Hey guys,

Here's what I believe I have. Realize I did not install or build this motor. I bought the car in November '02, and I do know for a fact its a GM Gen 6 crate motor, but with alum. rect. port heads vs. the iron ones it typically comes with. CR is ~9.0:1, I have an LS6 low-rise intake, Holley 800cfm Street Avenger carb, and Hooker 2 1/8" headers and sidepipes (uncapped at the moment).

Now that the car is tuned, the new Richmond trans is in, and I'm getting some seat time ... I've been driving it more aggressively. Knowing it is a bit more skittish (handling-wise) compared to late model cars I'm used to, I have been reluctant to hammer on it all the way past redline.

The thing makes decent power. My butt-meter says it probably runs high-12s. Nothing earth-shattering, but not bad for what it is. Pulls very hard to ~5600rpm, then tapers off pretty quickly after that (enough that I can definitely feel it nose over a bit). Seems like it revs to 6k in 1st gear, but that's b/c everything is happening really fast...once I got it out in 3rd and hammered on it, I could better tell where the power band starts and ends. :) I just didn't want to wrap my new toy around a tree before I got some seat time in it.

Here's what I'm thinking, and please feel free to disagree as I'm new to Chevy stuff, and certainly BBs. These heads should allow plenty of flow to 6500rpm or so, and the intake ... well, it may be a bit small, but will have to do b/c I want to retain the stock hood. The exhaust is plenty for what I've got. The bottom end is all forged stuff and should also be good for more rpm.

Given the relatively "low" CR, what would a good cam for this combo look like? I know the cam specs of the crate motor, but have no real clue if this is what is in there, or if the owner swapped it out since he put on the alum. heads. I'm betting its the stock crate engine cam, and if so, I know its small for a BB.


[Modified by WA 2 FST, 9:11 AM 1/7/2003]

 

There have been many discussions on cam choices....do a search and see what you come up. The first thing you need to determine if you want a hydraulic or a solid lifter, roller or a flat tappet cam. Once you determine the type of cam, then decide on the duration and lift that will meet your needs. Once you've determined those variables, members can fine tune your choice.

 

Thanks...I will do a better search.

I do know for sure I want to stick with the hydraulic roller setup. I'm not intersted in converting to a mechanical/solid roller at this time, and there's no sense in going to a hyd. flat tappet since its already set up with hyd. roller valvetrain now.

Looking for a powerband from ~2200-6200rpm range with the above listed combination. That's why I'm looking for duration/lift ideas. I also want to stick with something that has at least a 110 LSA as I have power brakes and power steering and want the thing to pull some reasonable vacuum. The cam in there now just doesn't have enough intake duration to pull as high as I think the current intake/heads/exhaust will support, but it is a great street cam.

I'm looking for something that is radical enough to allow power production just past 6k rpm, but streetable enough to idle nice (which a hyd. roller should help anyway) and have good manners for cruising around.

I'm not looking to build a 10-sec car on this one. :)

 

Is it a 454HO with aluminum heads? I'm just thinking that if it is, and still has the stock 454HO cam, it's a fairly mild grind. Also, if it still uses the stock valvetrain, then you'd be limited on the amount of lift you could use without changing to different lifters. You'd need to find out what you have in order to try and decide where you want to go. ZZ502 cams are pretty reasonably priced, and can be used with the factory net lash valvetrain. If you're sure it's a Gen.V/VI, does it have a mechanical fuel pump? 454 HO's had mechanical pump capability, and I think the 502's did not. Hope at least some of this helps.

 

Thanks for the info. I have confirmed its a Gen VI motor. It is a 454 that has a mechanical fuel pump. You're right...if it does have the original crate motor cam (and I'm thinking it does, the way the power band is...1500-5500+), then the specs are .510/.540, 211/230 dur. @.050, 112 LSA. Like I said before, not nearly enough intake duration to support more revs than I'm getting out of it.

The reason I'm considering a cam is that I think the intake/heads and exhaust (and bottom end) can support 6000+rpm. With the 5-speed trans and 3.36 rear gearing, I have plenty of gear that I could give up a bit of low end TQ at 1000rpm.

Again, I'm not trying to go nuts with this. Another 500+ useful revs would give me a nice boost in top-end power, and I think I have the other pieces to support the airflow.

RE: Limits of the stock valvetrain... could you please expound on this? I figured I would certainly need new valvesprings, but why are the lifters not capable of more lift/duration? I'm not well-versed in GM BB hyd. roller lifters, but I wouldn't think they would be obsolete with a cam swap. :confused:

Thanks for your help! :)

 

ORVette... you got me thinking, so I looked up the specs on the ZZ502 cam.

