mchicia1

iTrader: (5)

Didn't say you had to go 408, just said any 4" bore motor would do well with those heads. Even just a factory ls2 if you went that route. I would bet they would make more power than standard LS3 heads with the huge valves in an ls2.

What is your cam? I agree, if you're only gaining 8 hp with a fast you have a restriction somewhere. Either the heads or the cam.

FYI, my old setup was very mild...

AI 226cc 799 heads 60cc chambers
AI 226/230 Cam
Kooks 1 7/8" catless

This combo put down 435 with an ls6 intake

Added a fast and LS2 tb and it went all the way to 462 on the same dyno.

427zm

iTrader: (9)

4" bore with the LS3's would be optimal, and is something I've been looking into.

My setup is:

PRC 2.5 LS6's stock 64cc chambers
LS2 TB
Fast 92
230/230 Pat G cam
ARH 1 3/4 catted - just added yesterday

Put down 431.

mchicia1

iTrader: (5)

Yeah, you'd pick up a lot just by going to 58cc chambers and a cometic .040". That would most definitely put you at 445-450 rwhp. Taking out the cats would get you another 5-10.

Cam is not your issue for sure, that is a good cam, although a cam with some more overlap should make more power.

This is how I would proceed if I was in your shoes and it should be fairly cheap if you do your own labor.

1) Pull heads
2) Flycut pistons
3) Mill heads to 58CCs and get a cometic .040". You could also sell those heads and get AI 243s, which I think are better heads overall. They never DON't make power on the setups I have seen them on.
4) Put in a bigger stick (optional as I still say that cam is good for up to 460 rwhp in your setup)

Could also just be a stingy dyno, but compression gains a lot of power in these cars.

427zm

iTrader: (9)

I forgot to mention, Cometic .040's also.

I think if I change sticks, I'd at least change heads and most likely just add cubes. More cubes will get me to the power I'd like using LS3's.

427zm

iTrader: (9)

So has anyone else done this swap?

mchicia1

iTrader: (5)

Oh ok, you are pretty maxed out then aside from milling the heads...

You seem to just want to try something different, there is nothing wrong with that.

You can recoup a lot from selling your heads and fast, you could almost make it an even swap going to the new small bore heads and finding an ls3 intake with rails and injectors. I found mine for $350 shipped. You'd just need the adapters for the pig tails, FIC sells them. You can get $550-600 easily for the FAST and probably $800-1000 for your heads (I am guestimating here, I got $1000 for my AI 243s. The small bore heads are only $1400 after adding the offset rockers arms and pedestals.

I vote for doing that and using an ls3 friendly cam, like the 230/234 or the 230/238 like I am doing.

Then if it doesn't work out, you have a nice solid top end for going LS2 stroker or boost!

If you go that route, definitely mill the heads .030, use the cometics, and flycut your pistons or you will regret it. Unmilled the compression is too low for an ls1 IMO.

Good luck. I will keep you posted if I get any dyno numbers or track times.

427zm

iTrader: (9)

What CC are your LS3's and how shrouded are your valves? I already have most of the swap stuff actually, intake, injector adapters, and injectors even though, I probably don't need them.

mchicia1

iTrader: (5)

They are milled .030, so I guess they are about 65-66CCs then I use the cometics to bring them down further. Of course I am using -3.2CC wisecos, so this setup isn't exactly ideal for me, but it still works pretty damn well. I am going boost later, so I didn't care to mill them anymore than that.

Not sure how to determine how shrouded the valves are. All I know is that it is similar to regular LS3 valves on an ls2 bore since these valves are 2.08" on the intake and the stock ls3s are 2.16". Ls2 bore is 4" my bores are 3.908, so the ratio valve/bore size is very similar. Another plus is that these use nice ferrea valves which are very strong, which is nice for big horsepower later down the line ( boost, nitrous, etc)

427zm

iTrader: (9)

So, a little over 10.5 currently, but I'd guess you'll go to ZR1 gaskets when you go boost, which would put you @ ~ 10:1. I'm guessing you're going turbo, hence the manifolds as opposed to headers. Seems like these will be great w/ boost.

mchicia1

iTrader: (5)

Actually no. The cometics are staying, they work fine with boost. I have ARP head studs in there torqued to 90 ft lbs already. 10.5 compression is perfect for a car with a blower. You don't wanna go low on the compression unless you go turbo.

The only reason I am running the manifolds now is because when the **** hit the fan, I quickly sold all my mods and LS7 manifolds are cheap. They actually make great power on 347 cube cars, very similar to headers. The LS7 guys only pick up 5-10 rwhp with headers on the stock cam. GM did a great job on these manifolds. Theyre on the ZR1 too.

I am actually going with just a run of the mill a&a kit. A 230/238 cam wouldn't work well with a turbo.

