The engine in question is the LQ4 in my Tahoe, unknown bottom end mileage but completely stock as far as I can tell besides a 224/228 113lsa .600/.600 cam. Plan to run it on 93 as a DD and maybe one day put a small amount of boost to it and try to squeak out 500whp.

Contestant one: 862 cut for 2" valves and have SS valves installed all around, with factory LQ4 gaskets it has right at about a 10.5:1 CR. These heads have been on the engine for about a year/20kmiles

Contestant two: 243s from an LS6 ported by Wilkes Performance with a 5 angle valve job and milled .010 which nets 10.4:1 CR with lq4 gaskets.

Both heads will run the same dual valve springs, CHE trunion rocker arms, ARP head bolts, and hardened pushrods.


Question 1: What kind of power difference would you expect to see?

Question 2: Which would you prefer with boost?

Question 3: Would you replace the unknown lifters while in there? If so with what?

 

1. I think you should at least see 20+ from the 243s. I say that because looking at LS1 vs LS6 there was not a major difference between the two but they were rated at 350 and 450 respectively.
2. Can't really speak on boost personally but I don't think it would particularly matter.
3. Meh I guess so. If they are working I probably would not but if you want to then get something nice.

My vote is 243s

 

See for 20whp I hardly see the point in swapping unless something fails.

One other big factor is that I have a 212/218 high lift cam on the shelf along with some single beehive springs, a CHE rocker set, and several size pushrods. If I pull the 862s they would make a good combo package to sell to someone and recoup some cost of the 243s.

 

Was under the impression you were swapping out no matter what, like pulling the heads and doing some more work to 862s or doing 243s

 

Nope, the 862s already have the bigger valves and good valvetrain, I do have a lifter or 2 that make noise on cold starts occasionally that is annoying but no other signs of imminent failure and I cut filters every oil change at 5k. If I did want to pull the heads and swap lifters IDK what lifters are worth a damn anymore or in stock.

The 862s aren't a bad candidate for CNC porting just don't want to wait 6 months again for port work. Been waiting on these 243s since February. All the bad experiences I've had in the last 3 years with machine shops, in general, have made me want to just buy stuff from a catalog from now on.

 

With a small duration camshaft I'd just keep the 862's.
With a larger camshaft that sees 6800+ I'd go with the better flowing ported 243's.

 

Dude what? 5 months just for heads? I would've got my heads back within a week if it wasn't for my girlfriend's dad being retarded

If you are already getting the 243s I would just slap them on and rock them but that is just me.

Save them for another project maybe?

 

Even with boost? I figured the better flowing heads would be better for boost

 

That is kinda what I thought, at what duration would I really start seeing gains worth it? Something in the 23x/24x range?

I have absolutely no desire to put a cam bigger than this one in it.

It was a sorta odd deal, they were shipped from New Mexico to Alabama for the port work and when I called the shop they said 2-3week turnaround. Apparently, when you can't show up at the shop every week and bother them they take even longer. This is my 5th sorta bad experience with different shops.

 

After watching hours and hours of Holdeners dyno videos... boost is going to work well with either set of heads. RPM (boost or n/a) is flow related, you need more flow the higher RPM. The camshaft dictates RPM. So again small cam will not see high RPM whether in boost or n/a. Richard always says "all cams are boost cams" same as the heads. It's all where you want the power to peak and camshaft choice always dictates RPM range.