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Pump gas friendly race motor

Posted By: Bigcube

Pump gas friendly race motor - 10/13/11 01:51 AM

How much squeeze? It will be 572 cubes, figure an optimized cam for dealing with pump gas, will be a roller. Will see a shot of spray at the track with some better gas. Will see street time, must not be temperamental. What sort of compression should I shoot for... ballpark, I know it's a loaded question. I'm thinking 11:1 ish? Alum. heads and block.

I have a few ideas rolling around in my head, have to see how things pan out over the winter. Looking for opinions of people who know pump gas stuff. Not looking to push the ragged edge. I figure if I can make 750ish HP I can easily spay it to 8.50's and run 9.20's on motor, plenty fast enough to go get ice cream. And maybe start having fun with the car again at the same time...
Posted By: sixpackgut

Re: Pump gas friendly race motor - 10/13/11 02:05 AM

i'm at 12-1 with 185 cranking comp. that comp increase came from the indy heads. with rpm heads i was at 10.5-1 with 185 cranking comp.

credit goes to Dan @ Performance Only for specing the cam. it is more tame than the 590 mopar shaft i had before
Posted By: Bigcube

Re: Pump gas friendly race motor - 10/13/11 02:24 AM

Wow! 12:1? I guess it's all about the cam. I can see bleeding off cranking compression, but no ping under load? I never thought you could be safe at 12:1 with pump swill.... guess I have a lot to learn!
Posted By: Performance Only

Re: Pump gas friendly race motor - 10/13/11 02:28 AM

Quote:

Wow! 12:1? I guess it's all about the cam. I can see bleeding off cranking compression, but no ping under load? I never thought you could be safe at 12:1 with pump swill.... guess I have a lot to learn!



Jim, send it down here. 750 HP on pump gas won't be a problem. it is more than just a cam change to do it right though.

Ray, yours sounds tamer than the 590 MP cam until you push the pedal on the right.
Posted By: Butch

Re: Pump gas friendly race motor - 10/13/11 02:30 AM

That's good news Jim. If you want to make the trip back to Norwalk for some icecream at next season I'll buy.

Butch
Posted By: MR_P_BODY

Re: Pump gas friendly race motor - 10/13/11 02:32 AM

Quote:

Wow! 12:1? I guess it's all about the cam. I can see bleeding off cranking compression, but no ping under load? I never thought you could be safe at 12:1 with pump swill.... guess I have a lot to learn!




It ALL comes down to the dynamic compression... my
14.1:1 has 185 cranking pressure
Posted By: Performance Only

Re: Pump gas friendly race motor - 10/13/11 02:39 AM

Quote:

Quote:

Wow! 12:1? I guess it's all about the cam. I can see bleeding off cranking compression, but no ping under load? I never thought you could be safe at 12:1 with pump swill.... guess I have a lot to learn!




It ALL comes down to the dynamic compression... my
14.1:1 has 185 cranking pressure




but what does that cylinder pressure become at 3000 rpm? cars don't tool around the streets on cranking compression.
Posted By: MR_P_BODY

Re: Pump gas friendly race motor - 10/13/11 02:47 AM

It ALL comes down to the dynamic compression... my
14.1:1 has 185 cranking pressure




but what does that cylinder pressure become at 3000 rpm? cars don't tool around the streets on cranking compression.



I have no way to measure that
Posted By: Cab_Burge

Re: Pump gas friendly race motor - 10/13/11 04:14 AM

My 518 low deck motor with 440-1 CNC ported by MCH made 775 HP on Oregon pump gas with 10.8 to 1 compression and absolutely no quench to speak of.(at 4300 FT above sea level also, DTS dyno straight up no fudging ) The pistons have a 22 CC dish because the motor originally had a set of ported 906 iron heads on it I should replace the pistons to a set of reverse dome with some quench, I'm sure there is some power there It is way easir to turn up the squeeze HP than it is to start with to much compression Big motors(C.I.) make a lot of power without a bunch of compression I'd shoot for 10.5 to 1 or lower
Posted By: an8sec70cuda

Re: Pump gas friendly race motor - 10/13/11 04:23 PM

Jim, you know hemis are different than wedges, but I have about 11:1 in my hemi and it runs fine on pump 93...when I get the non ethanol stuff. It has 185 psi cranking. Summer time w/ ethanol blended 93 it will rattle and lose a noticeable amount of power.

My 440 is 14.5:1 and has 185 psi cranking compression also, but it'll never see anything but race fuel.

