I just got my rebuilt engine up and running and under WOT at roughly 4k rpms in second gear it begins to ping. I dont think my compression is to high but I don't think I have any way of finding out for sure. Here are my specs: 69 350 Holley street avenger 770 carb jetted 73 primary 79 secondary Poston s-divider intake Pocket ported and blended heads Heads milled down .020 Stock .040 head gaskets Speed-Pro Hypereutectic Pistons H522CP.40 Engine bored .40 Over Custom ground Erson cam Lobe 110+4 .509 intake lift .523 exhaust life duration is 284 intake and 295 exhaust Finished off with TA Headders Ignition is a MSD Coil and Pertronix Electronic Ignition. New cap and rotor. Current timing is at 0 on the balancer so it should be set at 30 I have been running shell premium (91) gas with gumout octane booster. Any suggestion on the ping? Could the carb be to lean? I have looked at the plugs and they look like the might be slightly lean but defiantly not bad.
Dude - it's not even hot out yet (look where I'm from). So I know what you'll see in a few months; it will be worse. What have you done to your ignition curve? Have you read Larry's timing thread? If your engine is still breaking in it will run hot for a number of miles.
As bad as gas is today, any carbureted engine should be treated to 93 octane at a minimum, unless it was specifically built for less.
A few years ago I set the ignition curve up based on Larry tutorial and I do have an aftermarket spring kit in it for it to kick in sooner i believe. The motor only has maybe 100 miles on it and I have only went WOT a couple of times to the extent where i can hear the ping. Ive been doing my best to drive it gently to help the break in process. As for running 93 octane I don't think there are any gas stations in my area that have 93 octane, 91 is the highest. I was hoping to be between 10:1 and 10.5:1 on the compression but that may not be the case. As of right now the engine is running pretty cool. It has a 4 core radiator, mechanical fan, and a 190 thermostat that seem to be working well together.
you did not note transmission /convertor size and rear end ratio/tire size. I would check your timing at 4000. yes I believe it could be lean.but if gear is too hi you could be lugging engine . stock head gaskets for a 69 engine are .020 . did you use steel gaskets or other? cam is quite large. I would think a 2800 stall and 3.42 or 3.73 gears would be needed.
Transmission is a th350 with a 10" 2600 stall and the rear has stock 3:23 gears. I plan to upgrade to 3:73 when I get my 8.5 rear ended done. I did not use steel gaskets I used standard felpro ones which I believe we're .040, I guess I misspoke when I said stock head gaskets.
was car an original 4 barrel car? if not you could not have the carb open all barrels completely . you would need a 4 barrel accel cable.also check your stall to see what it is flashing to. most rated stalls are rated if they are on a big block hi torque engine and usually stall much less on a small block
Yes it was an original 4bbl car and the Holley worked great before I had the car torn apart for 4 years. I thought the secondaries may not be opening either but there is no way to test it without driving the car and putting a paper clip in the linkage or something similar to that (I don't remember exactly what the manual said to do). The secondaries won't open unless the engine is under load and won't open while free revving the motor. I just double checked the converter and it says it's 2600-2800 stall.
Check your timing for sure, don't guess at it. What cam you have in there? I seriously doubt you have too much compression, especially if that cam bleeds off compression somewhat. Im going to assume the duration figures you quoted are advertised, NOT @ .050 lifter rise. With those duration numbers, I don't know how the engine even idles with "0" initial advance at idle, if it is, its got to be running hotter than helluzzled: Most cams with that duration use 18 to near 20 initial timing, then limit total to 34 to 36 deg. Recheck and verify your ignition timing:TU:
Is your vacuum advance connected? If so disconnect it. Did you install a new harmonic damper as you should have? If not then you need to verify the outer ring has not slipped. FYI all 40 year old dampers are ticking time bombs, replace them. And while you have it off measure and paint on lines at 10-20-30-40 degrees of advance. Will make it easier to check your total timing without needing a dialback timing light.
You know what they say about the word ASSUME? Did you limit the vacuum advance canister? Check the total advance where it maxes out (vacuum advance blocked off), and what RPM that is. All this is verifiable with a timing light.
Couple of things that stand out; The engine won't "break in" until you get some heat through the rings, gotta run it fairly hard. Yes, it will run a bit warm until then. Don't rev it all the way up or full throttle for long periods of time, just moderately abuse it. You will be testing the capability of the entire cooling system until your timing curve is correct. If the expanding gases from the burn do not push the piston at the right time the same heat is wasted right into the water jackets and exhaust instead of pushing the vehicle. It runs hot. Don't do any of that until your dampner and timing curve are actually verified. Do not guess. Actual running coolant temp (and air intake temp) will have more of an influence on ping and octane tolerance when your timing curve is incorrect. Going up 2 octane #'s isn't the end of the world. If you are close, you can tune it from there. A can of octane booster is only .2 #'s increase or so. You should be able to see signs of detonation or ping right on the plugs. read them. You can verify full throttle with the engine off. Often times a choke not fully open will prevent the secondaries from opening. The rating on the converter doesn't mean that much. Gotta see yourself where it flashes to when you stand on it. Although some of the responses so far do not appear to directly answer your question, there is truth to all of them. That stuff should have been considered before buying a cam or any parts. Good luck with your project.
