I am thinking of building the stock LS5 sitting in my garage to a more or less stock LS6 set-up for my '71. Several of you have many more years exp with cams and combo's than me. What do you guys think of this combo:

460 cubes, 10.5 CR, GM Roval port alum heads (already in stock), factory LS6 low riser intake, 750 dp BG Silverclaw (in stock), 2" headers, 2 1/2" exhaust, cam similar to factory LS6. The car is a 4 spd with 3.36 gears and will see 95% street duty.

I want a solid cam for kicks, but wonder what lift and duration will work best with the low riser intake (so I can go back to the stock BB hood). Can this combo deliver 400 rwhp and 475 rwtq? My current 433 may be headed to another project and makes 346 rwhp and 402 rwtq.

 

Sounds interesting. But 3.36's? (especially with a M21), not the hot setup for acceleration........or do you want a top end car?

 

Actually the car has an M20 wide ratio box. You are right, the gears are not ideal. That is part of the reason for more cubes, to help the bottom end. The intake should help too, but I wonder if it will give too much power away above 4000 rpm compared to the intake I currently have (RPM Air Gap).

The other reason is the factory look. I know I will give away some power with this set up, but still am interested in feedback, especially on the best cam to use. I want it fast, but with a stock appearance!

 

To use that intake you're going to need to do some head grinding on the port openings. If you're dead set on it, fine, but you WILL lose lots of power of an airgap Edelbrock.

The old LS-6 cam isn't bad...I've run 11's with it, but there are better out there. The 3.36's are going to limit how much you can stand. The oval heads will help....but really this is going to be a long way from an LS-6 spec motor other than some look similarity. 4 bolt mains, better rods, rectangular port heads, long slot rockers etc etc are all the makings of an LS-6. You're going to have a sweet little LS-5 which is great. No reason you can't make your HP numbers though and LS-5 parts can handle that with no sweat. Might want better pistons (forged) otherwise no big deal.

For a 95% street deal and oval port heads with your gear, you might want to step up to a mild street roller. I used the Comp 288 and it was great. It would lug down to 1000 rpm in high gear with 3.36's and a 427 (and a Dominator) and would also pull 7000 rpm when needed. It was a sweet little cam. Just make sure you get the right one..there are several versions. I used the 244/244@.050 .623/.623 on 110 LSA. Stray from that and the cam gets to be too small. I made 423 RWHP with that one through 2.5" exhaust.

I know of a few solids flat tappets that will work well too, if you decide away from the roller.


JIM

 

Jim, thanks for your response. You're right, it will be more LS6 in appearance than reality. But if it has the look I want, the sound, and makes around 400 rwhp, I will be very pleased. I hate to use such a restictive intake, but have tried the Torker II, and would rather give the factory LS6 intake a try.

The baby roller sounds great, but I will likely have to stick to a solid flat tappet-due mainly to budget. I would really like to hear suggestions on cam, and other enhancements to the package. I want plenty of bottom end, throttle response, and vacuum for power brakes, etc. Many thanks in advance.

 

I do remember some Super Stock racers running lo-compression LS-6's way back when. The rules allowed them to build '71 LS-6 Chevelles because it was supposed to have been an option.

Anyway, it was basically a relatively low rpm type deal and in a car that heavy they said they actually found very little difference in the pancake intake when they tried a 427/425 type hi-rise style. I think it surprised them a lot.

Sometimes a combination can actually go faster/quicker with a setup that really doesn't make max power. I mean check out some of the 10 sec C-4's with highway gears running high 10's/lo-11's with less than 400 rwhp. Just monster across the board TQ curve!

The cams you're going to want are going to be around .600 lift (net after lash) and probably 240-250*@.050. That will be a pretty hard hitting cam and will pull well. Vacuum will be much better with that street roller (14"+) but will be acceptable. I would use a 110LSA but you may want a 112 to smooth it out some. With the 3.36's and a four speed, this is going to be borderline, but if it were mine I'd be back up in the 255-260* range and would love it! I'd use the ex. side at 4-6* more duration than the ex. I don't have any cam catalogs with me right now, but this ought to give you a range to look around in.

For decent priced ones that are decent on parts, I'd look at Crane, Crower, Lunati (call and ask for Harold!) or Comp. On Comp stuff I'd really look through the available stuff. Stay away from the 282 and 294S stuff. Not that great IMO. They have great cams available, but do some research.

If you want smoother operation, you can go down to the 230-235 range. It will hold much more vacuum and be smoother, but of course power will suffer.

Just to give you an idea...A buddy of mine threw together a 460 with 9.8 compression, stock GM oval ports, headers, single plane intake and a Summit .540 lift "house" cam. The cam sounded great and idled well. It would also rev to 6500+ when needed. But power really was poor..like 285 RWHP!

He then pulled heads and installed a new ported set with 2.19/1.88's and a solid roller that was too big. He used a Comp 306 Street roller ( I think). It was like .650 or so lift or something and 260+*. It really was pretty sloppy on response but it did make 350 RWHP.

