Is Quench Required?

[mopowers]

@mopowers , FWIW my 410 stroker cranks over at 200-203psi. It does have good flowing heads. The calc’s say it should be around 185psi. Effective CR is at 8.7-8.8:1. Quench is at 0.036’’.

It doesn’t ping at all on premium unleaded fuel. It did ping only occasionally before I sorted out a lifter adjustment issue. It was cranking at 215-220psi ( ! ) before sorting that out.

I’m probably close to the edge of where you want to be with pump fuel, but it can be done. Close attention to all small details & good tuning will get you there.

View attachment 1716408646

Thank you very much. All of this is great information. When you say "premium unleaded fuel," what exactly is it? 91 octane, 92, 93?

 

[Kern Dog]

Ok sure, but do you think that may have been more about reaching the limitations of fuel available rather than quench & compression?

We can only speak from our own experiences, mine seems to be somewhat opposite to what yours has been.

"Reaching the limits of fuel available"....
Don't take the following as an attack, just my observation:
What could possibly be the point of that statement? The "limits of fuel available" applies to everyone, everywhere.
The highest octane gasoline station fuel here is 91 with "up to 10% ethanol." That is it. That is the rating here in the USA, the R+M divided by 2.
If I knew a pilot with access to 100 octane airplane fuel or if I wanted to run race gas at $12 a gallon I suppose those options are available but it absolutely not practical. To me, it makes zero sense to run the compression way up high to where you need race gas to run it....especially if I'm not racing the car on a track.
I like to drive my cars on the street as you would any other car. I want to run down the freeway at speeds in line with other cars.
Given the limits of a non computer controlled classic without fuel injection and antiquated cylinder head designs, that often means 10 to 1 or less if you want to get by on the available premium fuel in hot weather without detonation. I fell for the use a big cam to bleed off pressure myth too. Guess what that actually does? ANY pressure that is supposedly bled off at low rpms absolutely comes back double as the rpms increase. I gained nothing.
Way back when I was super frustrated with the engine knock, I saw the prospect of increasing the compression ratio to get quench comparable to a guy running out of gas going WIDE OPEN throttle toward the gas station. It seems like a huge gamble that didn't make sense to take.
I had an equal amount of supporters as I did doubters when I stated that I was going the route of thicker head gaskets. It absolutely worked for me.
In theory, I understand that quench makes sense but I also know that it is quite easy to sit at a computer and give advice when you'll never have to deal with the fallout of that advice resulting in a bad outcome.

 

[Valman]

Thank you very much. All of this is great information. When you say "premium unleaded fuel," what exactly is it? 91 octane, 92, 93?

All good mate, our ‘Premium Unleaded’ here in Australia is either 95 or 98RON. U.S equivalents would be 91 & 93. I run 98RON.

The importance of quench (we say ‘squish’ ) seems to become more prevalent as the comp ratio goes up, at least in my experience. For instance, a 10:1 comp with 0.040’’ quench is preferable to 10:1 with 0.070’’quench for pump fuel. Again, just my own experience.

 

[RustyRatRod]

"Reaching the limits of fuel available"....
Don't take the following as an attack, just my observation:
What could possibly be the point of that statement? The "limits of fuel available" applies to everyone, everywhere.
The highest octane gasoline station fuel here is 91 with "up to 10% ethanol." That is it. That is the rating here in the USA, the R+M divided by 2.
If I knew a pilot with access to 100 octane airplane fuel or if I wanted to run race gas at $12 a gallon I suppose those options are available but it absolutely not practical. To me, it makes zero sense to run the compression way up high to where you need race gas to run it....especially if I'm not racing the car on a track.
I like to drive my cars on the street as you would any other car. I want to run down the freeway at speeds in line with other cars.
Given the limits of a non computer controlled classic without fuel injection and antiquated cylinder head designs, that often means 10 to 1 or less if you want to get by on the available premium fuel in hot weather without detonation. I fell for the use a big cam to bleed off pressure myth too. Guess what that actually does? ANY pressure that is supposedly bled off at low rpms absolutely comes back double as the rpms increase. I gained nothing.
Way back when I was super frustrated with the engine knock, I saw the prospect of increasing the compression ratio to get quench comparable to a guy running out of gas going WIDE OPEN throttle toward the gas station. It seems like a huge gamble that didn't make sense to take.
I had an equal amount of supporters as I did doubters when I stated that I was going the route of thicker head gaskets. It absolutely worked for me.
In theory, I understand that quench makes sense but I also know that it is quite easy to sit at a computer and give advice when you'll never have to deal with the fallout of that advice resulting in a bad outcome.

