max compression on pump gas\steel cylinder head\241 @ 50 cam

-
T67POWER

T67POWER

Well-Known Member
Joined
Sep 30, 2009
Messages
669
Reaction score
9
Is anybody running 11.1 or more with a steel cylinder head on pump gas.
If so, what size is the cam @ 50 thousands lift.
Or better yet,what is the intake valve closing point.
Example:70 degrees ABDC
Also ,what kind of piston and cylinder head chamber do you have on your engine, and what grade pump gas do you use.(87 91 93 pump gas)

I have a dish piston with an open chamber head and want to see how far i can push the compression with a cam that is .241 at 50 on pump gas.
The engine has 9.5 to 1 right now with no problems.
I might try to advance my cam and mill the cylinder heads.
Looking to make a change possibly ,so any real world info will be a help.
Thanks :thumbup:
 
If you know your cylinder cranking pressure then please list it.
It really comes down to this part of the engine that makes the difference on what fuel we run.
If you don't know your cranking pressure, please still list your combination.
 
I have a friend running 87 octane with 11.2 comp by means of 915 iron closed chamber heads and a 300* solid roller in a 451 low deck, the cars runs 4.10's 4 spd and has about/around 34* total timing and mid 20's initial, revs to 7000 rpm

11.2 on 87 pump spew

I will ask what the @ .050 is.

but this will do nothing to your build with open chamber heads

180-185 psi dynamic is it with open chamber sb heads and pump 91, unless you have lots of gear. Ask crackedback this.
but who knows..
you could easily have the chambers spayed with iron and milled flat, then shape a heart, it's been done.

is that piston a quench dome or just a d cup or?
 
...and the hooha begins......
 
running a 360 +.030 with 915 "j"s cc at 59, the static is about 11.3, pistons are the speed pro h116cp's i think??? flat top with 5cc valve notch at zero deck. .039 gasket, cam is the comp 520/540 lift with 244/252 at .050 duration 110 lsa, intake closes at 67 ABDC, cyl psi is 205 to 210, i run 93 about 18 initial and 30 to 32 total, have to do all the tricks to keep it happy, but i love the instant start and idle, and great low end torque.
 
EL5DEMON340 said:
running a 360 +.030 with 915 "j"s cc at 59, the static is about 11.3, pistons are the speed pro h116cp's i think??? flat top with 5cc valve notch at zero deck. .039 gasket, cam is the comp 520/540 lift with 244/252 at .050 duration 110 lsa, intake closes at 67 ABDC, cyl psi is 205 to 210, i run 93 about 18 initial and 30 to 32 total, have to do all the tricks to keep it happy, but i love the instant start and idle, and great low end torque.
Click to expand...

ha ha whats cool about milling down to 59cc's.. theres almost no shallow side left, it's 20-30 thou 'tops' away from being a closed.
 
Crackedbacks running a true 10.5-.8 comp 340 with the .528 [email protected] 112cl cam w/60* o lap and he's got 185'ish dynamic, from what i know, and he still had to drop the timing down a lil to 30*

And we only have pump 87/89/91 octane here.

93 octane is a diff story 200 psi seems doable.
 
Ya i think its about .040 maybe a tad more if i remember right, the big drop in cc was when i replaced the stock valves with Milodon street valves, they dont have the concaved dish under them and are of a fairly thick margin.
 
I have a magnum headed 360 that runs 195 +/- 5 psi cranking pressure and runs on 89 octane with 17 initial and 34 total.
 
I checked my cranking pressure a while ago and it was 148 psi.
I did not pull all the plugs and the engine was kind of on the cool side.
I will warm her up good and pull all the plugs and then check it.
I am changing the plugs soon so it will be a good time to check.
I am going to check my piston to valve clearance and see what my choices are.
If i advanced my cam and cut the heads it would most likely help.

Has anybody advanced the cam in their engine and what was it worth in ET??
 
my 10.2 comp 410 has 170 psi on open chambers no issue=dish w/quench dome style pistons and 59cc heads with next to no shallow side left.-int closes 54* 110cl

my 9.7ish 340 w/kb243 flat tops and 241*@.050 has 155-160 psi. int closes 52* 112cl
thats what I'm running.

I'd like 15psi more, or 10.1 on the 340, though I'm happy with the 410's comp ratio.
 
If you have 148psi with that cam there might not be much gain from advancing the cam. I use the dynamic ratio to plan octane. Open chamber iron you can't have any quench. That does negatively affect how much you can do, but I use 8.25:1 dynamic and a cylinder pressure of 185 as my limit for pump fuel. We had the 87,89,91,and 93 here all with 10% ethanol and using those figures I can run as low as 89 octane with any timing I want.
 
