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Posted by: yeahmag Jan 8 2021, 12:47 PM

I'm starting to get the case(s) machined and inspected and parts ordered for my next generation engine. The car is mostly used for autocross.

78x96
96mm piston with 22mm wrist pin (stroker)
5.4" Type 1 Rod, 22mm wrist pin
WebCam 86b/86c
David Finch heads (from Len Hoffman many moons ago)
9.5:1 CR running on 91 octane pump gas
CB Dry Sump (heavily modified) or Thorsten Piper dry sump pump
Front mounted oil cooler

There are a few crank options out there now:

* DPR offset grind Type 1 journal
* AA Performance Forged Type 1 journal
* FAT Performance Forged Chevy journal

I've read about a few 80mm DPR cranks breaking, so I was planning on staying under 80mm as I like the car to be able to rev. I was considering Chevy journals for ease of assembly, but the two cranks I've read about breaking were 80mm/Chevy journals. Is there any new information on cranks out there? Any input on the config?

Posted by: 914werke Jan 8 2021, 03:21 PM

Following. Aaron interested in your approach to dry sump-ing the /4. I sold off the CB pump prior looking for a better solution.

Posted by: yeahmag Jan 8 2021, 03:35 PM

I’ve been running the CB Pump successfully in my current motor. I did do a bunch of work to open it up though.

Posted by: Montreal914 Jan 8 2021, 08:35 PM

Will definitely be following this thread.

Which cylinders will you be using?

Posted by: wndsrfr Jan 8 2021, 09:03 PM

FAT uses new forgings & will supply you with a flywheel doweled with 5 pins...hard to beat.

Posted by: Alapone Jan 8 2021, 09:57 PM

Definitely following this.

Posted by: yeahmag Jan 8 2021, 10:17 PM

I have NOS JE’s and AA cast iron cylinders that I got in a deal, but I’m thinking about trying AA’s biral cylinders.

Posted by: Montreal914 Jan 8 2021, 10:34 PM

Did ask in another thread if anyone was using Birals in a 2270, but no replies...

Posted by: 914werke Jan 8 2021, 11:05 PM

I used them on a 912E rebuild but that was only 2056

Posted by: groot Jan 9 2021, 10:22 AM

I have a 80x96 with birals. It's only run on the stand, so I can't comment on the biral performance.

Posted by: Jack Standz Jan 9 2021, 11:15 AM

My research lead me to use the forged stroker crank with VW journals because they're a little bigger, which (all else being the same) should be stronger due to slightly larger overlap. Downside is they seem to be getting harder to find.

With the VW journal, you can use the new Empi rods that are stronger and lighter: https://empius.com/products/empi-pro-series-i-beam-rods-5-500-vw-journal-2-165-55mm-arp-2000-5-16-rod-bolts/.

And I'm using type 1 tool steel lifters, which are durable and lighter.

Just my 2 cents which is probably worth about that much. Good luck with the project.

Posted by: yeahmag Jan 9 2021, 12:01 PM

Kevin,

I assume it’s AA on the birals, what crank did you end up using?

Thanks!

Posted by: Mark Henry Jan 9 2021, 02:08 PM

Longevity you want the 78mm with T1 rod journals, less crank flex with the bigger journals. I run DPR, you cant beat Swedish steel of the OE crank. China cranks have soft journals but I have used them in the 78mm/T1 rod, racing I'd likely tear down the block each season, where you might go longer with a welded crank.
80mm cranks flex, but there's no replacement for displacement, so if you have a big budget and you can afford engines go for it.
If you need the engine to last longer you want the T1 journal.

Clearanced CB rods stock T1 or 5.4"

I still prefer the EMW KB pistons.

Heads need dual springs, retainers, keepers and Manton pushrods.

9.5CR is really pushing it, I'd aim for 9.2-9.3CR.

I've used the same cam on several builds, you need reduced base circle. Big duration, good for carbs but almost no vacumm signal for a MAP sensor, so ITB FI has to run in AlphaN (TPS only), which is a pain in traffic but no issue on the track.

