Can we discuss quench vs softening?
Not trying to change anyone’s mind, just throwing my experience out there and talking about the hobby with others. Lots of different ways to get to the same goal. Unfortunately, there is no single answer for how much a setup can handle. Too many variables there. The load and how it is applied is just as important as the fuel, combustion chamber, tune, etc etc...
Regardless, the same rules apply regarding quench and compression. One extra pound of boost easily compensates for dropping a full point of compression and losing quench, in terms of power potential, thats still the best route.
That said, if your tune isn’t near the edge, there’s no reason to sacrifice response or efficiency—especially for a dual-purpose setup. So I’m not stating you shouldn’t’ run a 10:1+ Setup with a tight efficient quench either. Just putting the information out there.
I’m doing exactly what you’re describing: E85, twin 78/75s, cam-only 5.3, meth injection, no IC. It’s in a ’26 Model T, and an IC would look out of place IMO. The car’s light enough to run 8.50s (5.50 1/8th) without it. I drive to and from the track. I don’t own a trailer. To go quicker I’d need (want) a better cage and chassis anyway. So in my case an IC made no sense.
If you plan on similar, softer chambers and lower compression are even more important. Less compression means less risk of damage. Without an IC, the tuning window on E85 gets narrow around 220°F in my experience. Really need an aggressive timing ramp reduction from there on. I’ve also run a similar “hot air” setup in a notchback with twin 63s. Guys have been 4’s non intercooled on E85 or E98. So def. possible to go “Fast” without and IC. You just wont’ make as much power per pound.
If space/budget allows, I think an A2W is best for a street/strip car. (if needed) The only “race car” aspect of an A2W is running ice. Which is completely optional, though worthwhile for max performance.
A basic A2W core with a 5-gallon cell and pump is all that’s needed. Even ambient water outperforms most A2A units. I tested my large Treadstone 1245 A2A, VS a friends 5 gallon A2W. The smaller A2W with ambient water performed much better, keeping temps only a few degrees above the tank water temp at like boost and duration. Similar 5.3 setup, same day.
The expensive big Garrett A2A cores can keep charge temps near ambient at high boost too, but they cost about 5× more, block the radiator flow, and are still pretty dang heavy. And if you happen to be at the track and looking for that “hail Mary” super pass... toss a bag of ICE in the A2W and it’ll still outperform the expensive A2A units.
That is all assuming short bursts of course. But on a typical drag/drive car most don’t do 20 back-to-back passes. 5 gallons was plenty of water to keep charge temps in check for street driving/play. Just don’t circulate the water if you’re not in boost. As an added fun fact, even with the water pump off. Often an A2W does just as well as a cheap A2A.
Regardless, the same rules apply regarding quench and compression. One extra pound of boost easily compensates for dropping a full point of compression and losing quench, in terms of power potential, thats still the best route.
That said, if your tune isn’t near the edge, there’s no reason to sacrifice response or efficiency—especially for a dual-purpose setup. So I’m not stating you shouldn’t’ run a 10:1+ Setup with a tight efficient quench either. Just putting the information out there.
I’m doing exactly what you’re describing: E85, twin 78/75s, cam-only 5.3, meth injection, no IC. It’s in a ’26 Model T, and an IC would look out of place IMO. The car’s light enough to run 8.50s (5.50 1/8th) without it. I drive to and from the track. I don’t own a trailer. To go quicker I’d need (want) a better cage and chassis anyway. So in my case an IC made no sense.
If you plan on similar, softer chambers and lower compression are even more important. Less compression means less risk of damage. Without an IC, the tuning window on E85 gets narrow around 220°F in my experience. Really need an aggressive timing ramp reduction from there on. I’ve also run a similar “hot air” setup in a notchback with twin 63s. Guys have been 4’s non intercooled on E85 or E98. So def. possible to go “Fast” without and IC. You just wont’ make as much power per pound.
If space/budget allows, I think an A2W is best for a street/strip car. (if needed) The only “race car” aspect of an A2W is running ice. Which is completely optional, though worthwhile for max performance.
A basic A2W core with a 5-gallon cell and pump is all that’s needed. Even ambient water outperforms most A2A units. I tested my large Treadstone 1245 A2A, VS a friends 5 gallon A2W. The smaller A2W with ambient water performed much better, keeping temps only a few degrees above the tank water temp at like boost and duration. Similar 5.3 setup, same day.
The expensive big Garrett A2A cores can keep charge temps near ambient at high boost too, but they cost about 5× more, block the radiator flow, and are still pretty dang heavy. And if you happen to be at the track and looking for that “hail Mary” super pass... toss a bag of ICE in the A2W and it’ll still outperform the expensive A2A units.
That is all assuming short bursts of course. But on a typical drag/drive car most don’t do 20 back-to-back passes. 5 gallons was plenty of water to keep charge temps in check for street driving/play. Just don’t circulate the water if you’re not in boost. As an added fun fact, even with the water pump off. Often an A2W does just as well as a cheap A2A.
