Upgrades for 402 LS

[David Pozzi]

I bought a 402 LS from some guy named Steve Rupp, he says it was only driven to church on sundays...

But seriously, here's his build info and I need a little advice on perking it up.

LS2 block
AFR 205 custom ported heads
Comp hardened push rods
Bushed GM rockers (CME)
Lunati Pro Series Crank (4" stroke and 24x reluctor wheel)
Lunati H-beam rods
Weisco Flow-dome forged pistons (about 11.1:1)
Fast 90mm intake
All ARP bolts, head studs, main bolts
Includes FAST injectors/Fuel logs and sensors
Canton pan.

about 3,000 miles on the engine.

Runs REAL hard and made 488 rwhp and 475 rwtq last time it was chassis dynoed.

You can read about the build here... all the machine work was first class and it's a hard running engine.

Read the build story here:
http://www.camaroperformers.com/cama...ade/index.html

It's a really good engine but I realized a couple of things.
1. The 205 AFR heads were selected back when the engine displacement was 6.2L I think this is hurting top end power now that it's a 402.

2. There are now better heads around BUT I don't want to hurt low end torque, that's where this engine shines right now.



Is there a better head and intake setup that would still make good torque but boost top end? Step one might be to use the AFR 225's, but then there's the LS3 type...
Thanks, David

[CarlC]

8 psi make any head flow better. ;-)

[John Wright]

8 psi make any head flow better. ;-)

LOL...this is true

[Steve1968LS2]

I bought a 402 LS from some guy named Steve Rupp, he says it was only driven to church on sundays...

But seriously, here's his build info and I need a little advice on perking it up.



It's a really good engine but I realized a couple of things.
1. The 205 AFR heads were selected back when the engine displacement was 6.2L I think this is hurting top end power now that it's a 402.

2. There are now better heads around BUT I don't want to hurt low end torque, that's where this engine shines right now.

Is there a better head and intake setup that would still make good torque but boost top end? Step one might be to use the AFR 225's, but then there's the LS3 type...
Thanks, David

The problem with that Rupp guy is that he would any joker drive his car... guys like you! lol

When we dyno tested the engine the volumetric efficiencies were good so I don't think the engine was running out of air. Nonetheless, if you put on some larger heads you would see an increase in top end power but would most likely loose some low end torque. In other words it might just shift the curve around. I will call Mamo and ask he what he thinks.

And to clarify the 205 were custom massaged by Tony Mamo at AFR, so they flow better than a standard set of 205s.

If you want more steam I would simply bump up the cam a bit. Right now it's a 238/240 and is pretty darn mellow. I also think the LSA is 113 or so. Moving that to a 112 (plus 4) and upping the durration will give you some more power. Plus the 112+4 would be good for low and midrange torque. I would have to be custom ground since the cam in the car is the biggest "off the shelf one" but I connections.

Another thing that would help would be trading out the FAST 90mm intake for thier brand new 102mm cathedral port intake. If you did this then you would also want Mike Norris to port your TBW throttle body an he offeres a transition ring to smooth out the difference in diamerters.

Sure you could switch to some LS3 style heads, especially is your changing the intake. Care does need to be taken due to the larger intake valves but your PTV clearance should be ok. You can reuse half of your bushed CHE rockers and I have a set of offset rockers that could be bushed by them.

That route is pretty expensive since you're replacing so many parts. Think the best "bang for the buck" would be a cam, but you will give up a bit of the nice idle. I don't know if I would replace the heads, but I would consider the intake (and save the 90 for your other LS2). If you didn't want to buy a new intake you could port out the FAST 90mm on the car right now. It was worth about 10hp when we tested one on the engine and I know you love tinkering like that.

Keep in mind the engine put out about 570hp and 535 ft-lb (488 rwhp and 475 rwtq as I recall).. which is pretty stout.

[Damn True]

Where is this engine going to live?

[David Pozzi]

8 psi make any head flow better. ;-)

Yes, I've been thinking about that.

