simos

Jim nailed it very well, thanks. Different applications needs different cams

Wouldn't all of the elgin cams does have 114LSA?

65-6 Cam specs:
IN .414 lift 260 deg. duration @ .006 lash, 217 deg duration @ .050 lash
EX .370 lift 246 deg duration @ .006 lash, 208 deg. duration @ .050 lash
LSA 114, Int LCA 120,5, Ex LCA 107,5

This gives me something like 25 degrees of overlap, which supposed to be "just fine" for street/race application(something like 20 - 30 degrees).

Need to model different grinds to understand more about cam timing events to make them match to my heads. Now having stage II from Colin.
One of the most important thing to fill the intake ports with epoxy was to get back the torque, which the Porsche engineers lost with uber large volume ports in 32V engines.
To get higher smooth torque curve together with good power(perhaps only 450ehp or little more) the cams needs to match with rest of the engine setup.

Exiting project from my point of view, even it's not any all out high hp engine

UpFixenDerPorsche

Great to hear someone else talking about this simos.

Been on my mind for a long time, but without the means to experiment.

Interested to see your results.


.

ptuomov

The answer is right there with in the 968 cam specifications.

For emissions and idle, you want high LSA and low overlap.
For mid range torque, you want low LSA and high overlap.
For high rpm, you want again high LSA and low overlap, if you have to keep the cam lobe profile constant. But that's misleading. You want to have low LSA and high overlap, but you really, really want to have a late IVC which is more important than LSA and overlap at high rpms.

Graph from Greg Gray:

UpFixenDerPorsche

Terry, for some strange reason your post has seized my eyeballs and won't let them go.

Can you elaborate a little more on your engine details?

Plllllleeeaaasseeeeeeeeeeeeee .....


Upfixen.
'90 GT

terry gt

Jim , My car is the first 928 to run the tri flow cams ( staggered intake lobes ) looking at the dyno runs they all start at 2500 rpm and show 250-260 torque . I think the concept with the staggered opening of the intake valves was to maintain air flow at lower and mid range rpm , and create more of a swirl in the chambers .I have run 4 or 5 DE with it , 3000 rpm it pulls hard 3500 rpm and up it just a linear rush . Colin has posted some utube clips of the car idling ect . The motor is stock with cams and exhaust and tuning . 70k never had the heads off .

Strosek Ultra

Colin, what is so very bad about the Threshie camshafts? Cannot express myself about the quality of the welding and grinding job but this particular cam part no. 928-LI-4CS4 seems to be quite a mild grind. LI stands for level I. In my Threshie catalog the lift is stated .402" and not .407" as on Ebay. I do not know what is right. The duration figure of 260 degrees is big and cannot be at .050". Seems to be at 0,20mm (.008") relating to the duration figures Mr. Threshie is stating in the catalog for the stock camshafts. He does not say anything about the timing nor the LSA.

The LSA for S4 cams is 106,5 degrees, for S3 114 dgs, for GT 110 dgs, for GTS 118,5 dgs, for Colin´s cams 114 dgs and for some street (sports) cams made in Europe 110 dgs, for racing cams 105-108 dgs. The extremely mild S4 stock camshaft do not have hardly any overlap at all, about 0,5mm (.002") of lift at TDC. Racing camshafts up to 5,5mm (.216") of lift at TDC for this kind of engines. Stock S4 cams perform best retarded, racing cams best advanced.
And yes Simos is right the intake port is too large for a 5 litre engine and the floor is too low for best flow.

Åke

jcorenman

Åke, cam-grinders in the states specify lift at 0.050" or 0.006" (the so-called "seat timing"). The 260 degrees is certainly at 0.006", which would make them bigger than GT cams (255) and smaller than Colin's S2 (272) or Devek B1 (270) cams-- should be a pretty nice street grind.

Since they are welded S4 cams, I would think the lobe-center would be the same, and would work well with a set of GT exhaust cams (as Greg pointed out above). LSA would be be just slightly larger than GT, 110.5 (splitting hairs).

That's assuming they are straight, and stay together of course

terry gt

Got to ask , where are you going to find a pair of GT exhaust cams ? regrinds ? The straight and hold together part is what worried me , with Threshie cams .

17prospective buyer

I like that diagram for the 968 cams posted. Easy to interpret.

hans14914

FYI the old 928D site was still accessible through the way back machine last I checked.

Lizard928

This is the graph and numbers from Terry's 928.
You can see at 2900rpm it is over 290rw ft lbs, and stays over 310 rw ft lbs from 3000rpm to about 5600 rpm where it then drips down to 306 at the very end of the run.....

UpFixenDerPorsche

Hi Guys.

Would anyone know here can I buy the Stage 11 Tri-flo cams pls.


Cheers
.

Lizard928

Pm incoming or email me cjensan 'at' gmail.com

mark kibort

BC............................really? 335 vs 350rwhp....... YOU might want to increase reading comprehension! but maybe "substantially" bigger cams doesnt mean that much to you.
in all seriousness, my 335 was all stock, with 85 cams..... no mods other than headers and RRFPR. remember, i cant tune mine with out changing out the ECU. also remember that i have a safe tune as we did hook up the shark tuner and saw some decent characteristics, but its not tuneable, or as easy to tune as other "stock" S4s.

anyway, 350 with a street set up is pretty awesome. I think if i got some big cams in the stroker it might be hitting that 400rwhp mark with the stock intake and ECU.

BC

I'm basically joking with you Mark, but there is always truth to humor.

You don't see small details. You don't put any worth into them as the building blocks of a process.

From the decade I have "known" you online, that is what I see.

Tune your Todd Motor.