I've been doing a lot of reading on cams lately, specifically about SpinMonster's cam... but, this is all based on a stock cubed LS3. I've got a 402 (4.005" bore x 4" stroke) that I'm building with stock LS3 heads, and a stock LS3 intake manifold. Pistons are -3cc Wisecos with valve reliefs. Compression with a stock head gasket should be around 11.3:1. I'm trying to decide whether to use Spin's cam as-is, or if it can be modified to better suit the 400 inch displacement & higher compression.

Opinions?

 

Contact Patrick G. I believe he's a member here. One sharp cookie when it comes to custom cams.

 

A cam such as the 230/234 114+2 will peak too early in a 402. To extend the power band out to 6300rpm, you would widen the LSA to 117+0 and increase the static compression to 11.7:1 to compensate for the loss in dynamic compresson. This cam makes 510rwhp/500rwtq with unported LS3 heads with this compression.

If you want a more aggressive cam for more power and have less interest in maintaining stock like driving manners, contact PatrickG. More duration can be used and still stay under the 4 degree overlap comfort zone. I would avoid the ubiquidous big duration/naraow LSA cams as none of them have made any serious increase in power over the results I've seen with a 230/117 range cam.

 

Driving manners are very important to me, which is why I've been following your cam suggestions so closely. Patrick seems to get great numbers, but his exhaust duration is a bit extreme for my needs. But, getting back to your suggestion, I'm concerned about raising my compression any higher. I am hesitant to go with aftermarket head gaskets because I keep hearing too many people complain about them leaking/failing, but the stock head gaskets seem to receive no such complaints. I've never in my life used MLS head gaskets, so when people comment to just "lightly spray them with copper spray", I'm hesitant because I really don't know how to judge "lightly" on something that I don't have experience with. The stock gaskets seem to seal nicely without the spray.

By widening the LSA to extend the power band, what effects does it have at lower RPM? This will be primarily a street car, and I've always been a big fan of low rpm torque.

 

I think stock head gaskets are MLS. The wider LSA will "generally" move the peak hp rpm up. Again, generally, the wider LSA cams have better manners. Low rpm torque can suffer a bit with wider LSA's.

 

Your post covers so many different topics.

If you widen LSA and increase static compression it does nothing to the low rpm power since dynamic compression remains close to the same.

Wide Exhaust durations, for those that emply them increase overlap by 1 point for each two degrees added. The gains from this are solely for high RPM power over the HP peak....it makes the power band extend higher (so does a wider LSA in that it extends where the HP peak actually occurs with a given intake duration.

To put this into real world facts, I used a 230/242 as the first LS3 cam and it made 3HP more at the HP peak of 6300rpms over a 230/234 do for the extra 4 degrees overlap, there was no real power gain so why deal with the drivability. Yes people that are great tuners can make such cams liveable but if you start with less overlap, that same tuner can have that much better driveability. Im not a cam expert but thats the scoop on a very specifc use with a real cam in a real car. Narrower LSA's are a help for low end only in that if you cant bump static compression, it closes the intake valve sooner and makes more low end TQ. LS3 cars have limits of how much compression can be increased due to limited intake valve clearance. As proof of my position, to date the best result I have seen on a stock LS3 headed car is only single digit improvements over the 230/234 cam. You decide if you want a ton of overlap for the added few HP up top. Just as a revelation, I have sen a 238/252 112 LSA make 480rwhp on a 403 stroker. You tell me whats wrong with that picture. Aitqik's cam was a 236/242 114LSA and it made 499/480 on his 403 with ETP 215's. So if a 230/234 117 makes 500rwhp its doing fine and it will idle at 700rpm with almost no lope.....at -2 degrees overlap its actually a great FI cam.

My car is running 17PSI boost with cometic MLS gaskets and I have used them exclusively now for 8 years on corvette builds and we are talking a lot of cars. I never had a failure or a leak.

When tuners make cam recomendation like Patrick G, understand that he is using some really informed tuning skills and many shops out there really arent on that level. I have been in cars with that 230/234 cam at 4 degrees overlap and it drove like stock while other tuners couldnt get it to not buck and surge like an electric bull so you have to take into account the level of tuning expertise that is available to you. I am middle of the road. All my cars drive great but then I dont use mad huge cams.

I would defer to Patrick's expertise as I know of his work over past years and he has influenced my own path in modding. His being here is an asset to the forum but keep in mind your tuner may not be on his page of skill.

 

they are MLS but they have rubber like ends to certain sections making them more forgiving of surface imperfections. If someone has a leak its from the surface being imperfect.

