fbarnhill

Hi guys,
Been out for quite a while and still don't have my 86.5 back together yet. Thought I might make SITM this year but found a bunch of bad disks in my neck instead... Isn't life just great with its little surprises???

So, back to the shark content, I have heard many people here and at different events speak about a good stroker engine. So, I have to admit, that I just don't know how it is made up for a shark. Would some of you please take a few minutes and try to explain it. Also, what would I need to turn my 86.5 into a stroker? The engine is within 40 minutes of coming out. I only need to remove the stuff under the car(Bottom 19mm bolts, exhaust, AC etc) and pull the engine. I hope to have it out as soon as I get these disks fixed, assuming that they can be fixed. There was an attempt made in 2009 but it failed, so here we go again.

Thanks in advance for your help,

Bertrand Daoust

From Wikipedia:

A Stroker kit is an aftermarket assembly that increases the displacement of a reciprocating engine by increasing the travel of the piston (that is, the piston moves further up and/or down in the cylinder). This is done by using a different crankshaft where the crank pin is moved further away from the center of the axis of rotation of the crankshaft. While this increases displacement and torque it can potentially lower the limit to which the motor can rev safely compared to the stock configuration.

I don't know if this explanation is all good but close I suppose.
This is a complex job I'm sure.
That involves a LOT of time and $$$ too.

fbarnhill

Thank you Bertand. I understand that part, I just wanted to know what it takes to do it for our sharks.

Richards 928

Good explanation. I have built some of thes on a different platform. Principle remains the same.
Stroking a motor results in increased displacement which typically results in increased power. I had a 350ci chev (5.7L) and swapped a 400 crank in to get a 383ci displacement. This increased horsepower and torque.

I have to say I was keenly interested to read about strokers for the 928.

I think the start point for a stroker is a 5.0 or larger block/bottom end. I have a 4.5 which is a small bore, increasing stroke may introduce flow issues due to valve size. A stroker usually needs more valve to flow properly.

Hopefully someone who has done a stroker on a 928 will chime in. I am very interested to hear from direct experience.

atb

In addition to the stroker crank, you will need either custom (shorter) connecting rods to run the stock pistons or a piston with the wrist pin boss located higher in the piston (also custom). A custom piston typically requires nikasiling the cylinders since they won't run in the factory allusil. Typical stroker cranks add 1L of displacement.

Rob Edwards

Lots of good threads on strokers in the archives- here are a couple with which to start. These are what comes up if you search only for 'stroker', and I stopped at the first 25 pages of results. There is plenty more good material in the older portions of the archives as well.

dyno-results-from-bonneville-motor-765-whp-900-chp
https://rennlist.com/forums/928-foru...p-900-chp.html


building-a-16v-stroker
https://rennlist.com/forums/928-foru...v-stroker.html

new-crankshafts
https://rennlist.com/forums/928-foru...hlight=stroker

curse-you-greg-brown-and-your-team-at-precision-motorwerks-stroker
https://rennlist.com/forums/928-foru...hlight=stroker

fs-7-0l-640whp-itb-engine-add-your-car
https://rennlist.com/forums/928-foru...hlight=stroker

our-bonneville-2012-results
https://rennlist.com/forums/928-foru...2-results.html

new-product-high-performance-intake-runners-for-the-32v-928-a
https://rennlist.com/forums/928-foru...hlight=stroker

fs-104mm-pistons
https://rennlist.com/forums/928-foru...hlight=stroker

spring-6-5-liter-stoker-****
https://rennlist.com/forums/928-foru...hlight=stroker

fs-6-2-liter-2v-stroker-kit
https://rennlist.com/forums/928-foru...hlight=stroker

aftermarket-injectors-for-928-strokers
https://rennlist.com/forums/928-foru...hlight=stroker

stroker-parts-anybody-looking-to-buy-their-own-christmas-present
https://rennlist.com/forums/928-foru...hlight=stroker

what-company-best-at-building-stroker-engines-from-scratch
https://rennlist.com/forums/928-foru...hlight=stroker

110mm-bore-928-engine-project-plans-for-a-7-4-liter-in-the-works
https://rennlist.com/forums/928-foru...hlight=stroker

stroker-update
https://rennlist.com/forums/928-foru...hlight=stroker

the-sound-of-200-mph
https://rennlist.com/forums/928-foru...hlight=stroker

s4-budge-stroke-engine-build-question
https://rennlist.com/forums/928-foru...hlight=stroker

strok-question
https://rennlist.com/forums/928-foru...hlight=stroker

our-bonneville-report
https://rennlist.com/forums/928-foru...hlight=stroker

just-dusted-a-2009-bmw-m5
https://rennlist.com/forums/928-foru...hlight=stroker

6-5l-rebuild-adventure-finally-begins
https://rennlist.com/forums/928-foru...hlight=stroker

Bertrand Daoust

A lot of good read here!

