Your recomendations for conrod bolts and head studs

[ornas]

Hi, I am rebuilding my 86 3.3 turbo engine I have read that engines like mine suffer from weak rod bolts and delavan head studs. I would like to hear your opinion about and recommendations about it. I would be also interested if you have something to offer.

[kodioneill]

With a turbo I would use only Raceware hardware for rod bolts and such.

[Kemo]

Supertec makes a good headstud as well. There are a few threads comparing the different brands of aftermarket studs.

On a turbo, or any high compression motor, buy the very best headstud you can.

[millhaus]

I just finished rebuilding my 1980 3.3 and did the same research. I used ARP for the rod bolts and head studs. Very high quality and good tech support if needed.

Many use Raceware or 993 studs. I heard the 993's are preferrec due to the threads the entire length. Some felt this added strength and cooling.

What I learned was it really depends on how you plan to use your engine. Nornal daily type use or heavey track.

Do a "head stud" search of this forum and you'll find many strings.

Good luck.

[efhughes3]

I used ARP rod bolts and Supertec headstuds. Happy with both.

[Quicksilver]

The 993 twin turbo Dilavar head studs come with the highest recommendation (Who am I to doubt Steve Weiner...).

For rod bolts you aren't dealing with thermal expansion issues so it just comes down to who makes a really strong bolt. They have all been mentioned: ARP and Raceware. Seeing that the bolts are probably stronger then the stock rods and good for way beyond my RPM range, my unscientific selection would be "Which can I get a better deal on?".

[Wil Ferch]

There are 2 schools of thought on the headbolts. I recently asked this also on the engine rebuilding forum. To recap.....Porsche started to use the Dilivar ( not Delavan) head studs as a strong alloy that had thermal expansion/contraction much like aluminum...so it would "follow" the engine case properly. Porsche used 12 steel upper studs for the normally aspirated cars,and 12 lower Dilivar....the thinking probably that the upper row gets a fresh and cold blast of fan air while the lower row picks up heat having the air go past across the cylinder fins first....and were therefore more necessary below. The Turbo's got 24 Dilivar as they were thermally stressed throughout.

The problem with Dilivar was that they had a habit of spontaneously breaking. There were a number of revisions to Dilivar over the years.

So....the current engine builders said, "hey....the modern alumimum blocks arre plenty strong" ( compared to the earlier magnesium blocks where head studs "pulled" right out of their bores).... "why not go steel for all 24?"

So....you can go Supertec, Porsche OEM, ARP, Raceware....if you're of the school that says this is OK. Remember, however, that they will not expand/contract like the aluminum block, and they may end up "stressing" the assembly under certain temperature conditions.

The other school says..."What is the best available Dilivar?". The answer is the 993 Twin turbo version that is threaded along its entire length ( I think these are 993.101.170.51). It *seems* unlike the previous Dilivars, *these* latest versions don't spontanteously break....and going all 24 latest Dilivar seems to be the ticket to cover all bases. BUT....at $40/pop ( x 24).....these end up pretty spendy, unless yuo get job-shop prices. People like Steve Weiner endorse this method...a highly regarded recommendation.