Hey there,
Is there any way to increase compresion when doing a rebuild.
I have an '84 gsl-se was about 117K on it. It's got plenty of life left, but I don't want to just drive it untill something goes on it. So I figure when it's time for a rebuild I might as well get some more HP out of it. I am planing on a mild street port, as this car is my daily driver. I also think Max 7 has a very good Idea about using the 2nd gen intake assem. , I'm sure there's a few HP to be had there. Now I'm wondering about uping the compression a point or so for more down low hp. I'm thinking about going to 3mm apex seals w/ double springs and I always run premium anyway so no worries there. Can this be done? How?

 

well, the -SE has the highest compression rotors of any 13B I believe, and comes from the factory with 3mm apex seals. It's kinda hard to get much more robust. OEM compression is 9.4:1. It's not like a boinger where you can just toss in some crazy new rods and pull off 11.5:1 compression or something. Your best bet might be some creative porting, or different rear-end gears. You can swap in 4.44's from a REPU and it'll give ya more quickness off the line (at the expense of top end of course, 70mph in 5th comes 1000rpm's higher than it does w/ the 4.08's that come OE in the -SE rear).

Now if you're talking compression as in better sealing on a tired engine, a rebuild should bring the compression back into the OEM range.

And there was a debate about octane a while back, in which we basically surmised that there's no reason to run higher octane than an engine needs, and us n/a boys only need about 75 octane to be ok, so running premium really isn't helping you as much as you might think...unless you've got a turbo in there I don't know about

--matt

 

Even on a rebuild you will not get 9.4 unless you get new rotor housings. So I would go with the seals and new rotor housings. I was told when having mine rebuilt that I would not obtain 9.4 unless I had new housings, But now that I do I have a spec 7 engine that meets the facotry sceps when comming out of Japan.

 

the 89-91's had the highest compression at 9.7 to 1, they also had the lightest rotating assembly.
however the rotors and housings are not interchangeable with pre -85 motors
Racing Beat makes a set of higher compression / lighter rotors, but at $3500 a set, its a bit much
there has always been a big debate on weather porting 6 ports is really worth it $ wise for the gains.
some create a 4 port 13B with 12A parts and get much more flow.
then you'll need a modified intake.