[David Pozzi]

Steve,
Thanks for the added info. Do you have flow numbers for those heads with the extra port work?
It just seemed to me that those are the smallest port size they make and made more for an LS1. But it isn't worth buying new heads for an extra 20 hp top end. I don't want the idle to get rougher, or lose low end torque, but was looking at a way to boost top end a little. Maybe porting the intake and Throttle body would be a good idea.
David

[WS6]

I wouldn't touch the engine beyond maybe porting the intake and TB. Those torque numbers are fantastic. You rarely see anyone talking torque numbers and location when building the LSx engine. I have no doubt LS3/L92 heads would make more peak power. I also have no doubt that you'll lose low end torque.

If you want to try a cam change, go wider on LSA. Narrower moves power band up, wider brings it down because it keeps the intake charge in the cylinder longer. You could try the XFI grind possibly. I'm assuming this is a Comp XER cam currently. Check the mid range lift numbers on the XFI cam though. I know overall it is higher but power is made in the low lift area not at .600 lift. However, having just as good a base but even more top end flow could help you.

I'd still not change it though. I say run it. It's great the way it is.

[CarlC]

Yes, I've been thinking about that.

If you are at Willow on March 4 take mine for a ride. Yours would be MUCH faster.

[Steve1968LS2]

Steve,
Thanks for the added info. Do you have flow numbers for those heads with the extra port work?
It just seemed to me that those are the smallest port size they make and made more for an LS1. But it isn't worth buying new heads for an extra 20 hp top end. I don't want the idle to get rougher, or lose low end torque, but was looking at a way to boost top end a little. Maybe porting the intake and Throttle body would be a good idea.
David

They make smaller.. I think they make a 195.

That was forever ago.. I called Tony Mamo today and left a message.. I think he will have that info.

Port the intake.. or buy and port a 102mm and then port the TB. You could go one step bigger on the cam and most likely never notice it.

[Steve1968LS2]

I wouldn't touch the engine beyond maybe porting the intake and TB. Those torque numbers are fantastic. You rarely see anyone talking torque numbers and location when building the LSx engine. I have no doubt LS3/L92 heads would make more peak power. I also have no doubt that you'll lose low end torque.

If you want to try a cam change, go wider on LSA. Narrower moves power band up, wider brings it down because it keeps the intake charge in the cylinder longer. You could try the XFI grind possibly. I'm assuming this is a Comp XER cam currently. Check the mid range lift numbers on the XFI cam though. I know overall it is higher but power is made in the low lift area not at .600 lift. However, having just as good a base but even more top end flow could help you.

I'd still not change it though. I say run it. It's great the way it is.

The current cam is a 238/240 112+3 ... It was the biggest (at that time) in the XER line for off the shelf stuff.

Here's a dynograph, we were having problems with the XFI running the engine on the dyno and I think the peak numbers are a bit low (was breaking up a bit).

Still, the low end torque stuff is good.

Here's the engine dyno (compared to the before engine)


Here's the chassis dyno (rear wheel compared to with the broken spark plug)


Here's what I wrote about the AFR heads from back in '06

The LS2 crate engine ships with some pretty good heads that, with port work, can flow some respectable numbers. However, we decided to go with AFR’s newly designed 205cc Mongoose street heads. AFR states that the flow performance is 300 CFM at .600 lift (about 70 CFM over a stock LS1 head) and that the heads feature 2.020 intake and 1.600 exhaust valves with iron ductile interlocking valve seats. The AFR heads weight a bit more than the stockers, but that weight is in the right places with a .75-inch thick head deck, reinforced rocker stud bosses, and thick wall runners.

[WS6]

That's so pretty I'd be afraid it wouldn't like a cam change. Sure on paper a cam change should do better if spec'd correctly but that doesn't mean it will.