Issue with the dry sump pumps is the fan in the way. Personally I'd run a 30mm schadeck done full flow, steel cover, tuna can and a big accusump.

One of the best mods for a race car is a big ass pipe running air from the front end and dumping it into the fan.

Posted by: groot Jan 9 2021, 03:58 PM

AA crank, chevy journals... this is kind of a parts bin engine to get the car dialed in.

Posted by: Dave_Darling Jan 9 2021, 07:02 PM

Is the 78 stroke big enough to require a reduced base-circle cam? I think I remember that's right around where you start to need that.

--DD

Posted by: Mark Henry Jan 9 2021, 08:48 PM

Both 78 T1 and the Chevy rod flavors need reduced base circle cam and mod rods. All because of one pesky cam lobe in the way.

Posted by: Montreal914 Jan 9 2021, 11:02 PM

Reduced base-circle cam OK, but do these types of rods also need rework?

Posted by: Mark Henry Jan 10 2021, 07:59 AM

Yes, it's not a huge amount but there's still a bit of clearancing, if you buy rods from T4store this is already done. For chevy rod and 80mm you have way more rod clearancing to do than the T1 rod.
I use the CB rod for 78mm T1 and the SCAT rod for 80mm chevy.

Stroker cranks are a lot dry fitting, I often assemble an engine several times as I build. As I like to say "no two objects can occupy the same space at the same time."

Posted by: groot Jan 10 2021, 10:04 AM

Hmmmm... I didn't have much clearancing required for the Chevy rods and 80mm crank, but it's the only stroker I've built. I took my time and checked it a lot. Time will tell if I did an adequate job ;-)

Chevy/Buick journals are smaller than type 1, so should require less clearance work?... maybe you're comparing the clearancing required for type1 rod with 78mm versus Chevy rod and 80mm crank?

Posted by: Blown59 Jan 13 2021, 10:55 PM

Curiously... As a noob when it comes to T4 builds... Why not run the 2.0 rod journal and not reduce the cam base? Isnt the crank strong enough and the reduced cam circle weakening the cam?

If my idea is wrong, can someone please educate me as to why?

Posted by: yeahmag Jan 14 2021, 12:27 PM

It's all about reducing the amount of case and cam clearancing needed.

Posted by: Mark Henry Jan 14 2021, 02:02 PM

It's the rods with that T4 combo and a big lift cam, say the web 163/86b. One cam lobe comes close to a rod and you have to clearance the rod big end, so you have to match both sides and then all the rods must match.

Also I was confusing the Type one 2007cc, 78 X 90.5mm build I'm doing right now, lots of case clearing...dry fit over and over again....

Posted by: groot Jan 14 2021, 03:56 PM

You can, but your rod options are limited with the 2.0 journal. And the stock rods are pretty heavy and short for strokers.

Posted by: yeahmag Jan 14 2021, 03:58 PM

Kevin,

What cam did you decide on for your 2316 build?

Posted by: groot Jan 14 2021, 04:02 PM

Yeah, Mark, that's the combo I went with: 163/86b, reduced base circle, 80mm with Chevy journals, 5/16 rod bolts. I did have big end clearancing to do, not too much... very little on the case.... could have been lucky, though.

Posted by: groot Jan 14 2021, 04:04 PM

Aaron. 163/86b... not trying to turn 7000+... I have another engine for that. Purpose is reliable power without too much RPM.

I wouldn't be concerned about the amount of clearancing that I had to do... its was minor. The crank flex would be a bigger concern.. but, for my build, I'm okay with it.

Posted by: Dave_Darling Jan 14 2021, 07:08 PM

I'm not sure what level you are asking that question from, and the other replies require a bit more knowledge than a total noob would likely have, so I will try to fill that in.

When we talk about making the stroke of an engine longer, that is generally done by swapping in a crankshaft where the rod journals are farther away from the main bearing journals. Specifically, the center of the rod journals are farther than the center of the main journals. Because the piston is directly connected to the rod journal, that means the piston travels further up and down (or side to side in a 914 engine!) which is a longer stroke.

