probably one of the best threads on stroker stuff in a while!!!
does raise an interesting dillema however - at times I know a lot (ok really only a tiny, tiny, tiny, tiny bit) more than I dare tell, out of respect for the Deveks, Precision's, competitors, etc that have spent countless hours fine tuning specs on these things and the propriatery nature of some OEM stuff as well...

however I'm conflicted due to my natural tendency to help out and the essence of these forums which is to share info - so I tend to just leave bread crumbs and hope I don't offend by going too far or not far enough...apologies to all for that...

don't know where the line is, but perhaps on another thread it'd be interesting to hear/poll pro wrenches, and end users alike to see where/or if such a line even exists...

on that note, flutter - according to JE that doesn't build an offset piston, flutter can be controlled by ring and blowby control...apparently during an exhaustive study by GM engineers w/perfect seal rings, it was discovered that the perfect seal stuff fluttered badly w/na OEM style street motors...turns out that the comp ring sealed so well that oil build up around the oil control ring and forced the comp ring to unseat and skip along the bore.... racers have used the perfect seals forever w/good results...had something to do w/larger tols, ported pistons, vacume pumps and such high comp that the perfect seals had enough blowby to keep everything clear(imperfect seals )... ring gaps are apparently key on "normal" rings as a result - w/centered pistons... JE wants an end gap of .015" to keep stuff clear/keep flutter at bay...just an FYI for ring considerations WYIT if using centered stuff could also mean that you might get away w/perfect seals w/Pcar pistons too ...advantages are less blowby (might really help w/FI stuff), better emissions, more power....regards!

 

Thanks Rob,

Sounds like a possible solution on strokers due to the rod ratios.... Now what happens if you dry sump the motor, and ad some boost to that....?

Did JE mention anything along those lines for the Perf./Total Seal Rings...?

 

I'd like to, but won't be able to make it.

If stock '88 rods could post here, they'd say: BTDT!

 

Good to know Z.

Just bought my AEM and UEGO btw. Now I should really start to put this car together!

 

beats me!! (yeah, yeah, it doesn't take much) but you CAN call Allen at JE: 714 898 9763 x278 for the ring/piston/and rod ratio thing- he's got some good insights/contacts from nascar, drag, and other motor sport pros/insiders to give you some guidelines that might help...he's a nice guy/very helpful/really likes his job...as you know - lots of trade-offs that apply to any motor/situation (I was/am just focused on my "boring" NA stroker)...you guys are way beyond/very cool stuff though...

did hear vacume and dry sump was good for about 7hp/litre - seems like decent $$/buck compared to larger valves,etc...overkill for me (so far), but think greg at precision (714)879 9072 mentioned a cost effective dry sump setup for 928's that's very clean (uses stock oil pump w/electric)

 

post the 550 rwhp dyno sheet....I need some motivation

My boosted short block has been done for a while....hmmm. time to do the heads now, and then the big question...turbo (low parasitic drage/powes loss, but difficult plumbing, or SC 9more parasitic losses)....hmm....

Marc

 

Old news already.
556rwhp dyno chart

Not bad for those stock rods, stock crank, stock heads, stock intake, stock displacement block, modified stock pistons, stock engine management computers, and pump gas, eh? I can hardly wait until the high power engines being built up there are finished.

 

That has my vote for understatement of the Year!

You going to Sharktoberfest Brendan, youd better!

 

either way you choose im sure it will be a boost for your engine also.

 

Tony, understatement for which YEAR ?

 

Hi Adam, I was looking at this thread and I have a couple of questions, Marc Thomas asked.Now I would have thought it is because the rod big end width is narrower than the original Porsche rods. All chevy small blocks have pretty narrow rods. Normally they are .940" or .820". This must be because those motors have smaller bore centres? What size rods are you using? I presume they must be 0.940'' Does anybody know if this is the case with all strokers? Or do somepeople get custom rods made?

I'm quite curious about this as it is something that is not normally discussed.

Cheers and awaiting eagerly.

 

Hi Greg,

Sorry I don't know the answer to your question. My rods are 5.85". I think what your saying is that the rod blank is the same (within a certain range) and Oliver adjusts by where they punch the eyelette. So if I ordered a 5.65" rod, the whole would be more centered, and if I ordered a 6.0" rod it would be more offset. That's possible I suppose, although the prior post suggest that there is actually some advantage in the design for piston stability.

The rod I'm using is "custom" in that it is a SBC rod with the small end reamed for the Porsche pin. I believe that the large journal size SBC is pretty standard isn't it? DIdn't the small journal cranks go by the wayside with the old 283's and early 327's?

 

Hi Greg,

Sorry I don't know the answer to your question. My rods are 5.85". I think what your saying is that the rod blank is the same (within a certain range) and Oliver adjusts by where they punch the eyelette. So if I ordered a 5.65" rod, the whole would be more centered, and if I ordered a 6.0" rod it would be more offset. That's possible I suppose, although the prior posts suggest that there is actually some advantage in the offset design for piston stability.

The rod I'm using is "custom" in that it is a SBC rod with the small end reamed for the Porsche pin. It also isn't a "stock" chevy length, although it is a common hot rodder length. I believe that the large journal size SBC is pretty standard isn't it? Didn't the small journal cranks go by the wayside with the old 283's and early 327's?

 

Adam,

How is your project going?

 

Hi Adam, what I'm talking about is the big end width. Now your big end diameter is probably 2.1" but the actual width of the rod at the big end is what is in question.

The 5.85" rod is a little uncommon but still an off the shelf type of rod, yes I also understand since you went with the Mahles you would need to change the small end from 0.927 to 24 mm, which is about a half mm in difference. So to sum up yes the big end diameter will most likely be 2.1" but what is the width, (I'm guessing at 0.940) interestly enough, smaller journals are back in favour to some extent, 2" is good for cutting done weight and remaining servicable. The Honda size is really just for the Nascars, that size is 1.888". It cuts down on rotating masses.

Now to a question you may also have some info on, the deck height. This is my calculation. Stroke 78.9 mm + conrod length 150 mm + compression height 50 mm = 278.9 mm or 10.98 inches Ok go to the stroker, stroke 3.75" + conrod length 5.85" compression height 1.496 = 11.096 or 281.84 mm. Am I doing something wrong here?

That is a difference of 3 mm or 0.11" that is quite substantial, do you have any info on this?

As to my project I am just finishing off a car I started restoring a while back, it has had quite a few set backs, but I think I'm winning now, I need to sell 2 of my 928s to do any project, I have a buyer coming Thursday for the finished one. Fingers crossed.