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KPzypher 01-07-2020 04:58 PM

Blower CAM spec
 
Which blower cam would you recommend for the following setup?

6M, Centri., drop-in forged piston/rod, longtube

225/237 .648/.658 116+4
229/237 .651/.656 116+5

Will there be a big difference in drivability between the two in the low RPM range?

KingLT1 01-07-2020 06:55 PM

Too much lift on either for stock heads and rocker arms. I would personally keep the lift around .600 with stock style rocker arms. I don't understand why companies are producing these extra high lift cam shafts when valve guide scrubbing is a issue. It was a problem on LS and I don't see anything has changed to address it on LT. Now if you went with a ported head and roller rocker arms that maintains better geometry at higher lift then I could see either cam working well. Not to mention they are harder on lifters because you need stouter springs to control them.

So basically the cam above with a standard dual spring(btr platinum) and LS7 lifter is a recipe for valve-train failure within 20k miles.


Call kip at cam motion and tell him what you are looking to do.

oldman 01-07-2020 07:41 PM

Quote:

Originally Posted by KingLT1 (Post 10694913)
Too much lift on either for stock heads and rocker arms. I would personally keep the lift around .600 with stock style rocker arms. I don't understand why companies are producing these extra high lift cam shafts when valve guide scrubbing is a issue. It was a problem on LS and I don't see anything has changed to address it on LT. Now if you went with a ported head and roller rocker arms that maintains better geometry at higher lift then I could see either cam working well. Not to mention they are harder on lifters because you need stouter springs to control them.

So basically the cam above with a standard dual spring(btr platinum) and LS7 lifter is a recipe for valve-train failure within 20k miles.


Call kip at cam motion and tell him what you are looking to do.

You lips to god's ear.

oldman 01-07-2020 07:49 PM

Quote:

Originally Posted by KPzypher (Post 10694816)
Which blower cam would you recommend for the following setup?

6M, Centri., drop-in forged piston/rod, longtube

225/237 .648/.658 116+4
229/237 .651/.656 116+5

Will there be a big difference in drivability between the two in the low RPM range?

http://www.cammotion.com/gen-5-lt-ca...ger-camshafts/

look under supercharger cams for centri, the first cam is very similar to my first cam, the second one is smaller than my current cam. The first one is basically a zero overlap cam so it will be kind of hard to tell it from stock. The second cam has overlap at .050 so will have a lope, mine is one step bigger and it is a "defined lope" cam. At speed say 2000 RPM and above, part throttle both of my cams worked fine. If you have an auto, you will need a stall for sure on the second cam (don't know about the first).

I like the lopepe doop and you can search the NA forum for my idle / rev video.

I'll post one with stock exhaust too as soon as I finish the tune (need to remove one cat to run the wideband so not stock right now).

You can easily makeup for the power with a pulley change so the cam is more of a sound / driveability choice. For me I'm in love with my defined lope cam, the zero overlap cam was just too mild for me.

laynlo15 01-07-2020 09:46 PM

My new BTR Stage 2 lift is nothing like that lift and in the 630 range. Even my old Livernois blower cam was 641-641 lift 229-241 on 116, Btr is a lilttle lower lift 116+6. I agree with King

shinysun 01-08-2020 12:19 AM

Quote:

Originally Posted by KingLT1 (Post 10694913)
Too much lift on either for stock heads and rocker arms. I would personally keep the lift around .600 with stock style rocker arms. I don't understand why companies are producing these extra high lift cam shafts when valve guide scrubbing is a issue. It was a problem on LS and I don't see anything has changed to address it on LT. Now if you went with a ported head and roller rocker arms that maintains better geometry at higher lift then I could see either cam working well. Not to mention they are harder on lifters because you need stouter springs to control them.

So basically the cam above with a standard dual spring(btr platinum) and LS7 lifter is a recipe for valve-train failure within 20k miles.


Call kip at cam motion and tell him what you are looking to do.


Opps. Do I have to concern about the issue on Lt1 engine?

EDFHOBBIES 01-08-2020 08:18 AM

I'm in trouble then.. 217 / 245 Lift with 1.8 rocker .635 .661 LSA 121

Don't forget things like a cam lock out vs a phaser limiter..

And the fuel lobe 32, 38, or (44% only for the lingenfelter pump)

oldman 01-14-2020 09:08 PM

lift is one part (the most important) in the longevity equation. IMO 75% of engine failure is due to valve bounce. What causes the valve to bounce? higher lift, faster ramps (cam motion is know for gentle ramps and they grind BTR's stuff), dual springs vs conical vs beehive vs single (conical wins), RPM. For me my LS7 lifter failed on the intake IMO, it was a combination of 6800 to 7000 RPM shifts, upto 12 PSI of boost and a fast ramp profile causing the intake valve to bounce and / or lifter to fly over the deceleration ramp of the intake cam lobe. I can actually see impact wear on the flank side of all intake lobes. So if every thing stays in contact and I'd be checking or replacing valve springs every 20K miles. IMO I should have been OK, but nope.

I'm at sub .600 lift on a cam motion cam and Johnson lifters (should have got the bars). I will change springs every 40k miles, I'm on 8 or so of PSI now too. I lived through the LS1 valve train wars and unfortunately I'm doing it again on the LT1, this time around everything is the best from C5R chain, to Manley valves. I'm not risking anything like trunnion bearings or my hollow stock valves falling apart or anything. I'd even change to a real oil pump if one was made. I could get away with less stiff springs but I figure my sub .600 lift is cutting down on peak open pressure and I don't think it is spring pressure perse that is killing the valvetrain, I think it is bounce so I stuck with dual .660 lift springs just because I want the valve and lifter not to be in free float EVER.


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