I am considering buying an 85 or 86 coupe that is in need of some engine help,, I have a brandnew 355 in my garage that I was thinking about swapping in. I plan on keeping the original and getting it sorted out down the line. My question is this. My 355 has a Part Number 12-416-8 cam
Grind Number CS XM 264HR-12
Intake Exhaust
Valve Adjustment 0 0
Gross Valve Lift 0.488 0.495
Duration At 0.006 Tappet Lift 264 270

Valve Timing At 0.006
Open Close
Intake 22 62
Exhaust 69 21

These Specs Are For The Cam Installed At 110 Intake CL
Intake Exhaust
Duration At 0.05 212 218
Lobe Lift 0.325 0.33
Lobe Separation 112

this combined with edelbrock performer heads 1.6 roller rockers and stock approx 9 to 1 compression,, what would need to be done to the computer to get this engine running at its optimum. I do have a ram jet cam that I could swap but would rather not, as the engine is already assembled. the short block of my engine is out of a 98 pickup. I would like for this to go as smoothly as possible. Any info , is greatly appreciated.

 

the ram jet cam will not work with the L98 computer.
buy an 86, the computer has more ram, and is faster in fuel caibrations.
TPI specialties has various computer friendly cams for different RPM driving ranges (cruise, high RPM, etc.)

 

Can a custom prom be burnt to work with this combo?

 

I'm not sure I understand or agree with this reply. The L-98 was in 85-91 Vettes. If the ram jet cam will not work with an "L-98" computer, why suggest that it would work with an 86?. Yes, the 86 ECM is better than the 85, but that is because there isn't one "L-98" computer. The ECM capabilities of the C4 were improved pretty much every year. The 91 ECM was substantially better than the 85 version, but the 85 was a capable EFI system. As far as I know, the 85, 86, and all L-98s through 91 used only one O2 sensor for closed loop. The later ECMs are substantially better, but the inputs still come from only one O2 sensor source and similar temp sensors. Are you saying that the ram jet cam is so radical that it is beyond the capability of the 85 ECM to handle the closed loop sensor info? Or are you meaning that there isn't a good memcal bin available for that cam and the 85/86 ECM? What is your source for this?


johnfharding, Yes I believe that a custom chip could be burned that would work with your setup. You might check with
CF supporting vendor ski_down_it http://forums.corvetteforum.com/member.php?u=22200
or Alvin http://forums.corvetteforum.com/member.php?u=48394 of PCMs for Less.

I'm not that knowledgeable about your particular setup, but it seems to me that if you had a good operating O2 sensor and ECM, with a decent scan tool, you could supply a scan of the car to one of the above guys who could set you up. You might also be able to use an 86 or 87 ECM in an 85 by replacing the critical components of the 85 harness with those needed to support an 86 or 87 ECM, if the cost you save by buying the 85 is enough to afford the ECM/harness upgrade.

 

I don't see why not, that cam/set-up isn't very radical. Since you are looking for a car, newer is better, in your case because of using the L98, up to and including 91...see above

 

Coupe,, that should change things a little. What do you guys think. I made a mistake in my initial notes on the car I'm looking at.

 

I am sorry that you took my reply to infer that the ram jet cam would work with a 86 and up computer.
What I meant was that you won't be able to smog the vette with the ram jet cam. (in Arizona)
The cam will work with the computer to run, drive, but I do not believe it is smoggable with the 85-86 specs. I have a friend that bought a ramjet, and used all the L98 sensors etc. He tried and failed smog 4 times, and had to go to the arbitration board, they smog checked his car, and again refused to issue him the tag, and told him it was off-road until he fixed it.
He took it to a speed shop, and they said they thought it was the cam.
He pulled the engine back out, changed the cam to a TPI specialties cam, and then took it back to the speed shop, and they put the sniffer on it, and it passed.
He took it to the arbitration station, and they put it on their machine, and it passed there also.
The only change he made was the cam and gaskets.
the '85 computer only came out in '85, but the '86-'89 computer is the same one all those years.The '90-'91 computer is only those years.The burnoff module is an add-on that was introduced in that year only. They found out that the hotwire accumulated fuzz or dust, and needed to be cleaned, and the addition of this model was included only in '85. The burnoff function is inside the 86 and up computers, Burnoff relays are still required because the computer is only a controlling component, not the component that actually delivers high current. It would make sense if you were using the L98 equipment, to get a car with those years because the interchangeability in those four years would yield more parts, at less cost due to the larger number of cars produced, and conversely, more of them scrapped or parted out, giving you less expensive, easier to find parts.
The reference I made to get an 86 was using that logic, in addition to the added ram in the computer that makes faster calibrations. The chipsets are floating around everywhere on this forum, and you might be able to get someone elses chips since this breed of vette owner is constantly in search of more speed, torque, horsepower, driveability, and people chage them a lot. There are many ways to go, the ramjet engine is a good one, the computer is compact, easy to install, but it is a marine cam, and for street use, would be acceptable to a car that is older, and not subject to smog inspections of an 80's car..
Sorry for any misconception that was perceived.
Chris

 

Your cam is almost identical to the one I have in my '85 and I had ski_dwn_it (Jesse Azzato) burn a chip for me which really works great. I have a few more mods than you at this point but when you buy a chip from Jesse he will upgrade it for free as you add mods later on.

 

I read a lot on his website and customer reviews,, sounds like the guy I will need to talk to.

anybody have any idea what kind of horsepower this would make?

 

coupeguy2001, Thanks for the explanation. That makes a lot more sense to me now. You may indeed be correct, in that the ram jet cam is too radical for the given vehicle/smog requirements of Aridzona. However, it seems to me it would be worth a shot to at least having a go with a good OBD1 Vette tuner to make it work. What did your friend do in terms of chip tuning and mods for his 4 attempts? Did he try to tune the car himself or did he have a pro do it? Since the subject car is an 88 and not an 85, the ECM would be more capable, but the smog rules may be more restrictive.

 

it is all stock. he was under intense scrutiny since the arbitration boys got involved, they asked him to pull the computer to inspect the chip, and had a cheat manual to verify all of the components were installed, then they tested the EGR, the mas burnoff, the smog pump suction, diverter system, a tail pipe sniffer, the gas cap, a stick -on thermometer to insure the car was getting up to 185, yadda yadda yadda. we were there almost 4 hours while they played around.
He got so frustrated he parked it, and was talking about selling it to his uncle. That's when he took it to the speed shop, and they said change the cam.