Assuming mine is the 454 crate cam, this ZZ502 cam might be just the ticket for a mild upgrade I'm looking for.

It's specs are 224/234 @ .050", .527/.544, 110 LSA

Comparing that to what I've got, I should pick up another 300-400rpm in useable power band and probably 15-20hp with the airflow capability of the rest of my combo. And I shouldn't have any issues with valvetrain problems or P/V clearance issues.

I know most guys on this board have either hyd. flat tappet, mech. flat tappet, or mech. roller valvetrains. I'm kind of an odd-ball here with this hyd. roller setup.

Thanks for helping. Seeing as though I'm not trying to get real radical from where I am now, this cam might be a good choice.

 

I have the oval port version of your intake on a 427. The head guru here says the intake being nearly flat is the reason it won't rev much past 5500 rpm. So, for what it's worth, I wouldn't expect your motor to be able to use a cam that revved to 7000 rpm or so. The valvetrain might be able to go that high, but there wouldn't be enough air/fuel flow to make power. I would stick with your hydraulic roller set-up and shoot for something like a 230 intake @50 and 238 exh @50 with lift approx near .600 or so.And an LSA of 110-112.

Ganey is the cam expert here.

Good luck!


[Modified by marky mark, 4:47 AM 1/5/2003]

 

Not sure if the LS6 intake will do you much good over 6k rpm. Low rise dual plane + plenty of cubic inches... Definetely limited at high revs.

I have a similar cam to the one you are talking about in my 454. mine is 224/230 but with higher lift (573/585) and a wider LSA of 114. Peak power is 5300-5500 and it pulls strong to 6k, but that is it.

 

The ZZ/502 cam has more intake duration and lift (exhaust is the same), while the LSA on the ZZ/502 is 110 rather than the 112 on the 454. I know because I own them both. The 502 has more upper end than the 454, probably because of the cam difference. It also idles lots rougher.
Also, check out the cam specs on the 572 MK VI crate motor. I believe it's a hydraulic roller (in it's low compression form) and has over .600 lift.
:yesnod: :chevy :chevy :yesnod:

 

A roller hydrallic will give you more lift per duration, a good thing. Talk to either Comp Cams or Crane cams. They will ask you the power band you want and your intended use. They will help you pick the right one.

Talk to both and compare the specs they recommand to each other. If they are similar, it is probably the right cam.

 

Ok, guys. Great info here! Thank you.

Sounds like the LS6 low-rise intake is the limiting factor in the combo right now. Since I do not want to mess with a different hood at the moment, I want to stick with it. Now that I know ~6000rpm is all its gonna be good for...then the goal is simple (and not far from what I was wanting to do) and more defined. I appreciate the candor on my set up. I figured the low-rise would be restrictive at the upper rpms, but I didn't know when it would really start to hurt me.

ORVette mentioned that I might have to swap the hydraulic roller lifters. Anyone know what this is about? I have the stock ones that came in the crate motor. I assume that while they are an OEM-type hyd. roller that they will still be ok to use. Or not? :confused:

I certainly don't need a cam any larger than Zwede's, as my engine does not have the power potential his does (lower CR at the very least, and my heads probably are not as good). The ZZ502 cam is probably pretty good, but maybe a little low on the lift (.527/.544). But I agree that sticking with something in the 222-226^ intake duration is probably a good idea to maintain good street manners, low-end TQ and still give me power to ~6000rpm. I want the peak HP to be lower ... 5400 or so, but shifting it a few hundred rpm over peak will always show as a quicker acceleration run than shifting right at peak HP.

I will get the car to the dyno before I take the plunge on a cam. Who knows...my factory tach could be way off and I'm really only turning 4500rpm when I think I'm turning 5500. :lol:

Again, thanks for the great discussion! This has been a big help.

 

The lifter thing has something to do with the "net lash" rockers on the 454HO crate(not sure if it applies to 502's, etc.). Apparantly, you don't set the lash like you would on a regular hydraulic lifter, you just torque them down and that's that. I wish I could give you some good technical insight, but I'm only repeating part of what I read in Chevy High Performance magazine. They have been doing a 454HO crate buildup for a few months. Try going to Chevyhiperformance.com and looking up the articles on "FrankenRat". I am in the prcccess of putting a 454HO in my '73, and I have that same intake manifold. I picked up a ZZ502 cam to swap in before it's installed. Good luck with your project!

