I mentioned this in a previous post that my dad will ot let me do certain upgrades to my car becasue he says it has too many miles. My stock 90 Trans Am has 162,000 miles, which is a lot, but is that too many for performance? My dad says that the different ratio will throw off the "pattern" that the internals have worn into. If I switch to 1.6 self aligning 3/8 com cams pro magnum roller rockers, will that change anything in the engine?

 

No

 

Roller rockers, full or roller tip, are not gonna show any gains until over 6000rpms or so. If your current setup is fine and you dont break 6k rpms often... your prolly better off not mesing with it. For a 162k mile car there are some things you can do to birng osme life back to it.
Do you run RESTORE or BG 44k or some other engine oil additive? These additives often hlep to restore lost compression to oldermotors and prolong thier lives further.
Do you run a fuel system cleaner every oil change? Clean injectors will give you a much happier fuel system.
Cap, Coil, rotor, plug wires, plugs all fresh?
How about replacing that fuel pressure regulator if its never been done before. Fuel pressure bleed down from the injectors or regulator will seriously hamper performance.
Fuel filter, Air Filter all recent?
How about some new catylitic converters? 162k miles of carbon is almost guranteed to hurt mileage and performance. Freshening up the exhaust system prolly wouldnt hurt.

Without other serious motor upgrades, roller rockers alone prolly wont do anyhting for you.

 

There are a lot of bolt ons you can do before you need to start reworking the motor (such as full exhuast and air intake). I understand why your dad would tell you not to mess with a 162,000 mile motor. But hell, if it isn't a daily driver and you really want to, have a blast. Just know that taking that engine apart could open up a can of worms you weren't expecting.

 

At 162K on the clock, suddenly opening valves another 0.005-0.010" farther than they've ever gone before might create some problems. If you refresh the heads before changing the valve lift, there should be no problems. Instead of replacing the rockers, which have always been a little flexible, consider replacing the valve springs. They started out as 85# springs that were barely adequate for the task, and are probably a lot weaker now.

 

How would I make the heads able to take more lift? And what valve springs would be good for now and able to handle a new cam and rockers later on?

 

The amount of lift you will eventually be using determines what you have to do to prepare the heads. At 0.470" or lower lifts, you can probably use stock valve seals, stock diameter springs, and may get by with the stock (pressed-in) rocker studs. At lifts of 0.480" or more, there is a great potential for valve guide/spring retainer interference. To prepare for that, the guides usually need to be cut lower, and are typically cut to a smaller diameter to accept a smaller/lower profile valve stem seal. As part of this work, the rocker studs are frequently removed to alow the stud bosses to be machined flat and holes threaded for screwed-in studs that will not pull out under the higher loads.

If you are planning on lifts of 0.500" or more, you really should consider having the spring pockets machined at the same time to allow the use of larger diameter (longer lasting, cooler running) valve springs.

You should have an overall plan of what you want the engine to eventually become before you begin whatever modifications you perform. Considering the mileage, a valve and seat refacing would probably benefit you regardless of any modification, but don't be too surprised to find that your valve stems may be worn to the point of requiring replacement. That's not all bad, since the original valves are heavy and don't offer the best flows. Something like a Manley Street-Flo will be lighter, stronger, and allow better flow at all openings.

The first step is to determine what cam grind is going to be most suitable for your engine and its intended use. Considering that your fuel system is going to like a shorter duration profile, lifts may be limited a bit. On the positive side, the roller cam design used in your engine will allow some fairly aggressive lobe lifts while maintaining relatively short durations, giving a little of the best of both. Whatever you select, it almost has to be better than the factory cam, with net lifts under 0.400" and really lazy lobe ramps. Consider starting with something like the Comp Cams 08-300-8 and look from there.

 

Don't forget to work your budget into this. If you plan on working with more than 2-4k and you are pretty new to this but want to get some heavy exp. then vaders got the ticket for you. If you really want to go that route you might as well save the money on the old heads and buy something newer thats a direct replacement. Head machinging and new valves and guides is gonna run $700-900 (locally in SA, TX). You could get into a set of vortec heads(ive got a price locally $220 full assembled with a core) for that much and buy a 300 dollar lower intake from Scoggins-Dickey and prolly pick up 60 hp with a chip, maybe more. But even at that you are not considering the wear on you short block (pistons, rings, rods, crank, etc.). You can prolly have your short block Hot tanked, bored, decked and polished with a new crank, rods, pistons and rings done for around 1k. Now you need a cam for those new heads. Dont need much call Crane and tell them what you got and they can tell point you to a great cam for the job. Nickel and Dime stuff is gonna easily carry you to 2.5k by the time the job is done.
You can buy a crate motor for that much that may or may not make that much power, depending mostly on your cam choice.
For 3-4k you can pick up a crate motor that advertises 400hp with atleast a 6month warranty.
if you want to stay under $500, go with the freshen it up stuff from above.
If you've got a big budget then you can do lots more, assuming Dad says its ok. Believe me with 400hp, its a big if.