Dilavar Cautionary Tale

[afterburn 549]

heres what I think I know..you pros jump right in here and correct me wher I went haywire..-Steel is great steel is strong and it dose not hardly everbreak,But the expansion factor length wise is all wrong there for pulls threads...so along comes this alloy the for expansion remidy but they are prone to popping (breaking) least thats what i think

[Wayne 962]

Originally posted by jgparker
1) Wayne's recommendation is to use steel, and I got burnt last time I ignored his suggestion.

Happens more than you think!

-Wayne

[tab tanner]

I have a 2.7 with about 30k on a rebuild, The shop used Time serts and Dilvar studs The car runs very well!! My question is am I driveing a time bomb. I have headers on as well as weber carbs, my engine temp never gets over 210. Sould I tear it down and install steel studs? How long can these engines last? I have all the recipts from the repair shop, They did the work in 93 so it has went this far what sould I expect in the near future??

[tab tanner]

One other thing I have an 11 blade fan on my car, I has been on since the rebuild

[afterburn 549]

Its a catch 22...unless you go with something like ARP they are all probly going to break sometime..the thing is ,is to try to get the sometime into your time..steel with inserts works very well at least till the next rebuild at which time they are t b o (ed) . anyway

[Doug Zielke]

Failure of the Dilavar studs seemed to be due to corrosion. I guess the black (epoxy?) coating was intended to stop this, and probably will, as long as it lasts.

Anyway, I discussed this subject with John Walker** more than once.
For Al cases and stock motor, he said go with plain steel. They don't break. And the different rates of expansion is not a problem on Al-case 3.0 motors. The head studs on my motor are holding their torque values 100%.

** "In John We Trust"

[jgparker]

Just a comment. I did not see any nick or corrosion on the stud where it broke. The break may have been from a manufacturing flaw that was aggravaded by the re-build.

Thanks,

JP

[Superman]

I get my advice from the same guy as Doug. So, my studs are all plain factory steel studs ($11 each, I think). I'll be very surprized if any of them ever give me any trouble at all.

[afterburn 549]

thats what I am sayin the steel is the deal-and pretty cheap too!!

[Bobboloo]

I have a 2.7 with about 30k on a rebuild, The shop used Time serts and Dilvar studs The car runs very well!! My question is am I driveing a time bomb. I have headers on as well as weber carbs, my engine temp never gets over 210. Sould I tear it down and install steel studs? How long can these engines last? I have all the recipts from the repair shop, They did the work in 93 so it has went this far what sould I expect in the near future??

If it were me I would stick with the Dilivar particularly since you have a 2.7 mag case.

I don't think you can make a blanket statment when it comes to head studs. A statement like "you shouldn't use Dilivar, use only steel" or vice versa is short sighted.

IMO using Dilivar is a good idea on a 2.7 mag case motor. Cases I wouldn't use Dilivar on would be a 2.0/2.2/2.4 T mag case (iron cylinders)and 3.0 to 3.2 aluminum cases. Dilivar on a 3.6 aluminum case or Turbo motor (more HP=more heat) might be a good idea.

You know you won't break a stud if you use steel as opposed to Dilivar. You also probably won't pull a steel stud from a 2.7 mag case if you use casesaver inserts but you'll probably eventually warp the case requiring greater machine cost$ on the next rebuild as well as oil leaks along the way there.

Case in point. Most of the 75'/76' 2.7 mag cased motors require extensive machining costs do to excessive heat (thermal reactors) and the use of steel studs with Alusil or Nickasil cylinders. The motor Wayne rebuilt for his book was one of these motors. Look up the machine costs in his book.

I have a late 77' 2.7 (Dilivar top and bottom row studs) that doesn't leak and runs great. Of course the motor runs the risk of breaking a stud but should that happen I'll bet it'll have less warpage than a 75'/76' case with steel studs.

[Wayne 962]

Originally posted by tab tanner
I have a 2.7 with about 30k on a rebuild, The shop used Time serts and Dilvar studs The car runs very well!! My question is am I driveing a time bomb. I have headers on as well as weber carbs, my engine temp never gets over 210. Sould I tear it down and install steel studs? How long can these engines last? I have all the recipts from the repair shop, They did the work in 93 so it has went this far what sould I expect in the near future??

Don't worry about it until it breaks. You will probably be fine...

-Wayne

[Wayne 962]

Originally posted by afterburn 549
Its a catch 22...unless you go with something like ARP they are all probly going to break sometime..the thing is ,is to try to get the sometime into your time..steel with inserts works very well at least till the next rebuild at which time they are t b o (ed) . anyway

Hmm, not sure what you are you talking about? Do you work for ARP? Only the early Dilavar studs are prone to breaking, and they almost never break on mag case engines.

Do you have a copy of my Engine Book? (http://www.101projects.com)

-Wayne

[Wayne 962]

Originally posted by Bobboloo
Case in point. Most of the 75'/76' 2.7 mag cased motors require extensive machining costs do to excessive heat (thermal reactors) and the use of steel studs with Alusil or Nickasil cylinders. The motor Wayne rebuilt for his book was one of these motors. Look up the machine costs in his book.

False info - please don't misquote me.

The engine in the book was a 1974 2.7 engine. *ALL* magnesium cases will warp and deform - not just the 1975-76 ones (what about 1977) that you are referring to.

All of the 2.7 cases will show signs of warpage, and will require proper machining to return them to usable spec - not just the 2.7 cases...

-Wayne

[tab tanner]

Thanks Wayne i can sleep now!!!

[afterburn 549]

well what would you rather have to do machine you case at o.h. or put in new studs in the middle........I am not tring to milk this thread to death but is not steel the way to go?
And no I do not work for arp,have never used thir stuff.......just makeing the pt. steel is good and a mag case???? well after the 1st big rebuild are they not [petty much settled in?????]

[davidl]

Interesting point...

I do not know the composition of the alloy used by Porsche...

Does anyone have this data please?

Elektron, the grand-daddy alloy, was excellent mechanically, better than Duralumin, _( copper-aluminium), at low taemperature.

But around 80 degress celsius, becomes very soft...

So, no I do not think that mag cases "season" as many believe is the case ( oops!) for cast iron...

They will just keep on moving under heat and stress, and if Dilavar reduces that stress, it is a Good Thing..

But the main message of this post is, cool is cool...

Kind regards
David

[mark 74 carrera]

on a re-build with a 2.7 mag case the recommended studs are....Steel?????

[afterburn 549]

I do not know, it changes with the wind direction ,I used cheep steel and if it holds for 5 yrs I am happy. lots of peo say only this or that..I wanted to make sure the turbo did not blow the heads to mars !

[Wayne 962]

Originally posted by afterburn 549
Its a catch 22...unless you go with something like ARP they are all probly going to break sometime..the thing is ,is to try to get the sometime into your time..steel with inserts works very well at least till the next rebuild at which time they are t b o (ed) . anyway

I was responding to this post, which was less than clear with what you were trying to say...

-Wayne

[jgparker]

FYI, I just got my parts, and this is what the new 993 steel studs look like (993.101.172.02). No coating, or plating to speak of, and they are no longer all-thread. I included a 930 Dilavar for reference.



JP