 

That's ok. I understand _exactly_ what you're referring to now. I'm from the late model world where everything is hyd. roller. A stamped steel, non-adjustable rocker (which the 454 and 502 have... as well as the current production LS1/LS6 motors) means you just torque 'em down and go. There is no _adjusting_ the lash with a hyd. roller valvetrain.

As long as I use a cam designed for a hyd. roller lifter (which is my plan), I should be fine and shouldn't have to replace them.

I've considered roller rockers (which are adjustable...still, very easy to adjust and you do it once and forget it), but would need tall valve covers and I'm afraid interference with the brake booster would be a problem in my BB.

 

Sounds like you know what you're doing, but I just want to re-emphisise that the factory GM roller lifters are only good up to about .550 lift.They are retained with a cast bar that fits over the top third of the lifter. When a high lift-reduced base circl cam is used, the lifter can actually drop out of the bottom side of the retainer!! Page 64, Dec. '02 CHP.

 

Actually the lifters themselves are only good for .570 lift which is what I read somewhere. I think the GenVI lifter bosses are taller and the stock lifter can bind if there is too much lift. Crane and others make a rocker stud that is 1/2 inch on the bottom and 7/16 on top to convert you to a Mark IV adjustable system. Definitely check on the max lift of the stock lifter as I know there is one. Bill.

 

Wes, I've never used a Gen VI block, but this is what I've been told. You have to be careful with the Gen VI roller lifters because of the retainer that holds them in place. If the cam lift is too high, the lifter will "top out" on the retainer and damage the lifters. Also, the Gen VI lifters are taller than regular BBC lifters, and the lifter bosses are also taller to match. To install a regular BBC drivetrain, the block has to be milled. Some guys install 1.8 rockers to increase lift without requiring a bigger cam lobe.

I believe that Crane sells a few hyd. roller cams that are a step up from the ZZ502 cam, and they work with the stock drivetrain. Might be worth a phone call.

EDIT: Looks like I'm a little late to the party as usual... :lol: Just listen to Bill's advice above.

-Joe


[Modified by Flareside, 6:07 PM 1/6/2003]

 

Wes,

I really believe you are limited by the cam, not the intake. Yes there are better intakes, but the low-rise LS6 is good for every bit of 6500+. Also, you will not find a better intake that will fit under your stock hood than the LS6 low-rise, period! The low-rise tripower and LS6 intakes are similar in design to each other and would hit 6500 redline in an instant. The secondary vacuum springs on your Holley avenger may be a tad too stiff to allow your secondaries to fully open too.

The beauty with roller cams is that you can run either solid or hydraulic lifters with the same cam. Stay with the hydraulic setup if you like it. Calling Crane or Comp cams as has been suggested is a very good idea.

Chuck

 

Thanks for the continued discussion, gentlemen. Every bit of it helps.

I did not realize that I could run into the problem of having the lifter "top out" against the retainer. Obviously that is not a good thing. That's too bad it occurs at such a low lift. :(

1.8 rockers scare me a little bit. I guess if the geometry is right and you use the right springs/retainers it could work. But I'd rather get the extra duration/lift from the cam vs. the rockers.

Adding 1.8 rockers to my current cam would give me 223/243 @ .050, .540/.571 max lift. Not bad.

But, just going with the ZZ502 camshaft may be a good alternative as well. It looks superior to the off-the-shelf grinds by Comp Cams, although Zwede told me Comp will custom grind a cam for no additional charge.

Chuck, I have checked the secondaries, and they are opening fully now, but carbs are still foggy to me. But with my foot planted, the secondaries are open. They weren't when I bought the car two months ago, however. ;)

 

:iagree:

Regarding the lifter, you have to get gen VI lifters as the lifter retainers for the Gen VI block are taller then the gen IV blocks. They are not cheap, the Gen VI roller lifters.

What Chuckles stated, don't blame the intake, I am running the stock tri power intake, flat as a board and I pull to 7K all day long, and if I had the Kahuas as big as watermellons, I would pull to 7500, though have gone to 7200 a few times. Spring pressure is the limiting factor and is matched to the cam.

w

 

Chuck and GDaina: I e-mailed Wes privately because I thought maybe there was some new discovery about low rise manifolds reducing RPM. I never heard of that before and I've seen some manifolds in the past that looked absolutely SUNKEN reaching 6000+ RPM. I told Wes as much. I thought valve train was the limiting factor and it's nice to see confirmation from both of you that that is probably the case. A high rise manifold WILL give him more horsepower @ high revs, but it won't add RPM to his engine.
Since he is adament about not changing to an L-88 hood, I think his LS-6 should do quite nicely. I also suggested the possibility of weak valve springs or maybe an ignition not working properly as possible culprits in limiting his RPM.

Dep