Project Thread: LS6 Top End Swap
 

For those of you that don't follow my YouTube channel, I'm going to document my stock 98 LS1 to LS6 top end swap.

So for those of you that don't know, I purchased this 1998 Corvette coupe in October of 2017. It has a Vararam ram air intake, stock air bridge, Thunder Racing cam (we think it is a TR224), Kooks LT headers, x-pipe, and some custom axle-back exhaust that can't be identified.

It currently has the stock 1998 806 heads with the 9-bolt valve covers. To my surprise, the rockers and valve springs appear to be stock as well.

I've recently purchase a set of 799 heads (same casting as the Z06's 243 heads) and a used LS6 intake manifold.


The used LS6 intake manifold I purchased is in good condition, but it was caked in oil. So I decided I better clean it out before installing it. I also purchased a Mike Norris catch can to prevent that from happening again. I can't imagine that much oil going into the combustion side of the engine is good for anything. It literally looked like chocolate milk pouring out of the intake when I was cleaning it.


Now, before I go install this stuff, I needed to dyno the car to see what it's making before the mods. Just based on my knowledge of what was already done, I expected it to make between 380-390hp. I was pretty close. It made 392hp, 402ft-lbs SEA corrected. The only reason I'm going by the corrected numbers is because it was 103 degrees with 40% humidity (11% correction). Not exactly ideal dyno conditions, but I live in AZ, so not much I can do about that.


https://cimg2.ibsrv.net/gimg/www.cor...b691fb9500.jpg
https://cimg4.ibsrv.net/gimg/www.cor...6350078705.jpg
https://cimg1.ibsrv.net/gimg/www.cor...1a8ed28aa0.jpg
https://cimg3.ibsrv.net/gimg/www.cor...9b2c86f430.jpg

Next, before I start the swap, I need to upgrade the valve springs. So I got a dial indicator w/ a magnetic mount from Harbor Freight and my friend Simon at Brighton Motorsports helped me measure the spring lift so I could order the correct springs. This was a little more difficult than I really should have been. GM put the steering rack right in front of the main pulley, so you can't get a wrench on it to turn the engine. So we tried the bump start method....that didn't get us an accurate reading. So I pulled the spark plugs, we put it in gear, and rocked the car back and forth to turn the motor. That finally worked and we got the reading we needed.


With the LS6 intake back from the parts cleaner, I decided to go ahead and paint it. I also panted my fuel rail. I also removed the support fins on the bottom of the intake to make room for the coolant pass through lines.



Next, I needed to upgrade my valve springs. To my surprise, the springs in my heads were stock. Whoever installed the cam didn't upgrade the valve springs. So since I have new heads sitting on my bench, it made it easy to swap. I went with Brian Tooly Racing valve springs.
https://cimg4.ibsrv.net/gimg/www.cor...f82f99553f.jpg
https://cimg5.ibsrv.net/gimg/www.cor...48e66b1a2c.jpg



TEAR DOWN DAY! It took about 8 manhours to tear down everything down to the block, including removing the starter and headers. I'm sure a more experienced mechanic could do it faster.


Heat wrapped the headers. This took about 6 hours.

https://cimg5.ibsrv.net/gimg/www.cor...61981c7957.jpg


REBUILD DAY - This should have gone smoother, but the headers and starter, again, waisting crutial time.


Sadly, after all the hours of work, the engine wouldn't start. It wasn't holding compression in any cylinder. After some investigation, we found that we were using the wrong pushrods. We were reusing the 7.400" pushrods and with the LS6 heads you need to use 7.375" pushrods. So we ordered those, installed, same result. No compression. We determined that it must be the heads/valves.....so, tore it apart again, and sure enough the valves were leaking badly.


REBUILD DAY #2 - The machine shop inspected the heads and it was determined that as one time the metal between the exhaust and intake valves was cracked. Another shop hammered a metal rod in there to fix the issue but didn't do the valve job after. So ever single valve seat was slightly out of round and leaked. So we did a complete valve job as well as resurfaced the mating surface of the heads.


Now the car is back together and up and running. Next step is dyno tune.




To be continued....

What kind of Dyno was that. Good numbers but it seems just a tad too high given the modifications. Dynos can be all over the map sometimes. What matters really is measurability after mods.

I have no idea. It was an AWD dyno. I've never seen one like it.

Your planning to use the same dyno and correction later, no? Optimistic or not, changes should still be relevant.

I'm going to a different place to have it tuned, but when all is done I will bring it back to this same dyno to compare.

Added to the OP. Painted intake and fuel rails, as well as upgraded my valve springs.

Just asking:

Are you going to replace the:

Oil pump
Lifters
Lifter buckets
Timing chain
larger diameter pushords
Dampener

I upgraded to:
ARP Damper bolt
ARP Head Studs
DAYCO/POWERBOND Dampener

Short answer, No. I don't feel all of that is necessary. I'm literally just upgrading the top end to what later year LS1's came with from the factory. I do have new head bolts/studs. I also have a new MAP sensor for the intake.

nice thread, i'll follow you on youtube!!

Added the tear down video and heat wrapped the headers to the OP.

Updated the OP with a bunch of updates. Car is back up and running. Need to tune it now.

COOL!! Keep us updated on the R E S U L T S !!

BC

Love the exhaust tone. That just sounds right.

Added Varraram air bridge and oil catch can videos to the OP. Dyno tuning video coming Friday 10/26.

Subscribing!

Tuning results posted!