Quench talk

[Chevy1925]

So in the next year or so I plan to pull my motor out, tear it down, inspect it and change up a few things (fingers Pistons and af cam to name a couple). This is of course if makes it that far before something happens.

But I'm wondering about quench. Right now I have the tightest one at .029 and loosest one at .032. That's with a decked block, .010 off the Pistons and grade c gaskets. Now from what I read, that's on spec for a built motor running big power. Now had I known back when I was building the motor about how it affect mpg, I probably would have tried to tighten that up some more.

Question is, on a motor that sees 600hp 98% of the time and 750-800hp once or twice a year, can I tighten it up closer to stock without too much worry? I'd like to get down to .023-.025 if I can to get some mpg back towing. Is the piston really known for growing that much under this amount of hp that stock quench is too tight?

 

[Potthoffdmax]

Sub.

 

[02ilduramax]

Sub

 

[PureHybrid]

How is the material of the pistons that fingers uses compared to stock? With your turbo setup, it'll stay cool enough to not push anything to the extreme. I'd say put some thinner gaskets in it.

When you pull the head and there's valve marks in the piston carbon but no heavy contact, its perfect

 

[S Phinney]

It really depends on how hard you are going to run the truck. I wouldn't go too much tighter.

 

[Chevy1925]

How is the material of the pistons that fingers uses compared to stock? With your turbo setup, it'll stay cool enough to not push anything to the extreme. I'd say put some thinner gaskets in it.

When you pull the head and there's valve marks in the piston carbon but no heavy contact, its perfect

Ha! Valid point lol

It really depends on how hard you are going to run the truck. I wouldn't go too much tighter.

No harder than I do now, the motor never has been my worry, it's the rest of the drivetrain like tcase, drive shafts, front end parts, ect. Right now on the 600hp tune it sees WOT couple times a week and grandma driving the rest. Towing I usually don't get after the throttle unless I've gotta get to freeway speeds from a trucker slowing down up a hill or passing on a two lane.

Basically I'm looking at what I would want fingers Pistons cut too. I can't say I've heard of stock motor guys having issues running 650+ hp with the stock quench.

 

[Chevy1925]

figured this would have been a hotter topic

 

[S Phinney]

Most guys pay someone to build their and don't know what they have or the terminology. You can take one of pistons that you use now and determine compression height. Take those number and add or subtract to reach your goal. My triple motor has .0275 quench. It makes over a thousand but I usually don't turn it harder than 4500. It likes to run hard but I just don't believe in running it harder than you have to. Stock motors are usually near .020 quench.

 

[S Phinney]

Also camshaft lifts come into play and valve lifts help determine what you can do as well.

 

[PureHybrid]

Hey, I voiced my opinion

What cam are you going with? If it requires reliefs then you might as well tighten it up, you aren't turning it real hard. I would putty the clearance when it gets put together, not just rely on calculations. Do you have a dummy spring and dial indicator to map out the valve clearance?

IMO put it close to stock. If you don't have the tools and knowledge to push it, then don't. Because if it blows up and people ask questions you don't have answers to, guess who looks like the idiot :thumb:

 

[Chevy1925]

Most guys pay someone to build their and don't know what they have or the terminology. You can take one of pistons that you use now and determine compression height. Take those number and add or subtract to reach your goal. My triple motor has .0275 quench. It makes over a thousand but I usually don't turn it harder than 4500. It likes to run hard but I just don't believe in running it harder than you have to. Stock motors are usually near .020 quench.

Yeah ive noticed that but helping a buddy work on assembling his motor, we started checking protrusion and noticed the machine shop sent him the wrong sized gaskets. He would have been even tighter than stock with a high of .019 and low of .015. told him he had two options, the overbore/decked block HG or pull the pistons and shave them. saved him alot of grief i would think as hes going for the same power i am.

Also camshaft lifts come into play and valve lifts help determine what you can do as well.

thanks for the info Phinney. its appreciated

Hey, I voiced my opinion

What cam are you going with? If it requires reliefs then you might as well tighten it up, you aren't turning it real hard. I would putty the clearance when it gets put together, not just rely on calculations. Do you have a dummy spring and dial indicator to map out the valve clearance?

IMO put it close to stock. If you don't have the tools and knowledge to push it, then don't. Because if it blows up and people ask questions you don't have answers to, guess who looks like the idiot :thumb:

lol i know you did! cam will be stock or close to stock (what ever AF ones are availible close to stock). i wont be running a charger larger than my stock one in the twins, i like the tow-ability of it too much so i doubt a bigger cam would be worth it? not sure there.

yes i have a dummy spring and dial indicator to use so i can check clearance that way as well on my tightest cyl. bought a few different ones to use on dmax or my samurai as i was building my samurai motor for as much performance as i could squeak out of it. its funny, i spent alot of time on the bottom end checking bearing clearances and swapping a couple bearings around to get the best clearances i could on the dmax motor back when but when it came to the protrusion, i didnt take near the time there as i didnt know just how much of an affect it had on the motor. i just went by what guy and others said but never asked "why" or tried to figure it out. now im curious and want to improve upon it.

thanks for your time guys

 

[PureHybrid]

Maybe get a cam with a bit more duration, but with no valve reliefs there probably isn't much room to grow in that aspect. I'd work on the heads first, but that's just me. Being stock engines get pretty good fuel mileage I'd try to squeeze it back towards stock specs. But everything needs to be measured, not just calculated, since you're relying on the machine shops word about the deck height, as well as how much the pistons were shaved.

