How do I stop the detonation

The engine is a 460 bored .060 over, flat top lightweight speedpro forged pistons, eagle rods, balanced, c8ve heads home ported using scotty's web site, 2.20 and 1.76 manley stainless valves, cam research solid lifter cam 530 lift on both with 222 and 224 dur. at .050 with 110 ls this cam is so small because of the vaccum rule in our class, 1.7 crane rockers, guide plates, 3/8 pushrods, scj intake and exhaust manifolds, 2 1/2" exhaust pipe into a 3 1/2 Y pipe, prosystems 1000 holley carb, it is not zero decked the pistons are about 20 in the hole.

I have turned the timing down until it quite pinging but it runs like crap at 18 degrees. The distributor weights are welded out since it is race only. I tried a distributor with light springs in it that advanced out at 2400 rpms, but it still pings. He is using the hot plug right now. He is using 91 octane pump gas and the rule states no race fuel. We put a can of the torco additive in it and now it does not ping until 32 degrees of timing anything over that and it will ping. He is going to add the other bottle of additive and see if that helps. We are going to try some 100LL in it also. It only has detonation at the initial hit of the throttle, at 34 degrees of timing the detonation is their at just the initial hit of throttle.

The owner was thinking of buying the MLS head gaskets that are .023 thick and getting the quench back to where it should be. I think that will be cheaper, but will it still ping once it gets the quench back to what it should be? The thinner head gasket will make it act like it is zero decked correct, but will that make it ping still with 91 octane?

Since his is pinging it makes me nervous about the new engine I built for my mustang. It is zero decked with forged flattop pistons and geting some D0VE heads with big valves and a c-460 cam. Will it ping also with 91 - 93 octane gas?

Mmm, running a small cam and 12 to 1 compression and trying to run it on pump gas. As you guys figured out, that doesn't work. 100% of 100LL should do the trick.

And yes, you should be nervous too. You will require good gas as well.

Hope that helps,

Dave

Time to change race classes or start looking at E85 conversion.

Running the water temperature UNDER 140° will help the detonation problem.

Just like a high compression, pump gas race vehicle - you will need to be changing the water after every run to cool it down.

Like we talked about in the other thread about this motor, you need to look at the cam timing again along with getting the quench back in the thing with the thinner head gaskets.

And again you need to talk with some other pullers about using larger cams and tricks to get the vaccum for inspection.

Is water or water/alky injection legal in your class? Its easy to set one to activate right on the throttle hit. Also its old school, but check out using a Moroso "cool can" The blue one is best, put dry ice or ice water in it, you fuel will go very cold its a poor mans intercooler. I use one on the fuel going to my blower motor and another going to my water injection system , allows me to run pump with descent boost. The suggestions on keeping water temps down are good as well. The larger your radiator the better.

I talked to Brett Powell and we got it fixed. Put a bigger squirters in the carb and it quit.

Why not run some 110? I know you said there is a rule about racing gas but how is that policed? Do they look at the color of the gas? You might also try some 100 octane unleaded that's available from the pump at some locations. We ran that very effectively in a circle track engine with 11:1 compression and water temperatures that sometimes went as high as 230 degrees, no problem.

The rule says no race fuel it will check by color and smell. I have never saw this rule checked by anybody, but I guarantee if they smelled race fuel in that class they would check it by color and smell.

Who cares, I would at least run 100 octane "race" fuel.

Adding fuel via the carburetor "squirter's" seems to quite the "ping", could this indicate a lean condition that previously existed? Another thing that comes to mind although the actual compression ratio isn't mentioned (or I missed it), is the timing marks that are used to time the engine's ignition accurate? Also the "hot plug", could a colder range of spark plug help? As mentioned by others, a tighter "quench area" would help but there must be other areas to look at before engine dis-assembly! If you don't get the "ping" removed, it will be engine dis-assembly sooner than your planned!

As Captain Ramius said, "one ping, one ping only".

Dave.

tiger wrote:I talked to Brett Powell and we got it fixed. Put a bigger squirters in the carb and it quit.

