There are others on this board that can better answer your SCR and DCR questions as they pertain specifically to the LT1, most of my experiance is in gen I SBC, BBC, and small block ford, the efficient reverse cooling and quality tuning make more compression possible, The highest I have tried to go on pump gas in the LT1 is 11:1 SCR with the LT4 hot cam, making 8.53 DCR, 6.0" rods and polished chambers...no detonation. I prefer to error on the safe side when many customers cant hear detonation on hot days, or put crappy fuel in a couple times thinking "it's only once...it'll be okay."

 

If you are going to try and push the envelope, polish the chambers, de-burr the piston crowns and keep oil out of the cylinders.....

 

If ya heads are stock they are 54CC's
Don't know about the sniffer.

8.77 will be fine and so would 9.17.
I feel with the right tuning and my set up I could have gone 9.5/6 with no problems.
Am running stock timing with the 9.1 with a .038 quench.

 

Put a timing control in it and "Walk On The Wild Side".

 

I do this on stuff that is pushing the limit let alone what happens on the 9:1 DCR stuff....

You can go crazy with this, but when things go wrong they really go wrong. Even on Kaases dyno Engine Masters motors that run with 160 deg coolant and are beat on and built to detonate, not to mention extremely good chambers and reverse dome pistons he at the most is doing about 9.3:1 in a cool controled setup at sea level.

I've done the 9:1 DCR stuff, and the more stuff I do the more I pull that back, remember the better VE you get the higher your chance of detonation is for each point of DCR. Detonation proof bottom ends get expensive, detonation is hard on everything plain and simple.

Bret

 

Yes it is, IF ya have detonation.

I must have a couple of engines that are real screwy,cause they don't show any signs of it. I am not trying to run .050 quench either.

 

Has anyone realized that a LT1 is NOT a typical small block Chevrolet? Reverse flow cooling will allow higher DCR than a standard small block, how much higher will depend on how much money is spent on the cooling system and tuning. I would say the DCR "rule of thumb" does not apply to a reverse cooled LT1.

My .02


David

 

Partly it's gas and chambers too...

For example a stock head with a stock quench (which is HORRIBLE) ain't going over 8.3 DCR in some states without detonation period. Cut the quench port the chambers etc... and you can raise it some but the gas you have in there matters the most.

The big issue is the gas... Alabama might have a good mix, I know when we got the gas here for the Engine Masters contest the first year they picked a 92 octane gas from a state that had a good Motor Octane (which is the WOT portion to make it simple, where the Research Octane is the part throttle side of the MON/RON rating) Anyways... this stuff was serious street gas. We broke the motor in and dialed in the ignition curve on the local 94 Sunoco, then once we got where we liked it switched over to 92 Unocal EM special gas and added more timing into the bottom end (brought it in earlier) to push the boundy more and it liked it..... Basically the Octane rating that each state is a certain mix of RON and MON to that states specs. Some are better than others. It would be interesting to see what states have the best gas and which ones have the worst in terms of this mix. Problem is we all don't live in Alabama boss! By the sounds of it I wish we all did!

BTW this comes from a guy who spent the last day radiusing the valve reliefs on a set of flat tops that are going in a mid 8's DCR motor... It's not pushing the limits but in 10-20K miles the motor might be, unless you want to tear these things down, clean the pistons and chambers all the time and have a perfect tune on the thing you will get octane creap... there is a good article in Hot Rod about this.. 3-4 years after we started talking about DCR on this forum... a little late to the party but a good story none the less.

Bret

 

Bret this ain't the '60s,unlead don't leave carbon in the cyls and if you are getting oil in the chambers it's time for valve seals or rings anyway.
We don't have Sunoco down here and the stuff we get is nothing special as far as Mon/Ron it is 92 octane (and doesn't have oxygenated additives) written on the pump and the best we found was Shell at one station(maybe he don't cut it as much)

Wish ya'll all lived here,can ya imagine the racing that would take place,the beer drank,and the bench racing and war stories.Hard to visualize but it sure would be fun.

 

Have you tried the Mahle pistons? They are awesome for the price, and I have seen 10-20 hp over comparable JE customs.

 

Yeap... I push these things all the time because of this. Problem is the set I just did was a set of custom Diamonds. (not bad by any means... they advertise Anderson runs their stuff so can't be bad) The Mahles still need the radiusing, no matter what a CNC machine and a cutter cant do what ya need.

Bret

 

Been using Probe stuff in my builds and have had no problems.
I would take 20HP for a piston change.

 

Try a set sometime. Seriously nice pistons for the coin.

Bret

 

Either way you still gonna leave something in the chambers unless you WOFT all the time... yeah I know I try too.

http://www.n2performance.com/lecture...ionlecture.pdf

Good info there too..

Even with viton seals, and some serious rings and a vacuum pump your gonna get some build up in there.

I don't even wanna know about the bench racing, drinking and war stories lol.. it could get BAD!

Bret

 

Might get faster which is never bad.