steves86ta

iTrader: (5)

Long story short I built a 6.0 for a jet boat. Specs are
LFA block (aluminum 6.0), crank, rod and pistons (same as ls2 pistons)
243 heads milled .030
BTR ls1/2 stage 4 cam 221/232 .621/.592 on 111 (if I remember correctly)
Carbed with a 750 DP
Edelbrock Victor Jr intake
Msd 6012

It ran very well. Due to my own personal eff-up it threw a rod, first trip out.

Now I plan on building a 408, but I have the opportunity to get an early 5.3 for free. It is in running condition.

I am only getting the short block, but again it's free.

I spent a very long time building the boat and really want to enjoy it this season. Problem is I really cannot afford another engine build right this minute. Probably this winter.

My question is, can I run my cam and heads on the 5.3.

My understanding is I will lose compression, but I am cut .030 already. So I should be about the stock 5.3 compression.

I'm more worried about my BTR stage 4 cam not working. Will it work? Or should I look for a used smaller cam?

The boat runs in the 5-6k range so I need to make power in that area. I know the combo will not be ideal, but I just want to enjoy the thing for this summer

JakeFusion

iTrader: (7)

Stage 4 is a 235/242 111. If it cleared on the LFA/LS2 pistons, the 5.3 may also clear. However, I would check it. Cutting .030" off the 243s will make the Stage 4 a bit tight.

The smaller bore shouldn't affect anything. But it would work... it'll probably make about 40ft/lbs less due to the displacement difference 365 vs 325 and the compression loss. The stroke is the same, so the valve events would create a similar looking graph. Just down on power everywhere.

It would get you going again quickly.

steves86ta

iTrader: (5)

Thank you for correcting me. I couldn't remember for sure.

The heads were cut on the LFA also, same exact needs luckily they weren't hurt.


Memory is a little foggy but I want to say I had around .180 clearance. But again I could be off. I do remember there being plenty.

I will of course check PTV again. I was more worried about the cam being to big and the smaller engine being unable to swallow it.

Thank you for the good news

JakeFusion

iTrader: (7)

Stock valve drop on 243s is around .155 to .160" from the edge of the valve to the deck, so you have to start there (that's the max possible clearance). You probably were in the .040" to .050" clearance range with that cam and heads cut.

steves86ta

iTrader: (5)

You're right, it was a long time ago but the more I think about it, it was closer to the .050 range. Maybe .056 that number is sticking out in my head for some reason