The math on those is not even close to being accurate. Either way the same principal applies and yes it most definitely matters how you get there for all of the reasons mentioned in the previous posts in this thread. The answer 99% of the time is less compression and more boost when you are up against a knock limit of the fuel.
Care to elaborate on the correct math for the captured compression ?
You must be alluding to Inertia Momentum Flux (D•V2), being the difference in "math".
Bottom line is this....
I'm looking to find the minimum spark advance that produces the highest TQ before knock. Though means of quench, compression, temperature, fuel, timing and possibly softening the chambers. We all know you can reach and pass MTB and never see knock because the combo is not fuel limited.
I will go back and re-read the thread contributors, maybe I missed it. I see a lot of "what works" for John Doe. But no explanations of max flame speed vs knock. Or end gas temperature control, deflagration, how flame speed must increase proportional to engine speed caused by agitation,turbulence and density. Entropy loss from early pressure..etc
NoLift and Forcefed have had great input...just wanting to get into the weeds a little more on the discussion. You know, a little bit of boosted engine combustion chamber theory.
Sure, I could build the same cookie cutter LS combo as everyone else and be "happy". But my curiosity on why certain things are "fact" in the boosted world interests me beyond..."cuz Jonny says it works".
And at the end of the day, the John Doe cookie cutter combo maybe the best route for me. I'm just curious on the whys. And when I say why, I'm referring to the empirical evidence behind the parts choice..like softening the chamber.
To think "we" have it all figured out is laughable, we use bandaids to make it not destroy itself.
Or perhaps a better explanation is, I'm just to dense to grasp the information...lol. Highly likely!!
.
Last edited by LSOHOLIC; Feb 4, 2026 at 12:52 AM.
Not trying to change anyone’s mind, just throwing my experience out there and talking about the hobby with others. Lots of different ways to get to the same goal. Unfortunately, there is no single answer for how much a setup can handle. Too many variables there. The load and how it is applied is just as important as the fuel, combustion chamber, tune, etc etc...
Regardless, the same rules apply regarding quench and compression. One extra pound of boost easily compensates for dropping a full point of compression and losing quench, in terms of power potential, thats still the best route.
That said, if your tune isn’t near the edge, there’s no reason to sacrifice response or efficiency—especially for a dual-purpose setup. So I’m not stating you shouldn’t’ run a 10:1+ Setup with a tight efficient quench either. Just putting the information out there.
I’m doing exactly what you’re describing: E85, twin 78/75s, cam-only 5.3, meth injection, no IC. It’s in a ’26 Model T, and an IC would look out of place IMO. The car’s light enough to run 8.50s (5.50 1/8th) without it. I drive to and from the track. I don’t own a trailer. To go quicker I’d need (want) a better cage and chassis anyway. So in my case an IC made no sense.
If you plan on similar, softer chambers and lower compression are even more important. Less compression means less risk of damage. Without an IC, the tuning window on E85 gets .
Regardless, the same rules apply regarding quench and compression. One extra pound of boost easily compensates for dropping a full point of compression and losing quench, in terms of power potential, thats still the best route.
That said, if your tune isn’t near the edge, there’s no reason to sacrifice response or efficiency—especially for a dual-purpose setup. So I’m not stating you shouldn’t’ run a 10:1+ Setup with a tight efficient quench either. Just putting the information out there.
I’m doing exactly what you’re describing: E85, twin 78/75s, cam-only 5.3, meth injection, no IC. It’s in a ’26 Model T, and an IC would look out of place IMO. The car’s light enough to run 8.50s (5.50 1/8th) without it. I drive to and from the track. I don’t own a trailer. To go quicker I’d need (want) a better cage and chassis anyway. So in my case an IC made no sense.
If you plan on similar, softer chambers and lower compression are even more important. Less compression means less risk of damage. Without an IC, the tuning window on E85 gets .
Then discussing how and where we went wrong or right, based on practical and theoretical information.
And when I say "change my mind", thats merely a challenge to over come biased opinions with empirical data.
I'm not looking to live on the edge with a particular combo. I just want to understand why and where the edge exists. To become a better enginologist (pretty sure I made that word up).
By nature, I'm a attention to detail kind of guy. I enjoy being accurate when attempting to be quick at the track. To a fault!!
In all honesty, I'll probably go the tried and trued cookie cutter build. But I'm very interested in why everyone builds the same combo.
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TECH Fanatic
Joined: Dec 2017
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My setup is basically the opposite of how you're going about it. Mostly thrown together because "I had it" and didn't want to change it, lol.
Setup is as follows:
Sleeved 5.3 block
4.130" bore
Stock LS7 rods and crank
.082" thick head gaskets (~.051" quench due to piston stick out)
Heads started out around 58cc and softened to roughly 68cc.
