85z51vette

I am rebuilding the engine in my '85. The block is going to be bored .030 over. I will be using 8113 heads from an '89 Vette. With those heads, my CR will be right around 10.41:1. I plan on using the Comp Cams XE268H-14 cam. Specs on that are 224/230 @.050 .479"/.480" lift, 114 LSA. Induction may remain mostly stock TPI for now, except for a K&N filter and taking down the EGR walls behind the TB in the plenum and maybe some porting on the runners. Exhaust currently consists of stock header/manifolds, and MidAmerica true duals out to Flowmasters. I am using the Hypertech cap/coil/rotor setup and also the Hypertech chip and 160* stat. I know it will run with the current chip, but just how good/bad? TIA!

vader86

youll need a new chip for that cam, a custom chip. otherwise it will prolly run like crap

85z51vette

Thanks Vader. Anybody else wanna chime in?? :cheers:

cohocarl

You may want to get ahold of Marcho Polo for a chip. I don't know if he's still burning chips, but he burned me a couple for my 85 that work great. He may have some experience on how well that cam/computer combo will work in the 85.
Is that cam their bigger "computer" cam? With 114 lsa, I would think even with that much duration, you should still get enough vac, but I'm not sure.
I would think the tpi would be the "bottleneck".
I'm not 100% certain that this mod works, but have you considered siamesing the intake base?

65Z01

I don't think you need a chip, just an AFPR to tune fuel to air at WOT. Your stock 22# injectors at 50-55psi should support 350hp or more.

You might conisder an ECM upgrade as later years were faster.

You can port your stock exhaust manifolds to remove some restrictions.

Have those 113 heads worked: pocket porting, larger valves swirl polished, necked and cut back. A set of ProMagnum RRs on 7/16" studs would be a good idea too.

With your modified ignition, cut back the spark plug ground electrodes and gap to .045" for a HP gain and more efficient burn.

Gut the MAF and install a 52mm TB. I recently was at AS&M, saw their TB and liked the workmanship better than my BBK unit.

You might have the block decked to reduce the quench area and make that motor less octane sensitive. You can have the combustion chambers worked a little to retain that CR and it will contribute to a better burn.

Check your new motor/ECM with a scan tool. If you're getting any false knock counts, upgrade your ESC per my C4 Tech Note.

It sounds like you will be building some nice power soon, good luck.

85z51vette

I am pretty certain 85's came equipped with 24# injectors. I was told that by people here. An AFPR would probably still be a good idea.

I had planned on doing this; removing the AIR tubes protruding down into the tubes.

I think I may leave them alone for now, as $$ is of concern. But, how much would a job like this cost?

I descreened my MAF already. A bigger TB might be further up the road.

I certainly hope so! Thanks a lot for all the tips! Keep 'em coming! :yesnod:

85z51vette

Yes, this is their bigger "computer" cam. It is listed specifically for moderately modded TPIs on their cam chart. Vacuum should be fine like you said, and the '85 is MAF only, so there is no MAP sensor to worry about vacuum for. I know it would run better with a custom tune, but I wanted an idea of how the "stock" Hypertech chip would work with it. Thanks again...

cohocarl

Oops...didn't read about your hypertech chip. I think that would work fine.

If I get a chance tonight, I'll try and "build" your motor with those heads & cam on Dyno2000 to see what it would put out.

cohocarl

Sorry for the size of the file, but here's a pic of a motor I built in Dyno2000 with the L98 heads and that cam. (as close as I could come, 10:1, small tube headers w/mufflers, tpi, 660cfm) I don't know how close the program comes to real world hp, but this is what it says:




[Modified by cohocarl, 8:25 PM 2/26/2002]

85z51vette

Wow!! Thanks a lot man! 330HP and 405ft/lbs of torque I can live with! I know its just a guestimate, but much thanks! :cool:

65Z01

I'm not sure about head work but would think it's of the order of $500. It would realy enhance the benefit from that cam. Might be worth holding off on reassembly till you have the $$ to get it done. Check out the HP gain in the data I sent you.

85z51vette

Looks like they dropped another .4 second and gained nearly 3mph with the head work. Very impressive. Very tempting...

85z51vette

TTT. :crazy: :yesnod:

GlockLT4

Yeah, you're going to need a chip for sure.. stock idle is NOT good enough for a cam like that. When I drove my car home from the shop with stock programming, it would have died at every intersection if I didn't kick it into neutral.

85z51vette

ok, you guys with knowledge regarding ECMs chime in.. 85 was MAF only system, only measures air consumption and calculates fuel delivery based on that, so essentially it looks up a/f ratios in the fuel map based on coolant temp..corect me if I am wrong. so even with a healthier cam reducing the manifold vacuum, all the computer will see is the engines air consumption and bases load on that. maybe since it will breath a little better I can see maybe increasing the fuel pressure a bit to give the engine more fuel throughout the load range. you guys with MAP systems..well..this is a totally different ball game..once you drop in a bigger cam and lower the vacuum, the computer instantly sees this as an increased load and then increases fuel delivery..hence, rich running car. this is all based on theory, correct me if I am wrong again, just want to set things straight.

:cheers:

VetNutJim

Don't forget to plug the O2 sensor into the equation.
The air flow measurement is only half the picture.
O2 provides the feedback to allow the system to run in 'closed loop' mode whereby it adjust injector pulse width based on air intake AND oxygen content (A/F mixture) in the exhaust gas.

Essentially, this is how it works.

Hope this helps complete the 'picture' for you.