quench revisited with cranking compression - Chevelle Tech
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post #1 of 12 (permalink) Old Jun 30th, 20, 1:49 PM Thread Starter
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quench revisited with cranking compression

Just wanted to re educate myself on some of these topics in building a street 93 octane motor.

Its my understanding to keep that quench as tight at possible. .035 to .042 if possible.

Seems most of these rotating assemblies want to zero deck the block and that sometimes causes cooling issues.

Wiesco and Probe seem to offering taller pistons that you only have to cut the deck to .015 to get a zero deck.

Most of these builders who own shops arent as concerned with quench as much as the home builder or hobby guy. I wonder why. Some are getting quenches in the .050 to .055 and calling it a pump gas motor build for max power. At least in my area anyway.

If you have a tight quench, what are you guys considering a cut off on cranking compression? 200 psi? 220 psi?

With my build, I will have a DCR of 8.2 to 8.4, but I will be using a 4 core aluminum rad too.

67 chevelle malibu / SS/ custom

Currently undergoing a metal work to remove all rust, if I ever get there.

Cant decide on prostreet or cruiser with a 4 speed.
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post #2 of 12 (permalink) Old Jun 30th, 20, 2:25 PM
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Quote:
Originally Posted by Aaron View Post
Just wanted to re educate myself on some of these topics in building a street 93 octane motor.

Its my understanding to keep that quench as tight at possible. .035 to .042 if possible.

Seems most of these rotating assemblies want to zero deck the block and that sometimes causes cooling issues.

Wiesco and Probe seem to offering taller pistons that you only have to cut the deck to .015 to get a zero deck.

Most of these builders who own shops arent as concerned with quench as much as the home builder or hobby guy. I wonder why. Some are getting quenches in the .050 to .055 and calling it a pump gas motor build for max power. At least in my area anyway.

If you have a tight quench, what are you guys considering a cut off on cranking compression? 200 psi? 220 psi?

With my build, I will have a DCR of 8.2 to 8.4, but I will be using a 4 core aluminum rad too.
I used Racetek forged pistons from Wolfplace and they offset the pin .010 at no extra charge. Not sure how Wiesco and Probe do it.
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post #3 of 12 (permalink) Old Jun 30th, 20, 2:32 PM Thread Starter
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Re: quench revisited with cranking compression

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Originally Posted by 65cayne View Post
I used Racetek forged pistons from Wolfplace and they offset the pin .010 at no extra charge. Not sure how Wiesco and Probe do it.
Compression height of the Wiseco is 1.140 and I think Probe is the same.

67 chevelle malibu / SS/ custom

Currently undergoing a metal work to remove all rust, if I ever get there.

Cant decide on prostreet or cruiser with a 4 speed.
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post #4 of 12 (permalink) Old Jun 30th, 20, 3:19 PM
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Re: quench revisited with cranking compression

My 2 bolt 406 was zero'd with Mahle D dish pistons 62cc chambers. Deck plugs in large hole in the decks. Never an issue with cooling. Summit 2 row 1" alum rad and lincoln fan controlled by a Spal soft start controller. 170's*
Even in my sons C10 now with a cheap replacement rad and clutch fan same results.
I don't know what the DCR is tho but he's locked out at 34* and uses a a stock starter and lights off every time with heat soak.

73 nova,3515#(all steel)Pump gas!(91octane)406ci N/A, best 1/4,1.45 '60,[email protected],10.6 @ 122.38, short shifting,NO tuning!


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post #5 of 12 (permalink) Old Jun 30th, 20, 5:23 PM
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Re: quench revisited with cranking compression

There's more to it than just quench. A heavy stick shift car with tall gears will have more of a tendency to ping than the same engine in a light car with low gears. Twenty years ago before the internet could tell me the error of my ways, I had a 355 that had 0.057" quench, cranked 215-230 psi cold and ran on pump gas. The car weighed 3,150 without me and had 4.10 gears. That engine was in the car almost 6 years and ran 11.30's on the motor.
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post #6 of 12 (permalink) Old Jun 30th, 20, 11:11 PM
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Re: quench revisited with cranking compression

Machine shops err to the side of caution. Lower compression and less worry about PV clearance results in less returns.

Mine ran .028" clearance.

JIM
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post #7 of 12 (permalink) Old Jul 1st, 20, 5:31 AM Thread Starter
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Re: quench revisited with cranking compression

Quote:
Originally Posted by Steve69SS396 View Post
There's more to it than just quench. A heavy stick shift car with tall gears will have more of a tendency to ping than the same engine in a light car with low gears. Twenty years ago before the internet could tell me the error of my ways, I had a 355 that had 0.057" quench, cranked 215-230 psi cold and ran on pump gas. The car weighed 3,150 without me and had 4.10 gears. That engine was in the car almost 6 years and ran 11.30's on the motor.
Very interesting on the build.

Somewhat similar to your experience with a big gasket is the zz4 engine. That engine has a uncut deck and a .50 thick gasket on it for a quench of almost .070 and it has a small cam in it too. That motor does run on 93 octane, but it will ping going up hills or if you lug the engine somehow when running at max timing.

Nice running engine you had.

67 chevelle malibu / SS/ custom

Currently undergoing a metal work to remove all rust, if I ever get there.

Cant decide on prostreet or cruiser with a 4 speed.
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post #8 of 12 (permalink) Old Jul 1st, 20, 5:34 AM Thread Starter
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Re: quench revisited with cranking compression

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Originally Posted by 540Hotrod View Post
Machine shops err to the side of caution. Lower compression and less worry about PV clearance results in less returns.

