Solutions for too much compression

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roccodart440 said:
I'm seeing a lot of red flags here..

1. WHat fuel are you running? YOu should be running premium pump fuel.

2. Are you using vacum advance?

3. WHEN does the timing come in

4. What car is this in and what is the gear ratio

5. stock or auto

6. What converter?

180 PSI is nothing crazy nor is 9.7:1.

To remedy this you can run a wider LSA than you are running.

Beyond that, you need to adress the above questions to see what the issue is and how to remedy it further.
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Premium fuel.
Auto trans. Rear end is not highway gears and not drag gears. Somewhere in between.
Standard converter.
It’s in a 67 Valiant.
I’m trying to use vacuume advance.
 
Valiant360420 said:
Are you suggesting locking in the mechanical advance and using no vacuume advance? I am receiving my advance limiter disk thing on Friday, so I will give it a try. I previously tried to limit the dist advance to only about 10 degrees (by jimmy rigging the heavy spring from extending) and using more initial, and it did seem to run better.
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I'm saying to, yes, lock out the mechanical advance. That means skip the vacuum advance, because it will no longer function being that it uses the same plate.
 
Get a real straight timing light

Do not use the Vacum advance.

Find out what the actual initial/total timing is and where it comes in at.
 
So what ignition do you have? I know everyone wants to lock it out, but unless you are using points the ignition system WILL retard with RPM.

So you need to figure out what you have and how to work with it.
 
MOPAROFFICIAL said:
I'm saying to, yes, lock out the mechanical advance. That means skip the vacuum advance, because it will no longer function being that it uses the same plate.
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Not sure I agree with locking the mechanical but it might need to be recurved. I DO agree with disconnecting vacuum advance--at least until you get it sorted. And I don't like manifold vacuum, either. I use "ported" vacuum
 
67Dart273 said:
Not sure I agree with locking the mechanical but it might need to be recurved. I DO agree with disconnecting vacuum advance--at least until you get it sorted. And I don't like manifold vacuum, either. I use "ported" vacuum
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rightfully so. But I can assure you that I have recently run this combo or close to it and im fairly certain in no way will 22° locked ping in my opinion ...but I am not the final word on anything here he might find that maybe it needs to be 19 and 22. Max initial and max full advance timing. It could be it doesnt like starting at 22, hence 19 comment, but probably be fine.
 
Actually the title of the thread should be: "Solutions for engine pinging". I wouldn't do anything until I looked into what jets are in the carb, and go from there.....also the power valve.

"Holley 750 vacuume secondary with “stock” jets and such."
 
no telling till he shares math on engine built up and how cam is degree'd and cam details! could just be to lean a tune!
 
yellow rose said:
So what ignition do you have? I know everyone wants to lock it out, but unless you are using points the ignition system WILL retard with RPM.

So you need to figure out what you have and how to work with it.
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Mopar Performance distributor with vacuum advance and orange ignition box. Mechanical advance adds about 25 degrees right now, but I am putting in one
rumblefish360 said:
3 initial? Dang! 22 total?!?!

I run 18-20 initial and totals between engines varies between 32-36 depending on the head. Your cam timing sounds out of wack.
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I just checked because you mentioned cam timing.
It looks to be correct.
 
gregcon said:
A simple 1/4" hole ($2) drilled through the top of each piston will reduce compression.
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1/4" might be too much of a compression release. lol We like to start with 1/16 and work our way up. lol
1/2 " for dome pistons. lol
 
Ok guys. I am loving all the help coming in, but I think I need to reiterate some things I know, and also things I don’t know, and why

What I know.

Short block is a la 360, bought directly from Mopar 17 years ago with flat top pistons and advertised to have around a 9.5 to 1 cr.

Exact cam is unknown but it too is a Mopar Performance hydraulic lifter model, somewhere in the middle of the their offered selection. Not the mildest but not the most aggressive.
I just turned the motor over while observing the rocker opening points, and it looks to be dead on.

Heads are standard rebuilt 360 open chamber heads.
I extensively measured the head cc as well as the piston travel, and calculated the head gasket volume, and computed a static compression ratio of around 9.7 to 1 on average. I can’t seem to find my exact notes at the moment but I double checked them.

Yes I only run Premium gas... no I don’t use a dial back timing light... and yes I verified my timing mark on the balancer.

My distributor is a Mopar Performance vacuume advance equipped unit with an orange ingnition box.
The advance curve is ...
9 deg at 1500 RPM
17 at 2000 RPM
22 at 3000 rpm
Give or take
The Vacuume advance adds about 16 degrees.

Engine vacuum at idle in neutral is about 18.

Compression test with only 1 plug removed is around 180 psi.

Carb is a 750 Holley vac secondary. Never touched the jets.

I don’t know my exact rear end, but it revs around 3500 at 70 mph.

If there is some info missing here, let me know how I should go about getting it.

Thanks for your help.
This baby is dying to blow away some late model fools.
 
67Dart273 said:
Uh, what does this mean? You checked "what" and "what" is it that is correct?
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So I took off the drivers side valve cover and turned to motor over by hand. Had a friend watch the rockers and as I passed 360 degrees past tdc ( where the exhaust is just closing and the intake is just opening )I had him tell me where exactly the exhaust fully closed and the intake just started opening. I looked at the timing mark and the piston was exactly at the top. I repeated this several times to make sure he was seeing it right. I got this idea from another post on FABO and it made sense to me.
 
