atb

The 4.5L motor in the OB is officially dead. I have an opportunity to install a 4.7L, and was thinking of swapping in the '79 cams. If the heads are identical, then I would just take the heads off the 4.5L and put them on the 4.7L. Are the head castings the same on these two motors, or am I better served pulling the cams out of the 4.5L and reinstalling in the 4.7? These are both US spec motors.

Go-carter

Apparently, if there's no misunderstandings, I'm about to do the same thing next week... my 4,5 is shot, and I'm picking up a 4,7 on monday

I'm told that it should fit.

RCinXS

4.7 heads have oil check valves. 4.5 do not. Not sure if that is a concern.

Porsche added the check valves to keep some oil in the passages, probably to help in getting oil pressure up quicker at startup.

The 4.5 heads have scallops to hold the steel Cam Follower bushings into the 4.5 Cam Towers.

4.7 did not ust the bushings in the Cam Towers so the heads do not have the scallops.

The valves are identical. The springs, Guide Disks and Retainers may be different depending on the year, they changed sometime in 81.

Not sure on the CC difference between the 4.5 and 4.7 U.S. heads.

Bottom line is that the 4.5 heads will bolt on to the 4.7 block.

Iwanna928

Freshen up the heads and buy some bigger valves and see what happens!

PorKen

Maybe it was to keep oil in the lifters. My '81 always had cam follower noise if it sat for more than a day or two.

'81-'82 4.5L do not have the bushings.

RCinXS

+1 on what PorKen said.

The early cams have slightly more lift.

4.7 U.S. is a non interference engine.

I run Euro S cams (even more lift than your 79s) on a U.S. 4.7 with no problems, so far.

Taking it apart soon for more head upgrade modifications and this time I will check and make sure it is still non interference engine.

If I need to recut the eyebrows, I'm going to make a jig out of an old head, and have my machinist make fly cutters for me or buy an adjustable "through the head" Lindy flycutter.