Roughly 12.8 compression
Shortblock was built for a high compression NA setup. Rings gapped for a healthy shot of nitrous.
Twin 69/73 turbos
Solid roller (251/261 .750" lift)
A2W intercooled
E85 with meth injection (for octane)
Shooting for ~1200whp
So far, I love how responsive the setup is. Drives great out of boost and boost response is pretty quick. I've only done one full pull at about 3.5psi and it felt solid. Estimated about ~750whp. The engine would/should put down over 600whp, all motor, no doubt in my mind.
I've been seeing quite a bit more high compression/boost setups popping up lately. Not sure how long they will/are lasting, though.
Plan to put it on the dyno within the next 2 weeks.
Setup is as follows:
Sleeved 5.3 block
4.130" bore
Stock LS7 rods and crank
.082" thick head gaskets (~.051" quench due to piston stick out)
Heads started out around 58cc and softened to roughly 68cc.
Roughly 12.8 compression
Shortblock was built for a high compression NA setup. Rings gapped for a healthy shot of nitrous.
Twin 69/73 turbos
Solid roller (251/261 .750" lift)
A2W intercooled
E85 with meth injection (for octane)
Shooting for ~1200whp
So far, I love how responsive the setup is. Drives great out of boost and boost response is pretty quick. I've only done one full pull at about 3.5psi and it felt solid. Estimated about ~750whp. The engine would/should put down over 600whp, all motor, no doubt in my mind.
I've been seeing quite a bit more high compression/boost setups popping up lately. Not sure how long they will/are lasting, though.
Plan to put it on the dyno within the next 2 weeks.
Last edited by jayyyw; Feb 5, 2026 at 12:15 AM.
Absolutely nothing wrong with going that route. It’ll be much more fun to drive around town. Who wouldn’t want a snappy, healthy, big-cube 600+ HP base motor to start with?
Downsides:
It’ll cost a lot more, take much more time and labor to get running, and be very tune-sensitive. You’ll also see higher combustion temps, peakier cylinder pressures, and less “rev-happy” behavior compared to a smaller 8–9:1, shorter-stroke motor. That can lead to head gasket clamping issues, detonation, and more wear and tear.
The argument:
Why build a turbo motor if you’re not letting the turbo do the heavy lifting? The turbo is far more efficient at making power. Building a high-compression, big-cube NA-style motor and running low boost defeats the purpose — you’re doing more work for less gain.
Flip side:
A low-compression, small-cube, budget motor (like an SBE 5.3) costs $400–500, is practically disposable, and requires no machine work. Run 317 heads softened and a thicker head gasket to land around 8.5:1, then push 30–50 psi for the same 1200 HP goal. It’ll cost a fraction, handle higher RPM better, have a wider tuning window, and be easy to replace.
It’ll be laggier and less fun to street drive by comparison... but If you’re already on the two-step making target boost for launch, it doesn’t matter. They can feasibly run the same ET.
In my opinion:
At 1,000+ HP, stuff breaks. Doesn’t matter how much money is in it. That’s just Murphy’s Law of drag racing! At my income level, I’d rather window a $400 short block than a $10–20K “built” motor. If I had disposable income, sure... I’d be running the good stuff!
Downsides:
It’ll cost a lot more, take much more time and labor to get running, and be very tune-sensitive. You’ll also see higher combustion temps, peakier cylinder pressures, and less “rev-happy” behavior compared to a smaller 8–9:1, shorter-stroke motor. That can lead to head gasket clamping issues, detonation, and more wear and tear.
The argument:
Why build a turbo motor if you’re not letting the turbo do the heavy lifting? The turbo is far more efficient at making power. Building a high-compression, big-cube NA-style motor and running low boost defeats the purpose — you’re doing more work for less gain.
Flip side:
A low-compression, small-cube, budget motor (like an SBE 5.3) costs $400–500, is practically disposable, and requires no machine work. Run 317 heads softened and a thicker head gasket to land around 8.5:1, then push 30–50 psi for the same 1200 HP goal. It’ll cost a fraction, handle higher RPM better, have a wider tuning window, and be easy to replace.
It’ll be laggier and less fun to street drive by comparison... but If you’re already on the two-step making target boost for launch, it doesn’t matter. They can feasibly run the same ET.
In my opinion:
At 1,000+ HP, stuff breaks. Doesn’t matter how much money is in it. That’s just Murphy’s Law of drag racing! At my income level, I’d rather window a $400 short block than a $10–20K “built” motor. If I had disposable income, sure... I’d be running the good stuff!
As long as the fueling is on point and he checks plugs should be okay.
I had this thread on my mind when I was talking to a turbo ls buddy, he had his CID heads chambers softened, the cylinder head shop (Hooper) did them when they ported the heads.
I had this thread on my mind when I was talking to a turbo ls buddy, he had his CID heads chambers softened, the cylinder head shop (Hooper) did them when they ported the heads.