firemn131

Good morning,
So I currently have an 87 S4 engine (120K) that I bought ( Thanks 928 INTL) to replace the one in my early 87 S4 (thrust bearing) Still running strong, but showing some signs of sluggish in low RPM.
Then I found myself buying an early (non GT) 89. Not delivered yet.
Both are Auto's.

So, the 89 runs well (120K) but does have a cooling issue (radiator or fan module), interior and body are great. Previous owner listed this as a parts car because the local Porsche shop quoted him $$$ to get it up to a daily runner status.
it will need belt change, intake refresh, and fuel lines, etc. the usual. It has a good maintenance history but timing belt is 6 years old.

The 87 engine: I was going to send out the heads and rebuild the motor.

Debating current plan and looking for suggestions.

1. Are the engines from the 87 and 89 interchangeable aside from the sensors connections?
What are the differences and advantages.


2. Rebuild the donor 87 engine and install in the 87?
3 Rebuild the 87 engine and install into the 89?
4 Rebuild 89,
5 Sell the 87 with the donor engine?
6. Get the 89 sorted, drive it, and build the 87 engine at my leisure for the 89.

Too many options.


Currently my 92 968 is my daily driver that will be going up for sale soon.

Most opinions and advice welcome..
thanks

John

ammonman

As long as the bores in the 89 are good and no TBF damage I'd have the heads done and put fresh gaskets/seals on it and go. The '89 and up engines have the oil drain holes already in the piston skirts and the head bolt bosses are thicker by 20mm to prevent cracking that usually leads to coolant weeping into the oil. For the '87, do a refresh on it but install the later heads and then drop it in your '87.

James Bailey

Depends on the end goal ??? If you intend to keep both then perhaps rebuilding makes some sense but mostly as a hobby because you want to. If the 87 is going to be sold it currently is a " strong running car "....rebuilding it would add little to the resale value as it would still be a strong running car Plus a home DYI is a questionable rebuild in the mind of many potential buyers. After all there are videos and instruction on line for self trepanation but that does not make it a good idea !
I tend to think most people are better off concentrating their time, effort, garage space, and money on ONE 928 . Get the one you want and make it as good as you want it.

FredR

Jim,

As I understand John's intent is to take his strong running motor with TBF to a strong running motor without TBF.

James Bailey

Ah yes I see that now....

The Forgotten On

Put the new 87 engine in the 87 and sort out the 89's cooling issues then drive it.

SwayBar

+928

If the 87 engine cylinder-walls look good, I would leave the pistons alone in their bores, and just have the heads rebuilt. With the pistons in the bore, remove the carbon from the piston tops using carb cleaner and a piece of wood.

You can take a peek at the 4/6 rod bearings; if they're good, the rest more than likely are too. You'll need to get new rod bolts for the ones you check.

And of course, replace front and rear main seals, etc.