What's the highest valve lift anybody has run on their 60 V6? I know the 60 V6 manual says the max is .560, just wondering who might have come close and what mods they had aside from springs?
I can’t speak to the highest possible lift, because I’m running only a moderate cam and rocker arms in mine. However, I think I understand where you may be going with this, and your idea seems an interesting one.
A cam with a short duration (to retain low-end power) but with the highest possible lift (for top-end power) theoretically would be the best cam possible, except for that ever-present inconvenience of having to deal with the real world. There, a problem with super-high lift is a substantial increase in cam lobe wear, as well as substantially increased wear on valve guides, springs, and stems. It really doesn’t matter much if that super-high lift comes from the cam itself, from special rocker arms, or both. Substantially increased wear is likely.
One partial fix for addressing this limitation would be to use a roller-tappet camshaft since the roller design typically provides somewhat more lift more reliably at a given duration than does the typical flat-tappet cam design (like the hydraulic flat-tappet camshaft in the typical 3.4).
You probably can verify this for yourself by examining the camshaft specifications in any cam catalog offering different cam designs for one popular engine. My guess is that for any one engine, you’ll see that taking each cam’s specified lift and dividing it by its specified duration at 0.050” lift will produce a higher lift-to-duration ratio with roller cams that with flat-tappet cams.
That’s the good news, and I like the idea of using an aftermarket roller cam for higher lift at the same duration.
The bad news is that while I wish I did, I’m not aware of any manufacturer who now makes a roller cam for the pushrod 3.4 (as opposed to the DOHC 3.4).
A different partial fix would be to use aftermarket rocker arms. These could provide you higher lift at the same duration. However, unlike the roller cam, the rockers really don’t address the wear issue at all, so you might be better off using some moderate aftermarket rocker arms that permit slightly higher lift. Of course, then the question may be whether or not such a moderate change would be worthwhile in the first place.
IP: Logged
04:54 AM
tjm4fun Member
Posts: 3781 From: Long Island, NY USA Registered: Feb 2006
There's other info you should collect on this. Valve lift and...... Flat pistons? Dished pistons? Valve reliefs? Deck height? head mill? piston height? and oversized valves? (larger diameter valves that are angled in respect to the top of a piston require slightly more clearance)
Lifting a valve alot is one thing, not having it have intercourse with your piston is another! Just a reminder, I know a few people who forgot about this minor technicality and have paid the price.
IP: Logged
07:04 AM
AJxtcman Member
Posts: 1098 From: Rock Hill SC Registered: Nov 2006
What year? the reason I ask is GM changed the pistons several times in the V6. It is all about the compression height and dish for the most part. If you by chance you have the aluminum head. They use canted valves and can have bigger lift cam.
If you use aftermarket pistons please check them against this. Enginetech offers 1980-86 @ 1.578" this is a 8.5 to 1. 87-89 @ 1.599 this also is a 8.5 to 1 and has a different dish. If you can find casting # on the original pistons you can Identify them and then crossreference to the ones you are using and them use that to aid in max lift.
Piston #P1592 fits 88-92 cast Iron head 3.1L Dish .105” CH = 1.443 8.8 to 1 Piston #P1584 fits 88-94 alum head EX VIN M Dish .265” CH = 1.443 8.8 to 1 Piston #3025 fits 94-99 alum head VIN M Dish .247 CH = 1.450 8.8 to 1 Piston #3062 fits 94-99 alum head VIN M Dish .270 CH= 1.467 8.8 to 1 Piston # 3069 fits 99-05 VIN J Dish .259 CH = 1.488 9.6to 1 OEM Mahle Pistons Piston #27250 fits 90-95 cast Iron head Dish .106 CH = 1.461 Piston #27260 fits 88-94 FWD/Aluminum head Dish .257 CH = 1.461 Piston # 27290 fits 94-95 W/alum head Dish .259 CH = 1.448 Piston #599820 fits 96-99 alum head No info Piston #599810 fits 99-05 VIN J No info Potentialy the top of the pistons that the valve would contact could be about a .110" difference up or down. Depending on the piston you could increase the cam size and open the valve more or less.
Goat, I looked up that hydraulic Crower cam’s specs and it definitely will feel noticeably different not only versus a stocker’s, but even versus your hydraulic Crane H-272 cam. I see that the Crower has a tighter lobe separation angle than the Crane (108 versus 112 degrees, which in itself could yield a lumpier idle) along with noticeably longer duration at 0.050” lift: 226 degrees instead of 216 on the intake, and 234 degrees instead of 228 on the exhaust. It'll almost certainly feel different, just maybe not "good different."
I’m not saying you can’t run that cam, let alone some higher lift variant of it, because I don't know that. But maybe it would be a good idea to start with a call to Crower’s tech people before you install that thing. As you probably know, that’s a fairly big cam for a relatively small engine, so the car may not be very streetable. It may require additional modifications as well. For example, Crower’s catalog seems to strongly suggest you’ll need at least 10.25:1 compression, and probably a non-stock, numerically higher final drive ratio as well (presumably to help compensate for reduced low end power, and to let get you into the cam’s higher RPM power range sooner).
However, during your discussions with Crower's tech types, I suggest telling them up front about some of the non-stock equipment you’ve already run on the street (successfully I assume), starting with the Crane H-272 cam and the dual throttle bodies. Otherwise, I fear they’ll quickly just dismiss all your questions simply by saying “Stick with stock.”
IP: Logged
08:56 PM
Raydar Member
Posts: 41167 From: Carrollton GA. Out in the... country. Registered: Oct 1999
Interesting observations regarding the Crower cam. While I was in the process of reworking my 3.4, and hearing all of the horror stories about H272 installations, I thought about sending the 272 back to Summit and going with the Crower. The duration was the main issue I saw, too. I have to pass Atlanta emissions, so I just stuck with the 272.
I have a comp cams 260...I don't want the crower 03050. I only used it as a reference because it is the highest lift cam I could find that isn't custom. I run nitrous so I will stick to a 110 LSA. I might have a cam made that is close to that except change the LSA. The comp, delta and crower techs all said a 110 is good for what I want to do. I do have high compression in my near future, 11.3! My 3.65 gearing would be okay with the crower cam.
[This message has been edited by goatnipples2002 (edited 01-31-2007).]
I see that the Comp Cams 260H you have is a mild cam with only 212 degrees of duration on both intake and exhaust. You say you don’t want the Crower 03050 cam, but it sounds like you want something much like it. So what is your tentative plan? Is it to get a Crower custom grind with the duration at 0.050" of their 03050 cam (226 degrees on the intake, and 234 on the exhaust), but with an LSA of 110 degrees (instead of the 03050’s 108), and maybe (possibly with 1.6 rockers) get even higher lift than what their 03050 cam currently has (0.470” on the intake and 0.492” on the exhaust with 1.5 rockers)?
I do plan on a custom grind but not just yet my budget is being use on my nitrous system and KYBs. My intake changed and so did my "only run a 75 shot" idea. I will most likely get a custom grind similar to the crower with a 110 LSA. I need to talk to delta cams to see what the limitations on a regrind are. I wanted to see what others might have been running but I see no one is running over what LilChief posted.
In regard to the valve-to-piston clearance concern, it seems at least somewhat reassuring to learn that with dished pistons (presumably like yours), Lilchief was successfully running a cam with a 0.497” exhaust lift, essentially the same as the 0.492” exhaust lift that you sound like you’re considering for a custom grind down the road. But wouldn’t it be more reassuring to know that Lilchief also had no clearance problems using that much lift with compression that is at least as high as the 11.3:1 compression you’re considering?