Also holley vacuum secondary carbs are notoriously bad as far as getting the secondaries open. Ask JW about that.
If you have a tach inside car ,check what your convertor actually flashes to. If its rated 26-2800 I would believe your only seeing 2400. B&m and tci both have acted this way for my SBB.
Can't say much about the vacuum secondary Holley carb. If anything they are very conservative on opening the secondaries, usually too slow, and that may be causing tip-in problems at 4000 rpm which is probably where it is just starting to crack open. Possibly a little lean. You could always disconnect the arm from the vacuum pot to the secondaries. The carb would just act like a big 2 bbl. Power would be down somewhat but you could see if it pings. That would tell you if it is a secondary tip-in problem. I would give that Poston intake a second look. They are known for having lean cylinders and rich cylinders. At the very least I'd add a 1" open spacer to it to maybe balance out the cylinders a bit. I'd do as advised and make sure the timing is correct. Although it isn't used under full throttle get rid of the vacuum advance until all WOT and cruise testing is done. It is just another variable that you don't need at this time. The open chamber cylinder head makes them more sensitive to knock compared to the 455. No way, no how would I run a 190* thermostat on a high performance engine. 180* max and 160* if you are in a very warm climate. It just gives you more headroom to work with especially if the best gas isn't available. Did you plug off the exhaust x-overs in the heads? You don't need them unless you plan on driving in near freezing temps. I'm not sure what the stall speed has to do with anything unless you are getting ping right off the line. The car may be doggy off the line with a big cam also but by 4000 rpm I would figure you are way past where the converter has tightened up.
Check your timing for sure, don't guess at it. What cam you have in there? I seriously doubt you have too much compression, especially if that cam bleeds off compression somewhat. Im going to assume the duration figures you quoted are advertised, NOT @ .050 lifter rise. With those duration numbers, I don't know how the engine even idles with "0" initial advance at idle, if it is, its got to be running hotter than hell Most cams with that duration use 18 to near 20 initial timing, then limit total to 34 to 36 deg. Recheck and verify your ignition timing. When the engine was broken in my dad set the timing which is why I said assume and I dont have my timing light to double check at the moment. I also mis-spoke when I said my timing is at 0. The 30 degree mark on the balancer is (i was told) is on the zero mark of the indicator that mounts over the balancer. All of the cam specs I listed are the advertised numbers. I will get my timing light tonight and make sure my timing is set correctly. Is your vacuum advance connected? If so disconnect it. Did you install a new harmonic damper as you should have? If not then you need to verify the outer ring has not slipped. FYI all 40 year old dampers are ticking time bombs, replace them. And while you have it off measure and paint on lines at 10-20-30-40 degrees of advance. Will make it easier to check your total timing without needing a dialback timing light. The vaccum advance is connected. I will admit I did not install a new balancer. I did inspect the current balancer and it looked to be in good shape. It is not the original balancer my dad installed a new one when he rebuilt the motor the first time 10-15 years ago. You know what they say about the word ASSUME? Did you limit the vacuum advance canister? Check the total advance where it maxes out (vacuum advance blocked off), and what RPM that is. All this is verifiable with a timing light. I will get my timing light and recheck timing tonight. If you have a tach inside car ,check what your convertor actually flashes to. If its rated 26-2800 I would believe your only seeing 2400. B&m and tci both have acted this way for my SBB. I do have a tach... so just hold the beak and hit the gas and see what rpm the car wants to start moving at? Thank you everyone for your help and suggestions! :TU:
To see what your converter flashes at can be tricky. It's not as simple as foot braking it. I've been told a more accurate reading of converter flash is to load up the converter and then launch the car and see how high the rpms go as the car just starts to move.
No way, no how would I run a 190* thermostat on a high performance engine. 180* max and 160* if you are in a very warm climate. It just gives you more headroom to work with especially if the best gas isn't available. Did you plug off the exhaust x-overs in the heads? You don't need them unless you plan on driving in near freezing temps. I will have to change my thermostat to a 160. Where im from were consistently over 100 degrees in the summer. I do not believe the exhaust cross overs are plugged. Thank you for the suggestions!
Do you have the vacuum advance set on manifold vacuum as a factory 69 would have or ported vacuum . seems as you have tuning to do but I believe the carb isn't working for your combo. The vacuum secondary I believe is holding you back.
If the 30* mark is aligned with the 0 on the timing tab, it means that the timing is 30*. I hope the timing wasn't set there at idle as that means you have a lot more timing as the engine RPM rises, and the mechanical advance maxes out. The total timing needs to be set at the point where the mechanical advance is maxed out. I also suggest you do as Mike said and disconnect and plug the vacuum advance until you sort out the total timing (initial + mechanical)
