I currently have 706 heads on my cammed NA 4.8 I know that they are 9.5:1 CR. What I'm wanting is to get the most out of 4.8 while its NA. I plan to add a 76mm turbo in a year or two but I want a little more out of the 4.8 in the time being. My question is what would be the best CR for the 4.8, should I have my current heads milled, P&P. Or go with another head to have worked over? I was kind of thinking a good bump in compression would net me a descent gain, thinking somewhere in the 10.5:1 range. I would just throw some 243 heads on but I think the 64 CC would be a little large for the small bore 4.8. Also would I benefit from port matching my stock truck intake? The heads will be coming off and stock 706 heads will go back on with a good P&P after I add the snail. What do y'all think????

 

Also if I did run the 243 heads would I lose what down low TQ I have switching to a LS1 style intake?

 

Pick another cast 706s crack mine did anyways it would suck to spend money on them getting them worked over and then they crack

 

I've heard that, but I think its only the sand castings that have this problem? Could be wrong though

 

How do you know which ones you have

 

You can tell from the surfaces that haven't been machined, like inside ports and so on. The sand castings will be rough with a lot of inconsistencies while the die casts will be smooth and symmetrical