LT1 Conversions

[91lt1]

Okay, I know some of you will not agree with what I am doing, but it works for me. I have a 89 L98 that needed a total rebuild, so I have installed the crank, rods, pistons, cam and roller lifters from a 91 LT1. As the L98 has TBI and normal distributor, I am questioning where I should set the initial timing? L98 would have been set at 0 BTDC. My thoughts are that the new version should be set 8 to 10 BTDC. Has anyone used this combo, or have any info or thoughts on what I'm doing?

 

[hoosierdaddy]

Welcome To Corvette Action Center

Okay, I know some of you will not agree with what I am doing, but it works for me. I have a 89 L98 that needed a total rebuild, so I have installed the crank, rods, pistons, cam and roller lifters from a 91 LT1. As the L98 has TBI and normal distributor, I am questioning where I should set the initial timing? L98 would have been set at 0 BTDC. My thoughts are that the new version should be set 8 to 10 BTDC. Has anyone used this combo, or have any info or thoughts on what I'm doing?

The only LT-1 that I am familiar with is the 1972 LT-1 350CI/350HP, timing setting will be regulated by where it runs the best I would say! Not sure you could even begin to preset the timing and expect that to be right when nothing else is engineered for it, maybe I'm missing something here While I'm not an expert, hopefully someone else will tune in here.

I did want to welcome you to WELCOME YOU TO THE GROUP THOUGH

-Bill

 

[KANE]

Okay, I know some of you will not agree with what I am doing, but it works for me. I have a 89 L98 that needed a total rebuild, so I have installed the crank, rods, pistons, cam and roller lifters from a 91 LT1. As the L98 has TBI and normal distributor, I am questioning where I should set the initial timing? L98 would have been set at 0 BTDC. My thoughts are that the new version should be set 8 to 10 BTDC. Has anyone used this combo, or have any info or thoughts on what I'm doing?

I think it sounds kinda neat actually. Non-stock stuff is fun!

L98 cam...
.415" IN /.430" EX

LT1 cam...
.447" IN /.459" EX

That should be higher lifting cam- I don't think that will throw a code. The MAF system should keep up with demand- but it also might be too much outside what the ECM can account for.

Anyway... start with the L98 setting. The ECM thinks that's what it is anyway.

FWIW- your timing tables are largely related to the heads. I've worked a lot with my SA tables to get to what my combo needs- but I can rewrite my SA table and upload a new one with the ECM I'm using. With a stock ECM, you should add or subtract from the base timing in 2* increments. Yes- that will move the entire spark table- but it should get you in the ball park for spark.

To get the most out of that cam, the heads, and the intake system... the SA tables may need to be tweaked and may be some other settings.

Have you thought about a custom burned chip or stepping up to something like EBL from Dynamic EFI ( DynamicEFI )?

 

[91lt1]

Thanks for the feedback. I set the initial timing at 0 per the L98 spec. Engine turned over and fired right up. Sounds good, can't wait to get the breakin runs completed and see what this thing can do. I can already tell, it has a lot more power than the stock L98 ever had. I also like non-stock stuff, kinda like taking a good ride, and making it better.

 

[Tom Bryant]

Welcome to the CAC

Sounds like a fun car.

Tom