A.R. Shale Targa

iTrader: (2)

Gonna be putting my 4.021" bore 368 inch LS2 into my vette here in the next few months. Have a 226/232 @ 114 camshaft and some Wagner 228cc ported 799 casting heads which supposedly flow 297 @ .600 with the 2.00" intake valve
Factory LS6 intake and self modded throttle body
Buddy of mine offered me some 0821 casting heads off his 12' GS vette with less than a thousand miles in them since new. He's trying to get me to go with his LS3 intake/throttle body on my short block.
I checked and the chambers measured 4.060" so about .020" shrouding will be the case on my engine.
My pistons are at zero deck so a .040" Cometic puts my squeeze at 10.8 without milling. Down about a half point from my current heads at 62cc with the much cheaper LS2 gaskets
Thoughts on if I should stay the plan with my 3.42 geared M6 car or consider running the LS3 top on my LS2 short block and whether or not I should also change the camshaft even though I would DIY port the 821 exhaust side
I'm only shooting for around 440 rear wheel but want near stock drivability with occasional 1/4 mile blasts. Mostly cruising type driving.
Comments welcome

mchicia1

iTrader: (5)

LS3s because you get almost a fast and bigger injectors (with publicly available data) for about $300.

440 is a cake walk for either setup though.

redtan

iTrader: (5)

Personally I'd stick with the 799s in this case, especially with that cam.

If it was more than just a mild street cruiser I'd say LS3s with a new cam for sure, but those heads will perform better on the street with the smaller runners and higher compression.

Rise of the Phoenix

iTrader: (27)

^^^ I agree completely.

KCS

iTrader: (20)

I'd stay cathedrals as well. Unless you can fit an LSA blower in there...

MuhThugga

That cam would work fine with the LS3s. Milling the heads and using factory gaskets, you'd be around 11:1 without issue, and I'd bet that you would hit the high 400s without issue and with perfect street manners.

However, if you already have the 799 heads and don't plan on buying a new throttle body to bolt to the LS3 intake, then I would just keep what you have.

DavidBoren

As stated, the cathedral port heads are probably your best bet. And you already have them.

A.R. Shale Targa

iTrader: (2)

The buddy of mine kept his injectors/rails so I'd end up needing to find some.
My cathedral combo will most likely need some FAST36 injectors to meet my target power level.
I'll probably end up staying the plan as my short block and heads are all together and I'm happy with all the clearances.
For me the temptation comes from the intake and TB being better and the heads having such few miles on them, practically new.
He also has his original LS3 block/rods/Pistons/rings which he pulled at around 2K
I just can't justify starting over with his stuff for eight more cubic inches.
I'm thinking you guys have convinced me that I've picked the appropriate combination for the intended usage I have for my car
Thanks again 👍

NAVYBLUE210

I would definitely stay with your original plan for your
Goals, very well thought out it will exceed your
Expectations, and drive very well!

Camaro99SS

iTrader: (4)

Keep the cathedrals. There have been some who have made around 500rwhp on LS2's with ported 799's so you have plenty of head flow for ~450rwhp. The smaller chambers will also be more responsive on the street.

Jason

spawne32

iTrader: (2)

If this was a matter of stock 799 cathedrals vs stock LS3's and we were talking about port velocity id be inclined to agree with the latter, but since we are talking about CNC'ing the cathedrals vs LS3 heads, don't bother wasting the money hogging out the 799's to achieve LS3 type flow when you can just swap the LS3 heads on and LS3 intake for cheaper. Port velocity is always hurt on the cathedral heads no matter how you CNC them, it's just a matter to what degree. There is nothing about the LS3 heads that are going to make your car less "streetable".

redtan

iTrader: (5)

There's more to a set of heads than just flow. And if you do want to use flow as a benchmark, look at the size of the heads for the given flow. Those ported cathedrals with something like 22x cc runner flow the same as an LS3 with a 260 cc runner...not exactly impressive.

No it won't make a car less streetable with LS3 heads sure. But a car with small port high velocity heads flowing the same as some monstrous rectangular heads will drive a helluva lot better and snappier on the street.

Rise of the Phoenix

iTrader: (27)

Amen to that.

spawne32

iTrader: (2)

Maybe you didnt read my entire post, but as I said, hogging a cathedral port head out to make it the same size as an LS3 head port is pointless when you can do the LS3 conversion for less money and achieve the same results. Using advanced induction's flow benching of CNC ported 243 heads as a reference point, you would need a 232cc CNC ported cathedral head to match the flow rates of an LS3 head and would have LESS port velocity then the stock LS3 head would have making the CNC ported cathedral heads worse in terms of low rpm streetability.

redtan

iTrader: (5)

But he's not hogging them out, he's got the 228cc ports...those are hardly hogged out.

How do you figure a well ported/designed 232cc runner with a good valvejob is going to have less velocity than a completely stock 260cc runner? Have you ever driven these 232cc heads?

KCS

iTrader: (20)

Are you saying that a 232cc cathedral port would have lower port velocity than a 260cc rectangle port flowing the same amount of air? And that the 232cc port would be less streetable?

How do you explain that?

Camaro99SS

iTrader: (4)

It's not just the port size, but a 2.16" intake valve will make a big difference in airspeed compared to the 2" on a ported cathedral head.

PTV clearance is also much less on the LS3 head with it being the same 15 degree valve angle. Your cam may not be large enough to pose an issue, but you certainly won't have as much cushion in the event of an over rev or if the valve springs begin to weaken over time.

Jason

spawne32

iTrader: (2)

I didn't say it would be "less" streetable, and said there is a negligible difference between a stock LS3 port and a 232cc cathedral port in terms of what you are describing as being problematic with an LS3 swap. The ls3 heads are designed that large, thats the reason they perform leaps and bounds better beyond the cathedral design, where as you are trading one for the other with a CNC ported cathedral head. You arent going to try to argue that there isnt a significant decrease in port velocity of cathedral heads when you widen them are you? For christ sake the AI 232cc heads are widened out as big as the LS3 ports are stock. lol Ultimately up to the OP to decide whats better but as others have pointed out, going with an LS3 swap isnt going to hurt the drivability of the car with that cam, and youll be upgrading to a more modern setup. You arent going to see GM backpedaling to cathedral ports in any future motors because of "port velocity" because its not an issue on rectangular port heads.

KCS

iTrader: (20)

Really? Then what did you mean by this:


Highly debatable.

That's not what we're talking about. YOU stated a 232cc cathedral port would have less "velocity" than a stock 260cc rectangle port. That's the statement I am calling BS.

No they're not.

Crf450r420

iTrader: (1)

Keep the cathedral ports reasonable and you can get the peak power you want with great torque. The LS3 heads are good for more power stock and they won't have the port flow you want to keep a broad torque motor. I like the cam specs I've seen. What lift is it?