omc8

iTrader: (7)

Ok here is the battle 383 with LS7 heads versus 427 with LS3 heads.
Both engines would have the best cnc versions Both appox 11:1 cr both would have comparable cams spec to displacement and heads . And both would be running factory style intakes . I think I know who the winner is hear but, I would like know the estimated power of these two are .

briannutter

Bore is too small for either head on a 383 3.903 bore size. Physical contact of intake valve and bore with LS7 and poor performance of LS3 on that bore compared to cathedrals. Go big.

omc8

iTrader: (7)

No no no , let me clarify the 383 would be a 4.10 bore with 3.622 stroke . The 427 would have approx. bore of 4.125 I believe the problem with running the LS7 heads on a smaller bore is contact with the exhaust valve not the intake .

briannutter

Ok, that makes a lot more sense as 388's are more common, but why 4.100 instead of 4.125 or greater? Coincidentally, Danny Popp is a Corvette roadrace buddy of mine just had a LS7 headed 388 done by Lingenfelter for his Optima car for the reason that he wants to extend the RPM range and lower the torque to manage the 200tw tires used in the Optima batteries USCA series.

omc8

iTrader: (7)

That's cool , how much power is that 388 putting down ? Too bad they don't run that at Mid Ohio or I would go up and see that. May end up going with a bigger bore just depends.

Bout'ItZ28

iTrader: (19)

What is the goal of the car? Short answer is I would go with the better head (LS7)

omc8

iTrader: (7)

Are you saying you think the 383 w/LS7 heads will make more power . The car is not going to be an all out race , it will need to have good drivable manners as it will see time on the street .

omc8

iTrader: (7)

Anyone what to guess which one and how much power they can put down .

Bout'ItZ28

iTrader: (19)

Yes!!! Getting air in and out is the game. The ls7 is a better flowing more efficient head along with a better intake manifold. Now if you cam the ls3 for a 427 motor and run something along the lines of a 250/260 duration in comparison to a 383 ls7 with a 240/250 duration cam you would be selling yourself short on the 383 motor. Just my opinion I would run a cam close to the same size as the 427 motor and shift a little higher.

Its about setup and what you do with it. Either one can make more power than the other. Which setup is the car more optimized for (ex gearing, converter, shift points, weight etc.)

gnx7

iTrader: (28)

The motor I bought was a 4.185" bore 3.27" stroke (360ci approx) and made 625rwhp at 9000 rpm on AllPro LS7 430cfm heads and AllPro single plane intake. It spun to 10k. With a Marcella tunnel ram and dual carbs it made 675rwhp approx.

omc8

iTrader: (7)

Interesting , what was the rod length ...... 6.30 maybe ?

gnx7

iTrader: (28)

yes... 6.3" Howards billet rod