I have a 52 8rt with Edelbrock heads and 3x2 setup with SU1-A cam and Bubba ign. timing is set right on the mark.it starts and runs great.after it gets to full op temp and i start up a hill or go throtal up it pings like hell. its .030 over w/ no added compression. I have tryed setting the timming all over the place and it still doe's it .48 jets in main carb (94).and power valve does not have a number on it .it came from vintage speed as there 3x2 setup ie end carb bases long shafts and carb setup kit .it runs so good till its 180 deg eng temp and then it pings very bad ...any help???...
When you say "on the mark", what exactly does that mean in terms of crankshaft position at firing? How many degrees before TDC? Bob
Suspects: Too much clearance over quench area of piston, could be from wrong chamber shape or pistons with pin location off or gaskets too thick. Will require pulling heads, claying or foil balling clearance to measure. Poor heat transfer upstairs...heads internally corroded or full of lime deposits, likely only if used and abused. Degree front pulley, I've posted ways to do this easily so you can just do it in pencil or marker in a few minutes, and do***ent timing in steps from idle to about 2500...check your TDC first so this is meaningful. Find one of my old posts on finding TDC with head on by interference method. Reason for all of this is that you might have an incorrect TDC mark and so totally wrong timing. Obviously third suggestion is one to do first before you do anything heavy...it can be done in an hour or so for free.
The timming mark is correct as it was checked when I ***y,the engine tdc and mark lined up. I am more than sure the timming is correct. the pin and mark on this engine is 3*at tdc. Ign, total Is 24*by 2200 rpm. Heads are new, 900 miles on engine. Tell me more about piston to head squish area clearence.
Hey, John, I do believe Bubbas ignition needs a bit more advance timing vs the stock location. I would check with him. I've got my timing set about an inch past (to the right) the stock setting in my 40 coupe.
You may be running lean with the #48 main jets, as the 94 had #51 as "stock". Have you read the spark plugs? If you induce the pinging, pull over immediately and pull a few plugs. If they're ashen white, you're too lean and should fatten the mains a notch or two.
Sounds like you've already checked a lot of possibilities, but here's one I'll throw out there. Check to make sure your running spark plugs with the correct thread reach for your heads. Too long a reach and you have exposed spark plug threads in the combustion chamber. Exposed threads will cause pre-ignition because the threads get hot enough to ignite the mixture even before the plug fires. This is a free and easy thing to check too....before tearing into it too deep.
I was thinking "hot spot" when I first read the post, the plug threads cound do that since they're sharp enough to mimic a deposit somewhere in the combustion area. At a higher running temperature it could be the final straw that puts it over the ping threshold. But do read the plugs, I'd be curious how they look and some light detonation may be visible on the last plug thread. Bob
More advance in the timing certainly wouldn't do anything to eliminate the pinging. Squish, or quench, is when the combustion chamber has minimal piston to head clearance in the area which is typically furthest away from the spark plug. The very small clearance creates a lot of turbulence during compression which helps to reduce detonation. If you do a google search on quench and detonation you'll find a lot of info. In a flathead, the quench area will be the area above the piston where the combustion chamber in the head is flat. Usually engine builders will try to keeop the piston to head clearance somewhere in the .030 to .040 range. this can be adjusted using varying thickness of head gaskets which is the simplest way. Decking the block and cu$tom pi$tons are other options.
Yes, more timing will make it worse. Good explanation of what happens in the combustion chamber here. I'd go with more octane (not knowing the CR..) just to see if it makes a difference. Bob
OK, here is something else for consideration. I just saw this in my own flattie going to and fro LSRU. You don't say what kind of fuel pump you are using. I have a Carter low pressure with a Holley low pressure regulator. On the way up to Austin, I thought I heard a little pinging and I got a few misses. We made it to parking and I checked my fuel pressure and it was down to nil from the 2.5 to 3 psi I normally have. I readjusted the regulator and figured we were good for the trip home. Not so fast, she started missing really bad. At this point I noticed that my temperature started rising from about 175 to 185 right before the missing would start. Pulled over and saw that we were not getting good fuel delivery although the pump was running. Checked my filter and it was clean as a whistle. Did some more tinkering, not really sure what worked, but fuel delivery picked up and we made it home. So, I think the temp was coming up as she was being leaned out and as I said, I thought I heard some pinging in the morning. I'm still trying to figure out what I will check next to make sure the problem is eradicated.
My car does the same thing. Got a 2x2, uncle max 97's, stock cam, heads and a bubbas dizzy, stock fuel pump, runs 180. Running premium helps. Im running like 2 degrees advanced (where it runs best). SO im no help but your not alone.
Have you considered a tank (or partial) of AV gas? The regular premium at the pump is maybe 93 octane at best. It would be interesting to se if the condition improved. Bob
Couple of EASY checks...48 is barely on the lean edge, but to check just get the car into ping mode and slowly pull out choke. If the problem is leanness, you will get immediate relief with partial choke. On timing...simply retard it a few degrees and see if anything happens. Your curve is a shade longer than most, but not by much. Do not ever check or change 2 things at once! The tighter piston domes are to head the more combustion turbulence you have, giving quick burning and resistance to pinging. Around .050 clearance is good, much more increases likelihood of ping.
golee, what a great responce guys. I am an old drag racer and will only change one thing at a time and will be looking to trying each suggestion one at a time. I might note that bubbas ignition read my post on the ford barn and posted that he has sent me a ping repair kit, containing several spring combos to try .now thats real customer service....also thank you all for your help.I been building engines for a long time but (this my first flathead, and this is a new challange)cause it aint da same, she's different to say the least..but I love how it sounds. thanks everyone ...John
You might check over on the fordbarn, GM has been posting some testing that he's been doing checking underhood temps and he claims that high temps around the stock fuel pump with the current gas formulations are causing a significant drop in fuel pressure...
Bob No im hoping to corect it without having to run special fuels .I realy don't have that much compresion 120 lbs with all plugs out and carb open no breathers on top
bruce, I have .065 head to piston at squish area above the piston at its tightest spot .Could that be too much??
Randy and Ebbsspeed, I thought of the vent and the heat issues. I have one of those tanks with the turnover vent connected by a hose. I thought a mud dauber could have took up residence and I am still checking that. In preparation for LSRU, I mounted a darn big 19 1/2", 6 bladed fan that really moves air in the engine compartment so I have a hard time envisioning the heat build up in there. So, still checking, thanks for the inputs.
065 is enough to really weaken the necessary turbulence. Measure your gasket thickness...there may well be a simple option. I am not sure what range of gasket thicknesses are currently available, but I think there is a wide selection of thicknesses. Timing of course can be crudely checked by just retarding the whole curve to see what happens, but your curve sounds at least close to OK and you don't want to run a weak curve to compensate for loose chamber. Remember the '70's SBC...quench ruined by the round piston depression, extremely low compression but continual ping problem along with no power, very retarded timing... a total package of bad news. A couple years on like 1985, D dishes allowed quench to function, they could crank in a lot of compression again and build engines that ran. Think of the contrast between a 1976 Corvrtte and an '86.
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