Wanting to build a 421 out of a 6.0 . Want to run 14:1 compression ratio. And e85 fuel In this class im required to run stock intake and stock exhaust. Wanted to run stock heads but with big valves. Any help or suggestions?

 

Hard to beat L92 heads if a stock head is required by your class.

 

Without a huge dome on the piston, you won't hit 14:1 with an l92 head with any cam.

However, if you get a domed piston the stock intake and exhaust will work good as they flow killer stock.

 

If your allowed to by class you can get l92 heads and have the chambers welded up and cut back to whatever cc you want...welding works great end really doesn't cost that much.

 

was going to run a +5 dome piston with milled heads.
what is the biggest valves and the most i can mill a set of l92 heads.
Any idea of hp?

 

What are the class limitations?

 

Anything goes on inside.must be stock appearing on out side. Needs to ideal stock

 

Well I'm in for a bit of learning on this thread instead of trying to give advice. Have you talked to an ls-based engine builder about this application? I'm only familiar with pump gas when it comes to n/a v8s. I'm wondering if an LS could make use of compression like that with a factory vortec manifold and exhaust manifolds. The amount of cam needed for that compression ratio would probably be useless with a factory intake on a pump gas setup. IMO you're gonna want a super wild split between the intake and exhaust durations but L92s are shown to like small amounts of overlap and small intake lobes compared to cathedrals because of the large size of the runners and valves and to prevent reversion. My guess is you're gonna need a small cam anyhow due to the weight and the fact you'll want tons of torque to tow with.

So with that being I'm gonna sit back and take notes. Where's the popcorn?

 

FOUND IT.

 

I dont know of any builders other than Texas Speed.
I will be running E85 I think it is 104 octane and will handle 14 to 1 comp.
the spec on the cam that Texas speed gave me is:
Intake lift 592
Exhaust lift 608

duration-226 234
lobe sep. 115-116

 

I am wanting to purchase a 421 short block from Texas speed.
Any one have any opinions on this ?
Any info on this motor build would help im used to a big block these things are new to me. The things im stuck on are beehive springs vs. dual springs, valve size ,oil pump, rocker arms, and balancer.

 

I wouldn't worry so much about the valve size, just run the stock LS3/L92 ones.

Going bigger is not going to do much for you given the rest of the intake/exhaust and with a 4.030 bore you're not going to be able to run bigger anyway.

Do you can about longevity in the motor? That 4.125 stroke on the stock block is not too bueno.

 

redtan what you mean about longevity ?

 

The 4.00" stroke will let the parts last a lot longer...with the 4.125" stroke the piston skirt comes farther down out of the bottom of the cylinder bore and let's the piston rock more which leads to premature wear

 

Love builds like this. Even with the stock heads, intake, and pipes it should still make over 500 HP. As far as the cam i'm going to say you will need as much lift as possible and something with a very wide centerline. Like 116-120.

 

I like that cam choice with a stock truck manifold, and I vote for a pair of milled AI 243s. With a +5cc domethat compression will be easy you can cut the heads a long ways, my 243s are 47cc.
I vote for a 4.1" stroke at the absolute most for the reasons above. 6.0L blocks have very short sleeves. If you want cubes you will need to do a sleeved block or a LSX
Gonna need good head bolts and .040 gasket. +5cc dome, .040 gasket and 60cc heads
You can find 4.125" sleeved LS2 blocks for a decent price used from time to time. With that you can do a 4.1 or 4.125 stroke without issues, with that I would definately do a L92/LS3 head setup and a flat top or small dome

 

would a 408 be better? Can i make good torque with a 408? i want to turn atleast 6500 rpm. or more lol

 

I spin my 408 to 8,000

Once I get the car finished I plan to head back to the dyno and see just how high I Feb get it to spin before power drops off, at that point the fuel cutoff might get raised to 8,500+ rpms

 

If anything, run a bigger bore like 4.060 but stick with a 4" stroke, that nets you 414ci. Should be able to easily spin it to 7,000 with the right valvetrain, though on the stock intake and exhaust that would be pretty pointless.

 

is there anyone out there that ports stock intake and exhaust manifolds?