I think he was trying to say yall have crappy gas in Cali, that's all. And he's right.

 

[Valman]

What could possibly be the point of that statement? The "limits of fuel available" applies to everyone, everywhere.
The highest octane gasoline station fuel here is 91 with "up to 10% ethanol." That is it. That is the rating here in the USA, the R+M divided by 2.

No problem, no offence taken. You’ve answered my question by showing the only fuel you have is the 91-E10 stuff.

I’m not suggesting that you’re wrong about anything, my point was that with the heads you have, at the higher compression ratio, you may have reached the pre-ignition limits of that less than ideal fuel. Lowering your compression obviously solved that issue for you. Maybe better heads & quench would’ve worked as well? Obviously, that all costs money.

I do have closed chamber heads with a decent chamber design , and probably better fuel available than you do so that’s worked in my favour. I agree that using race fuel for street cars isn’t practical at all.

 

[RustyRatRod]

No problem, no offence taken. You’ve answered my question by showing the only fuel you have is the 91-E10 stuff.

I’m not suggesting that you’re wrong about anything, my point was that with the heads you have, at the higher compression ratio, you may have reached the pre-ignition limits of that less than ideal fuel. Lowering your compression obviously solved that issue for you. Maybe better heads & quench would’ve worked as well? Obviously, that all costs money.

I do have closed chamber heads with a decent chamber design , and probably better fuel available than you do so that’s worked in my favour. I agree that using race fuel for street cars isn’t practical at all.

If he has access to leaded racing fuel, that would be an option......although extremely expensive in California.

 

[Kern Dog]

I had and still have the closed chamber Edelbrock heads. The gas we have here isn’t much different than what is sold in many other states.
A 5 gallon pail of 110 octane was $55 in 2013. I can’t imagine what that would be today.

 

[RustyRatRod]

I had and still have the closed chamber Edelbrock heads. The gas we have here isn’t much different than what is sold in many other states.
A 5 gallon pail of 110 octane was $55 in 2013. I can’t imagine what that would be today.

I've seen lots of guys here complain about it. I don't know either way since I don't live out there.

 

[Valman]

If he has access to leaded racing fuel, that would be an option......although extremely expensive in California.

Is it legal to use leaded fuel on the street in the US? You’d be in deep trouble here if you got caught with it on the street.

 

[mopowers]

"Reaching the limits of fuel available"....
Don't take the following as an attack, just my observation:
What could possibly be the point of that statement? The "limits of fuel available" applies to everyone, everywhere.
The highest octane gasoline station fuel here is 91 with "up to 10% ethanol." That is it. That is the rating here in the USA, the R+M divided by 2.
If I knew a pilot with access to 100 octane airplane fuel or if I wanted to run race gas at $12 a gallon I suppose those options are available but it absolutely not practical. To me, it makes zero sense to run the compression way up high to where you need race gas to run it....especially if I'm not racing the car on a track.
I like to drive my cars on the street as you would any other car. I want to run down the freeway at speeds in line with other cars.
Given the limits of a non computer controlled classic without fuel injection and antiquated cylinder head designs, that often means 10 to 1 or less if you want to get by on the available premium fuel in hot weather without detonation. I fell for the use a big cam to bleed off pressure myth too. Guess what that actually does? ANY pressure that is supposedly bled off at low rpms absolutely comes back double as the rpms increase. I gained nothing.
Way back when I was super frustrated with the engine knock, I saw the prospect of increasing the compression ratio to get quench comparable to a guy running out of gas going WIDE OPEN throttle toward the gas station. It seems like a huge gamble that didn't make sense to take.
I had an equal amount of supporters as I did doubters when I stated that I was going the route of thicker head gaskets. It absolutely worked for me.
In theory, I understand that quench makes sense but I also know that it is quite easy to sit at a computer and give advice when you'll never have to deal with the fallout of that advice resulting in a bad outcome.

I'm glad you found a solution. I may end up in the same boat. haha. I'm curious though - At the time you were having issues, did you ever consider retarding the cam 4-6 degrees? That should've lowered or dynamic and effective compression considerably with minimal expense. It would've been at the expense of a little bottom end torque from my understanding, but with a stroked big block that may have actually been a good thing in a street car.

Just playing with a calculator, it seems that retarding the cam in my SB build 4* would lower the dynamic CR from 8.25 to 7.98 and the cranking pressure from 170 to 163 psi. That seems like a great option should detonation issues arise.

All good mate, our ‘Premium Unleaded’ here in Australia is either 95 or 98RON. U.S equivalents would be 91 & 93. I run 98RON.