What pistons are in it? Stockers cut/ coated? Want to sell them?

 

[Chevy1925]

Maybe get a cam with a bit more duration, but with no valve reliefs there probably isn't much room to grow in that aspect. I'd work on the heads first, but that's just me. Being stock engines get pretty good fuel mileage I'd try to squeeze it back towards stock specs. But everything needs to be measured, not just calculated, since you're relying on the machine shops word about the deck height, as well as how much the pistons were shaved.

What pistons are in it? Stockers cut/ coated? Want to sell them?

only reason im changing cams is to go AF, larger duration/lift isnt first priority. ill more than likely just stick with stock cam specs. the motor works and runs awesome as it is with stock heads/cam, im just looking to improve upon the "weaker points". plus i wanna tear the motor down and just see how its doing after 40-50k of use. it will be measured but i have to calculate some things so i have a starting point. before i rip the pistons out, ill basically do a whole run down on protrusion again, check current valve clearance and give myself a good base to start from. then ill order my pistons and cam.

my only concern was what i could get away with for quench.

pistons are stock LB7, delipped and cut .010, not coated (nothing i read deamed it worth putting on to keep pistons together cause people still cracked them). They will be for sale when the time comes and they are out

 

[Fingers]

The stock numbers take into account piston rock. Not a huge issue with Stock or most Cast pistons, but if the bore is big or you are running forged, it will show up and need to be accounted for.

Measure your protrusion across the pin line. This is what the stock spec is based off of. With the piston full out, move your indicator to the top or bottom edge and rock your piston in the bore. Use the max number to determine you clearance.

 

[Chevy1925]

The stock numbers take into account piston rock. Not a huge issue with Stock or most Cast pistons, but if the bore is big or you are running forged, it will show up and need to be accounted for.

Measure your protrusion across the pin line. This is what the stock spec is based off of. With the piston full out, move your indicator to the top or bottom edge and rock your piston in the bore. Use the max number to determine you clearance.

thats what ive done but ive only ever worked with stock bores that have been honed out to clean them up and stock cast pistons. So PTW clearances have been close to stock in each of them

 

[Chavez91]

Yeah ive noticed that but helping a buddy work on assembling his motor, we started checking protrusion and noticed the machine shop sent him the wrong sized gaskets. He would have been even tighter than stock with a high of .019 and low of .015. told him he had two options, the overbore/decked block HG or pull the pistons and shave them. saved him alot of grief i would think as hes going for the same power i am.

That's me! :hug:

Ended up going with the Overbore/decked .047 Thick Gaskets that after all the measuring, will give me a .026 quench at the tightest spot. I took a little more time than James, and swapped pistons around to get them all as close as possible to the same protrusion height all around. But Im looking at an almost Identical setup to James. Unless he talks me into the Danville 68.

And Im running .020 over Delipped Stock LB7/LLY pistons. They seemed to rock quite a bit. Piston to wall clearance was a little loose but just inside stock specs and on par with James's. But after talking to James again, I ended up measuring the protrusion the way Fingers described.

 

[Chevy1925]

That's me! :hug:

Ended up going with the Overbore/decked .047 Thick Gaskets that after all the measuring, will give me a .026 quench at the tightest spot. I took a little more time than James, and swapped pistons around to get them all as close as possible to the same protrusion height all around. But Im looking at an almost Identical setup to James. Unless he talks me into the Danville 68.

And Im running .020 over Delipped Stock LB7/LLY pistons. They seemed to rock quite a bit. Piston to wall clearance was a little loose but just inside stock specs and on par with James's. But after talking to James again, I ended up measuring the protrusion the way Fingers described.

you have no balls if you dont :angel:

 

[gmduramax]

Why would you stay stock cam specs. You can get much better response.

 

[PureHybrid]

I'm sure he won't stay "stock" but close. He wants compression back already, a cam that requires valve reliefs won't help his case. BUT if fingers is custom milling his pistons he might get away with it.

 

[Chevy1925]

Why would you stay stock cam specs. You can get much better response.

out of a stock turbo??? im not against it, i just have not seen/read anyone doing it on a stock turbo. not really looking for anymore performance out of the motor either. if anything, id just be going for quicker spool up.