I'm no gearhead by anymeans so this is all assumption. Anyway I've heard that L76's are capable of producing just slightly more power (stock for stock) than LS1's with 87 Octane. Of course to run lower Octane you must have a lower Compression Ratio. How did they achieve this? Different Heads? Pistons? Tuning?

For curiosity's sake, if it were to be the heads, would they be interchangable into an LS1 Motor since it is Aluminum and would it be a direct fit or would the bore's be different?

Lets say it were the heads and pistons and these were all swapped from an L76 into an LS1, the next step would be tuning before you could take advantage of the 87 Octane benefit...

This is all just curiosity, I'd doubt the cost of this project would overcome the benefit of saving .20 at the pump... ...well...maybe in the longrun it could but has anyone ever attempted this project? any drawbacks to it?

Edit: Just realized I confused the L98 with the L76, edit the post

 

If you run 10000 miles a year and get 25 mpg you'll use 400 gallons of gasoline a year. @ $0.20 per gallon savings is a grand total of $80 dollars a year. If you only get 20 mpg then it's a whopping $100 a year.
It would take a years worth of savings just to pay for the gaskets for this swap.

 

The L76 heads are designed for a 4.00" bore which is larger than the LS1 and you have to use the L71 intake because of the different port design. The LS1 also doesn't pump enough air to reap any benefit from those heads so you'd lose power and efficiency. Those heads are flat designed for a larger displacement engine.

Now if you wanted lower compression heads that will work for the LS1 then look at the 317casting. They're basicly an Ls6 head with 72cc chambers. IMO, if you're that worried about fuel milage and have/want to drive youe car daily then keep up with your tire pressure and tune up intervals. Or, if you have an A4, then sell the car and get an M6 or swap to an M6.
While stock mine averaged 28 mpg highway and 23 mpg city and I don't drive conservatively.

 

I see, I keep forgetting that it is a 6.0L (correct?) I get pretty good fuel milage anyway, not worried about gas. I was just tempted by the lower octane and more HP benefit, and yes I do understand that there are far cheaper / easier ways to get that kind of power. It just kind of stood out so I thought I'd inquire... thanks for the info.

 

I ran 87-86 octane in my SS while it was stock. In spite of what most say, they are fully capable of it. Says so right in the owner's manual too. You'll just have reduced performance because the ECU will retard the timing.

 

The L92 heads are not useable on a 3.9" bore motor.

They are a Gen IV head and designed for the 4.0" bore stuff.

Mike