mcdonaldheat

I am about to convert my l98 with lt1 heads and intake. All the required machine work to the heads and intake are supposed to be done. Here is my question. It is a 86 model so will I need a new wiring harness and also what headers to get now that the lt1 heads will be on it? Thanks.

ANTI VENOM

You don't need a new harness. I thought the headers were the same.

mcdonaldheat

I think my heads are straight plug and lt heads are angle plug, right? Will the same headers still work?

Tom400CFI

Headers should interchange fine. So you had someone weld up the LT1 heads?

mcdonaldheat

Well I am buying off ebay. The seller said the intake was drilled for distributor and that the heads were welded. I dont have them yet but I should receive them on Friday. What else should I do while I am in there? I have a 282 duration .480 lift cam with 1.52 roller rockers I want to install. Will I have to get a custom tune?

Tom400CFI

I think so. I'm sure it will run on the stock tune being Mass Air, but w/that intake and cam, you're changing the shape of the tq curve (and thus, the fuel curve) pretty radically.

mcdonaldheat

Should I just buy a custom "chip" or take it somewhere. I have read there are ways to program and tune with a laptop? After headers go on and a good tune how much hp gain do you think I will get? Thanks so much for this info.

Tom400CFI

That is out of the realm of what I have first hand experience. I know that you can buy hardware and software to tune w/a lap top. Rather than regurgitate that which I have read, but don't know first hand, I'll let someone else who does have first hand experience give you the details.

DanielRicany

Try Lt1pcmtuning.com for email order tunes. You will data log and send the logs to him and he will send you a tune. You will keep doing this until the tune is good, unlike some other places that give their best guess. As for the power gain, depending on the cam that you're using, if it's equivalent to the LT1 stock cam or superior it should be at least 300 hp at the crank. With the headers I'd say 320. If the cam is superior to the LT1 cam, then obviously you're going to be able to get a little more.

ANTI VENOM

What are your goals and the reason you are switching if I might ask?

mcdonaldheat

Sorry, I have been out for a few days. The reason in why I am changing to the LT1 is the engine overheated and blew a head gasket. Rather than just replace that head gasket I am changing to LT1 and rebuilding engine while I am at it. I have gotten my parts in and removed all the top of my engine. I did find out it has been bored .30 over.
With all my research everyone says the L98 heads and intake are very limited in what you can do in performance. I would like to see 350hp at the crank but we shall see.

cadmaniac

Interesting way of having an LT1 without the opti....Gonna keep that in the back of my mind.

Drew95

I was thinking the EXACT thing as I was reading down....

mcdonaldheat

Well I got my intake all cleaned up and painted. Got the heads having the valves lapped and installed with new springs. Now just hope this combination works. I did have to purchase a new dizzy as the large cap hei will not fit without major machine work to the back of the intake. I am gonna go ahead and install a msd ignition while I am at it. Is the .30 overbore ok on a 86 block? I know they go .30 over on a 383 stroker but mine is not a stroker. I measured the stroke and it is 3.5 inches which I think makes it a standard 350 crank.

mcdonaldheat

Ok. I hope someone can help me out here again. Like I said above I now have my engine tore down and I have found something that kindof makes me nervous. As per my above post when I got the heads off I measured my bore which was 4.03 which I assumed a .30 bore size. Well today I was cleaning it all up and found P1534 060 stamped on top of the pistons. According to my research these are Enginetech pistons with a .60 overbore. This bothers me as to the engine build previous and having a block bored .60 over. But why does my calipar only measure 4.03? Please Help!

WVZR-1

OK first off it's .060 and .030 but anyway I'd guess you didn't "ZERO" your vernier caliper before you measured. I'm guessing you're using an inexpensive vernier that can be "ZERO'D" at any specific opening. You need to collapse the vernier to 'closed' and then 'ZERO' it. Not knowing exactly what tool you're using it's difficult to relate but that's the only explanation that comes to mind. Look inside of a piston and see what's cast on the inside. Maybe you've got some mis-stamped pistons. Maybe they were stamped .060 intentionally by someone. Stranger things have happened!

mcdonaldheat

It is one of those caliper tools like from AutoZone. I closed the tool all the way then pressed the zero button. I then slide it open until the flat edges contacted the cylinder walls. It read 4.032. Id this is the case there is no way they got .60 over in that cylinder and still be able to rotate engine, right? Also, if it is .60 over, thats not good either, am I right on this. Thanks.

856SPEED

Hmmm..

interesting.....I was thinking the water jackets would not line up with the LT1 heads with the Gen I block...the LT1 is a reversed cooled system.....learn something new every day I guess...interesting thread....

vl5150

I think it's an interesting project idea however there's nothing that the L98 can't conquer.*


*[with enough money]

WVZR-1

Have you removed the "ridge" at the top of the bore? Likely not and that would/might explain your vernier dimensions.