Before I put the cam in I'm going to be swapping in my 3.70 gears for the 9-bolt.

my little xe262 makes for a great streetable car, but Im a little bored with it. I want more. According to a nastyz28 article/post, Vortecs are good for 480hp. I also know that Vortec intake ports start to stall around .475 lift or so. So going much beyond that isnt necessarily a great idea. I also dont know exactly how much retainer to guide clearance I have, only that I know it's fairly tight and my machine shop told me it would be fine for my current cam, which is .462/.469 lift. Since I have Comp Pro Mag rockers (1.52 ratio), that comes out to about .468/.475 actual lift at the valve.

So Im thinking maybe I should just get a custom grind cam. I dont want to pull the heads and pay out the behind to get my valve guides milled down when it doesnt really accomplish much (see above about ports stalling). The vortecs strength is low/mid/middle-high lift flow, and within those constraints they're excellent.

I think there's power on the table for me to get, so Im looking at comp's lobe catalog and have a few options.

For Hydraulic roller lobes I have a couple of xtreme 4x4 lobes:

3308 - 230@.050, .474
3309 - 234@.050 .474

Then I found some mustang lift-rule cam lobes that looked pretty interesting, can be solid or hydraulic roller:

3329 224 .468
3390 236 .468
3391 238 .468

Then there are some super duper xtreme versions of the lift rule lobes that have even faster ramp rates:
3330 230 .468
3331 236 .468

My concern with those is that comp's catalog says "RACE ONLY!" all over the place. How much of a problem would that be in a street car? I would be picking the smallest they have, basically. and 230/236 at .468/.468 lift doesnt really sound THAT radical. There are street cars with bigger cams than that. I worry it would require some hardcore valve springs or wear out the valve seats more or something.

And there are some xtreme energy solid lobes I like a lot:

6017 224 .468
6083 224 .470
6084 230 .470

My vortecs have a 1.94 intake valve, and a 1.60 exh valve. The exh valves are .100 inch longer too I believe. So I have, in theory, an extra .100 inch to play with there, I think.

I still think I'd be better off running a split pattern, but Im hesitant to go past .470 lift. Theres an xtreme 4x4 cam that's almost perfect, and I think it's the off the shelf version of the first two lobes I listed. It's recommended valve spring is the same as what I already have installed, so since all the lifts and durations are fairly close on all of these, I figure I can safely re-use my current valve springs.

So what do the cam engineers here have to say about it? Is using one of those "RACE ONLY!" lobes a terrible idea? I like the 4x4 cam a lot, but I dont want to push the lift any more than I have to. So I mleaning the most towards a 224/230 .470/.470 solid roller xtreme energy cam (the last set of listed lobes), but I worry that may not give me that much of an improvement over my current flat tappet 218/224 .462/.469 xe262 that I already have.

As far as supporting hardware

Holley 650DP
Performer RPM intake
Vortecs with 1.94/1.60 valves, screw in studs, guideplates, around 10:1 compression
Long tubes, dual 2.5s into a single 3.5 exhaust with a glorified glasspack muffler
and a 355 underneath.
and i will have 3.70s in the 9-bolt.
I run a T56 so a stall isnt a complication.

 

Isky cam #201278.. You won't be bored any more.

The modest .450" valve lift makes it a bolt in.

278-278 234 234 @.050" .450" lift 106LSA

This cam has proven to work very very well in this applciation.



www.iskycams.com

 

Those "race" lobes are brutal, they'll bend most pushrods, they'll kill springs in no time, and they may even contribute to collapsed lifters.
I'd go with the 3052 lobe for the intake, and the 3053 for the exhaust.

 

A big part of the reason for the swap is so I can move on to a roller camshaft and not have to worry about oils and break ins and additives and whatnot. Otherwise that cam sounds great. But I want to move into the 90s with a roller setup.

 

You know I actually had those written down for consideration in my list, but I worry that maybe .480 lift will be too much. But it's sooo close...

I wish there was an easy way to check valve/retainer clearance with everything assembled in the car.

