Another hot rod

[TRE Cup]

One can make some assumptions on the tensioner rollers for both belts. Did they think fan belts would fling off under hard up/down rpm ? Same for the mfi belt? Looks like a vw rabbit timing belt rollers adapted to the task

[Flunder]

One can make some assumptions on the tensioner rollers for both belts. Did they think fan belts would fling off under hard up/down rpm ? Same for the mfi belt? Looks like a vw rabbit timing belt rollers adapted to the task

Hello Dave:

Good observation. Apparently so. But no idea actually, the tensioner rollers were on there when the motor arrived and the original owner passed away some years ago. He was an active PCA member and from what I have been told he continued to bring his car to DE events and ran it hard until he was pretty well near the end. I expect that he was experiencing problems with both belts given the mods.

I assume that the guys in Santa Ana did not put those parts on there!

It will look factory correct when it goes back together except for the inlet funnels which will remain pale gold (already sent to the plater) rather than being finished in ST period correct black paint and we will keep the toussled head fuel injection lines rather then using correct metal lines.

Of course, the Ti rods are also incorrect for an ST. They were never homologated for Special GT Gr 4. The 911/70 engines used nitrided steel rods from one of the standard production, but very specific, 911S connecting rod weight goups shown as being 727p in the Sports Purpose Manual.

I referred to Wayne's book How To Rebuild and Modify Porsche 911 Engines and at 727p this places the spec rod at the high end of the heaviest weight group, Weight Group 9.

Maybe someone can chime in and tell us why the heavy Code 39 rod is recommended.


The steel rod was apparently then modified to allow "more free motion" so it sounds like they set them up a little on the loose side to keep the customers from ruining too many cranks. The standard Rod Width at the at Crankshaft with Bearing is 24.00 to 24.10 for the 127.80 rod (measured center to center) used in a long stroke engine. The standard rod clearance is +0.200 to +0.400. The Sports Purpose Manual makes no mention of the exact rod clearance provided by the ST spec steel rod with "more free motion" but I suppose it was +0.400 at a minimum.

The measurement of the flanged rod bearing used on the Typ 917 titanium rods measures 23.90, or 0.10 under the minimum rod width for a long stroke engine off the production line.

This measurement of 23.90 may well provide an indication of what the "more free motion" amounts to for a steel rod as modified by the factory in prepping an ST 2,5 long stroke engine.

Would be grateful for any other thoughts or observations on the ANDIAL engine. Still looking for a set of Ti rod bearings...

Thanks,

Tom

I updated this post with a pic of the non-original belt tensioner mentioned in Dave's post nbr 107 above.

This image also provides a good view of the lubrication line for the injection pump in the upper left quadrant of the image.

[Mike_Moore]

So as not to hi-jack Tom's great thread anymore, have posted some 'grenade' filter pictures in the technical section:

http://www.early911sregistry.org/for...421#post192421

[edmayo]

In case you may be wondering who John Truman is, he was a mechanic at Stoddards and someone who was always willing to answer my questions back when I was a punk kid trying to learn all I could. He basically handled all the performance work back then, at one time I ran into him at Mid-America Raceway when I was running my E/P 356. He was there crewing for Mike Rahal's 906. (yes, that would be Bobby's father) To say that John has forgotten more about Porsches than most of us will ever know is a huge understatement!

[Flunder]

Ed-

Thank you for closing the circle on where the old Spare Parts List came from.

John sounds like exactly the sort of person who would qualify to be on the factory's limited distribution list for such information.

His old factory list is still providing a helpful hand.

[Flunder]

First batch of engine hardware is back from the plater.

Here you can see the

-cross bar for high butterfly throttle linkage

-RSR crank pulley to drive the small 906 fan

-2,5 ST/RSR fittings for injection pump lubrication line

-oil line for injection pump lubrication

-misc linkage and bracketry for the throttles

-pump support bracket in pieces




PS: Eagle eyed viewers will recognize the flat latches for the aircleaner set up of a SWB in that box - for a 67S project, not the hot rod.

[Flunder]

The crank is set up to work with the special thrust bearings on the big ends of the Ti rods but is otherwise unremarkable looking to the casual viewer - or even to close personal inspection for guys like me.

[Flunder]

At the risk of boring all but the most energized of the gear heads on the board, here is a scan of the page in the factory manual Information Regarding PORSCHE Vehicles Used for Sports Purposes that discusses crankshaft and connecting rod prep as discussed above.

We are still hoping to use the Ti rods but may need to use steel rods if we cannot find at least a few of the Ti rod bearings.

[Flunder]

Every hot rodder knows The First Axiom:

THERE IS NO SUBSTITUTE FOR CUBIC INCHES.

When last rebuilt about five years ago, ANDIAL 129 was treated to a set of new Mahle P&Cs sent east to New England from back home in Santa Ana.

The GTU series had long since folded its tents and John D, the first owner stateside of this engine from 1982 until he passed away in 2005, was taking his car to PCA DE events and time trials.

He was getting tired of running a small bore motor against 2,8s 3,0s and the big blocks.

He took heed of The First Axiom.

ANDIAL 129 had its case and old factory 2,2 / 2,5 twin plug ST heads opened up for the 93mm Mahles for a 2,9 conversion. The high crowns of the 2,9 pistons indicate 10.3 compression.

John D only got one event on the engine in its 2,9 displacement before he passed away. Upon inspection, we were suprised that the crowns don't even have carbon build up on them yet. They are good to go.

The engine builder thinks this displacement should work well with "little" 41mm ports of a 2,5 long stroke and RSR "endurance" cams.

[Cornpanzer]

Interesting side note about Truman...he is the guy who built the 2.5 engine in Curt E's car and the 2.2 S in mine.