.

Over the past couple months I replaced the cam and valvetrain. This time around, I used Valvoline Racing Oil, and ran the car at a high RPM for approx 20 minutes. The car is runnning so much better than before.... although I do still have to "fine-tune" the timing.

Just some thoughts... ..

 

[10752]

You've got that backwards,
fires out the usally lean
out the exhaust, usually rich.

Sounds like you should get your carb straightened out first before disassembly anything and advance your timing to 36* total without vacumn.

Then check your rocker arm heights with the valve cover off to determine cam wear.

If it backfires out the carb AND you are too rich, it may be a tooth off on the dist gear.
Get timing right first, then carb.

 

[Jack]

Dunno if you have a Holley or Demon carb ... if so ... when it popped out the carb ... that pop may've blown a powervalve ... & that alone'll make it run crappy.

10.67:1 CR ... pings on 93 oct ... does 383 have iron or alum heads?

 

[Docmacs'77]

Dunno if you have a Holley or Demon carb ... if so ... when it popped out the carb ... that pop may've blown a powervalve ... & that alone'll make it run crappy.

10.67:1 CR ... pings on 93 oct ... does 383 have iron or alum heads?

It has aluminum heads (Edelbrock Performer RPM). Holley 4160 with vacuum secondary. I pulled the needle and seat assembly out and blew it out with compressed air awhile ago, started it up and it still ran crappy. One thing I read on another post was that if the coil gets hot, it can make the engine stumble. Makes me kinda wonder, because the auto electric guy who installed my electric fans, MSD Pro Billet Dist. (8361), 6AL ignition box and blaster 2 coil, screwed the coil bracket to the rear of the intake so that it's laying on it's side (see pic). Seems like it would get pretty hot right there. Maybe too hot. I mean, maybe that's why after driving around for almost an hour, it heated up the coil to the point to where it cooked it a little too much. Dunno. Also, I think I read a post somewhere once where somebody said that if a coil is positioned on it's side, then the oil in it won't be at the top, or something like that. I don't know jack about coils (or much of anything else for that matter). Any ideas about the coil?
Marc.

 

[goingballistic]

The coil will work just fine in any position that's it's mounted. I would however be concerned about the heat to the coil. Being a coil is a series of wound wires that provide resistance, heat will change the resititve properties of the coil. I don't think this is what's casuing your problem UNLESS something went really wrong with the coil. The change in resistance should be minimal from the temp and honestly think that unless the coil is bad, would not cause this problem

I'm leaning, like everyone else here, that there is something wrong with your timing, distributor etc. Do you have another coil you can put in to at least eliminate that from the equation?

Is it possible you blew a head gasket?

 

[Docmacs'77]

The coil will work just fine in any position that's it's mounted. I would however be concerned about the heat to the coil. Being a coil is a series of wound wires that provide resistance, heat will change the resititve properties of the coil. I don't think this is what's casuing your problem UNLESS something went really wrong with the coil. The change in resistance should be minimal from the temp and honestly think that unless the coil is bad, would not cause this problem

I'm leaning, like everyone else here, that there is something wrong with your timing, distributor etc. Do you have another coil you can put in to at least eliminate that from the equation?

Is it possible you blew a head gasket?

Not sure about head gasket or not, but I guess I can do a compression test to see. I don't have another coil, but do you know if it's possible to take the coil off and take it somewhere and have it checked?
Marc.

 

[JohnZ]

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.

Sounds like the throttle plate is too far open at idle, and it's idling on the transfer slot instead of from the idle mixture orifice; have you adjusted the idle mixture screws with a vacuum gauge for highest steady vacuum? If the gauge doesn't respond to the idle mixture screws, the throttle plate is definitely too far open.

What kind of distributor do you have, and is the vacuum advance connected to full manifold vacuum or "ported" vacuum?

 

[Docmacs'77]

Sounds like the throttle plate is too far open at idle, and it's idling on the transfer slot instead of from the idle mixture orifice; have you adjusted the idle mixture screws with a vacuum gauge for highest steady vacuum? If the gauge doesn't respond to the idle mixture screws, the throttle plate is definitely too far open.

What kind of distributor do you have, and is the vacuum advance connected to full manifold vacuum or "ported" vacuum?

JohnZ, I adjusted the idle mixture screws with a vacuum gauge just before I ended up jacking it up and replacing all the calipers awhile back. After I let it down, stuck a new battery in and cranked it up, it ran great. But this really rough idle started the other night after driving it around for almost an hour (btw, the engine temp stayed pretty cool the whole time - 150-160). I'll definitely throw the vacuum gauge on again and see if it responds, thanks. I have an MSD Pro Billet Dist. (8361), a 6AL ignition box and blaster 2 coil.
Marc.

 

[Docmacs'77]

I really don't know how it could be the timing since it was idling really good and had good response prior to the hour drive. I threw on the timing light and advance and retarded it from like 2* to 12* and it made no difference in the sputtering and crummy idle (except it got worse of course when I retarded it to 2*). The distributor is new, as is the engine ( I've got like 2 tanks of gas on it). Can't tell you the exact miles since the speedo cable's been broke for awhile - that'll be the next thing to fix AFTER I get this other garbage cleared up. I was thinking that I should check the power valve (can it be checked, or should I just replace it?), replace the needle and seat, and maybe swap out the coil for another one to see what happens. I'm really playing some guessing games here. BTW, can anybody direct me to a good diagram/description for removing the power valve? Thanks, Marc.

 

[Jack]

blaster 2 coil, screwed the coil bracket to the rear of the intake so that it's laying on it's side (see pic). Seems like it would get pretty hot right there. Maybe too hot. I mean, maybe that's why after driving around for almost an hour, it heated up the coil to the point to where it cooked it a little too much. Dunno. Also, I think I read a post somewhere once where somebody said that if a coil is positioned on it's side, then the oil in it won't be at the top, or something like that. I don't know jack about coils (or much of anything else for that matter). Any ideas about the coil?
Marc.
http://corvetteactioncenter.com/forums/attachment.php?attachmentid=10679&stc=1&d=1152491985

I realize this may be bit late ... but I just noticed this coil issue. What you heard about coil on side affecting its oil level & it getting too hot ... VERY TRUE! You must not lay an oil-filled coil (Blaster 2) on its side ... it will overheat & become weak ... and eventually burn up. Do mount it as near-vertical as possible ... even better, mount it off the motor AND mount it vertical.

 

[Docmacs'77]

I realize this may be bit late ... but I just noticed this coil issue. What you heard about coil on side affecting its oil level & it getting too hot ... VERY TRUE! You must not lay an oil-filled coil (Blaster 2) on its side ... it will overheat & become weak ... and eventually burn up. Do mount it as near-vertical as possible ... even better, mount it off the motor AND mount it vertical.

Jack, thanks for that info. I just talked to an engine builder yesterday who told me the same thing when I drove the car over to him and asked him to get the missing issue resolved. Frankly, I just got totally frustrated with it. I had checked the spark on a few of the plugs and they were skipping sparks like: pop______poppoppop___pop___pop______poppop, etc. Just really missing bad. Also, I'm afraid the flat tappet cam that this friend originally put in was probably history - he never took it to 2000 rpm to wear it in. Everybody I've talked to since then has said if you don't wear a cam in by keeping it at 2000 rpm for 20 minutes, you'll flatten the lobes and ruin it. Well, live and learn. Anyway, I told the engine builder to go ahead and replace it with a hyd. roller and roller lifters. I'm tired of messing around with it and I want to get this bad boy on the road. I'll post some info after he finishes it up. Marc.