The pump 93 isn't what it was a few years ago, so I'd go conservative on the compression if it was me.
Posted By: Dragula

Re: Pump gas friendly race motor - 10/13/11 07:48 PM

I have not had my hemi togather and running on the new ethanol based crap, but it is 11.6:1 and was not an issue on 92 octane. I think the big chambers expand a little when up to temp though. It might be 11.6:1 at room temp, but I am sure its not 167cc chambers at 180*...
Posted By: 383man

Re: Pump gas friendly race motor - 10/13/11 09:46 PM

I am at 10.6 with the aluminum heads. Have not checked cranking comp but I can tell you I have no ping at all and the total is at 37. The timing is all in by 2000 and the eng has good quench. Ron
Posted By: Bigcube

Re: Pump gas friendly race motor - 10/13/11 11:01 PM

Thanks everyone for the responses. Seems like 10.5-11.5ish compression with the correct cam should be fine. What do people do to pick a cam and have cranking compression end up where it needs to be? Is that adding more duration? Or overlap? Just curious what would be different in a pump gas cam compared to a high compression/race fuel cam? I would leave spec'ing the cam to the professionals, more just curious ow they would be different.
Posted By: moparniac

Re: Pump gas friendly race motor - 10/14/11 03:05 AM

11.89 to 1

162 low 170 high cranking compression Races on junk 93 BaBy
Posted By: an8sec70cuda

Re: Pump gas friendly race motor - 10/14/11 01:10 PM

Quote:

Thanks everyone for the responses. Seems like 10.5-11.5ish compression with the correct cam should be fine. What do people do to pick a cam and have cranking compression end up where it needs to be? Is that adding more duration? Or overlap? Just curious what would be different in a pump gas cam compared to a high compression/race fuel cam? I would leave spec'ing the cam to the professionals, more just curious ow they would be different.


Dwayne spec'd the cams in both of my motors. The 440's cam is a more radical profile...pretty much race only. Yet you see the compression difference.

My little 440 makes my Hemi sound like a 383, lol.
Posted By: PJ68RT

Re: Pump gas friendly race motor - 10/14/11 02:46 PM

Later intake closing...shortens the effective stroke giving less compression pressure.

http://www.wallaceracing.com/dynamic-cr.php
Posted By: moparniac

Re: Pump gas friendly race motor - 10/14/11 03:21 PM

Quote:

Later intake closing...shortens the effective stroke giving less compression pressure.

http://www.wallaceracing.com/dynamic-cr.php



That's what I like. Mine is 73! Dynamic compression is more important overall .... IMO... at altitude that program has me' at 165 and like I said 11.89 to 1 and my low is 162 and high 170. ...
Posted By: Performance Only

Re: Pump gas friendly race motor - 10/14/11 07:25 PM

Quote:

Later intake closing...shortens the effective stroke giving less compression pressure.

http://www.wallaceracing.com/dynamic-cr.php




that's only one part of the puzzle though when you need to make good power too. other things need to be done with the cam depending on the power needed. just moving the closing point isn't the answer.
Posted By: Stanton

Re: Pump gas friendly race motor - 10/14/11 08:51 PM

From the looks of things, 185 PSI of cranking pressure seems to be the target # for pump gas - right ???
Posted By: Bigcube

Re: Pump gas friendly race motor - 10/14/11 10:35 PM

Here's what that page spits out for my current compression/cam
Quote:

Your dynamic compression ratio is 11.21:1 .
Your dynamic cranking pressure is 244.55 PSI.


So it's safe to assume this WON'T run on pump gas
Posted By: POS Dakota

Re: Pump gas friendly race motor - 10/15/11 12:38 AM

Quote:

Here's what that page spits out for my current compression/cam
Quote:

Your dynamic compression ratio is 11.21:1 .
Your dynamic cranking pressure is 244.55 PSI.


So it's safe to assume this WON'T run on pump gas



LOL

i know a guy a couple miles from me with an iron headed 390 and around 225 psi on pump 93.

But 244...likely not.
Posted By: Stanton

Re: Pump gas friendly race motor - 10/15/11 04:18 AM

Quote:

Your dynamic compression ratio is 11.21:1 .
Your dynamic cranking pressure is 244.55 PSI.





With a dynamic CR of 11.21, I gotta ask ... what's your static CR ????
Posted By: Bigcube

Re: Pump gas friendly race motor - 10/15/11 12:30 PM

It's 15:1
Posted By: Bad340fish

Re: Pump gas friendly race motor - 10/15/11 01:53 PM

Quote:

It's 15:1



E85 cornfed bigcube dart maybe?
Posted By: fishy340

Re: Pump gas friendly race motor - 10/15/11 01:59 PM

hey bigcube 11.1 ur fine w sunoco ultra or good 93 octane..mine is 11.5 i run ny garbage gas for the street with little bangin of the throttle here and there- its fine,now when i go to the track i put a gal of 110 or 116 mix with 3 gals of 93 and have no problemos
Posted By: Bigcube

Re: Pump gas friendly race motor - 10/15/11 04:46 PM

Quote:

Quote:

It's 15:1



E85 cornfed bigcube dart maybe?