I would like someone to explain how putting in bigger squirters is going to stop detonation?

LivermoreDave wrote:Adding fuel via the carburetor "squirter's" seems to quite the "ping", could this indicate a lean condition that previously existed? Another thing that comes to mind although the actual compression ratio isn't mentioned (or I missed it), is the timing marks that are used to time the engine's ignition accurate? Also the "hot plug", could a colder range of spark plug help? As mentioned by others, a tighter "quench area" would help but there must be other areas to look at before engine dis-assembly! If you don't get the "ping" removed, it will be engine dis-assembly sooner than your planned!

As Captain Ramius said, "one ping, one ping only".

Dave.

Dave, he has flat top pistons and C8VE heads which is going to give him at least 11.5 to 1 compression, and he is using a small cam, all on 91 octane.

Something is funny.

Dave

DJO, as my concern of the squirter (performing it's duties) assisting in the removal of "pinging", at the moment the detonation was about to occur, the additional amount of fuel was introduced possibly providing a "cooling effect". I suppose the "pinging" occurred as the engine was loaded and the throttle applied. Hence adding the fuel at that time allowed a cooler combustion chamber....... I think!

As to the compression ratio issue (if one exist), and mind you I'm not trying to measure peckers at this point! A customer of mine insisted a cam with the stock 429 SCJ specs be installed in a 466 cubic inch short block with D0OE heads. I used a piston which originally possessed a small dome. I removed the dome making it a true flat top with two valve reliefs. Cleaning of the intake ports was simply that, the exhaust was cleaned up a bit more and the combustion chambers were immaculate, if I do say so! The compression ratio was 10.66:1. Now I do understand we are a bit less than your prediction of the discussed combination, but we were using a much smaller camshaft. There was NO detonation issues using 91 octane pump gas and a very consecrative RATE OF ADVANCE as well as total amount of timing was tuned in the ignition.

If the piston to deck measurement was a bit tighter it may help, I'm not sure but that seems to be popular belief.

I do understand your concerns of cylinder pressure, and the engine discussed may need some changes, but I would look at other areas before dis-assembling it.

Just my $0.02, for what it's worth!
Dave.

Yep ... running it cold and on the rich side with a conservative mechanical advance curve and a lot of vaccuum advance will probably get near the desired results.

It seems like I've said this before...

rmcomprandy wrote:Yep ... running it cold and on the rich side with a conservative mechanical advance curve and a lot of vaccuum advance will probably get near the desired results.

It seems like I've said this before...

I understand what you and Livermore Dave are saying. If running forged pistons, would you run the piston clearances tighter, knowing the engine temps are not going over 140 degrees?

Dave

Randy let me ask this question..... if the guy went down and got some lead additive to put in his premium unlead would that help the detonation?

just curious


Randy

DJOHAGIN wrote:

rmcomprandy wrote:Yep ... running it cold and on the rich side with a conservative mechanical advance curve and a lot of vaccuum advance will probably get near the desired results.

It seems like I've said this before...

I understand what you and Livermore Dave are saying. If running forged pistons, would you run the piston clearances tighter, knowing the engine temps are not going over 140 degrees?

Dave

The cooler the engine ... the MORE the piston to wall clearance should be.
The piston runs at the same temperature but, the cylinder wall runs cooler.

YES ... a fuel additive would probably help.

Not that I'm kissin Randy's ass or anything else .... .... but I concur with Randy's thoughts relative to the question(s) ask of him. Remember guys, each of us are simply giving our idea of a possible remedy to a possible ill thought out engine! I'm not sure an engine is efficient at a coolant operating temperature of 140 degrees, are y'all?

Dave.

This is getting good.

You have 2 engines:

A) The one that is tiger is running, and you loosen up the clearance on the bore, don't let the temp get over 140 degrees, run it rich, have conservative mechanical advance curve and a lot of vaccuum advance.

B) Same engine except drop the compression to 10.5 to 1, polish the chambers, add a singh groove, tighten the quench to .045 static, run it at 180 degrees, correct jetting, correct mechanical advance curve with correct vacuum advance.