427zm

iTrader: (9)

So, meth injection as well? V2 or V3? Also, I'm guessing, headers will come w/ the charger, and I'm guessing your running a 115 or 116 LSA for the blower cam?

mchicia1

iTrader: (5)

Meth yes, although to start I will probably just run pump gas and the biggest pulley. I dont need more than 550-600 to start.
Probably v3 so I dont have to drill a line
No headers, no need for them.
Yes, cam is on a 115 to keep the overlap at 4.

Some guy on vette forum is making 700 through these manifolds...even through the cats. He swapped his headers for them and only lost 15 rwhp.

I gutted the cats on mine.

JakeFusion

iTrader: (7)

Honestly, I'd run my cam. It's actually an LS3 designed cam. On an LS3 376, it makes around 480-490 with stock heads. Why? Overlap. You don't want a ton of overlap using LS3 heads. This has 4 degrees of overlap. I wanted less overlap so it'd cruise around with no bucking. But with an LS3 (or any of its derivatives) you want to keep overlap under control due to reversion.

Since you're looking at aftermarket options with smaller intake valves and higher exhaust flow, you could probably get by with a slightly larger cam. Reversion becomes less of an issue. You could do something like a 234/242 114+2 and still be ok (especially if you go 383 - you want a later IVC with a 4" stroke) or 114+4 on the 346.

mchicia1

iTrader: (5)

I don't think the same rules apply to these heads on a 347 as they do on a 376. I put the 231/239 cam in and the car got slower over the 224/230.

I am now putting in an Ed Curtis cam, which has very low duration on the intake side and a wide split to the exhaust side. Going right to the track.

I was only hitting 12.4 @ 119 with the 231/239 cam...it was VERY lazy in the 1/8th. Could only trap about 91, so picking up a huge 28 mph on the back half. Hopefully the new cam will fix the 1/8th mile portion and I can dip into the bottom 12's at over 120. I'd be happy with that considering it's still on manifolds.

KCS

iTrader: (20)

With such a big valve and big port, I think the smaller intake durations work better for these heads, especially on the smaller engines. I think they're more sensitive to IVC and overlap, and should end up with the smaller intake durations to keep the ports working effectively.

I also think the manifolds are hurting you pretty badly. As one very knowledgeable cylinder head guy stated, on these lower RPM street engines overlap is where there is really the most inertia in getting air moving through the engine and thus getting that delicate balance between clearing the residual exhaust gases and scavenging the intake without it all going out the exhaust will pay big dividends. OEM manifolds certainly don't help with this.

mchicia1

iTrader: (5)

You're absolutely right about the IVC. I knew right away the 231/239 cam was too big. It was so lazy touching the throttle anywhere below 4500. Even at 4k, it is lazy. At the track I was picking so much on the back end because once I got going, I was never really below 5k as I revved it to 7200. But rolling out in 1st gear was NOT fun with 3.42s lol. Talk about lag.

Well, they're LS7 manifolds connected to a full 3" exhaust all the way to the bumper. Pretty nice pieces, not like I am running on the crappy ls1 manifolds. I am sure I am giving up .2 et and 2 mph or so, but nothing more than that. Mostly torque in the mid range probably.

But that is why I went to Ed, he specced me a cam specifically for my application knowing I had the LS7 manifolds.

If huron speed ever puts back the C5 xspower headers, I will hop on them. Sorry though, not paying $1600-1700 for American catted headers and no way I am going back to catless Kooks like I had before. The Kooks cat pipe alone was more than I spent on my manifold, cats, and 3" crossover pipe setup. I just couldn't take the catless + cam smell anymore. Tired of going into the office smelling like it.

badassracing

iTrader: (13)

I would call and talk to Mast about your setup. I had a guy that wanted to run small bore LS3s on a 347 and mast told me they would be too lazy down low.

dr_whigham

iTrader: (49)

I had a good conversation last week with Damon at Mast. He agreed about them being a bit lazy below 4-4.5k, but said they'd turn on like a ******* LIGHT SWITCH there after. He said for a mainly street car, their 215's would be better suited, but it's still personal preference.

Ed really wants me in the Mast SB LS3's, and I have a quirky trick up my sleeve next year if I get them. But I believe he truly knows what to grind to actually take advantage of the heads. I'm glad you made this thread, bc I was just about to start my own. I think aside from a cam swap, I've taken my heads about as far as I can.

OP, hope you don't mind me piggybacking in here. There really isn't a lot of info available on these, other than the magazine test.

JakeFusion

iTrader: (7)

Ed told me the same thing when I was looking at AFR heads.

I'd still stick Cathedral port on a 346...

427zm

iTrader: (9)

Not at all Dr. My plans have changed here, since I started this post. Cubes are on the way! Three legendary numbers..... 4...2...7...

Picked up some LS7 heads and the intake for a good number, now I'll need to send them off for new SS exhaust valves and porting!

I think it's going to be neat to see some folks run the small bores. They may be lazy down low, but as I've hearth said many times, who races below 4k? The LS3's should freight train at high Revs!