I'm looking at installing a cam and ported 5.3 castings on my lm7 5.3 truck. The cam I am leaning towards is Crane's 265LR HR12. As for the heads I would prefer a set of ported stock valved 5.3s with a possible mill to achieve desired compression. Using the SCR and DCR calc from http://www.kb-silvolite.com/calc.php?action=comp I input a few numbers to get an idea of what I could be working with.

For reference the cam timing is Adv. Duration 265/273, Duration @.050 215/223, .604/.611 lift, LCA 112, ICL 107, ATDC 20, BBDC 72, BTDC 24, ABDC 60.

5.3 lm7
5.3 heads milled to 59cc
.040 head gasket
Plug in the cam and I come up with a SCR of 10.233 and DCR of 8.449.

5.3 lm7
5.3 heads milled to 59cc
.036 head gasket
SCR 10.335 and DCR of 8.531. The .036 head gasket is probably closing the quench distance too much.

5.3 lm7
5.3 heads milled to 58cc
.040 head gasket
SCR 10.364 and DCR 8.554

5.3 lm7
5.3 heads no mill 62cc
.040 head gasket
SCR 9.860 and DCR 8.148

So help me out here. I was personally leaning towards the .040 gasket with 59 or 58cc chambers. From what I have researched that should be a nice responsive combo. What type of powerband will I be looking at? Thanks and all suggestions are appreciated.

John

 

Try here, or here...

 

Thanks, but all those links are dead. Plus I don't have a ls1, 2, or 6. I've already calculated everything correct to my knowledge however they are only numbers to me since I am not experienced in this area. I am no cam guru! Just trying to make an educated guess out of some numbers and ideas thats all.

John

 

No milling on 5.3 head is on the lower end of 61cc's