I've read the article about the 706's being the best factory head for performance, ok, but my question is how much better do you think the 243's would be if you just milled them to get the same compression ratio as the 796's. Btw this is for a 5.3, I don't remember what motor they tested all these heads on. Thanks

 

The 706 isn't "the best factory head for performance"; it's the best on the 4.8 and 5.3, in unmodified condition. That's IT. They have smaller valves and otherwise less flow than any others.

243 is better generally. Has larger valves and better ports. They might be better on a 5.3 but only if it was set up for higher RPM use. Not in a truck w stock converter for example.

 

I think people forget that particular context. The 706 keeps the flow velocity up for those smaller engines, making good torque for them. The 706 would choke anything larger.

 

Thanks for the responses guys, like I said it's going into a 5.3, with a small cam, but then if I were to get work done to the heads, which should I do it to?

 

243 milled

 

I would go with some 706's as they are quite common, and do a bowl blend on them (that is where the majority of improvements of a port job are) and mill them to the desired compression. I think you will have surprising low end and throttle response!

 

on that test, the 706 was only 2 hp better on a 5.3. That can be attributed to the compression increase.

 

^^^ This ^^^

Which means, cleaning up all the weird angles where the seat cutter got jammed into the casting, and the irregularity around the guide, and any particularly obnoxious casting flash anywhere. All without changing the basic shape of the port, and by removal of the least possible amount of metal.

Most of the rest of that stuff you hear about, above all "gasket matching", is just eye candy to dazzle those easily distracted by shiny things.

 

Lol, I like shiny things,only kidding. I appreciate your answers, the reason I asked is because i have both sets of heads, but the 706's were on the motor when I bought it.

 

Send the 706's to Texas Speed and you will be amazed what they can do, 243's also then HANG ON!!

 

You can also have 2.0 intake valves put in 706 heads.

 

TSP's Stage 2.5 includes 2.02 intake valves. $950 plus springs on your head cores

 

I know tsp does very good work, but this is,was, suppose to be a budget build, lol. I was basically wondering if I just had both heads milled, without having to change pushrods, and cleaned up and some kind of valve job, which would be better? I'm assuming they'd be pretty close yet.

 

What's your opinion on the 862's on say a 5.3 LS stroker 383?

 

Better than my opinion of a 5.3 stroker.

 

I'd suggest the extra port volume of the 243 casting on a stroker.

 

I have a 4.8/5.3 over here with some 862s on it that I'm looking to do something with. I picked up some 243s from a member on here last year so I'm keeping my out for an LS2 block.

 

862's and 706's are like 243 and 799's same head just different casting process. I just got my 862's back from the machine shop with 2.00 intakes and 1.57 exhaust anxious top see how they perform..