The importance of quench (we say ‘squish’ ) seems to become more prevalent as the comp ratio goes up, at least in my experience. For instance, a 10:1 comp with 0.040’’ quench is preferable to 10:1 with 0.070’’quench for pump fuel. Again, just my own experience.

Okay, so your numbers you posted above are based on the equivalent to our 93, so it's a bit apples to oranges. Unfortunately, I'm limited to the same 91 pump piss as Kerndog. I appreciate the info though.

For instance, a 10:1 comp with 0.040’’ quench is preferable to 10:1 with 0.070’’quench for pump fuel. Again, just my own experience.

What do you mean "preferable?" I'd like to keep this focused on detonation resistance based on the components of my build and I think we've already established that a quench motor is more resistant to detonation than one without quench at a given compression ratio. The question I was trying to get input on is which of these combos would be less prone to detonation.

1. 10.02 SCR/ 7.91 DCR w/ 0.059" quench (161psi calculated),
2. 10.17 SCR/ 8.02 DCR w/ 0.052" quench (164psi), or
3. 10.45 SCR/ 8.24 DCR w/ 0.039" quench (170psi calculated).

 

[Newbomb Turk]

I'm glad you found a solution. I may end up in the same boat. haha. I'm curious though - At the time you were having issues, did you ever consider retarding the cam 4-6 degrees? That should've lowered or dynamic and effective compression considerably with minimal expense. It would've been at the expense of a little bottom end torque from my understanding, but with a stroked big block that may have actually been a good thing in a street car.

Just playing with a calculator, it seems that retarding the cam in my SB build 4* would lower the dynamic CR from 8.25 to 7.98 and the cranking pressure from 170 to 163 psi. That seems like a great option should detonation issues arise.


Okay, so your numbers you posted above are based on the equivalent to our 93, so it's a bit apples to oranges. Unfortunately, I'm limited to the same 91 pump piss as Kerndog. I appreciate the info though.


What do you mean "preferable?" I'd like to keep this focused on detonation resistance based on the components of my build and I think we've already established that a quench motor is more resistant to detonation than one without quench at a given compression ratio. The question I was trying to get input on is which of these combos would be less prone to detonation.

1. 10.02 SCR/ 7.91 DCR w/ 0.059" quench (161psi calculated),
2. 10.17 SCR/ 8.02 DCR w/ 0.052" quench (164psi), or
3. 10.45 SCR/ 8.24 DCR w/ 0.039" quench (170psi calculated).

Before you install and degree your cam, go to MGI Speedware and use their camshaft calculator.

Regardless of what the cam card says, if you want to make power you want to center the overlap triangle.

Most of the time that means not using the cam card number for ICL.

 

[RustyRatRod]

Is it legal to use leaded fuel on the street in the US? You’d be in deep trouble here if you got caught with it on the street.

It is here in Georgia. I don't know about California.

 

[RustyRatRod]

I'm glad you found a solution. I may end up in the same boat. haha. I'm curious though - At the time you were having issues, did you ever consider retarding the cam 4-6 degrees? That should've lowered or dynamic and effective compression considerably with minimal expense. It would've been at the expense of a little bottom end torque from my understanding, but with a stroked big block that may have actually been a good thing in a street car.

Just playing with a calculator, it seems that retarding the cam in my SB build 4* would lower the dynamic CR from 8.25 to 7.98 and the cranking pressure from 170 to 163 psi. That seems like a great option should detonation issues arise.


Okay, so your numbers you posted above are based on the equivalent to our 93, so it's a bit apples to oranges. Unfortunately, I'm limited to the same 91 pump piss as Kerndog. I appreciate the info though.


What do you mean "preferable?" I'd like to keep this focused on detonation resistance based on the components of my build and I think we've already established that a quench motor is more resistant to detonation than one without quench at a given compression ratio. The question I was trying to get input on is which of these combos would be less prone to detonation.

1. 10.02 SCR/ 7.91 DCR w/ 0.059" quench (161psi calculated),
2. 10.17 SCR/ 8.02 DCR w/ 0.052" quench (164psi), or
3. 10.45 SCR/ 8.24 DCR w/ 0.039" quench (170psi calculated).

I'd go with the .039 quench and not think twice about it. If you get any rattle, tune on it until you get it out. That's what I DID.

 

[mopowers]

I'd go with the .039 quench and not think twice about it. If you get any rattle, tune on it until you get it out. That's what I DID.

