JE 9.5:1 for 2.7 worth doing?
 

I'm building a 2.7 and I have a nice used set of stock 8.5:1 Nikasil pistons and cylinders. I'm thinking about going with JE 9.5:1 instead. Everything else will be stock, is it worth the extra $1000 to go with the JE pistons ? In other words will I gain enough horse poower to notice it? Anyone out there that has done this and can comment?

Thanks

Yes and you can get at least half of the $1000 back selling the 8.5 pistons.

Hello David,

I live and race in Albuquerque, just over 5,000 ft elevation. I installed JE 9.5 pistons 3 years ago hoping to regain some hp lost to high altitude. Retained the CIS and stock cams.
After running this way for the next year I felt it wasn't what I hoped for. Very little gain.

The next year I got rid of the CIS and stock cams. Weber 40 IDA's and Solex cams brought the motor to life.
I already had my exhaust back dated to the more free flowing '74 system with a low back pressure muffler.
I knocked 3/4 secs from my lap times.

The next year I replaced my 8:31 915 Trans with a 7:31 915 trans from a '72.
On the 1.66 mile 14 turn track I picked up 2/3 seconds. I went from 1:39's to 1:36's.

To answer your question, to fully obtain the benefit of higher compression pistons you need to help the motor breath better with more aggressive cams that cannot be run with a CIS system, free up the exhaust and and add 40 mm Webers. This is a great combination, reliable and proven.

The down side is of course it will not pass smog in many states. '74 and earlier models are generally exempt from smog.

The carbs can be set up for performance or mileage by going with larger venturi's for performance or small vent's for better mileage.

My car is a track car. I rarely run it on the street, although it is licensed and legal where I live.

so 2.7racer, bottom line on the JE with stock CIS was you didn't notice much difference? I will be using an 74 and earlier exhaust but otherwise stock.

I went with 10.5 JE's on my 2.7 w/Webers. Runs fine w/premium gas. Absolutely a BIG jump over 2.7CIS motor. This is primarily a street car BTW.

cams?
 

Hi Jeremy,

Did you change the cams?

I have some JE pistons for stock 2.7 barrels that have maybe 500 miles on them. When I rebuilt the motor again (very shoddy work on the first rebuild) I decided on 2.9 Mahles. Make me an offer.


Daniel Cooper

David,
Keep in mind that with the stock CIS pistons you cannot upgrade the cams (much) because of limited clearance. The J&E's have deep valve pockets so you can upgrade the cams at a later date if desired. If you have no plans for future upgrades the boost of compression is not cost effective. Just my $.02
Lyn

2.7 Je
 

Hi Daniel,

Since I'm sticking with CIS it sounds like the JE will not give much advantage. I have a nice used but in spec set of Mahle 2.7 nikasil that I think I will go ahead and use. I might consider them if they were real cheap in case I change my mind in the future and decide to go with carbs. and a bigger cam. I'll make you a low ball offer, $250 shipped?

Let me know,

Thank you,

David

For a hot 2.7 CIS motor, Wayne in his book recommends 9.8:1 JE pistons with 964 cams and backdated exhaust. Basically the same thing as the 3.0, FWIW.

Aurel

JE Pirstons
 

I read that in Wayne's book and I was hoping to hear from someone that did his recommendation, 964 cams etc and what the results were (dyno or seat of the pants).

I'm definately going to back date the exhaust and I'm wondering if just that and JE 9.5:1 will make a difference? of if I should just stick with the stock 8.5:1 Mahles?

Hey Daniel, I sent you a PM- are your JEs still available? They may be worth doing for me!

_curt