Sorry cant figure out a better title to describe my question. I just ordered a 440 shortblock from texas speed (4.185 bore x 4 inch stroke) to replace my ls2 that threw a wrist pin out the side. I'm plan on using a lot of parts from my old motor, including the entire top end. Being that its very similar to an LS7, I've been shopping ls7 cams. It just occurred to me that I can't just buy an LS7 cam for this because of LS7 rocker ratios are apparently 1.8:1. Is this the case? If so, do I just need to have a custom cam specc'd to achieve the lift that I'm going to need on this new motor with a 1.7 rocker? I'm not going to be using ls7 heads. I'm leaning towards something similar to a BTR 4 LS7 cam because my old build had the LS1 BTR 4 cam and it drove great and made excellent power.

 

This very easy to use calculator will tell you what lift you will get switching between various rocker arm ratios (ie: between a 1.7 and a 1.8 ratio)

http://www.wallaceracing.com/rockercalc.php

 

Example:

My LS3 has the stock LS3 cam in it. With the stock 1.7 rockers, the lift is .551” / .525”

I installed 1.8 ratio Comp Cams roller rocker arms. The stock LS3 cam now gets .583" / .556" lift.

 

Alright awesome. So custom grind time. Forgive my lack of knowledge on the topic, but I won't run into any physical size limits of the lobes on the camshaft compensating for smaller rocker ratio will I?

 

I can't see that you would. Just tell the cam grinder what intake and exhaust lift you want based on either a 1.7 or a 1.8 ratio rocker arm.

Just give Cam Motion a call

 

Appreciate the knowledge, thanks

 

I re-read your initial post ... I understand you want to use LS3 heads on a LS7 block ?

I don't have the answer, but maybe someone here can tell you for sure if the LS3 heads can be used on an LS7 block.

If you can use the LS3 heads on your LS7 block ... just make sure you are clear about telling Cam Motion that the cam is going into an LS7 block with LS3 heads and LS3 1.7 rocker arms ... then give them the cam specs you are wanting for use with 1.7 ratio rockers.

.

 

Kind of. As far as I know the heads will work just fine, I just need to get the cam specs correct. The Texas Speed motors actually start life as a 5.3 aluminum block and are resleeved. It just so turns out to be that the displacement is really similar to an LS7 so I figured that would be a good starting point for cam research.

 

I will say that I'll 100% be going through cam motion though. I forgot about them and that was the only regret I had about picking my last cam.

 

You're going to use LS2 heads on an LS engine with a 4.185 bore and 440 cubic inches?

 

yup. I'll post the dyno numbers and let y'all know how it goes. car made 495 rwhp with them on an 364. If the results are bad i'll swap em out, not really a big deal.

 

As you may already know ... The combo stock LS2 cathedral port heads and LS2 intake manifold don't flow nearly as well as the LS3 rectangular port heads and LS3 intake manifold.

Just saying ...

 

You can probably get decent 821 heads and intake for around $700 with some shopping.

 

Yup ... And then he can buy from me my low mileage matching LS3 intake manifold . . .

He's going to be fast ! . . .

 

​​​​​​​They’re CNCd, and paired with a ported fast and a nw102. It was either build a regular old stroker or do the 440 for an extra couple hundred bucks. Seems like a no brainer to me.

I already own everything else, I had no intention of doing the upgrade otherwise so it’s not really a detractor for me. It’ll be interesting to see how the combo fairs though haha.

 

It'll be a torquey **** for sure. Those heads are really going to limit you though. The good news is that the top end you have now is a really good one...for a smaller engine. Good trade bait for when you want to get serious about making some hellacious power. That foforty is going to want to breathe.