When you do that, you are going to take up more space inside the engine. Due to the layout of the internal bits, there is one place in the cam and crank rotation where a connecting rod on a long-throw crank will try to occupy the same space as a cam lobe. Whether or not this happens is influenced by a bunch of factors, very much including how long that stroke is, how big the big end of the rod is, how tall the cam lobe is, and so on.

It's not really feasible to move the cam down, or the crank up, so you try to make room by carefully taking material off the outside of the rod (which then needs to be balanced again along with the rest of the rods) and possibly by making the cam's base circle (the part that doesn't open the valves) smaller. This latter means that you can get the same lift from the cam but the edge of the lobe will be closer to the center of the camshaft, so it takes up less room in the case.

This is a simplification of what's going on, but I hope it helps.

--DD

Posted by: Blown59 Jan 17 2021, 03:38 PM

I sort of understand what youre saying... I get that fundamentally there is a shift where at one point the outer edge will be further away in the rotation. What Im not understanding is what the differences of each are.

For example, I was going to use a 78mm welded crank with a 2.0 rod journal, 2.0 H beam rods (5.325) 22mm pin, and KB 96mm pistons with 80mm stroke. My understanding is this allows to run in the case of my build a 163/86b without a reduced cam base. I was under the impression a reduced base with this cam would weaken the cam. So, to keep things as robust as possible on the top and bottom end, this was the route we were going.

What I dont understand is how that is any worse than the type 1 or Buick?? FYI the rods will be lightened and balanced by my builder.

Just looking to understand something maybe I just cannot see or that isnt computing for me...

Posted by: Jake Raby Jan 18 2021, 11:45 PM

The standard base circle of a 163/86B is 1.150"
The combo you are trying to use will still need a reduced BC, of 1.065" or so, if you try to run it otherwise, the rods will need to be clearance to an unsafe level.

Posted by: Blown59 Jan 19 2021, 10:31 AM

Jake, thank you for that clarification.

So, if I am understanding correctly... The BC of the 163/86b will need to be reduced slightly, but still giving the cam most of its rigidity. Along with the bottom end clearancing, should give a good balance of top and bottom end machining as to not have one more robust and leaving one weaker?? Or am I wrong?

Posted by: Jake Raby Jan 19 2021, 01:07 PM

Run a 1.065"BC and then clearance the rods as necessary.
Don't worry about cam rigidity.

Posted by: Blown59 Jan 19 2021, 01:35 PM

Jake, thank you for the info.

Posted by: Mark Henry Jan 20 2021, 06:53 AM

You're worrying about the wrong thing, the crank is where you need to limit flex. I run and have built many engines with HD dual springs and I've never worried about the RC cam.

Posted by: Jake Raby Jan 20 2021, 07:57 AM

Same here. The reduced BC only calls for a little longer pushrods to be used as a negative.I have ran cams with a BC of 1" and one of them is still on the road now after 21 years. Its in my 356C.

Posted by: Mark Henry Jan 20 2021, 08:09 AM

You do realize high lift cams like the 163/86b require dual springs and all the valve train upgrades right?

A stroker crank is far from the easiest engine to build and while it's been done it's not one I'd recommend for your very first engine build.

Posted by: Blown59 Jan 20 2021, 03:06 PM

Thank you for correcting my cam flex concerns. And yes, dual springs, valve train and head work are all part of the build amongst other aspects.

Everyone needs to learn one way or another. How many engines have how many people screwed up in learning?? Its all part of the process. And if I spend money building one to learn on and spend more to build the next stroker... The cost is still more than one stroker engine. Either way, it cost more than one build. And who knows.... First stroker may last 70k???? In which case, money well spent.

Time will tell... In the meantime, I enjoy reading.

