What is the difference btwn. 901/02 & 901/26

[gtgroupe3]

Ok I give up...

Can someone please tell me how the 901/26 ('70 914-6 rallye with IDS) engine rates 20 HP more than a 901/02?

Is it the equivalent of adding a sport exhaust, Sport Kit II and doing the work noted on pg. 11-12 (i.e., compression bumped to 10.2:1) of the “…for Sports Purpose” (’68) to the 901/02?

Any help would be greatly appreciated.

Thanks much,

Sumner

[Neil '67 911S]

"What's the difference between 901/02 and 901/26?"

Oh, 'bout 24.

- Neil
'67 911S (Ol' Ivory & the Rust Bucket)

[gtgroupe3]

Thanks for your answer.

Pardon my lack of clarity; I didn’t want to trouble anyone too much.

The gist of my question, understanding the differences between a 911 & 914, was how and why is the 901-26 rated at 180BpH and the 901/02 rated at 160 BpH.

I intend to spend part of my summer holiday, building a back-up engine for my ‘67S and have acquired enough parts to build two full engines.

Noting that the 901/26 (914-6 rallye) in every piece of lit, parts manual, and historical reference noted the 69 non-MFI heads and as you correctly stated has heads with I 43 E 38 port I 32 E 32, while the 901/02 heads have the same I 42 E38 but with larger porting.

Since both use or start with the same cams and have 9.9:1 P/C, and excluding the differences in the cases (i.e., Mg-Al), the bottom ends or short blocks are identical.

Not wanting to get into a long discussion about flow characteristics of the heads….

But does the smaller porting make the difference? Or is it since the 901/26 was a race-prepped (port matched and polished) engine the gains were found there; maybe the 901/02 was just conservatively rated?

Currently I run 2.2 heads (I 46 E 40) with 85mm P/C on my 960XXX case and was looking to just build a solid 901/02 on my other 960XXX with the stock '67S heads.

I was thinking of having a set of heads taken out to I 45 E 39 (‘69S/906) and ported while they were being refreshed, but if there is no tractable performance gain, why spend the extra time or money.


Thanks again, Sumner

[gtgroupe3]

Thanks and it is as I thought; the increases are inline with most of the race prepped 901/01 2L engines (150-160 bhp at the rear wheels).

In ’67 Alan Johnson and Rodger Bursche recorded 143 Hp at the rear wheel Hp prior to tuning and 150-160 after (p.g., 29, Road and Track 1968).

This places the 901/02 at 177.32-180.18 crank hp prior to tuning and 186-201 after, if their reported numbers are accurate. Since they were casting their own pistons, it looks like the compression was a bit higher, as well.

All of which can be accomplished by proper fit, finish and attention to detail; i.e., no golden BB with the 901/26 and the 901/02 was conservatively rated at 160 bhp in typical Porsche fashion.


Thanks again,

Sumner

[t6dpilot]

Not to hijack your thread, but I have to pose a question to you guys since your are talking about 2.0L and 2.2L heads. Would you see a problem running a 2.0L case with all S internals, 2.2 P&C, and 67S heads? Would the motor freely rev up to 7300 revs? I cannot see why the 67S heads would prevent that, but I have to ask - there is a reason for my question.

[gtgroupe3]

The '67S heads would have to be modified to fit the 84MM P/C of the 2.2.

It would be better and cheaper to run non-MFI 2.2 heads with the 84mm P/C, than modify the '67S heads to fit.

The rev limit would be dependent on a number of other things.