GT1 Cam VS. 1.85 Rockers

[Taheen]

Stock Rockers with GT1 Cam:

.507 Intake and .507 Exhuast
210 Intake Duration, 210 Exhaust Duration
113 Lobe Sep. Angle, 108 Intake Centerline.



Stock cam with 1.85:1 Intake and 1.8:1 Exhaust rockers:

.477 Intake and .459 Exhaust.
182 Intake Duration, 190 Exhaust Duration
115 Lobe Sep. Angle, 111 Intake Centerline.




So looking between the two what would be the smarter choice HP wise? The cam would have longer duration, more lift, and such. Thing is I'm trying to figure out a small power gain from something like one of the above mods but still keep it reliable and emmission legal. I don't want to have to get a retune if I can avoid it as well.

So I was thinking a mild cam like the GT1 would be good but then I started to think what about just doing rockers. The engine has 166k miles on it, it's a 99. The are near all highway miles though, and easy driven for the most part. Engine still runs strong, no leaks, nice ~65psi oil pressure, and all.

Point being, doing rockers or cam I'll probably replace needed items while in there, was going to see what everybody recommends be replaced on sole principle of having high miles. New springs? Should I expect to find a worn timing chain dampener/lifters/etc?

Also I'd love a nice noticable lope on idle. Would the GT1 have this or would it have a stock sound to it? Would having the extra lift from the rockers have any effect? If you can't tell, it'll be my first valvetrain mod.

[IDoVoodoo]

Re: GT1 Cam VS. 1.85 Rockers

the cam would be a smarter choice HP wise hands down. replace everything you can while your at it. not necessary just insurance, especially with high mileage.

[Nachius]

Re: GT1 Cam VS. 1.85 Rockers

2nd vote for doing cam.
The GT1 cam isn't extreme enough to REQUIRE a tune, and you'll also see good power and some lope.

As mentioned replace everything as well as timing chain/damper.

[youngsc]

Re: GT1 Cam VS. 1.85 Rockers

3rd for the cam. Remove the sprocket from the balance shaft while your in there. That will free up a little parisitic hp loss from turning that 15lb dumbbell.

[Taheen]

Re: GT1 Cam VS. 1.85 Rockers

Awesome. I was thinking about doing new springs/retainers, and was going to do a new damper. But it looks like the double roller chain is only like $140 if down the road I need the double. What's the feeling on replacing lifters and pushrods due to high milage? I would rather not if I don't have to.

This is all a ways down the road, but it'd be good to set the goal early for what I want to do.

[98 3.8]

Re: GT1 Cam VS. 1.85 Rockers

You don't need the double roller with 105# springs or less.

But if you do get the double, you also need to have a plate modified for clearance.

[youngsc]

Re: GT1 Cam VS. 1.85 Rockers

double won't be neccesary. Shouldn't need new lifters and pushrods just yet, just make sure they're 100% when doing the upgrade. As I said disconnect the balance shaft too.

[Taheen]

Re: GT1 Cam VS. 1.85 Rockers

What would be the recommendation for Springs? Strait replacement of stock (70lb right?) or make a small increase to LS6 90lb w/retainers? Don't want to overkill if I don't need too but at the same time as long as I'm in there should I not go for a heaftier set?

So I should consider, starting off at:

Cam - $300
Springs (lets say LS6 yellow 90#) - $85
Retainers - $35
Misc Gaskets - $100
Rollarmaster Timing Set (single) - $100 (As I understand you remove the tensioner with these right?)

So $620 so far. What am I missing?


As a side note I need to start reading up more on cam swaps. Like when removing the springs I want to hold the valves closed. I don't want to remove the heads, Do I just turn the crank over to the compression cycle of that cyl and that will have enough pressure to hold the valves closed when messing around with them and pulling springs off?

[IDoVoodoo]

Re: GT1 Cam VS. 1.85 Rockers

you might want to look at the comp 105's. With the single chain you keep the tensioner and 95# will wear it out quicker.. Use an air compressor to hold the valves closed. Roll your push rods on a flat surface and check for any wobble. Put lifters and pushrods back in there original spot.

[Dawizman]

Re: GT1 Cam VS. 1.85 Rockers

I personally would lay down the $100ish dollars for new lifters. I know the rollers arent as bad as the old school lifters, but they do still wear and will cause exsessive wear on your new cam compared to new lifters.