Hi People,

I'm in the UK where cheap LS motors are pretty rare but I've come across a 2007 LY5 5.3L that I'd like to do a cheap turbo motor for a sleeper project.

Plans would be to pretty much copy Parish's Fairmont build for a gen 1 RX7. So basically a budget turbo etc with a glide for some cheapish fun. No daily driver stuff but a street car and decent fuel and meth wouldn't be a problem.

From what I can see these motors have 9.9:1 compression ratio that isn't great but whats the general opinion on these for a boosted donor motor?

A mate in LA works for Isuzu and can get L92 heads cheap, do they have a bigger chamber that would help lower the compression for boost?

Thanks in advance

Steve

 

I believe the L92's won't work due to bore size. Maybe the 317 heads? Do you know the combustion chamber size of the LY5 heads?

 

The only thing I've been able to find was on a truck forum which said castings 799 or 243 with 64.5 cc chambers.

Just found this which backs up your comment on the bore size, cheers for that - http://www.crateenginedepot.com/stor...ty-W63C10.aspx

Been looking on Performance trucks and the 317's would drop the compression a point so would do the trick.

What's peoples views on boosting on top of 9.9:1 compression?

Would ultimately like to been in the 500 - 550 range.

Thanks

Steve

 

I dont know the difference between the LY5 and the 5.3 I have, but mine came out of 2000 silverado. But the 317 heads on mine drop it down to 8.6:1 compression.

 

Hey Gotzy,

So, I am looking to Turbo my Avalanche and it has a 5.3 LY5 engine. my question is, will the 317 heads work? I would like to know if they worked for you?

 

Lots of people boost the higher compression 5.3s with no issues.

This isn't the 90s.

 

Lol. You mean 8.0:1 with a 6-71?

 

I just found out that I have the 243 heads. So I am thinking I will be OK with the stock heads.

 

Im running a 7875 .96 @ 17psi on a LY5 right now, the stock heads are 243 which makes compression 9.9... i swapped my stock 241s on because it has a bigger combustion chamber, im guessing its in the 9.25:1 area now.... i wouldnt do 317s because mine is pretty sluggish out of boost as it is, if i could do it over i would have used a bigger cam or even stayed with 243 heads, higher compression and boost is becoming more common with proper tuning...9.9 isnt even very high anyways