That's pretty much where I'm at. I've just gotta drop the block back off at the machine shop. I've got plenty of other stuff to keep me busy though. I'm in the middle of wiring my other Dart and have been procrastinating by playing with engine parts. haha

 

[mopowers]

Before you install and degree your cam, go to MGI Speedware and use their camshaft calculator.

Regardless of what the cam card says, if you want to make power you want to center the overlap triangle.

Most of the time that means not using the cam card number for ICL.

I'll have to look that up. My cam is ground on a 110 +4. I'm curious where MGI would want it. Then again, I'm really not aiming for max power. If I was, I'd have chosen a much larger camshaft to begin with.

 

[273]

I'd go with the .039 quench and not think twice about it. If you get any rattle, tune on it until you get it out. That's what I DID.

Agree, And even if that don't work he could run the thicker gasket 0.059" that he would anyways if he don't try running quench with a 0.039" gasket so there's nothing to lose, this thread just keeps going in circles lol.

 

[RustyRatRod]

That's pretty much where I'm at. I've just gotta drop the block back off at the machine shop. I've got plenty of other stuff to keep me busy though. I'm in the middle of wiring my other Dart and have been procrastinating by playing with engine parts. haha

......and I tuned it out with NO quench. The motor I'm running now has the pistons .180" in the hole. I have no quench to help me. I can tell you this, though. The one thing that helped the most was getting the engine to run as cool as possible. Once I did that, the detonation was gone.

 

[mopowers]

Before you install and degree your cam, go to MGI Speedware and use their camshaft calculator.

Regardless of what the cam card says, if you want to make power you want to center the overlap triangle.

Most of the time that means not using the cam card number for ICL.

Is this the one? I'm failing to see how this is any different than the cam card. It also calls for a 106 ICL. Can you explain it for my dumbass?

 

[Valman]

@mopowers I would use the 0.039’’ gasket option. - I’m using this gasket.

If you’re still concerned about the compression with your available fuel, you could smooth & polish the combustion chambers. This will increase the chamber volume by a few cc’s (around 4-5cc) and get rid of any sharp spots, casting texture etc. Also will drop the SCR down a little as a result.

 

[mopowers]

@mopowers I would use the 0.039’’ gasket option. - I’m using this gasket.

If you’re still concerned about the compression with your available fuel, you could smooth & polish the combustion chambers. This will increase the chamber volume by a few cc’s (around 4-5cc) and get rid of any sharp spots, casting texture etc. Also will drop the SCR down a little as a result.

Heads are Trick flow, so they're already smooth as hell. I'd be a little hesitant to touch a carbide or tootsie roll to them. If I attempted to remove 5cc's from them, it wouldn't be pretty. haha!

 

[Valman]

Heads are Trick flow, so they're already smooth as hell. I'd be a little hesitant to touch a carbide or tootsie roll to them. If I attempted to remove 5cc's from them, it wouldn't be pretty. haha!

Yeah, I did mine by hand just for that reason! Turned out really well. The chambers had the CNC tool marks in the chambers, which I polished out. Wish I had a photo.. oh well.

 

[RustyRatRod]

I'll also come back and add this. After I got mine all tuned and running without detonation, the issue cropped back up a few months later. Turns out, the carburetor had loosened up on the intake and it had a vacuum leak. So, that tells you the small amount of change that can lead to it doing it again, so don't try to lean it out looking for power. I advise running them a little fat anyway. Not 450 pound fat woman fat, but just a little baby fat.

 

[autoxcuda]

Run what gets you under 10:1 or closest that direction.

We run California spec 91 octane. California spec gas is different. That’s why we have special refineries for it and pay up the butt for it.

My 416 stroker with under .035 quench with 9.7:1 compression and I have to retard timing a tad.

I have an E-curve dist. and experimented with timing curves too

Aluminum heads, sharp edges chamfered, chambered fitted to bore. Heads cc’d, piston to deck height measured.

236/242 050, 511, 110 separation cam

 

[mopowers]

Well, ****...

For comparison sake, I run iron heads on my 9.6:1 340 with a small cam with fast ramps (61* IVCA) and have never had an issue.

 

[mopowers]

Run what gets you under 10:1 or closest that direction.

We run California spec 91 octane. California spec gas is different. That’s why we have special refineries for it and pay up the butt for it.

My 416 stroker with under .035 quench with 9.7:1 compression and I have to retard timing a tad. I have an E-curve dist. and experimented with timing curves too

Aluminum heads, sharp edges chamfered, chambered fitted to bore. Heads cc’d, piston to deck height measured.

236/242 050, 511, 110 center solid cam

View attachment 1716408710

What's advertised (seat) intake duration on the cam?