contacted summit racing about a 4.2l gear drive they offer. Have 97 4.2l and they only offered it for 80's models. Tech said stick with chain as gear drive did not do well on computer controlled engines and that was it. My question is since the mechanics appear to do the same thing why would it not work. Please help me understand

 

not sure about that one... maybe the gears lash too much or less slack is too much force on the valve train.

 

Well, gear drives are used in very specific racing applications and in street vehicles, they have some drawbacks. In most dyno testing, gear drives (on chev V8's) at peak hp levels, when compared directly with chain drives, typically loose about 8-10 hp (with very few exceptions- it has been suspected for years that it is the increased friction but I don't think anyone has ever really id'd the cause, only the effect).

The increased noise (though that may be a positive if you like it) is a possible issue as well.....they do make a bit of a hummmmm/Wrrrrrr.

While their timing accuracy cannot be denied nor duplicated by a chain, unless your turning over 6000+ rpm, the benefits will be negligible. A good quality nylon coated double roller timing chain with matching gear set will work excellent for you.

 

ok, summit made the gear drives for the early 80's 4.2l 255 ci which was an 8 cylinder. so doeas anyone know who sells a gear drive for 4.2l six? and beechkid, you hit the nail on the head when you mentioned the noise factor- I love that noise and would like to put a gear drive in despite the pro's or con's. I am not going to build a six to blow peoples doors off but I would sure like it to be stout.

 

If you like the noise of a gear drive, buy an old F-150 with a 4.9 I6. They don't get much more stout than that.

 

I beleve the reason behind not offering the gear drive is the noise. On fuel injection engines there are knock sensors. They "hear" predetionation or pinging and retard the timming. W the gear drive the knock sensor would hear the "noise" and retard the timming for no real reason