The point of all this is he continually had a mismatched combo. The first one was a good reliable motor that never gave any trouble, but new Camaro's kicked his butt. The single plane didn't match the mild cam, theheads were weak and the cam was just not very aggressive. This is how most "house brand" cams are. They will work, but cams with similar specs will spank them.

The second one was actually closer...the much improved heads could feed 450-475 RWHP easily, the intake was great with them, but the cam was all wrong. In fact I have never been too impressed with that particular street roller. The one I mentioned that is right below it is a much better overall street cam.

He was always mad at me because I was getting that 423 RWHP with a smaller motor, smaller cam etc. Mainly had great flowing heads that didn't need a huge cam. I was using a high lift/ short duration one that just worked well.

If you would either use a 5 speed or more rear gear, we could step up to a couple of Crane's that I KNOW will work great.
Or maybe, how 'bout a little 'ole 4.25 stroker to get 496"??? Those rear gears would sure lover it!


JIM

 

Thanks for such a detailed response. My current cam is 224/232, so a 250 or so duration would be a big difference from my mild mannered setup. Since I am staying with the gear and tranny, I may need to think more about your 496 suggestion!

It is ironic, but last night I came across a Car Craft mag from '87 that featured a 496 build-up using 3 different cams. The one they raved about was the same one you recommended (AR288?). It pulled 612 hp at 6000 rpm with 9.2 CR and mild heads. I think they got 570 ftlbs at 4000 rpm. That would equate to around 500 rwhp. My block is a 2 bolt. Would I need to upgrade to run a stroker on the street? What about rods. Mmmm, this could have some legs.

 

Your 2 bolt will be fine, for added insurance get some ARP studs. The 288 AR is a nice little cam, sorta depends on your definition of streetability. With a 496 and the tranny / rear gears you have the 288 would be a good fit. Eagle +.200 rods would be a good deal for your stroker, run the L-19 rod bolt upgrade.

A port job would be a good investmate also. The GM heads with a little work can flow some decent #'s. I have the Edelbrock ovals and when they were worked over they flowed 318.5 cfm at .650 lift. The car went 123.6 mph the first time to the track with a 10.75 to 1, 454. 491 rwhp.

 

That 288* is just a sweet little cam. Doesn't look like much on paper, but just about always does well. DO NOT get it with a 112 LSA, especially with a 496. It just isn't big enough in my mind to do well with that little overlap. In a 496 it might help it on the top end a little ( I think Lingenfelter liked 112+ LSA) but he was also playing with EFI. It needed lots of vacuum. On a 110 LSA it will hold 14" for sure.

An oval port 496 is going to be a TQ monster. There are still some flat tappets that will work well in it too, but the roller will be better. It's mild enough to have great life also.

Wouldn't worry about the 2 bolts..it will hold. As mentioned studs wouldn't hurt. Pistons are readily available for them these days. Spend the money for an SRP or something forged piston. I wouldn't use the hypereutectic stuff in any motor I was really liked. Not worth the trouble. You can get by with stock rods, but usually most inexpensive stroker cranks are designed for 6.385 (+,250) rods. Just get some SCAT H-Beams. They are good pieces.

With your gears, you'd love a 496!


JIM

 

After mulling this over, it looks like I am going back to building a 460. I want to do a 496, but think it might be better in a '70 Chevelle that is my next project. That way I can run a good intake, and 3" exhaust vs. pancake (great description Jim!) intake and 2.5" exhaust in the Vette. Trying to get a balanced package built around the low riser intake and street gears that will be in the Vette.

So, can you guys tell me about the street manners of the AR288 in a 460 vs. say a Lunati solid flat tappet (110 lsa, 238/238, .625/.625, I think). Will they have similar vacuum and off idle response? I assume the roller would make better overall power (just trying to justify the additional bucks!)

 

I've never actually run that Lunati cam, but considering it is a flat tappet AND 6* smaller across the board my guess if power will be drastically different not to mention driveability. You would have to obtain the .200 duration numbers to help compare the actual rate of lift. I have a buddy with a little 230 something degree flat tappet out of a roundy pounder deal, and his cam is actually almost as aggressive as my solid roller. Of course it's not as big but it really moves the valves fast. You really have to look at lots of numbers to compare cams.

It's also hard to compare flat/rollers because initially the valve movment is less with a roller, but it really accelerates once it starts going.

If you can swing the extra bucks, the roller will be a nice addition. It will allow your "sleeper" motor to make more power than folks expect it to without raising suspicion. But you can also build quite a handful with some solid flat tappets. Check the Crane Powermax flat tappets. i don't rember the # off hand, but there is a sweet little .580/.600 lift on 110 LSA with around 250 something @.050 and 290 adv. that I just love. It's easy on parts, drives decent (might be on the edge with the 3.36's) but it will be OK. having 460" will help along with decent heads. The .600/.620 one right past it on the list is a killer outer edge street cam. With some gear it will pull to the moon and also be easy on parts.

But the 288* is still a sweet little one. It is mild enough to not give trouble with lifters etc and still turn on well. I know for a fact the 288 will hold 14" plus of vacuum and drive great. These others I like will be in the 8-10" range at best. The 238* one might be in the 11-12 maybe I would guess, bit lotsof factors influence that.


JIM