FredR

Gerrit,

I would not be in the least bit surprised if what you have done lasts as long as you do and hopefully many years. No guarantees of course but remember the head bolts are holding everything in place and they have not been compromised and all the Belzoona is doing is acting as a sealant over a very small effective area against a very low pressure to start with.

By all means have a spare block standing by just in case the worst happens but do not think such is "bound" to happen- such could of course happen but it is far from a racing certainty as I am concerned. 40 km is a reasonable proving mileage I would say and if no leaks are evident "so far so good" I would politely suggest.

GerritD

hello Fred, well car has been MOT approved, so I am good for next 2 years. However, there still is a minor leak. I noticed it today. So spare block will need to be acquired.
my further questions regarding a used M28.21 block with Ljet :
- what must I change on this M28.21 block
in order to use my Kjet of my faulty M28.12 block ?
- is it sufficient to just put my kjet and mechanical injectors with WUR and AAR valve?

- can I use my mechanical injectors on the M28.21 block ? Or do I completely need to
replace the heads by my M28.12 heads?

I don’t want the Ljet with Bosch ECu since
this is a major makeover

kr
Gerrit

Petza914

You can use all your K-Jet fueling and air flow setup on the new block. I did this when I swapped the 4.5L from my 79 with a 4.7L from an '83.

GerritD

So the only advantage I would have is more compression, not ?
Or is this compression only higher with Ljet injectors?
Is the spider intake the same? Because with the 4.5 there is a difference?

Gerrit

GerritD

Yes, I also saw it but the price is above my budget and there is no guarantee that no faults are on the engine...price is a bit high for a refurbished used engine.
Better will be a good running, used engine.

Darklands

I'm very sceptical about the quality of used engines.
My used engine has 2 destroyed bores after opening after 15 years in my storage.
Doing a 928 engine complete Revision is near 10.000 € if someone else is doing the Job.

If the engine is out of the car you should do all the maintenance and maybe the M 28/12 is the cheaper engine on the long run.

GerritD

I am talking about a used engine with good compression figures and preferably still in the car and running. I also use a special endoscopical camera to inspect the bores
of the engine.
When doing the revision yourself, it will cost you max 5000€

karl ruiter

In my '79 I have a 4.5l US (low compression) bottom end on Euro S heads and cams on top. I cannot really recommend this combination. Perhaps if the correct cams for a low compression motor were used instead of the Euro S cams? For sure you can put your CIS injection on an Ljet motor. However, I think the cams are different again, and I don't know exactly how. I think the L jet cams are detuned somewhat to avoid rapid flow spikes that cause problems with the Ljet flow meter, but not sure. Anyway, you can use your complete CIS system with either the heads you have or the 4.5l heads, but there is a question about which cams to use: Euro S (no, I think), 4.5l CIS, or 4.5l L jet.

GerritD

Hello, I have a question : will a 1982 engine M28.12 shortblock be a good replacement ?
I am looking in buying this engine, does it look okay :

Petza914

Does that M28/12 come with the heads and intake? That's one of the 4 best 16v 928 motors you can get, with the others being the 11, 21, and 22 as these are the high HP, High compression engines, but think that has more to do with the heads and cams than with the block.

GerritD

No it is only the short/base block without heads and intake.
But I will put the heads and intake of my cracked M28.12 engine on this one. Ofcourse I will need new pistonrings and bearings as well as complete headgaskets.

Darklands

The bore’s look good. Go for it.

belgiumbarry

check crankshaft play as it "was" a automatic ?

GerritD

I will but it is very rare that old automatics (3speed) have issues with this.

GerritD

Hello Fred,
I just want to give you an update about the cracked engine. Engine is still holding with the Belzona. Only minor loss (500cc within 6 months) of coolant .
And I measured also the compression on each cylinder :
1: 10,3 bar (149 Psi)
2: 10,2 bar (148 Psi)
3: 10,4 bar (150 Psi)
4: 10,2 bar (148 Psi)
5: 10,5 bar (152 Psi)
6: 10,2 bar (148 Psi)
7: 10,5 bar (152 Psi)
8: 10 bar (145 Psi)

Porsche compression specs for my M28.12 engine is 10:1 .So all great numbers which means my engine is in good condition.
For the moment I did not have the time to replace the engine by the spare engine I bought...