Maybe Greg will chime in as he is THE stroker expert here.

fbarnhill

Thanks Guys, Rob especially. I should have been more thorough in my search. So, I have a good 5Ltr block so I need a stroker crank and some shorter rods. Ok, just need to find a source and price as I am going to have them out anyhow. I like the idea of the shorter rods instead of the higher pistons. The reason, this came up, is that last time I had the engine out, I found a mark on one of the journals between where the two rods join. I took the crank to the machine shop to see if there was a problem. The guy said there was no problem but if this thing had more stroke, it would be one hell of an engine. I have been considering it ever since. The last engine I worked on before the 928 was a pretty awesome dodge 440. I swear the pistons in the 928 are just as large. I know this because I just happened to have the same ring compressor after all those years. I wish I still had the 69 charger. LOL

Alan

This is not normally a build it yourself at home type of project... you typically want an expert with lots of build experience to build it for you, lots of details to take care of - you need a new crank, main bearings, new con rods & bearing - probably new pistons/rings & wrist pins and significant refresh elsewhere (heads) to get everything up to snuff - a pretty big bottom up rebuild. You'd be likely to need some valve and injector work for a significant displacement increase.

If I were doing this I'd only consider Greg Brown for the job - he's built more strokers than anyone else with good results, getting it wrong likely means a trashed engine and a big expense to do it all over - makes more sense to pay for the best up front.

Technically the GTS engines were strokers since that's how they gained the extra displacement.

Alan

fbarnhill

Thanks guys. Seems like I have the answer to my question. From one of Greg's threads, he just might have a 5.4 kit lying around somewhere by now. I will check with him. I was just tossing around the cost of SC vs Stroker engines. Alan, I have plenty of engine building experience and have fallen in love with these engines. They seen to be well designed and for what I want it for, (driving the **** out of it every day and sometimes on the track) it is just the thing. I think it just crazy that I would rather have a 928 than any Ferrari I can think of, except maybe a Dino for a while, but for everyday, give me a shark.

What you say Greg, are those kits ready to market yet? I think that thread is dated 2012... Man I got in trouble for spending so much time reading your stroker kit thread. Wife is pissed I am not spending all my time with the grandkids... LOL

Rob Edwards

If you increase the stroke but keep the pistons' compression height (top of piston to centerline of the wrist pin), yes, you'll need shorter rods, but then the piston will travel further 'down' in the block. Too far down and the piston skirts start smacking the block webbing. How far you can go depends on the stroke and the piston skirt profiles.

The compression height on an S3 or S4 piston is 42.75 mm, and the compression height on a GTS piston is 39.25 mm, or 3.5 mm less. Which works out to half the (7 mm) distance between a 78.9 mm stroke of an S3/S4 motor, and the 85.9 stroke of a GTS motor.

ptuomov

There are three ways to make meaningfully more power: forced induction, increased displacement, higher revs.

In terms of hp/$, forced induction > increased displacement > higher revs.

In terms of the known problems with the 928, such as oiling and windage, the problems are higher revs > increased stroke > increased bore > forced induction.

Increased displacement is the best solution if you have to (illegally) pass your (illegal) hot rod car thru California or similar smog examination.

The logical answer for most 928's is forced induction, but hobbies don't have to be about logic. A lot of times, "because I can" is more than good enough answer to whatever you choose to do.

mark kibort

if you do it yourself, and have some decent engine building experience, the easiest and most bullet proof way to build a stroker, is to find a stroker crank and then use the custom rods needed to use the stock 968 piston. (rare used, and expensive if new). then, all you need to do is bore the 5 liter block out to 103-4mm (or whatever the spec is for the 968 piston), and assemble it all.

if you don't go that way, I would use someone that has done this before like Greg Brown or the GreenBay folks. because the other way to do it, by boring the block and nicasiling it, then specing custom pistons, rods and special oil rings (to name a few) , is a formula for disaster if you don't know what you are doing. even the wrong rings, will leave the engine junk after 1000miles, and that's not fun.

Lots of folks have been down this road before, so there is a lot of info here.

Adamant1971

Strokin!

fbarnhill

Man, you just have to love they way these girls do it