 

Consider this: The reason Comp uses 0.006" for advertised duration is because their testing has shown that that's how much lift you lose to the hydraulics of the hydraulic lifters. So that 0.480" cam is really a 0.474" cam. However, your rockers being 1.52:1, now you're back at 0.480"
Now, Vortec heads are mass produced, so that means variations. If you test 100 intake ports, you'll probably find that most of them won't stall at exactly 0.475" lift.
And when flowing heads, who ever bothers to test at 0.475", and 0.480", and 0.485" and so on?
I'd propose that what possibly happened was "they" wondered why flow at 0.500" was no better than at 0.400", and sounded different, so they tried 0.450", then 0.475".
I also have to wonder if you did venture into the stall zone by 0.005", would it stall? On the bench, it takes at least half a second to adjust the lift, then are they waiting for the display to stabilize? But in a running engine, the valve is at that lift for like 0.001 seconds, is that enough time?
This merits testing at a top facility, rather than leaving us guessing.

 

I've seen way too many vortec setups work way too well with lifts up to .500 and beyond, I'm more worried about hardware incompatibilities than performance ones. It's just the diminishing returns at .475 or so make spending money and effort removing the heads to mill down the valve guides a bit harder to justify.

So even though they're listed as hydraulic lobes I can use a solid roller on them and basically end up at .475 lift where I started? I always assumed you could, but sometimes this cam stuff does turn into voodoo and Im not quite sure. Would I see a performance gain with solid roller lifters vs hydraulic? Im not even that hung up on hydraulic lifters, it's just that they're closer to the weight of flat tappet lifters and would probably agree with my current valve springs more. They also seemed a little cheaper, but not by very much.

 

The limited lift rule stuff is very harsh on valvetrain. they have fast ramps with alot of area over the nose. Like a square lobe Race only means race only. For a street car, i think the 4x4 lobes will be a great choice provided you can clear the lift. Swap the valve springs, install a +.050" lock with shims to get extra clearance as necessary.

If your going to a roller cam lobe now and had a flat tappet, you'll want to replace valve springs anyway for a slightly stiffer double spring or a good single like the manley 22410's. I like doubles in the 130lb seat range 350+ open. Good with hydraulic rollers to 6500 rpm on MOST cam lobes. Some of the ultra aggressive stuff you will need ALOT more pressure.

 

I've seen the same, but I can't help but wonder if they wouldn't see the same results, or better, with custom lobes having the same duration at 0.300" lifter rise, but no more than 0.320" lifter rise.
Right now I have a pair of used 906 Vortecs off a '96 Chevy pickup. They're still wearing their original valve seals, and I still have their original valves, retainers and locks. Every one has right at 0.483"-0.486" of clearance, but your results may vary.

 

It doesnt always work this way but anytime you can get more area under the lift curve when keeping the same opening/closing points and same lift, you will make more power. Usually more at the top end.

So duration at .006 and .050 may be the same but duration at .100, .200, .300 and over the nose can be completely different and the difference in power can come from there. However, this usually leads to a hard to control lobe. Lifter acceleration is higher and it will require heavy spring rates to control these lobes.

 

Sounds like you want the X4280hr (4x4 cam)
http://www.compcams.com/Company/CC/c...?csid=200&sb=2

 

Comp's recomended springs for the 4x4 cam that is measured 230/234 .474/.474 lift are te same as the springs I have for my xe262. I don't think a spring change will be necessary for these lifts regardless of it being a roller setup.

Is there any easy way without takin apart the valvetrain to check for retainer to guide clearance with any accuracy?

Also, how do I find these +.050 locks? They may be the ticket to makin this work. Do I need new retainers to go with them?

 

Rollers have slightly more aggressive lobe than flat tappets and the heavier lifter will require abit more spring most of the time. If you have the 981's then that may be ok but also note comp recommends the 986 spring as well. They have a good bit more pressure. I take comp cams valvespring recommendations with a grain of salt. They recommend 26918s for the XFI series cams and those are not really enough spring for those cams depending on which heads you use. Hollow valves or 8mm lsx style valves with the smaller xfi lobes, maybe... but if you run a big standard valve head and put one of the bigger cams in a small motor that will turn rpm, you will run into problems with the 26918 springs! A strong double with alot more pressure is needed and or lighter valvetrain components.

If you went with the 26918 beehives you can gain extra lift clearance as well, if needed and handle any cam for those heads.

Check out some of the Lunati grinds...they have a bunch of decent duration but low lift cams that may work out well.

Or call a custom cam guy and limit your setup to .465" and see what they come up with. Adding another 10 deg duration to what you have should pick up some pep. Also porting the intake abit could help