Valiant360420 said:
I had him tell me where exactly the exhaust fully closed and the intake just started opening. I looked at the timing mark and the piston was exactly at the top.
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This statement doesn't sound right unless you are generalizing.... ^^^^^

The exhaust does not fully close before the intake starts opening...

The intake starts opening before the exhaust closes, that is what they call overlap - how many degrees the intake valve and exhaust valve are open at the same time...
 
years ago i was working at a gas station when a customer drove up complaining of an engine knock. mechanic came out . listened to the engine. started to pour atf down the carb until the knock quit. seems there was enough carbon build up that it was actually hitting the head. Point is , after 17 years. is it possible that stop and go driving has allowed carbon build up to the point where you get 180lbs in a 9.5 -1 motor???
 
Damn....
First off, you are supposed to remove and PLUG the vacuum advance line when checking timing. You are looking to check the mechanical advance rate and amount. Most stock LA and B/RBs will make the most power with 8-10 degrees initial and 33-36 degrees total. A higher performance engine with more cam and compression often need MORE initial, something starting at 15-17 degrees.
My own 440 based 493 runs 18 degrees initial and 34 total.
Secondly, the belief that using a bigger cam to "bleed off cylinder pressure" does not always work out. That theory is based on the idea that the bigger the cam, the more overlap that it has and that supposedly reduces cylinder pressure. The fact is, it does.....BUT only at low engine speeds. That big cam starts to close that gap as rpms increase and at high rpms, it builds a LOT more cylinder pressure and will knock worse, maybe rattling the engine to death while you can't hear it over the moaning exhaust! I have dealt with this personally. I was close to 11 to 1 in my engine and was looking for some way to stop detonation. I was stupidly stubborn and did NOT want to pull the engine to put in dished pistons. I sent with Cometic .075 head gaskets to lower the compression. It is a crutch, but it did work. A better way to go would have been to use dished pistons and regular head gaskets. I would make more power and have quench that way.
 
Valiant360420 said:
Mopar Performance distributor with vacuum advance and orange ignition box. Mechanical advance adds about 25 degrees right now, but I am putting in one
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There is your problem(s)

That distributor brings in the timing FAST and LOW.

Disconnect and plug the vacuum advance. Use a NON-ADVANCE timing light preferably or use yours with no advance dialed into it. Use another light to confirm yours works properly as I've first hand seen one that doesn't. Mark your harmonic balancer at 34 degrees with a sharpie or paint pen. Shoot the light at it and rev to 3000 and make the line you made line up with zero on the pointer. Lock the dizzy down. Now check initial timing. Rev to 3500 to check total at 34 degrees again.

Let us know where the initial falls.

Then, with the vacuum advance still UNHOOKED AND PLUGGED, go drive it. Let us know how that goes. Your issues IMO are 100% timing related.
 
Valiant360420 said:
So I took off the drivers side valve cover and turned to motor over by hand. Had a friend watch the rockers and as I passed 360 degrees past tdc ( where the exhaust is just closing and the intake is just opening )I had him tell me where exactly the exhaust fully closed and the intake just started opening. I looked at the timing mark and the piston was exactly at the top. I repeated this several times to make sure he was seeing it right. I got this idea from another post on FABO and it made sense to me.
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That might not be accurate enough especially with hydraulic lifters, and just eyeballing the dampener as opposed to actually having it degreed / or degree wheel. ALSO has the TDC mark been confirmed with a piston stop? You know how to do that?
 
67Dart273 said:
That might not be accurate enough especially with hydraulic lifters, and just eyeballing the dampener as opposed to actually having it degreed / or degree wheel. ALSO has the TDC mark been confirmed with a piston stop? You know how to do that?
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Thanks. Yes TDC has been confirmed with a piston stop. And I realize my rocker watching method is not perfect, but I figured it is telling me that the cam is pretty darn close. And I didn’t have to tear anything apart yet.
Really, the motor doesn’t run bad, I’m just trying to make it run great.
 
roccodart440 said:
There is your problem(s)

That distributor brings in the timing FAST and LOW.

Disconnect and plug the vacuum advance. Use a NON-ADVANCE timing light preferably or use yours with no advance dialed into it. Use another light to confirm yours works properly as I've first hand seen one that doesn't. Mark your harmonic balancer at 34 degrees with a sharpie or paint pen. Shoot the light at it and rev to 3000 and make the line you made line up with zero on the pointer. Lock the dizzy down. Now check initial timing. Rev to 3500 to check total at 34 degrees again.

Let us know where the initial falls.

Then, with the vacuum advance still UNHOOKED AND PLUGGED, go drive it. Let us know how that goes. Your issues IMO are 100% timing related.
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I will do it this afternoon.
 
krazykuda said:
This statement doesn't sound right unless you are generalizing.... ^^^^^

The exhaust does not fully close before the intake starts opening...

The intake starts opening before the exhaust closes, that is what they call overlap - how many degrees the intake valve and exhaust valve are open at the same time...
Click to expand...
Yes. There was a slight overlap when both valves were overlapping, so we eyeballed the middle point. It seemed dead on.
 
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