Rexv8

Hi guys had a few questions about my possibly blown 5.7. First a little back ground on my car and its current engine:

1991 Mazda Rx7 FC
Engine: LS1/T56 out 2001 Transam 90,000 miles
Exhaust: Dual 3.0 Inch straight pipe
Headers: JTR Long tube

The engine is mainly stock but I did add a 230/234 .600/.602 111 LSA cams in them few years back. The heads are 241 with LS6 Intake. Car made about 400 whp.

The other day after a 400 mile round trip I realized that there is a knocking sound that is coming from the engine. It was idling pretty rough too at the end. This might have been due to oil starvation as these engines are prone to I read somewhere. After parking the car and checking the dip stick I did find light metal shavings (Maybe Spun bearings). Anyways I am planning to take the car back to my builder and he will open up the engine to inspect it to see what the damage is.

I am now researching to get some information on the bottom end replacement of my engine. I came across a lot of people switching to 6.0 LQ9 engines as they can just plug in the ls1 stuff without any modification(Except the alternator hole) and I am looking at that direction. I am planning to switch over the 241 heads and the cams to the new engine.

This is where I would need some help from you guys I was looking at the LQ9 370s and 408s. If I use my heads with the cam which one would you guys recommend? I am not sure if I am going to go FI in the future but I am hoping to hit 450-500 hp NA.

Or should I just get a replacement new short-block 5.7 Aluminium since they are the same price as a Lq9 370s?

Any input would be highly appreciated.

Thanks

HCI2000SS

iTrader: (2)

How it basically works is take the same top end from the LS1 and put it in 370 or 408, and you'll make roughly the same peak power, but you'll make a broader torque curve overall. This is what happened when I went to my 370 from the LS1

Rexv8

Thanks for the reply HCI. Can I ask why you chose the 370 over the 408? The reason I ask is trying to find out if I want to dish out the extra cash for the 408 (I think they are about 1000$ more than the 370)

HCI2000SS

iTrader: (2)

Yes about a grand more is what I saw as well, and that is exactly why I chose the 370....budget. If I was going to upgrade the heads and whatnot then I would've considered the 408, but my budget was very tight at the time.