Mine ran .028" clearance.

JIM
That they do!

If you also hire a professional engine builder for a street or race engine, they also always take a conservative route.

Anytime I have had to work with people on engine building, I have had to convince them to push the boundaries a little more. Its not in their nature to do so, if they might have to deal with negative results later on.

67 chevelle malibu / SS/ custom

Currently undergoing a metal work to remove all rust, if I ever get there.

Cant decide on prostreet or cruiser with a 4 speed.
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post #9 of 12 (permalink) Old Jul 1st, 20, 8:04 AM
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Re: quench revisited with cranking compression

I ran .028" on a 350" with 54cc heads and later went to .051" clearance and the car ran exactly the same et.
BUT one difference was I did not need to pull timing with the .051" or rejet when the weather got really hot outside 90+

I ran 2.29 gears and 4.56 gears and some gears in the middle of that depending on how i felt that week.
I pulled trailers with it also.
91 octane vs 93 and I would have to pull 2-3 degrees timing out of it for the lower octane.

My intake runners from below the carburetor to the valve seat were very roughed up.
Not smooth.
I wanted the atomized fuel.
Chamber shape is very important when running high compressions.
My pistons were flat top 5cc reliefs.
70,000 miles with those 54cc heads and did that in 18 months of driving.
I drove a lot.

I still have the short block but with 305 HO heads now 57 cc after massaging and .051" clearance 10.78 actual compression.
Runs great. and has for decades.
It is a 1969 300HP 350 and the crank has never been touched and cylinder walls are still standard.
Over 400,000 miles on that block crank and rods.
Many 7000+ RPM shifts
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post #10 of 12 (permalink) Old Jul 1st, 20, 3:37 PM Thread Starter
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Re: quench revisited with cranking compression

Quote:
Originally Posted by jeff swisher View Post
I ran .028" on a 350" with 54cc heads and later went to .051" clearance and the car ran exactly the same et.
BUT one difference was I did not need to pull timing with the .051" or rejet when the weather got really hot outside 90+

I ran 2.29 gears and 4.56 gears and some gears in the middle of that depending on how i felt that week.
I pulled trailers with it also.
91 octane vs 93 and I would have to pull 2-3 degrees timing out of it for the lower octane.

My intake runners from below the carburetor to the valve seat were very roughed up.
Not smooth.
I wanted the atomized fuel.
Chamber shape is very important when running high compressions.
My pistons were flat top 5cc reliefs.
70,000 miles with those 54cc heads and did that in 18 months of driving.
I drove a lot.

I still have the short block but with 305 HO heads now 57 cc after massaging and .051" clearance 10.78 actual compression.
Runs great. and has for decades.
It is a 1969 300HP 350 and the crank has never been touched and cylinder walls are still standard.
Over 400,000 miles on that block crank and rods.
Many 7000+ RPM shifts

So going to that big quench, you didnt have to change the tune?

67 chevelle malibu / SS/ custom

Currently undergoing a metal work to remove all rust, if I ever get there.

Cant decide on prostreet or cruiser with a 4 speed.
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post #11 of 12 (permalink) Old Jul 1st, 20, 8:51 PM
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Re: quench revisited with cranking compression

"Seems most of these rotating assemblies want to zero deck the block and that sometimes causes cooling issues."

Yup, absolutely right, but, backwards. Quench of .039 thru .045 actually helps cool the engine, not heat it up.

Interesting about the compression heights, discussion on ChevyTalk right now about not needing to hang the crank, rods and pistons in a couple of cylinders and actually measure the deck distances, one person says a simple measure the block is all that is needed, I say do the parts install, and measure, for absolute clarity and accuracy. Opinions vary.

I doubt you will get that much pressure out of a low DCR engine.
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post #12 of 12 (permalink) Old Jul 1st, 20, 10:19 PM
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Re: quench revisited with cranking compression

Quote:
Originally Posted by Aaron View Post
So going to that big quench, you didnt have to change the tune?



No change in jetting or anything.
I currently have the .051" piston to head distance on my 57 chevy and it pulls my 20 foot Pontoon very well.
I have pulled it with 3.00 gears and 3.70 gears I do pull 3 degrees timing with the 3.00 gears.
Normally run 38 total but 35 total is only 3 HP less at the wheels so very good power still.


I did that little piston to head experiment on my own personal vehicle over 25 years ago.
So much talk about perfect quench distance I had to find out for myself if there was any difference.


You would be surprised how many experiments I have performed just to put hear say to rest.


There are a lot of smart folks on this forum and I am sure they have also experimented.


Those years back i was driving 70,000 miles a year and the wife was also.
She put 67,000 miles on one car in 11 months and I quit counting.
I had multiple vehicles and that 70,000 miles was logged on the ones we drove the most .
Her Escort and my 78 Nova.
I also had an 82 Mustang and 78 Skylark an 1980 Pinto, 1981 280Z and 1985 V65 Magna and her bike also which is a 1987 Honda Magna.
Get tired of driving one car then hop in another one.


I thinned the herd when I moved.
I experimented / tweaked on all of them.
The little Pinto would put 305 chevy trucks to shame. Even when pulling trailers.
Tweaked 2.3

Head gaskets are inexpensive.
Oil changes on 2 cars every 2 weeks gets a bit crazy.
The V65 Magna got oil changed sometimes after 2 days. Hard racing ya know.
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