which size cylinder heads ?!

[Camarosseasttn]

Hey everyone, I have a setup I would like to get advice on, it’s a 376 cubic inch ls3 block stock bore with a LS1 crank, arp main studs, TSP H beam rods with ARP 2000 bolts, Mahle 4032 material Pistons , 235/240 629-615 112 LSA cam, ls7 lifters, and PRC 247 cathedral port heads, fast 90 intake , 92 NW throttle body, and 36 lb injectors, I plan to spray a 200-250 shot thru a plate kit with a stand alone fuel cell, my question is the heads, do you think they are to big for this setup if so how bad are they hurting me? This is what was recommended to me when I got them. Thanks

[SMWS6TA]

Those heads need a minimum 4.003" cylinder bore. What is your bore, confirmed?

They will fit a LS3 block, it's designed for a 403/408 stroker. I still think they will perform ok on your stock block.

My bigger question is why are you running a stock LS1 crank? All of the other parts are solid it's just the stock crank is now the weak link in the build.

I would also consider bumping up to a FAST 102 intake with those heads and the nitrous you plan on using. It's going to want more air flow. Also you need to make sure your piston rings can handle that much nitrous and what the gap needs to be, otherwise you risk damage to the rings.

[Camarosseasttn]

The bore is a 4.065

[SMWS6TA]

You're good then.

[Camarosseasttn]

Do you think they will produce as much power as the ls3 heads and intake ?

[SMWS6TA]

Hard to tell. They have to capacity for big HP gains. A couple of things greatly effect power output. Not saying the heads aren't worth it. My semi-concern is still crank stroke with the bore you already have and a 4" stroker crank you would greatly benefit with those heads. The cam is a decent bump up over the stock LS3 cam specs. Is your intake a FAST 90 or 102? I know it's not a LS3 because those heads won't work with it.

[Camarosseasttn]

The intake is a fast 90, and I plan on spraying about a 200-250 shot on this setup ?

[SMWS6TA]

What type of piston rings you using?

Also plugs and injectors? You need to know what temp range you need for the plugs IIRC NGK BR7 plugs are optimum, I'm using TR6 in my 403. If using LS3 injectors they are rated 42-48lbs, need to check to see if that's enough for that shot.

Get a solid tune for the Nitrous. You may need to talk to a tuner to see if they are enough for that high of a shot.

Have you found a tuner yet?

Also are you using a Nitrous window activator (it auto hits the nitrous when you're at WOT and closes it when you let off) and/or timing controller?

[Camarosseasttn]

The Piston are Mahle 4032 material, I believe it's called the power pack they come with rings that's what I'm using
The spark plugs is a NGK 7 for a 175 shot I plan on going to a 8-9 on the 200-250 shot
The nitrous has a WOT activation switch, and RPM window switch, with a progressive controller and a stand alone fuel cell his time for the nitrous
The injectors are 36 lbs

[SMWS6TA]

You seem to have a solid setup then. But seriously talk to a tuner about the plugs and injectors.


Let us know how it runs.....

[Camarosseasttn]

I’ve ran it with the stock 10 bolt rear end and 3.42 gears on motor it ran 7.33@94 mph on motor on a 175 shot it ran 6.48 @ 106 with a 1.4x 60’ ramping the nitrous in trying to be easy on the rear end but it ended up breaking lol I was wondering if that time on motor was decent for that setup ? This was on a 28x10-15 Hoosier slick also

[SMWS6TA]

Yeah that's hauling ass. 9 sec car on the 175 shot. You're going to need a good rear and a cage.

Do you have a cage yet? If not I'm surprised they haven't stop you from running yet. Our local track will stop you from running if you break into (these are qtr mile time equivalent>>) the 11's without a helmet, low 10's a cage, and if you make it in the 6's better have a chute.


You have several options in rear ends.

For heavy duty racing &/or power 9"

Good amount of pwr and still want some street manners a 12 bolt or Custom Ford 8.8.

They all run about the same if you have to buy them. Only one that you can shave some $$$ off is making a 8.8 yourself. But if you don't have the skills, tools, or need it right now then you're better off getting made, ready to drop in. I made my 8.8 because I had the time and desire to learn & make it. Going strong over 2 yrs now. Made another one for a friend on here. Waiting on him to get his running again.

[Camarosseasttn]

I wasn't just wondering if the times on motor without nitrous was decent for that setup? And I'm curious to see what it will do on a 200-250 shot and leaving with all of it off the line? . I'm actually looking at the MWC 9" setup, what's ur opinion on them, do they have a lot of gear noise and are they a good choice for a street / strip car ?

[SMWS6TA]

On motor with slicks hell yeah. My best time on street tires was 7.5ish with my 403. Haven't gotten slicks yet to see how it will really performs. They're on my get list this yr. But I want to have the car painted 1st.

MWC has some great products. I know 2 ppl that are running their 9", one is mostly a track car and the other a street car. Both love 'em. If you ever want a Driveshaft safety loop get theirs. It by far is one of the best in designed. It tucks up inside the tunnel, no low hanging that can cause issues with trailers and speed bumps.

Gear noise depends on how tight your tolerances are on the gears. My gears on the 8.8 are set kinda tight so that there is not to much play for when I launch. Setup in the middle of the tolerance zone specs usually gears are quite.

I run Yukon gears in mine. I not a fan of Motive or Ford Performance Gears and Richmond are now owned my Motive.

[raynor139]

All but 2 of MWC rears in cars I've ridden have been pretty quiet and the two that weren't were hardcore track cars.

As for the MWC driveshaft loop I'll second. Love it proven strength and doesn't cause clearance issues and in a lowered car that's a great thing.

[SMWS6TA]

All but 2 of MWC rears in cars I've ridden have been pretty quiet and the two that weren't were hardcore track cars.

As for the MWC driveshaft loop I'll second. Love it proven strength and doesn't cause clearance issues and in a lowered car that's a great thing.

And I say that as a HUGE fan of UMI Performance products. All my suspension is from UMI except the DSL. I tried theirs but like you said with a lowered car it just doesn't provide a lot of clearance. I talked with UMI back then and even they say now they recommend it only for track only cars.

[Camarosseasttn]

What options is good to have on a rear end when getting an aftermarket one, like tow loops, fill cap etc ..?

[Camarosseasttn]

And will the MWC 9" hurt my ET over the stock 10 bolt much ? Like will u be losing a few tenths ?

[SMWS6TA]

tow loops and fill caps are definitely a mudt have.

You may see a pwr lose on dyno but your et's and speed depends on several factors. GR, tire size, traction etc....

The pwr loss will be from a bigger diff. But honestly you won't notice it with a 200 shot.

[Camarosseasttn]

I'm wondering what will be a good gear ratio for the new rear end with 28" slick ? It has a built 4l60e with a 3600 stall .