243's or worked 862's?
 

Is it worth porting 862's to flow the same as 243's? If I recall, the 862's have an even smaller combustion chamber than 243's, but they don't flow as good. I'm talking about putting them on a LQ4. Reason I ask is because my dad's Silverado has them, and if he wrecks it or the tranny blows up or something, could I throw the heads on mine after they've been ported? The motor will most likely have a cam, long tubes, and a good tune.

I am curious to this as well. I have a set of 862's on my LS1 and know that they do have the smaller combustion chamber for higher compression. I believe Ported 243's will flow much better than ported 862's.
I am sure someone will chime in with better info.

Better port in the 243's vs. more compression with the 862's. The difference is probably negligible, however, some of the 862 casting were prone to crack and leak water. Those are the Casttech castings, which have the battery logo.

Unless you get some hack-job hand port, you're going to end up spending 1k for a quality port job vs. ~400 for 243s. That right there would not be worth it to me unless I'm building some sort of racecar, at which point I'd just spring for the ported 243s for a few hundred more.

For 1k, you can find quality ported 243s used on here that will blow the 862s out of the water.

$1000 to port heads?

For some reason, I had in my mind that it was about half that. I suppose it could be, for a crappy job.

243 it is! Thanks guys!

Cnc porting is expensive because of the R&D and the tooling/machine needed to do the job..

Hey KCS, sound familiar? Lol

Places like AI, TEA, WCCH, Livernois, Lingefelter, Cartek, Landspeed etc. are all in the 1k+ range.

A random no name porter might charge you 7-800, and an amateur with a grinder prolly 4-500.

LMFAO, deja vu...

If it were me and I had a budget of about $400, I would go with the 862 castings without a doubt. For $400, I could have a set of 862's that would annihilate a stock set of 243 heads that just about anyone could replicate with the same budget.

$1000 usually involves a lot more than just the porting. That typically includes valvejobs, milling, chamber contouring, etc.

So what would you do to a set of 862's to make them run? I had considered putting 2" valves in mine, but decided against it to keep my intake velocity up and not sacrifice my torque (5.3 truck).

Couldn't you mill the 243's down 0.030" and have a hair higher compression than the 862's with higher flow?

I'd get the 243's and just mill them to get the same compression.

I would put in 2.00" intake valves, valve job, blend in the bowls and chambers, and mill them about .030". For all that, those freshly machined heads would perform better than stock 243's for about the same price. 799 heads with 2.00" valves come stock on 4.8l and 5.3l engines, so I really don't think they'll hurt velocity or torque.

Stock 243 heads milled .030" would perform better than a stock 862 head, but not better than an 862 head like what I described. Just the valve job and blending will put the 862 head flowing better and making more power than a stock 243 head. Dropping the chambers down to about 56-57cc for a bump in compression will just be icing on the cake.

stock 243s also aren't going to get you a ton of power either...15-20rwhp

heads $350-450
milling $50+ (optional)
gaskets $40+ (required)
bolts $40+ (required)
tune (required)
plus add in labor or your time plus coolant, oil, and odds and ends

if you put the cost of the 243s towards ported 243s used or cost to port the heads you have, you will be looking at an easy 40+ rwhp gain and only doing all the other parts/labor once

IMO leave it alone or spend the money on heads that will REALLY make a difference otherwise you will be doing it again once you get bored with the extra 15-20 you get from stock milled 243s

That is really good info that I haven't heard elsewhere. Hell, when I was considering the 2" valves, I could only find 1 guy that had done it on a stock bore 4.8/5.3, but he had gone FI at the same time, so he couldn't tell me what to expect NA.

Who would you trust to do the 862 work?

Those were 706's not 862's.

I thought both. I think that TSB only specified 4.8L/5.3L engines and didn't specify which casting number.

OP, I have the 862 heads that were done by Texas Speed, and I am really impressed with how the car runs for such a budget head

i thought both sets could be castechs as well

Everything I have seen points to the 706's. I could be wrong though.