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Difference between 10.5 and 11.0 cr
Posted By: Wedgeman
Difference between 10.5 and 11.0 cr - 08/10/12 09:35 PM
Hey...!
My 408 has 10.5:1 cr...my 60ft is 1.47...
I wonder if I could notice any difference in performance if I step up to thinner heads gasket and get 11.0:1 cr ?
Speculate on that please
Dan
67 Barracuda
Posted By: Sport440
Re: Difference between 10.5 and 11.0 cr - 08/10/12 10:40 PM
You will notice a difference with a 1/2 point jump in comp.
On my old 440 906 I saw 2 tenths with a .040 shave or about .7 comp jump.
With your little 408 you will see less, but you will still see a gain.
Posted By: B3422W5
Re: Difference between 10.5 and 11.0 cr - 08/10/12 11:10 PM
It is well documented that the power difference regarding compression will be larger with lower compression to start with.
In other words, you would gain more power going from 9 to 1 to 10 to 1 than you would going from 13 to 1 to 14 to 1.
Hope that makes sense.
Posted By: MR_P_BODY
Re: Difference between 10.5 and 11.0 cr - 08/10/12 11:47 PM
A difference in heads will be a factor also... alum
heads may see a bigger benefit due to alum heads like
more compression to equal out to iron
Posted By: BobR
Re: Difference between 10.5 and 11.0 cr - 08/11/12 12:02 AM
Quote:
Hey...!
My 408 has 10.5:1 cr...my 60ft is 1.47...
I wonder if I could notice any difference in performance if I step up to thinner heads gasket and get 11.0:1 cr ?
Speculate on that please
Dan
67 Barracuda
Very little difference. Less than 10 HP.
Posted By: 440Jim
Re: Difference between 10.5 and 11.0 cr - 08/11/12 12:37 AM
Depends on the cam, intake, headers, converter stall, etc. etc.
But until you list that, I would say 2% more power.
So if you are making 1000 hp that would be 20 hp.
And a 12 second car adding 20 hp would be 0.2 seconds in the 1/4 mile. So it depends what you have and what it runs ...
Posted By: Wedgeman
Re: Difference between 10.5 and 11.0 cr - 08/11/12 02:09 AM
408 Indy headed
I was hoping to gain .2 sec in the 1/8 mile...
just by swaping to thinner head gaskets....cheap horsepower to me , go from 6.75 to 6.55..
Dan
Posted By: MR_P_BODY
Re: Difference between 10.5 and 11.0 cr - 08/11/12 02:23 AM
Quote:
408 Indy headed
I was hoping to gain .2 sec in the 1/8 mile...
just by swaping to thinner head gaskets....cheap horsepower to me , go from 6.75 to 6.55..
Dan
I think your asking alot for just the head gasket
but thats... JMO
Posted By: Dunnuck Racing
Re: Difference between 10.5 and 11.0 cr - 08/11/12 02:28 AM
Depends on where your quench distance is now,and where it will end up after the swap. Not hard at all to gain 20 hp fixing a bad quench.
Keith
Posted By: radar
Re: Difference between 10.5 and 11.0 cr - 08/11/12 02:46 AM
I have read about the diminishing returns in torque from CR increases. That makes sense, but I also wonder how it could possibly fit into the 'whole picture' of matching parts. Like Jim said- depends on the other parts.
I have 0 experience with race gas territory compression ratios but I suspect that if increases give diminshing returns then the primary reason for a 15:1 cr in a race setup would be to maximize the performance of a wild cam with lots of overlap.
So if your CR is low for what your cam wants maybe your gains could be greater?
I'm only guessing- I'd love to hear from someone that actually knows.
Posted By: Darryls-Demon
Re: Difference between 10.5 and 11.0 cr - 08/11/12 03:40 AM
I think you should check your cylinder pressure, you may be able to bump it up one whole point if you find out your cylinder preesure is around say 150 pounds now.
