maverick18

iTrader: (5)

Looking at a 408 iron block now... Just wondering what needs to be done to my ported 241s to make them work well on a larger bore set up. What size valves can I upgrade to? Looks like a little more material could be taken out around the valves but im no head porter... How much would I have to mill to get them around 11 ish to 1 CR?

maverick18

iTrader: (5)

bumpppp

00MaroonZ28

iTrader: (3)

241's would be crap for a 408 block. Scrap them and get some AFR 225's, Trick Flow 225's, or L92 heads.

Abdullah

iTrader: (2)

go with trickflow 225cc heads with touching up by a good porter (very light porting at critical areas).

teke184

iTrader: (5)

maybe he doesn't have $2500 to spend on the heads alone


call up one of the vendors who do porting, and talk with them. i'm sure they can steer you in the right direction.

241s won't be ideal on a 408, but if its what you have...its what you have.

nice thing is that if they are hogged out and the runners are big...they will actually fit the 408 better than they would a 346.

some ported 241s can easily end up having a 225-230cc intake runner....which would kill low end on a 346, but they will fit the needs of the stroker much better.

92 silverado

iTrader: (11)

my buddy made 450/435 untuned stuck in open loop on STOCK 241 heads and a patrick g cam.HE ran an 11.6 at 120. they will do pretty good with a tune and porting around the bowl area and on the ehxaust side. id guess 475whp-480

R1ch

iTrader: (4)

I came here to post this.

Jonathan@Tick

iTrader: (5)

We did some 853 heads on a 408 bottom end for a good friend of mine. They were unmilled with stock valves, I just cleaned up the ports a little myself (and I don't claim to know anything about porting heads). We slapped a used cam I picked up that was a 252/256 dur. @ .050" with something like .640 lift on a 113 LSA.

The end result was 470 rwhp and the torque was in the 470's, just not sure of the exact number. This was using pacesetter 1 3/4" headers and an Ls6 intake.

Basically, he needed a bottom end because it threw a rod so we fixed it with a 408 as cheap as we possibly could.

Black02SLPSS

iTrader: (5)

Wow i didnt think stock heads would work that well. Obviously it would be better with aftermarket heads but thats a pretty respectable number with stockers, with minor port work at that.

maverick18

iTrader: (5)

This is correct, im not looking to drop $2500 on a new set of heads. I allready have $600 invested for the port job on these. The main reason I was thinking about doing a 408 iron block is because I could transfer most if not all of my current set up oer to it, maybe upgrade the cam.

About the hogged out runners, If you look a my Tq numbers(368 peek) they do look a little low for a heads/cam car. Anyone think this could be because the runners are too large for a 346? I know it would be hard to tell but how do the pics look?

maverick18

iTrader: (5)

Those are great #s... Would think my ported 241s with some bigger valves and up the CR could do in the 480s (granted every set up is diffrent)

382ssz28

iTrader: (24)

I used my 241's on 382 with 2.05-1.570 valves that came with Stage 2 CNC from ETP. Check on a Stage 3 CNC port job. It will probably work very well. By the way, I'm at 486RWHP, 455RWT. You'll do better.

JPH

iTrader: (2)

Is the exhaust port round and the size of a golfball now? Just wondering. Make the best of your heads if possible. An aftermarket head would be a better choice imo. Since your on a budget, get a set of good used patriots, pay a local head porter $400 bucks or so and have them tuned up and the chamber opened up to your bore size.

maverick18

iTrader: (5)

I guess I could scroll the for sale section for a niche used set. Those exhaust ports are matched to the GM MLS header gasket, he also did the header to match the gasket...

JPH

iTrader: (2)

Would rather see the header tube to be a slightly larger opening then the head imo.

got-a-ls1

iTrader: (12)

throw on your 241's and go enjoy your car!!! your obviously going to be making 460-470 hp at the rear wheels ON A BUDGET! and that aint bad... save up for a couple years for new heads you can and then pick up that extra horsepower if you want.

Beaflag VonRathburg

iTrader: (176)

What size valves are in them right now? I would have a 2.04 intake with a 1.57 or 1.60 exhaust valve installed on the stock seats. Then, have a valvejob done with a radius throat cut and deshrouding cuts done to the chambers. With that work and blending the throat cut you should pick up a good amount of power.

The milling is completely dependent upon what size your valve reliefs in your pistons are, what head gaskets you run, and how much in or out of the hole the pistons are. Roughly milling .007 is equivalent to removing 1cc of material from the combustion chambers.

teke184

iTrader: (5)

"About the hogged out runners, If you look a my Tq numbers(368 peek) they do look a little low for a heads/cam car. Anyone think this could be because the runners are too large for a 346? I know it would be hard to tell but how do the pics look?"

that does seem low for that cam.

hell with a crappy tune my Torquer V1 made ~375ftlbs on STOCK heads

and actually i'll be getting new dyno numbers tomorrow....and then throwing a FAST on it and checking for gains.

i'll try to update.


but i think your torque is WAY low!!