Steve, why didn't you have a "custom" cam spec'd when you had the 402 built? Comp lists the lobe numbers online. They did have them in the back of the master catalog for a long time. I used to laugh at all the people selling "custom" cams to customers for a huge mark up. They went through such secrecy to hide the cam info too. All they did was flip to the back of the catalog and order based on lobe numbers and told Comp what LSA they wanted it on. Truly custom would mean they spec'd the lobe design which very few really did.

[Steve1968LS2]

That's so pretty I'd be afraid it wouldn't like a cam change. Sure on paper a cam change should do better if spec'd correctly but that doesn't mean it will.

Steve, why didn't you have a "custom" cam spec'd when you had the 402 built? Comp lists the lobe numbers online. They did have them in the back of the master catalog for a long time. I used to laugh at all the people selling "custom" cams to customers for a huge mark up. They went through such secrecy to hide the cam info too. All they did was flip to the back of the catalog and order based on lobe numbers and told Comp what LSA they wanted it on. Truly custom would mean they spec'd the lobe design which very few really did.

We did have a custom cam in the old LS2.. when it died from an oil failure we had to rush an engine together.. at that time it was almost 2 weeks for a custom grind so we picked the best from thier "off the shelf" offerings. Not sure if the lobes were one-offed but the cam was designed by COMP and worked well, just no time to do it on the new engine.

And it's true that there are very few "truly custom" cams.. most are just a mix of existing lobes.

[WS6]

Understandable. When you have a dead line you have to meet you may have to make compromises. I'd say it worked well for you in the end.

[BonzoHansen]

Where is this engine going to live?

See how he skipped your question? See that?

[Steve1968LS2]

See how he skipped your question? See that?

Nothing to see here... move along...

[David Pozzi]

I just need to keep it out of Mary's evil grip! I have 2 cars it could go in, or a third I haven't even built yet.
One problem is, I was fairly far along building a Brodix tall deck block 18 deg headed 427 for my 67 and I don't know if I should sell it or finish it and use it in the car.

I like how smooth Steve's engine runs on the street, and the torque is great. It looks like working on the intake and Throttle Body would help. Cam change? Maybe.

Two things about a supercharger, I think the compression is too high, and it would add some extra weight.
David

[79-TA]

Perhaps old fashioned cylinder head shaving is an option? Maybe a comparable but thinner head gasket is now available? Or are the valve clearances already too tight for that?


You could get really fancy and start looking into variable cam timing. Cam phasers are becoming more common on the new GM engines. Sadly, I have no idea if it is remotely practicaly to retrofit such a setup onto an LS2.

[John Wright]

I have 2 cars it could go in

one being a red 73 camaro?<fingers crossed for Mary>

[WS6]

I just need to keep it out of Mary's evil grip! I have 2 cars it could go in, or a third I haven't even built yet.
One problem is, I was fairly far along building a Brodix tall deck block 18 deg headed 427 for my 67 and I don't know if I should sell it or finish it and use it in the car.

I like how smooth Steve's engine runs on the street, and the torque is great. It looks like working on the intake and Throttle Body would help. Cam change? Maybe.

Two things about a supercharger, I think the compression is too high, and it would add some extra weight.
David

I wouldn't put an SC on the engine.

Something to keep in mind if you aren't already aware. The FAST 102 has different runners available for it. You can test and tune the intake essentially. It's not a cheap setup but I think I would lean this direction so you can hopefully optimize the power with a day worth of dyno tunning. VMax Motorsports offers a cable operated 100 or 105mm billet throttle body that is gorgeous and will fit the front of that intake. I'm betting you'll want a 95 or 100 and not the 105 for great throttle response. Check with Pete at VMax or Mike Norris as he carriers VMax parts as well.

Going with a carb style intake may be possible also. I can't remember but I believe they are all single plane only which could hurt bottom end if the runners are too large. It will definitely help top end though. I think the FAST 102 would be better simply because you can change runners.

Then again, loose just a tad on the bottom but gain a bunch up top may work better on the courses you'll run. See how this could get out of hand quickly, lol.