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HighwayThunder
11-07-2016, 10:20 AM
I'm giving some thought to reverting my 390 FE from performance back to stock.

If I were to take out the CompCams performance cam and reinstall the stock cam, could I use the same hydraulic roller lifters with the stock cam?

In the process if re-degreeing the engine (the only hardware change being the cam), how likely is it that the pushrod lengths would stay the same?

Opinions and/or excoriations welcome. Thanks.

Cheers,

Deanj
11-07-2016, 10:55 AM
You'll get a lot of response here. I would replace the lifters, pushrods, and timing chain. I might consider a double roller timing chain, but a timing chain for good measure since they wear and stretch. The cam surface, lifters, and pushrods wear together if I remember.

Joe Johnston
11-07-2016, 11:11 AM
New cam = new lifters!

For no more than new timing gears and chain cost I wouldn't think of using the old ones. Not worth my time to re-use parts when its just as easy to put new on. Consider it the cost of peace of mind insurance - or the cost of education should it fail in a short time.

pbf777
11-07-2016, 12:13 PM
The hydraulic roller lifters will not function properly on the flat tappet camshaft, therefore the appropriate flat tappet lifters will be required.

And since the roller lifters vs the flat tappet units are not the same length/height (rollers are taller so pushrods are shorter), this will require proper length pushrods at the time of conversion.

Also, a review of the procedure for establishing proper pushrod length and valve-train geometry (for the FE engine) may be in order. Scott.

Yadkin
11-07-2016, 01:01 PM
I'm giving some thought to reverting my 390 FE from performance back to stock.

If I were to take out the CompCams performance cam and reinstall the stock cam, could I use the same hydraulic roller lifters with the stock cam?

In the process if re-degreeing the engine (the only hardware change being the cam), how likely is it that the pushrod lengths would stay the same?

Opinions and/or excoriations welcome. Thanks.

Cheers,

Use a cam designed for hydraulic roller lifters, not the original designed for flat tappets. The profiles are very different.

All FE cams should have the same base circle, so your pushrod, rocker set shouldn't change.

simplyconnected
11-07-2016, 01:52 PM
Why do we buy roller cams when flat tappet cams are hundreds of dollars less expensive??? Why do OEMs use roller cams almost exclusively when all of them are grocery getter-mild? Reduced friction, therefore no need for ZDDP (that kills catalytic converters). Conventional dinosaur oil works just fine in a roller cam.

There are more benefits to a roller cam for racing but we're not racing. Novice engine builders almost always buy a cam too aggressive for the street. A street machine needs to idle at low rpm, maintain good vacuum and deliver plenty of torque at low end with a torque converter that locks up early. This is what produces good gas mileage. If you ever compare Mustang GT cam grinds you will see that they slightly depart from common street engines to maintain good vacuum and low end torque for all season operation.

Summit and Jegs offer very mild (but improved) street roller cams through a host of brands. Your lifters will work just fine but pay attention to the lobe height compared to the cam you have installed.

By all means, find a good engine build shop that has done hundreds of engines, use their experience and take their advice. Then call Comp Cams at 800-999-0853 because the base circle on aggressive cams are much smaller in diameter than stock cams. They do that for extra lobe height. - Dave

pbf777
11-08-2016, 11:58 AM
[QUOTE=Yadkin; All FE cams should have the same base circle, so your pushrod, rocker set shouldn't change.[/QUOTE]

Yes, they "should", but, the aftermarket camshaft suppliers do not seem to acknowledge such, and therefore the base circle diameters vary greatly.

And yes, on very aggressive lobe configurations the base circle is often reduced, but in the application range relevant here, it depends more on which cam core is selected by the grinder, so it may not be.

So, one should measure and establish proper relationships of the components involved. Scott.