jreid1000

Well I got my 94 MX-5 with the used 99 Z-28 LS-1 finished enough to be driveable. Did 300 miles of medium duty test drives and developed an engine knock.
Dropped the oil pan, and found a badly spun #1 rod bearing. Crank isn't worth saving...36 under.

Engine is now out of the car, stripped down, block is cleaned and honed with new cam bearings.

Any suggestions on mild affordable upgrades or engine rebuild parts sources would be appreciated.

Jerryg

I have built several LS based engines and I have some suggestion but first I need to know:

1. Will you be tracking the car specifically will the engine be seeing high RPM frequently?

2. How comfortable are you with doing the work yourself (are you handy with tools)

3. Are you willing to have the ECU re-tuned

Jerry

Do you have the 241 heads or the 243

jreid1000

Hi Jerry,

No plans to do much tracking, Lots of autocross and it's a daily driver.

Very comfortable doing the work myself... I don't press in cam bearings, wrist pins, or surface my own heads.

I had the ECU preliminarily reflashed locally to eliminate the VATS, 1/2 the O2s, and the evap canister. They will do more when I get to that level.

I actually have to check to see what heads I have....Senior moment lol. I will let you know.

Thanks,
Jim

Jerryg

Ok Jim my suggestions fall into two groups cheap horse power mods and reliability mods

Cheap horse power

The number one best mod for stock heads is to do a hand porting job, I’ve seen between 20 and 25 HP increase by doing a hand porting job in my garage using $40 worth of tools and the best thing is the second set of heads you do is almost free. I know you can send them off to be ported or better yet buy a set of AFR heads and get more HP but remember CHEAP is the goal. If you have never ported heads before go to YouTube and search for “How To LS1 DIY Head Porting” he showed you everything you need to know. Now he uses an expensive looking die grinder that kept me from trying it for a while “remember CHEAP is my goal” but I finely tried it using an ordinary drill motor and it work fine.

The seconded Cheap mod I would suggest is to bump up you compression ratio by going with a thinner head gasket. The stock LS1 head gasket is .051 thick and has a CR of 10.1 you can push the LS1 to 10.5 with no detonation issues at all. Since you will have to buy new head gaskets anyway look at Cometic they make a .041 and a .036 for the LS1. But for reliability I stick with the .041 and since the .051 and .041 are the same price FREE HP!!!!

Now the reliability mods

First balance you piston assembly its free, fun and will reduce vibration. I’ve seen as much as a 5 gram difference in a set of stock piston and rod assemblies. I like to match them until they are all within .5 grams

Now we start to spend money.

Replace the stock timing chain with an LS2 stock chain it’s stronger and a busted timing chain is a very bad thing.

And finally consider upgrading your rocker arm trunnion bearings with a captured bearing set for CompCams it will cost $150 (I know NOT CHEAP, but I lost a rocker bearing once and it pissed me off)

Hope this was worth the time you spent reading it, and to brag a little this is the 6.0L I just finished for my upcoming NB build. Should put out 420 Hp.

jreid1000

Jerry, Thanks for the great info! I do have the 241 heads. I have a few more decisions to make and will keep the rebuild progress updated. Thanks again! Jim