Posted by: VaccaRabite Jan 21 2021, 08:28 AM

My first motor ran about 10 miles before I had to tear it apart due to low oil pressure because I was learning. I missed something that anyone with experience would have taken for granted and I just didn't understand fully at the time.
Second motor ran hundreds of miles before I tore it apart to try something different. Nothing was "wrong" with the motor, but I had learned more and wanted to change things on the top end.
Third motor has run thousands of miles. I have to fight the urge every season not to tear it down to build something else. I really want to build a stroker to replace my 2056, but with the 2056 running so well...

Zach

Posted by: Jake Raby Jan 21 2021, 10:57 AM

Everything I know about all the Porsche engines I work with came from direct experience, and mistakes. It is truly THE ONLY way to learn. It is also the hardest path.
I didn't have forums or etc to use as resource material. I did something, and if it blew up in my face, I knew not to do it again. The first time it isn't a mistake, but the second time the same thing is done, with the same result is is a mistake.

Today the amount of resource material for these engines is almost too great. There's as much misinformation, as proper information, which is actually worse than no information.

People are too timid these days. Build it the best way that you think, and if it blows up in your face, you'll understand what it's like to walk in the shoes of an engine builder.

Posted by: yeahmag Jan 21 2021, 11:24 AM

Zach,

That's exactly how I ended up where I am. Built 2x 2056cc (with parts from Jake, Thanks Jake!) over time and now I'm starting to build up a 2270 that's much more aggressive. My class is all about power to weight, I want more power, and the I'm not that far off the pace of the guys who have a much lower ratio than I do. Should be interesting.

I've been spending some time trying to figure out what static CR I want with both the 86b/86c and the 163/86b. The easiest design puts me at 10.8:1 static, which is way outside my normal rule of thumb of low 8:1 dynamic CR (above 9:1 dynamic). I'd need to add quite a bit of volume to the chambers or a big dish in the pistons to get down to 9.5:1 (which puts me right about where I'm comfortable with in dynamic compression). The fixed numbers I'm working with are:

Bore: 96mm
Stroke: 78mm (maybe 80mm, still debating)
Head CC: 50cc
Target Deck Height: .040"
Rod Length: 5.325"
Intake ABDC (86b/86c): 54 degrees

Dynamic CR for the 86b/86c At 10:1 static I calculate 8.56:1 dynamic. At 9.5:1 static I calculate 8.14:1 dynamic.

So, I can move around the DH a bit and add a dish to the piston, but I'd prefer to keep the quench area that a tight deck affords me. I *think* an 80mm diameter, .2mm deep dish in the piston will get me to the needed 60cc combined (piston dish + heads), but I'm still modeling. I also need to mock up the motor and see if I need valve reliefs, which will add some cc to the volume.

Posted by: Jake Raby Jan 21 2021, 03:31 PM

10.8 is too high for a 163/86B on 93 octane unless operating above 5,000' elevation.

Posted by: yeahmag Jan 21 2021, 03:37 PM

Thanks, Jake. I'm really leaning towards the 86B/86C as I can benefit from the RPM and not having to take a shift in autocross. The 86B/86C would let me have a bit more compression (9.5-10.0), but I really don't want to have to use race fuel and I only have 91 octane easily available. That's why I'm thinking of shooting for 9.5:1 with the bigger cam.

Posted by: Mark Henry Jan 21 2021, 03:48 PM

What heads?
With Len's heads you don't have to worry so much, if do your own/local head work with big lift cams you have to do all the checks, every little detail. For example you have to trim the valve guide tops and check for coil bind.
I like to think every part of a stroker build is trying to kill your engine, all you have to do is figure out how to make it live without it self-destructing.

Posted by: Mark Henry Jan 21 2021, 03:51 PM

I personally would be slightly more conservative, say 9.3:1, gives some wiggle room and is better suited to 91 gas.

Posted by: yeahmag Jan 21 2021, 03:55 PM

They are heads from Len, but not Len's heads. This PDF has the history and info. I'll be looking them over carefully, checking spring pressure, etc...

 finch_heads.pdf ( 966.88k ) Number of downloads: 68