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Maximum CR closed chamber w2 heads 0.040 quench- pump gas #2510990
06/20/18 07:19 PM
06/20/18 07:19 PM
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Lima, Peru
domingo Offline OP
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Hello

I was wondering what would be the maximum CR that could be run with 93 pump gas and NO DETONATION using:

-55cc closed chamber w2 cast iron heads
-proper 0.040" to 0.050" quench with a 4" crank and dished pistons
-245° @050 street solid roller with about 600 lift.

would 10.9:1 put me in PING territory???

Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511038
06/20/18 08:54 PM
06/20/18 08:54 PM
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Originally Posted By domingo
Hello

I was wondering what would be the maximum CR that could be run with 93 pump gas and NO DETONATION using:

-55cc closed chamber w2 cast iron heads
-proper 0.040" to 0.050" quench with a 4" crank and dished pistons
-245° @050 street solid roller with about 600 lift.

would 10.9:1 put me in PING territory???


What are the rest of the cam numbers? With the correct cam you shouldn't have issues. That head doesn't like much over a 109 LSA.


Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511063
06/20/18 09:49 PM
06/20/18 09:49 PM
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Lima, Peru
domingo Offline OP
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I dont have the exact cam specs, as I dont yet have the cam, but would be nice to hear what kind of cam would work best for making power and avoiding pinging at that compression and pump gas.

this is for a stout full weight 70 Challenger TA 4 speed street car on pump gas.

Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511076
06/20/18 10:18 PM
06/20/18 10:18 PM
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Originally Posted By domingo
I dont have the exact cam specs, as I dont yet have the cam, but would be nice to hear what kind of cam would work best for making power and avoiding pinging at that compression and pump gas.

this is for a stout full weight 70 Challenger TA 4 speed street car on pump gas.


Gearing makes a difference as well. You want to run a 3.23 gear it will be more prone to detonation.

Can you post all the details?


Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511101
06/20/18 10:50 PM
06/20/18 10:50 PM
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domingo Offline OP
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Its going in a real TA Challenger. so its gonna be in full street trim = heavy.

4 speed trans.

3.55 gears.

Stockish sized wheel/tires. Most Likely 275 rear tires and 235 front radial tas on 7" rallyes

stock intake and six pack setup. Heads redrilled to accept stock intake bolt pattern, and intake modified to match w2 intake ports.

Stock exh manifolds, but might go with tti headers, undecided yet.

Bear in mind that I dont want to back up timing or setup distributor in a way it doesnt ping, because it would kinda defeat the purpose ofhaving the extra compression to make more power. I want to setup the engine right for max power and avoid pinging. Its just that with the heads I have and piston/stroke combo I have I am gonna end up with around 10,9:1 compression if I shoot for a zero deck and 0,040" quench with the closed chamber heads.... If it pings I will have to take heads off and install thicker cometics to lower compression. I would loose the quench effect and I guess I would just have to go with around 9,5:1 compression so it doesnt ping w no quench and iron heads.

I guess thats about it....

Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511221
06/21/18 09:09 AM
06/21/18 09:09 AM
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Tulsa OK
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I have a 416" Closed Chamber W2 combo. It has dished pistons with no quench pad, it is right about 10:1 and has a big roller camshaft. It cranks 170psi and runs fine on 91, makes 580-600HP.


68 Barracuda Formula S 340
87 "Chrysler" Conquest
Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511342
06/21/18 03:03 PM
06/21/18 03:03 PM
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HotRodDave Offline
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I run more compression and smaller cam in my 410 with magnum heads, I think youll be fine as long as your not sucking hot air right off the headers or boiling the fuel in the line running next to the exhaust or something.


I am not causing global warming, I am just trying to hold off a impending Ice Age!



Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511363
06/21/18 03:36 PM
06/21/18 03:36 PM
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Bend,OR USA
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Is your fuel straight gas or does it have ethanol added to it?
Is the octane rating their the same as here(RO+MON divided by2) in the U.S.?
All the stock 340/360 NHRA class motors I helped like 30 to 32 degrees total timing, same on the hot street motors with good gas shruggy
I wouldn't run that much compression up here on our pump gas with iron heads twocents


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511395
06/21/18 04:52 PM
06/21/18 04:52 PM
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Lima, Peru
domingo Offline OP
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We do have some ethanol in out gas....what about it? Does it make it more or less ping prone? I would think its less ping prone?

Our rating is 98, i dont remember the specifics, but in the end it would be an equivalent to 92 or 93 on your octane ratings.

Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511405
06/21/18 04:58 PM
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i'm very skeptical that 93 octane will support 10.9:1; good or bad quench.

Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511411
06/21/18 05:13 PM
06/21/18 05:13 PM
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Lima, Peru
domingo Offline OP
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for the record.....

I run 9.4:1 on a 440.6 pack with open chamber cast iron heads.

it has a small comp hyd flat tappet cam
224° @ 050
LSA 110°
.470 lift

Engine runs great with our 98 octane but its right there on the edge of pinging. It will not tolerate 97 octane gas (which we also have at the pump) or it will start to ping.

I guess thats about as high as I want to go with no quench and a small cam on a cast iron headed motor. Its what I have tested with our gas.

Now, If I did have an engine WITH quench and with the bigger solid roller....how much higher do you guys think I could push the compression based on what I said above?

Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: lewtot184] #2511453
06/21/18 07:11 PM
06/21/18 07:11 PM
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Originally Posted By lewtot184
i'm very skeptical that 93 octane will support 10.9:1; good or bad quench.


You can if the combo is right.

I think the OP needs to drop his CR. He's asking a lot. He has tall gears, and IIRC he wants to run exhaust manifolds or something.

Just asking too much from what he has.

OP drop the CR.


Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511475
06/21/18 08:40 PM
06/21/18 08:40 PM
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polyspheric Offline
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Tall gear + 2.65 1st gear + stock ignition curve = problem.
The same engine with 4.10 gears, a 700R4, + 9" converter will never ping.


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Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511476
06/21/18 08:46 PM
06/21/18 08:46 PM
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domingo Offline OP
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why is it that extra load on an engine makes it ping?

Isnt pinging just because of pre-ignition and colliding flame fronts?

But I do know from experience that when there is extra load it will be more ping prone, but whats the science behind that????

Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: polyspheric] #2511479
06/21/18 08:47 PM
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Originally Posted By polyspheric
Tall gear + 2.65 1st gear + stock ignition curve = problem.
The same engine with 4.10 gears, a 700R4, + 9" converter will never ping.




That's what I meant. You just said it better. It's exactly correct.


Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511490
06/21/18 09:32 PM
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Originally Posted By domingo
why is it that extra load on an engine makes it ping?

Isnt pinging just because of pre-ignition and colliding flame fronts?

But I do know from experience that when there is extra load it will be more ping prone, but whats the science behind that????
volumetric efficiency increases and this increases cylinder pressure. it's all about cylinder pressure and keeping oil and water out of the chambers.

Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511535
06/21/18 11:07 PM
06/21/18 11:07 PM
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Not a sb/w2 but My 383 has quench style dome pistons with closed chamber heads.
Around 10.8:1 with 250@.050 solid cam and it doesn’t like pump gas. Loves 100 octane tho

Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511579
06/22/18 12:56 AM
06/22/18 12:56 AM
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polyspheric Offline
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And the cylinder pressure is easily managed by spark control - which you specifically decided not to use.
An engine retarded to 10 ATDC will not develop enough power to idle. The advance position is a rheostat... if you want it to be.
Vizard described using an unregulated turbo @ WOT for road racing using spark advance instead of throttle 30 years ago.


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Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: domingo] #2511783
06/22/18 03:38 PM
06/22/18 03:38 PM
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Originally Posted By domingo
why is it that extra load on an engine makes it ping?

Isnt pinging just because of pre-ignition and colliding flame fronts?

But I do know from experience that when there is extra load it will be more ping prone, but whats the science behind that????


The higher gear means it wont accelerate as fast meaning more heat will build up in the chamber meaning more likely to have a hot spot and a place for the spark to start at the wrong spot and wrong time. Also the piston will accelerate away from TDC faster meaning a slightly faster than normal flame front could still be chasing the piston instead of coliding with it witch causes more pressure and a faster burn that causes more pressure and a faster burn... long story short it burns so fast it is more like an explosion and damages your engine and causes audible knock.

Exhaust manifolds probably help reduce detonation as they reduce cylinder filling efficency plus there is going to be a slightly higher amount of inert exhaust gas left in the chamber that will slow down the burn of the next air fuel charge.


I am not causing global warming, I am just trying to hold off a impending Ice Age!



Re: Maximum CR closed chamber w2 heads 0.040 quench- pump gas [Re: HotRodDave] #2511919
06/22/18 10:01 PM
06/22/18 10:01 PM
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Yes... I think that will put you in ping territory.

With iron heads (even with decent quench) suggest you shoot for 9.5 CR max. Better a little less.

A few 10'th's too much compression can be a PITA.

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