Hey guys so Recently I had the heads off of my 97 vette to replace the lifters.
The casting is 339k which I have never heard of but based on some research it seems they are very early LS1 heads

Does anyone know the flow characteristics of these heads?

mainly, do they flow any worse than say an 806 or 241 head?

I have full bolt ons and a cam and im trying to figure out likely reasons for a very low dyno number

Does anyone have more info on these heads??

 

If they do flow worse, I'm sure it's minimal. I would bet that there is something else going on why the dyno number was so low, or it could just be a stingy reading dyno.

 

There is something else going but im trying to rule that out too

 

What did it put down?

 

With mods in sig, it only put down 368whp.
I know that my pushrods are too long (7.450 on an ls7 lifter)
Causing the valves to hang open most likely. Im also going to get my springs tested and make sure they arent worn because I had a different cam previously. Im also on a stock muffler still. 27 degrees timing at WOT

BUT I just want to make sure its not my crappy stock heads ruining it for me.

Here is my dynosheet. you can obviously tell something is wrong



I should be able to hit 400whp with that cam and mods on stock heads if they flow close to other ls1 stock heads. but I just cant find any info on them to verify that

 

Was the car street tuned, and then you had it on the dyno to see what number it put down, or was the car dyno tuned? Did the dyno operator say anything to you? I honestly don't see you going up power wise by going to a 241 casting over what you already have. Might be very minimal gain, but not worth it in my book. If you're going to go through all the trouble of pulling the heads, might as well at minimum get a set of 243/799 heads.

 

oh yeah I definitely wouldnt change to to 241's but I just wanted to see if my heads flow about the same. No the car was tuned on the dyno but I do know that this shop tunes kinda conservatively. Im down 30hp without a doubt. Ive spoken with Pat G (spec'd the cam), Martin smallwood and whoever specs cams for texas speed and after telling them about my situation and looking at my sheet, they all agreed that I have a valve control issue due to my long PR's and possibly worn springs (25k on them). So im fixing both those things but I was just trying to see if they heads are holding me back.

The car put down 401/402 with a smaller 227/234 .614/.576 113+2 on an ls1 intake
So I know im down on power.

 

If you're in the market for heads, just keep your eyes open on here. Oftentimes you can find brand new heads for sale at much less cost than buying them brand new from a vendor.

 

Yeah its just sooooo much money

 

Yes and no. You can find good.deals if you're patient. Used heads could also be an option for you. Just make sure to see lots of pictures.

 

My last build I kind of cheap'd out on the heads. (Ported 243, sodiums with PRC duals and stock rockers) My next build (car.. not the truck) that will be the first thing I do. I heard a saying once "The best cam on mediocre heads will make mediocre power... a mediocre cam on amazing heads will make very good power." Or something to that extent.

IMO, I'd like a real money set of heads with a mild cam... Like an LS7 or equivalent 427 with a sick set of WCCH heads and a real mild cam. The LSs make great power because of the head design.

 

if you buy used heads try to get lucky and find the assembled ones that are "fresh" from the machine shop. meaning cleaned up, valve job, resurfaced.. ect. i got lucky and found a set of LS3s with all of the above plus brand new dual springs and ls3 rockers. cost me about the same as i see them go for with stock springs minus the machine work and rockers. if you find a cheap set that needs to be sent to the machine shop you're gonna drop $500 on them anyway so spend a little extra and be patient to find a nice "fresh" set.

 

Very good point about buying used heads. I personally will never buy used heads again; I got burned on a set of used AFR heads. There were material missing between all of the intake and exhaust valves and it appeared that a valve had dropped as well. Every set of used AFR heads for sale on here look like they all have that missing material between the valves. Maybe you could find a used set local to you. That way you could check them out in person.

 

I got lucky on the used AFR heads I had. 10k miles, already milled to 59cc... 1450 shipped. Those deals are few and far between, but if you're vigilant in the classifieds you can find them. They go quick though.

 

Funny thing is I had bought a used set of AFR heads years before I bought that second set of used AFR heads, and the first set was legit. Same thing; milled to 59cc with new springs, and they were flawless. All they did was sit in the garage. I ended up meeting a guy in Chicago and trading them off for a set of Fikes wheels.