Posted By: Wedgeman
Re: Difference between 10.5 and 11.0 cr - 08/11/12 04:33 AM
Cylinder pressure is 180lbs.....may be the cam is asking for more ???
255*/263*@ .050 solid roller..
Dan
Posted By: Dunnuck Racing
Re: Difference between 10.5 and 11.0 cr - 08/11/12 05:03 AM
What's the lsa ?
Keith
Posted By: Wedgeman
Re: Difference between 10.5 and 11.0 cr - 08/11/12 06:15 AM
lsa is 110........
Posted By: Sport440
Re: Difference between 10.5 and 11.0 cr - 08/11/12 08:31 AM
Quote:
408 Indy headed
I was hoping to gain .2 sec in the 1/8 mile...
just by swaping to thinner head gaskets....cheap horsepower to me , go from 6.75 to 6.55..
Dan
At your level of performance, you will not see a 2 tenths gain with a 1/2 point comp increase. Nope/No way!
If your running 6.75,s now, with that 1/2 point bump, Id expect high 6.68,s or so.
Posted By: polyspheric
Re: Difference between 10.5 and 11.0 cr - 08/11/12 03:52 PM
Posted By: Darryls-Demon
Re: Difference between 10.5 and 11.0 cr - 08/11/12 04:22 PM
Quote:
Quote:
408 Indy headed
I was hoping to gain .2 sec in the 1/8 mile...
just by swaping to thinner head gaskets....cheap horsepower to me , go from 6.75 to 6.55..
Dan
At your level of performance, you will not see a 2 tenths gain with a 1/2 point comp increase. Nope/No way!
If your running 6.75,s now, with that 1/2 point bump, Id expect high 6.68,s or so.
With 440sport, its not like your cylinder pressure is low now so I just can not see how a 1/2 point more will make that much difference.
Posted By: Wedgeman
Re: Difference between 10.5 and 11.0 cr - 08/11/12 08:53 PM
Oh Thanks for all the good advice !
Dan
Posted By: BIGSPEED
Re: Difference between 10.5 and 11.0 cr - 08/11/12 10:20 PM
Little to no gain unless the tighter quench fixes something,maybe 10 hp.Bill C.
Posted By: Ian
Re: Difference between 10.5 and 11.0 cr - 08/12/12 02:19 AM
what is your complete combo/weight .your 2 tenths may be in advancing cam ,gear change ,stall etc
Posted By: MR_P_BODY
Re: Difference between 10.5 and 11.0 cr - 08/12/12 02:37 AM
Quote:
what is your complete combo/weight .your 2 tenths may be in advancing cam ,gear change ,stall etc
Yes... advancing the cam a few degrees might give him
the same cyl pressure as using the thinner gasket...
if he has the piston to valve clearance... also the
cam advanced would increase in torque on the low end
so that is a plus
Posted By: emarine01
Re: Difference between 10.5 and 11.0 cr - 08/12/12 02:55 AM
If your considering a head gasket change look @ the size of the gasket bore compared to the engine bore, If you have any dead space in a larger gasket bore you can find some more cyl pressure there
Posted By: Dunnuck Racing
Re: Difference between 10.5 and 11.0 cr - 08/12/12 04:14 AM
As a couple of us have said now,if your quench needs fixed it will help some. Maybe not a full 2 tenths though.
Combine that with a few other things,depending on how sorted out the car is and yoyo can get it. I would think that cam would probably be happiest in at 106 if I were to guess based on the cam/ compression and what you have given us.
Keith
Posted By: Wedgeman
Re: Difference between 10.5 and 11.0 cr - 08/12/12 04:52 AM
Thanks for all the help guys...I have my answer
Dan
Posted By: Wedgeman
Re: Difference between 10.5 and 11.0 cr - 08/12/12 03:51 PM
I can advance timing 4* by changing the timing gear slots.....would it be ok ?
I already have lots of top end power, doing so is supposed to give more low end torque and cyl presuure....so I read
Dan