I'm sure this has been asked about a million times but I havent found it in exactly this form.

I have a 1991 coupe with over 125000 miles on the engine. It's a little woren out. I'm thinking about droping in an LT1/4 engine and trans. By looking under the hoods of several C4's at our club meeting it looks to me like everything is the same except the radiater hoses, A/C hoses and dryer mount and power steering resovier. The LT1 PCM/ECM mounts in exactly the same place.

Am I missing anything? Or is this as easy as I think?

 

The motor mounts are slightly different as well, but I'm not exactly sure how. To use an LT1 PCM, you will need the complete wiring harness as well.

Why do you want an LT1 anyway? You can make tons and tons of power with the L98. Swap to a converted LT1 intake, some long tube headers, and a cam, and you will be making more power than a stock LT1, and you won't have an opti-spark to deal with.

 

Must be pretty hard. Bogus has been trying to get one done for a year.

 

[QUOTE=Mojave;1561958411] Swap to a converted LT1 intake, some long tube headers, and a cam, and you will be making more power than a stock LT1, QUOTE]
Where Can I get a converted LT1 intake? I have heard there are problems with the thermostat when using this set-up. What do you have to do to the ECM. Can you keep the L98 ECM and just get a chip burned to deal with the mechanical changes?
Initially, it just sounds to me like a bigger hassel than changing everything out for the LT!/4 parts.

 

An intake swap could save you a heck of a lotta headache and youll be driving it, not working on it going, "why the he$# did I do this?"

Im not knocking the conversion, but unless you are real adept with wiring and have a lot of patience dont waste your time.

 

How about this for an option...

Modifying the LT1 intake that you have on the LT1 engine to accept your original HEI distributor (or go the F-body small cap distributor route with external coil), plug the vacuum port for the MAP sensor and use as many L98 sensors as you can , including the original ecm.

The only thing that you will lose is the EGR system.....

 

http://lt1intake.com/services.htm

I have not heard of problems with the thermostat. What do you gain by swapping to LT1 over L98 if you use your original electronics? Slightly better flowing heads? What about the opti hole? Put an opti-spark there and leave it not hooked up? What about the accessories? Use LT1 water pump and acessories? Since LT1 is reverse flow coolant, can't use L98 pump. There are issues here that need to be dealt with.

The biggest advantage you would gain is the intake manifold. The heads only flow slight better, and with the craptastic stock L98 exhaust, won't matter that much. Swapping over to all LT1 stuff: harness, injectors, MAF sensor, opti-spark, computer, etc, will be a giant pain in the butt.

I personally think it is WAY too much work with WAY too many sticky points to make it worth the swap. With stock L98 exhaust, we are talking maybe 15-20 hp over an L98 with an LT1 intake manifold. L98 will make plenty of power, just have to fix a few of the things holding it back, namely intake and exhaust. Add a cam, and you will be ahead of LT1 numbers with way less work.

 

It depends on what you are trying to achieve. Why not just bore and stroke your machine? Mine will make 410HP at the wheels but I had to go with a Holley Stealth Ram

 

AFAIK, if you go max out an LT1 and an L98, power difference may be about 10HP because of the reverse flow heads.

 

Rebuild your engine to a 383, put either an LT1 intake or Miniram on it.

You have a screamer.

BTW There's lots a crate motor for non-LT1 SBC.

You can even get a 454sb if you want.

 

Or if you are willing to cut your hood and put a hood scoop there you can run a Holley Stealth Ram or whatever you want.

 

Yeah like a blower

 

Mine was modified to accept a HEI, but I'm running an Opti.



Jake

 

The stock LT1 beats the stock L98 by about 60 hp with no work. Primarily due to the induction system. The LT1 also has a broader power curve for the same reason.
I have access to a LT1, complete with engine harness, ecm, motor mounts, etc. Which ever engine I go with, it wil be converted to 383 cid during rebuild (along with Comp cam, tpIs long tube headers, Random catalitic converter, Tricflow heads, 30 # injectors, 54MM throttle body and many other bells and whistles). To use the L98 and replace the induction system with the mini ram or a modified LT unit, I'm looking at $1,000.00 to maybe $1,200.00 over and above what the same rebuild would run on the LT1.
Many people make things harder than they need to be by trying to jurry-rig wiring and such, but I prefer to change out all the wiring to engine-appropriate factory harness/ecm. I would have the engine put on a dyno for initial start-up and have a new chip burned prior to installation into the car.
My primary concern was the physical layout of the engine compartment. The power steering reservoir, mounting bracket and hoses look differant. The A/C compressor, dryer/accumulator and hoses are obviously differant and the radiator hoses will have to be changed. The LT1/4 engine has a water bleed tube off the back of the heads which needs to be tied in and I would need an electric motor driven smog pump. If that's all that needs changing, it should be a snap.
However, I am considering tha L98 rebuild too.

 

 

I would not do this on a post 90 vette. The CCM electronics will bone you.

read my posts in this thread: http://forums.corvetteforum.com/show....php?t=1818318

 

True. However, when you max both systems out, I don't think you get more than 20HP difference, IIRC.