If they had it around here I'd consider it. But I really want to tame it down some and drive the car more. I've always ran VP C-16 in it.
Posted By: firefighter3931

Re: Pump gas friendly race motor - 10/15/11 05:55 PM

My PRH 572 is right at 10.75:1 and runs fine on 93UL pump swill. Cam is a 266/272 110lsa Comp Roller. The engine idles nice at 1050rpm and is easy to drive on the street


Ron

Attached picture 6872547-572-9.jpg
Posted By: Bigcube

Re: Pump gas friendly race motor - 10/15/11 07:38 PM

What heads? Did Dwayne dyno it? It would be a good comparison because mine was run on his dyno.
Posted By: hp340nos

Re: Pump gas friendly race motor - 10/15/11 07:45 PM

jim i look forward to seeing the car out again.people need to see your car in person,to appreciate the detail you have gone too in the car,beautiful and fast,and you have not cracked the fogger yet,good luck and see you in the spring time mike d.
Posted By: firefighter3931

Re: Pump gas friendly race motor - 10/16/11 01:15 PM

Quote:

What heads? Did Dwayne dyno it? It would be a good comparison because mine was run on his dyno.




Jim, the heads are EZ 295's with some massaging by Dwayne

Here's a thread on the build with dyno numbers using different manifold/carb combos :

https://board.moparts.org/ubbthreads/show...e=0#Post5622009



Ron
Posted By: moparniac

Re: Pump gas friendly race motor - 10/16/11 01:24 PM

Firefighter you ever run that at the track?
Posted By: Bad340fish

Re: Pump gas friendly race motor - 10/16/11 01:28 PM

Quote:

Quote:

Quote:

It's 15:1



E85 cornfed bigcube dart maybe?


If they had it around here I'd consider it. But I really want to tame it down some and drive the car more. I've always ran VP C-16 in it.



Its kind of available around here but not everywhere. I have considered sourcing it in a drum if I decide to go that route. Its easier to avoid all those gas station stories about the 383 six pack hemis anyways lol.
Posted By: Bigcube

Re: Pump gas friendly race motor - 10/16/11 03:00 PM

Quote:

Quote:

What heads? Did Dwayne dyno it? It would be a good comparison because mine was run on his dyno.




Jim, the heads are EZ 295's with some massaging by Dwayne

Here's a thread on the build with dyno numbers using different manifold/carb combos :

https://board.moparts.org/ubbthreads/show...e=0#Post5622009



Ron


Very nice, Dwaynes the MAN!
Posted By: mopar65

Re: Pump gas friendly race motor - 10/16/11 05:33 PM

Quote:

My PRH 572 is right at 10.75:1 and runs fine on 93UL pump swill. Cam is a 266/272 110lsa Comp Roller. The engine idles nice at 1050rpm and is easy to drive on the street


Ron



looking great there ron. but i have a question for you.on the mopar 337 intake.did you use it to cover up the valley? i mean did you use it instead of useing the indy valley plate or did the intake bolt on top of the indy plate? sorry for the weared question.but in the pic the 337 intake almost looks like it is bolted on top of the indy valley plate? i might be wanting to try this intake latter on down the road.thanks Mopar65
Posted By: FastmOp

Re: Pump gas friendly race motor - 10/16/11 06:36 PM

If you replace your current headgaskit with something like a thick copper one and gain .080 or so where would your compression be?
I'd run as much stuff as I could if I had what you have sitting around. That thing is fresh so I'd really look at doing as little and as cheep as I could. Pistons would be as far as I would go. Then you could spend the cash saved for 110 or E85
I would stick exhaust with electric cut-outs on it. Cause you know "ice cream is better with open headers".
Posted By: firefighter3931

Re: Pump gas friendly race motor - 10/16/11 09:32 PM

Quote:

Firefighter you ever run that at the track?




Yep, been trying to work out all the gremlins ; fuel delivery and the Tq converter been giving me grief !

The car is also real heavy (4200 lbs raceweight) so i'm making some off season changes to lighten things up.



Ron
Posted By: firefighter3931

Re: Pump gas friendly race motor - 10/16/11 09:35 PM

Quote:

looking great there ron. but i have a question for you.on the mopar 337 intake.did you use it to cover up the valley? i mean did you use it instead of useing the indy valley plate or did the intake bolt on top of the indy plate? sorry for the weared question.but in the pic the 337 intake almost looks like it is bolted on top of the indy valley plate? i might be wanting to try this intake latter on down the road.thanks Mopar65




Bobby, with the raised port EZ heads we had to install an Indy valley cover underneath the 337 manifold. Good eye !



Ron
Posted By: moparman63

Re: Pump gas friendly race motor - 10/16/11 11:47 PM

my 499 low deck is 11.1:1 with 175psi cranking.it lives great on 90 octane.even with 150hp nitrous and 36 degrees timing.i believe camshaft and rpm are where its at.mine has sr head,a torque monster cam and 5700rpm shift point.i dont spray it anymore but i did for the firzt 10 years of its life.
Posted By: fast68plymouth

Re: Pump gas friendly race motor - 10/17/11 03:28 AM

Jim,
some pistons, rods, a cam, and a set of valve springs and you'd be right in pump gas/grocery getter heaven
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