rusty vango

I would like to use a set of comp cams steel rockers "ultra pro magnum" in a 1.6 rto. I have a 87 roller cam 305 block, with a set of 86 "416" heads. the cam is stock.as are the heads.im feeling that it aint bolt em on and go.what would you all suggest?(and, no , not a 3fiddy) has anyone else here used these?

sofakingdom

iTrader: (1)

Should be pretty much a slap-in.

It'd be a good idea to change the valve springs though; the shortcomings of a bunch of wore-out stockers will largely invalidate any good that the rockers might do.

rusty vango

yeah, that is gonna get done as a matter of course. obviously as I have a TPI motor ,im not doing it for hi RPM use. but more for reduction in friction as well as more accurate valve timing. should make it run cooler some too. my main concern is ,, will it make the push rods rub the heads? about all I can do at this point is mount it up and check.all comp says, is I have to run a set of push rods with a ball at both ends. nothing mentioned about push rod length.correct me if im mistaken. but isn't it lift of the cam x 1.6= actual valve lift?

AlkyIROC

1.6 rockers are a poor mans cam swap. If you need more lift, install a camshaft with the lift that you want.

All things being equal, if you had two sets of rockers exactly like those in 1.5 and 1.6 ratio, swapping from 1.5 to 1.6 you'll only gain about 5hp from the slight increase in lift.

Increasing the rocker ratio moves the pushrod closer to the pedestal to get the increased ratio and changes pushrod length very little. There needs to be enough room in the pushrod hole to allow the change. Not all heads have a hole big enough and some heads need to be modified.

Increasing lift also has other effects. Too much lift can cause the valve springs to get coil bind. OEM springs are not the greatest to begin with and a high mileage engine is even worse. You could also have the underside of the spring retainer hit the top of the valve guide/seal if lift is too great.

For most people however, a stock cam with stock heads etc can easily go from a 1.5 to a 1.6 ratio with no clearance issues anywhere. You'll see some gains just by going from a friction rocker to a full roller rocker but not as much as a proper cam swap with a valve train to match the camshaft.

rusty vango

well, its not as if I need or want more lift. I was thinking that they would be a fine way to de crease friction AND get a lil lift at the same time. the engine only has 16,000 miles on it since I built it. considering the stock rockers are questionable at best .and the comps are dead on .I thought it would be worth the $550. I just didn't know if they would need additional work to use.

sofakingdom

iTrader: (1)

I should have mentioned, you'll need to check the push rod guide slot in the heads; since "ratio" is the distance from the valve stem to the stud, divided by the distance from the push rod to the stud, and changing rockers can't change how far the valve stem is from the stud, the thing that has to change is, the other distance; and it has to become shorter. Therefore the push rods may rub (or worse) on the end of the slot. Some heads will work, some will not. You may even find that one head on your motor will work and the other won't.

Main benefits will be, CONSISTENCY in the valve motion on all cylinders, since you won't have that stamped sheet rubber in the system any more; and, decreased oil temp, from doing away with the rocker *****, which usually get hot enough to turn the rockers blue. The decrease in friction isn't noticeable any other way, and the gain in lift is trivial, on a stock cam; especially any cam that would been "stock" in a 305 in 87.

rusty vango

excellent response! this is what I was suspecting. I just wanted to hear from someone else that had done it. so , off with the heads, while im at it . I will port,gasket match ect.

sofakingdom

iTrader: (1)

Port, yes; gasket match, don't waste your time. It is nothing more than eye candy to deceive the inexperienced. Concentrate on where it will actually accomplish something: the bowl right behind the valve, the guides, the roof of the port especially on the side where it meets the "common" wall. (not the push rod side... don't bother with the "push rod pinch" either") IOW, zero in on th eplaces that actually disrupt flow, and don't worry about "looks" "good".

When you put them back together and get around to selecting your new push rod length, pay no attention to where on the valve stem the "sweep" pattern falls, as it will almost certainly be biased toward the exhaust side. (that being the only other way, short of offset trunnions, to change the ratio) Instead, adjust for the narrowest possible sweep.

rusty vango

will do, and thanks.