hyperion

iTrader: (1)

Hey all,

This post is a bit long, so thanks in advance for any thoughtful responses.

I'm building a 427 motor for my street car. I'm starting with a Katech short block (4.125" bore). Based on the upcoming FAST LSXR intake I'm leaning towards an LS3 or LS7 head (as the LSXR intake won't be available for the cathedral port heads). I have a 4" CAI that can take advantage of the FAST intake and 102mm TB.

Here are some key requirements for my motor:

1. Stock driveability (easy start, no surge, etc.)
2. Solid reliability (street and road course use)
3. Optimized power, but not at the expense of #1 and #2

This leads me towards heads with high port velocity, i.e. not aggressively ported heads. That also means a smaller cam with low (or no) overlap. This in turn means that reving past 6500 won't provide any benefit--and keeping revs low helps with reliability too.

When I add all this up, it seems that a set of LS3 heads, perhaps with a little cleanup and a good set of springs, would work very well for my application. Or, to put it another way, a set of worked LS7 heads would be a waste of money and (with the increased port volume) would potentially hurt driveability.

My question is: am I on the right track? Is there some advantage to the LS7 head over the LS3 that would help me achieve my goals above? I'm not adverse to spending the extra money here, but in my case it seems like the LS7 heads would just be a waste.

Thanks!

-ch

Haans249

iTrader: (24)

Get a set of LS7 heads no question. The larger intake valve will allow you to make more power with less cam duration hence better drive ability. On top of that, smaller cam doesn't always mean lower revs, split and overlap can dictate that. The cam i'm running right now on my LS7 heads has 15 degrees split, 235/250, and stock drive ability and pulls hard all the way to 7k. Also the availability of the stock GM LS7 intake/exhaust valves (and the fact that each valve only weighs ~75 grams each) allow you to run more aggressive profiles without crazy spring pressures. Lastly, the power potential on Stock GM LS7 heads far outweigh the potential of the L92/LS3 heads.

Go for the LS7 heads and don't look back!

red02Hawk

iTrader: (9)

^-------------im with him

Black02SLPSS

iTrader: (5)

Stang's Bane

iTrader: (22)

1) Believe less of the BS you read
2) Listen to Haans. He is dead on.

Jason 98 TA

iTrader: (4)

Definately agree with these guys, the LS7 heads are the best bet hands down. Our PRC LS7 head made about 25rwhp over the standard LS7 gm cnc ported head, but I'd take either over the ported L92 heads.

Checkout our new valve spring, it would do very well controlling that LS7 valve even with larger lift. We have a set testing right now with hollow stem LS7 valves on a PRC LS7 head with great results. Think about it with the hollow stem we're talking about a near 400cfm LS7 head that ships for right close to $2300 or so!!

hyperion

iTrader: (1)

Thanks for the responses, guys. Right now I'm considering a cam a little more conservative than in Haans' car. I'm thinking about a Katech torquer (220/244 @ .050, .615/.648 lift 110LSA) or maybe even smaller. So, based on this kind of cam:

1. Would the stock LS7 head (or the PRC version Jason mentioned above) work?
2. This is really important--is there any downside to a ported LS7 head like the PRC? Again, I'm looking for absolute driveability here with no surge. If that means an unported head, so be it. But if there's no downside then maybe the PRC ported LS7 is the right one for me.

If there is a spectrum of 1 to 100 where 1 is stock and 100 is a bucking, fume-sptting, stoplight-stalling monstrosity, I'm shooting for about a 5 on that scale. After building many street cars that aren't fun to drive more than once a week, I'm really looking for something that is absolutely hassle-free. I know a lot of people think that CFM is the end-all, but for me if it hurts driveability I don't want it. I won't miss the extra 20HP, I assure you.

Thanks again for your guidance,

-ch

pharmd

iTrader: (4)

What is the intake runner size on this head? Chamber size?

DutchmanSS

iTrader: (6)

I would go with LS7 heads touched up by Richard @ WCCH.

Stang's Bane

iTrader: (22)

A properly ported head will not make road manners any worse, in fact it may make them better.

Your camshaft selection and tuner selection is what will determine that.

The ls7 stuff will be the absolute best for what you are looking for. That Katech cam will be a great DD type with the added benefit of a bit better sounding idle. As far as off the shelf sticks, it is one of the better choices.

Haans249

iTrader: (24)

He is correct on this point.

I would also point out that while the Katech Torquer cam is a great choice, the cam that I'm running right now drives LIKE STOCK. It only has 12 degrees overlap at 50thou and a 15degree split. It generally is not the cam....to an extent - it is the TUNING/TUNER that makes all the difference on how a cammed car acts and drives. Regardless, the Katech cam would be a good choice for you.

See5

iTrader: (53)

Ported LS3/L92 heads will make about the same power as LS7 heads and more torque. Two of the advantages of the LS3/92s are cost and no valve train issues with TI valves, and 1.8 rockers. The LS7 intake flows a bit more than LS3 but maybe with the new FAST the LS3/FAST combo is overall winner?

1FASTBIRD

iTrader: (21)

I would second that

DutchmanSS

iTrader: (6)

Richard is an exellent guy to deal with. I was very happy with the service and quality of work.

Haans249

iTrader: (24)

What valve train issues are you referring to? The lighter TI valve makes it much more rpm friendly, and you can get your lash spot on with custom thickness lash caps.

As far as power, do you have any dyno results showing a comparison between the two heads? I haven't seen any L92 combo that makes more power/torque then the LS7 headed setup. Possibly intake limited? Maybe, but the new FAST L92 intake shows only 10hp/10trq increase on an engine dyno, compared to 30/30 gain for the LS7 version same engine dyno.

Cost concerns are getting to the point of not really being an issue. The amount it costs to get the L92 head to the point of the LS7 is getting you to the point of just getting a set of stock LS7 heads, ie (porting, TI valves).

Simplicity, consistency, power potential, intake choice are all winners with the LS7 head in my book. But that said, its just my book haha.

99blancoSS

iTrader: (115)

LS7 heads all the way unless your budget can swing the All Pro LSW head
With the small cam you'll have excellent street manors.

71CamaroLS1

LS7 heads, definitely. The Torquer cam is not a bad starting point, but the standard 110 LSA grind for that cam has a fair amount of overlap (12 degrees @.050) and a very early intake valve close. This creates a bunch of low-end and midrange torque, but limits high-RPM extension. In a lighter car, you might consider getting that cam with a 112 to 114 LSA, which will smooth the idle and create a little bit flatter torque curve, which may be easier to manage on a road course.

Drivability and idle are very much affected by the tune, as everyone here is saying. Ideally, a pure speed density tune with one of the earlier (LS1) ECUs makes it easier to maximize drivability. But good tuners get fine results with the later ECUs as well.