 

I think the LS3 (or maybe it's the LS9's) head gaskets have more layers vs the LS2's and are better for high power applications. Not sure of thickness or if they're any other differences. Something to consider.

 

Good info if someone can verify that.

FI benefits from having minimal quench distance so thinner gaskets are better for detonation suppression. As far as boost and high power, my cometics are fine with 17PSI and a 75 shot on top of it. I know Mr big's car used stock LS2 gaskets and he was at 15psi.

If anyone is afraid of using MLS gaskets, a .040" is available for the LS2 from felpro and its a great gasket. Tony Mamo at AFR swears by them.

 

A 402 will want 4 degrees more overlap than a 376 in order to have the same street manners and power/ci. More cubes with the same heads will make the motor more "undervalved" than it was before which means you typically pick up power by narrowing the LSA slightly, but higher compression allows you to widen the LSA some. For this application, call it a wash. Basically, if want to replicate the Spinmonster cam in a 402, a cam 4 degrees larger on both intake and exhaust, with the same 114 LSA and same 2 degrees of advance would work great.

 

I tried a 236/242, both XER lobes on a 114 and it barely hit 500rwhp in a 403. I would expect the optimum cam to at least beat the 6.2 liter LS3 due to extra cubes. The TQ was huge tho.

The info above is good and Im sure it generally works with trick flows and AFRs but the LS3 heads dont react well to overlap (due to reversion I suspect). I see lots of LS3 head 403s over on LS1 tech making 480rwhp with bigger durations and tight LSAs while stock head LS3 376ci with a 227 to 230 intake duration cams make in the 490's to 500 pretty consistently. Most of the stroker LS3 head builds tend to use ported LS3s so its not apples to apples.

Is it that the 403 shrouds the intake valve due to its 4" bore? I get the undervalved point but Im not sure how the 2.16 intake valve on a 4" bore fits in the tech point.

One point is that the 230 117lsa would run more static compression due to the lower dyamic compression.

Pat, are you getting, or did you get a corvette? Good to see you posting here.

 

Does anyone know any actual results seen with a 403 and LS3 heads and what cam was used?

 

The smaller bores hurt the LS3 heads. The intake valve is very shrouded and has a harder time breathing. More lift will help get the large valve further away from the cylinder bore. It's not surprising that the 402 did not make as strong of hp/ci as the LS3. The larger bore of the LS3 block really helps that large valve shine.

For what it's worth, the added cubes require more overlap to maintain the same driveability and power per cubic inch. Not excessive overlap, just an appropriate increase in overlap. That's why I only recommended a 4 degree increase in overlap on the 402.

 

FWIW, sometime ago, I installed a TSP 418 with their ported versions of the LS3 heads. This engine was installed into a customers C6 coupe. The engine came from TSP with a 236 244 cam ground on a 115 if I remember right. The customer never liked the way the car ran. A few months later I swapped out the cam for a 234/236 on a 114 and the car made a drastic turn for the better. I gained a bunch of power under the curve and made more peak power as well. Plus it gained a lot in terms of street manners and much improved driability.

 

Sorry to bring this back from the dead, but my build has finally progressed to the point where my cam needs to be purchased. I'm still waffling on what cam to get. There still seems to be conflicting opinions, primarily on exhaust duration and lsa. Lately I've been leaning heavily toward a 227/239 115+2, but wondering if I'm not a little better off with a little more intake and less exhaust. Ultimately I want area under the curve with great torque, so long as I'm not sacrificing too much horsepower to get it.

Tjwong, did you ever dyno the car with the 224/236 cam? Your description makes it sound very appealing.

 

I would talk to Pat G and get him to spec you a cam.

 

I intend to talk to Pat, but I'm not yet ready to blindly trust the advice of just one person (even if it is Pat G!) until I have developed enough of an understanding of what's going on to feel confident in what he comes back with. As even just this thread shows, even the experts seem to have more than one viewpoint on this topic, so I feel that I need to learn more and get more feedback in order to feel comfortable with whatever choice I ultimately make.

 

Right, but I'm saying you should call him up and talk to him, lol. No need to blindly trust anyone

1 or 2 posts doesn't explain much about what is going on. Calling the guy and getting him to explain what's going on and why he's choosing certain specs is far more valuable.

He's a good guy to talk to and will answer any and all questions.

He recently specced me a 238/242 110lsa on proprietary lobes for a max-effort cam only setup. Explained everything to me and I was in communication with him for an additional week about how to specifically set my entire valvetrain up to match it.