Which engine is going to:

1) Be better for what tiger is doing, all running on 91 octane?

2) Last longer between freshen-ups?

3) Have better average power?

Thanks,

Dave

We did put some torco accelerator additive in the gas and it seemed to help, but it did still have detonation at anything over about 32 degrees of timing. The we put in bigger squirters in the top of the carb and it quit having detonation and we turned the timing up to 36 degrees and it has no detonation. As I stated above it only had detonation at the first initial hit of the throttle and nowhere else.

About 10 years ago we built an engine exactly like this one, but a bigger camshaft and it was driven on the street and it had zero detenation. It ran the cheap gas and was in a 1979 4x4 truck with 35" tires and 3.50 gears. The engine had some flattop forged pistons with D0VE heads 2.2 and 1.71 valves, the block was not decked, was a 460 bored .060, aluminum intake, factory ignition system. That engine had over 100,000 miles on it before it was pulled out. I think the gas has gotten worse since then.

Most marine engine thermostats ARE 140° ... Super Stock drag race engines run with water in the 120° range and, also with hot oil. There IS a reason for it.

Use that information as you wish, lol.

tiger wrote:We did put some torco accelerator additive in the gas and it seemed to help, but it did still have detonation at anything over about 32 degrees of timing. The we put in bigger squirters in the top of the carb and it quit having detonation and we turned the timing up to 36 degrees and it has no detonation. As I stated above it only had detonation at the first initial hit of the throttle and nowhere else.

About 10 years ago we built an engine exactly like this one, but a bigger camshaft and it was driven on the street and it had zero detenation. It ran the cheap gas and was in a 1979 4x4 truck with 35" tires and 3.50 gears. The engine had some flattop forged pistons with D0VE heads 2.2 and 1.71 valves, the block was not decked, was a 460 bored .060, aluminum intake, factory ignition system. That engine had over 100,000 miles on it before it was pulled out. I think the gas has gotten worse since then.

And with that said (wrote), have we used a band-aid to mend the scratch?

Dave.

rmcomprandy wrote:Most marine engine thermostats ARE 140° ... Super Stock drag race engines run with water in the 120° range and, also with hot oil. There IS a reason for it.
Use that information as you wish, lol.

Once again Randy, I agree although I do have a question or two ..... if I may?

Marine engines do (the few I've seen) use a cooler thermostat and generally operate in the range you mention. Is the reason they operate at such temperatures is to assist in removing the heat from the oil? The engine oil temperature usually is a bit elevated in marine applications compared to most other applications I'm familiar with, which is little to none! Also as you mentioned earlier, with the constant load that is exerted on a marine engine, would the cooler operating temperature assist in keeping detonation at bay?

My second question of a Super Stock drag race engine operating at or near 120 degrees, I assume at the start of a race, not the end. Is this simply an effort to keep the fuel charge as dense as possible? To some extent as some EMC competitors choose not to stop the engine unnecessarily to make adjustments simply because the intake manifold becomes more of a "heat sink" than it already is?

IMO, true race engines although most are very efficient as to producing power are not as concerned of service internal parts will provide during an extended period as most are usually "freshened" very often, I think. Will the lower operating temperatures elevate internal part wear?

Just a question or so!
Dave.

Most inboard marine engines have seperate water/oil heat exchangers and the water in them is whatever the outside water temperature is. Running the engine on the cold side does hinder detonation however, because the engine is usually in a captive environment it is done also to curb fuel vapor lock and excess bilge heat build-up.

YES ... a Super Stocker will run hotter at the end of the pass but, still less than probably 150°, (actually the water temp on "start-up" for that particular pass is under 90°). As you say, there are MANY reasons to start out at around 120° water temp. To gain a alight advantage they usually run smaller volume 6 cylinder radiators to get the weight down. Keeping the fuel charge as cool as possible is part of it, especially under a stock, (non scooped), hood. Simply speaking, for them, cooler water makes more power and goes faster which is ALL that really matters to them.

Colder running water temperatures does induce a bit faster wear characteristics.