The shape of the port doesn't matter. The small bore LS7 is a better architecture and opens up better manifold options. The CSA and port size should be the same or similar to a large cathedral, but the raised floor and better intakes will make more power and torque.

I guess the question is do you want to spend a lot of money for a small gain, or spend a lot of money and actually feel like you got something new...

The point where you're at with an NA motor it is a lot of money no matter what you do and the gains will be incremental.

Unpopular opinion...keep your bottom end, throw some stock LS3 heads on it, and put an LSA blower on it. Run an A2W intercooler with an ice tank and ethanol if you've got access to it, or meth injection. LS3 heads will drop your compression to ~10:1 which is plenty low for big boost and 93+ octane if you keep it cool.

1) you'll get sick blower whine and make everyone jealous
2) you'll have insane tip in power and way more power everywhere
3) you'll get sick blower whine and make everyone jealous
4) your car will be louder than humanly possible with an NA motor

People get worried about boost, but the maintenance of a lower reving boosted motor is way way less than a high strung NA motor. You put a bigger NA cam reving higher and you'll wear things out faster. A boosted motor can use a smaller cam, milder lobes, less lift and still leave everyone in the dust. We see this all the time in the drag race world...people go from a crazy big block motor with $20k in the top end alone making 1000 hp at 14.5:1 compression and needing a rebuild every 100-200 runs to a blower motor with conventional heads on low boost and a mild camshaft making 1300 horsepower and they barely ever work on the thing and go a half second faster in the quarter mile.

From what I read recently you can get all the stuff you need in the US for about $3000-4000 to put an LSA blower on an NA LS3 engine. Stock LS3 heads will run you about $600. Total you're under $5k which is close to what you'd pay for cylinder heads alone if you went with something high end and you'll pick up 200+ horsepower from where you are now.

 

AMEN.

Completely agree with this, but I get crap for recommending boost even though its the logical choice for some applications. Given the 3 choices offered by the OP I'd go small bore LS7, but if boost is in play, it'll own NA for a torque curve all day and be easier on parts.

 

The Ls7 is a better architecture yes but the benefits you see are high up in the rev range.
Small bore LS7 heads are so so.
You are crutching a design that was originally made for large bore big cubed engines.
The smaller LS7 does not work the same. I haven't seen any combinations that impressed me running small bore heads.
The blower suggestion is pretty cool but I doubt the OP wants to go this route.

 

The car is a dedicaded driftcar so no worries about idle and streetability. What you call a street strip motor is what i need. In drift competition you sometimes compete with slower cars and a lot of times in the rain. thats why i need flexibility. I have no need for Superchargers because these engines do not live long in competition because of bearing wear. The belts also do not like the rpm fluctuations

 

WOW, can't believe I am saying this,... I completely agree with Bortous.
For the OPs 7000 RPM limit the MMS 235s are the best Heads for his goal and are available with a 62 CC Chamber which could be milled down to 56 CC.. I even agree with his cam spec although with 12.0:1 Comp I would go 243/247 with standard port and 243/243 with the NFI port. (I like odd #s becoause Im an odd guy lol)

I would expect a 40-50 RWHP gain from 5500-7000 RPM and 30-40 lb' gain from 3000-6000 RPM.
Phenominal throttle response and control from 3000+
Just my .02
Good Luck

 

Haha. I'm getting better.

You could get away with a single pattern camshaft with the NFI port but i would probably go with a 247/247 so it doesn't roll over too much in the top end.

OP is running 93 fuel so i am unsure if he could run 12:1 compression

 

You have formally gone off the deep end

 

You will too one day.

 

We run euro 102 that is at least 95 octane us
Do these mamo heads accept powdered metal guides?

 

You assume I'm not already there

 

and a video link

 

When you make statements like that it discredits the good info you have shared.

How about small bore ls7's going 8 seconds in the 1/4 mile on a n/a sbe ls3 ?

 

The heads work but the original design was for big bore big cubed engines.
NASCAR LS7 heads are different.
I was looking at some too in the early days.
The ones from higgins.
Those are some quick times.

 

It all comes down to what you want from your car. All ls7 heads be it small bore or otherwise, work well for all out 1/4 mile times, wide open throttle and shifting at high rpm's. That has been proven too many times over now.

My nascar ls7 heads are just basically a trick ported set of small bore ls7's, they are really not that different to the PRC small bore ls7's on the car in the vid i posted above. They still both share the basic ls7 port layout, location and shape.

With the small bore ls7's they just typically keep the intake port size a bit smaller in volume to suit the smaller bore and CI of the engine they are intended for. That isn't crutching of the design, it is taking an already good port shape and valve angle, and making it work for a smaller size bore/engine.

How much is between the cathedral and ls7 .. Tony told you straight how it is. If you wanted the highest HP number at higher rpm's and wide open throttle, and didn't care as much about mid-range or part throttle torque.. LS7 heads. And to take advantage of that the car needs a big rpm converter (if auto) to keep the rpm's up over 5500rpm during a wide open throttle run. That's how LS7 heads work their magic and how Texas Speed ran that crazy 1/4 mile time. They were shifting at 8300rpm.

 

Its a stroked LS3.....not a 4 cylinder Honda. Part throttle and lowend torque shouldn't even be a concern. If anything a cam change only would make the car considerably better without changing the heads and save a bunch of money.

 

Yes he did but he was referring to the big bore LS7 head.
Not sure about the smaller bore versions.
These were actually my first choice if I was to ever get another set of heads.
I contacted so many people, compared flow numbers at various lift points, and then it all went together after some long correspondence with Tony.
We discussed many different options including those heads too.
One day just for curiosity sake it would be interesting to fit them on my 434 to see how they go because I have always wondered about them.

 

Financially it's a good point.

 

The following cam fto EPS is advertized at Brian tooley.EPS CAMSHAFT - STROKER - 34456143

Specs: 244/256 .629"/.604" 114+3 This cam is intended for 400+ cubic inch LS engines that are utilizing cathedral port heads and a stock style intake manifold (i.e. LS6 Intake, FAST, MSD Atomic, etc.). This cam will provide a choppy idle, but still retain some level of streetability. This cam has made 596 RWHP when coupled with TFS 245 CNC LS cylinder heads in a 2001 Camaro with a 6-speed manual transmission.
It has 22 degrees of overlap. Mij 239/254 has 18. Could it be that the camshaft is quite ok? Because changing the camshaft and lifters and pushrods makes things a lot more expensive.. The mamo heads even need roller rockers.

 

It's a healthy sized camshaft.
Have you decided what head you want yet?
This can have an effect if that camshaft is suitable.
If you end up with Tony's AFR 235cc as an example, you would need something like a 244/248 or a 246/250 due to the efficiency of the exhaust port.
Having the wider split will help the power hang on a little better after peak but it does reduce the low and mid range torque response and under the curve power.
Everything is a compromise.

 

I have not decided yet. I first want to understand before i make a decision.
Are those Yella Terra rockers safe for extended high rpm use?