Roller rockers and 650 CFM on 1999 Yukon?

[eazye]

I have a 1999 GMC Yukon 4x4 4-Door and am curious as to whether the onboard computer can adjust to the extra lift provided by a set of 1.65 or 1.7 roller rockers. If the computer can not adjust I was thinking of getting a programmer to make the adjustment. Although for the price of the programmer, I could remove the tuned port injection and install a 650 carb and really reap the benefits.

My question is has anyone on here installed these mods with any success and what problems have they incurred. Thanks in advance for any replies. They are greatly appreciated.

 

[jac6695]

I wouldn't do the carb. Huge step backward. I think that you would be fine with the rockers. Check with Westers Garage or PCMForLess for programming.

 

[dyeager535]

Gains of a higher lift rocker on a motor is NOT going to be worth a swap to a carb, nor a programmer.

Yes, they will make a difference, but losing the driveability of EFI for those benefits is a big step backwards.

 

[Thunder]

Why do you want roller rockers? Planning on revving 6K or higher? If you are installing them to get more power, you wont see much diference on a stock engine. Waste of money IMHO. Unless you have a built engine.
Also you have vortec heads. Have to watch out for coil bind in the springs. You will have to do some machine work on the spring seats if you are adding a lot of lift. I dont think the valve guides can handle much over the stock 1.5 rockers without excessive wear. Need to install 3/8" screw in studs also. Recomend you elongate the pushrod hole. It may hit the side if not hogged out a little.Oh and last but not least you should get new valve springs matched for the increased lift stock springs are not up to the job.

hand heled programmers dont really do a whole lot. You are way better off getting a new PCM These guys do excelent work and will give you some power you can really feel:http://westers_garage.eidnet.org/scprice.htm

 

[beater_k20]

I dont think the valve guides can handle much over the stock 1.5 rockers without excessive wear.

i dont think excessive wear is the term you're going for, i think you mean excessive contact. put those rockers on an engine that doesnt have the guides cut, you might as well kiss your valvetrain goodbye before you fire it up, because when you do you'll trash your spring retainers, bend your pushrods, and most likely lunch your cam and lifters.

 

[bowtiewrench]

You will not have to reprogram for the roller rockers but you would see more of a gain if you did. Roller rockers on the vortech 5.7's is a nice little mod, it will rev easier and have a bit more power as well as torque. My buddy has a 97 silverado with dougs headers, higflow cats, ported throttle body, k&n fipk, msd plug wires, and a set of harland sharp 1.6 self aligning roller rockers. He says that out of everything he has done the roller rockers made the biggest difference and their only $180 from jegs.


Alex