I wonder how much power you can gain, going from lets say 150 psi of cylinder pressure to 170 psi??
Has there been a cylinder pressure test on a dyno before????
Now that i think of it, there was a couple of dyno test with advancing the cams position and what it's affects where.
I will try to find it.
Thanks for all the information.:supz:
 
T67POWER said:
I checked my cranking pressure a while ago and it was 148 psi.
I did not pull all the plugs and the engine was kind of on the cool side.
I will warm her up good and pull all the plugs and then check it.
I am changing the plugs soon so it will be a good time to check.
I am going to check my piston to valve clearance and see what my choices are.
If i advanced my cam and cut the heads it would most likely help.

Has anybody advanced the cam in their engine and what was it worth in ET??
Click to expand...
ive advanced it a 2 different 318s,it shifted the rpm range about 500 rpms lower,cranking compression came up some,it was more responsive,but the idle got a little rougher it seemed.couldnt tell you an actual "et gain"it just felt like it picked up low end.
 
based on a 8.1 400hp engine , going to 10.1 would gain around 15-25 hp

4-7% increase in current hp, per point increase, something like that.

so 300 hp going from 8.1 to 9.1 get about 9-12 hp increase.
 
EL5DEMON340 said:
Ya i think its about .040 maybe a tad more if i remember right, the big drop in cc was when i replaced the stock valves with Milodon street valves, they dont have the concaved dish under them and are of a fairly thick margin.
Click to expand...


Hmmm, that is good to know!

(now why did I forget to water that money tree of mine)
 
My 360+.030 has open chambered X heads, cam is 234 at .050" with the intake valve closed at 42 degrees @ .050", static is 9.91 to 1.. Cranking compression is 165 lbs. Run it on 93 octane at 34 degrees total. Very much more timing and it's spark knocking.
 
I have run 11.13 to 1 in my iron 360. Zero deck SRP pistons, with a 59cc chamber from cutting the 915s .040. I never did check the cranking compression. The cam is [email protected] .547 lift 110 LSA but I dont have the cam card anymore and dont know any of the events off the top of my head. I ran this on 91 octane with 36 degrees total locked out. I even ran a 150 shot of juice on it with no signs of detonation. 3420 pound car with 3000 stall and 4.56 gears. Hope this helps.
 
hey fish ....Thanks for the info.

When the cam company's tell you that you can run so much static compression, and with such and such a duration @ 50 cam and you will be fine, but then you wind up having spark knock problems because you have an open chamber head.
This is what i call THE GRAY AREA..
I have dish pistons and an open chamber ,so i want to be careful.

Your engine has 165 lbs of cranking pressure.
With that size cam(234 @ 50 ) most people would never think that you could have spark knock with 9.91,but you do with any more then 34 degrees timing.
My cuda has a .225 @ 50 cam \\ valve closes at 38 degrees ABDC.
It's 9 to 1 and will ping with any more then 31 degrees on 87 gas.
If i run premium i can turn the timing up more.
It has the same cranking pressure as my 360. 148 psi.
I thought that was really strange them being so close.
I mean the 360 has a intake valve closing point of 70 abdc.
The 318 on the other hand has a stock flat top piston and a closed chamber.
Cylinder pressure and power are important and i need more but it makes me wonder how much is to much and how to get there from here.
ADVANCE CAM OR CUT THE HEADS MORE \\\ OR BOTH
I will most likely advance the cam first.
It went in at 110 and should have been installed at 108..484 purple shaft.
I might install it at 106 if i can.
I have to check my piston to valve clearance first before anything.
THANKS AGAIN TO EVERYONE WHO GAVE INFO :thumbup:
 
T67, Another thing to consider is the timing curve. Once the engine goes into ping or detonation, it won't "get out" until you let off. However minor changes in the timing curve, meaning the rpm points at which the advance comes in, can stave off the first signs of it and thereby stop it altogether. Also, ping and detonation come from liquid fuel, not vapor. So anything you can do to help make the mixture more thorough the better. I've found by slowing the advance to bring it all in by say 3000 rather than 2400, and using the power valve ratings rather than the acc pump or jetting to richen things I can tune ping away without any loss of response or power. Not all engines need the standard "34-36° all in by 2400" deal. Many open chamber combos relly don't.
 
150-175 is about 20 hp ball park if your timing, fuel mix etc is adjusted for it.
 
moper..........
The 360 never pinged, and i could put the timing any where i want to.
I most likely could run 87 in it but have never tried.
Your right on the money on how to fix a car that's pinging by less timing down low and more on top.
I guess that being a traditional hot rod dude means never being completely happy.
The engine run's great, but it could be improved.
Thanks for the info.
 
My 440 Chargers got 185 psi (cranking)with 915 closed chamber heads milled down to 60 cc chamber volume on a stock 69' bottom end with a solid MP .528 cam. Runs fine on 87 octane . Violent bottom-end torque and plenty of power up top .
 
crossram...

185 on 87.
That's not to bad.
What is your timing set at????
 
Everybody! Write this down now and stick it under your hood or on your timing light!

Not all engines need the standard "34-36° all in by 2400" deal. Many open chamber combos relly don't
Click to expand...
 
You must log in or register to reply here.
-

Back
Top