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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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 Posted: Thu Sep 06, 2007 5:37 am Post subject: Short Block Internals for Ideola's Ultra Wide Body 931 |
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Check it out: rods just arrived today 
Custom rods:
Comparison of custom rod to stock rod:
These are designed to be direct replacement for stock. I haven't done the math, but I believe these are about 40% lighter than stock. They are a much lower profile in order to accomodate a stroker crank without requiring the block to be notched, but there's no reason they couldn't be used on a completely stock setup. The big and little ends are the same diameter and the length is the same as stock.
Here are the specs:
Engine Make: Porsche 2.0
Rotat Wt: 447
Recip Wt: 173
Total Wt: 620
C to C: 5.669
Big End Dia: 2.0316
Big End Thks: 1.100
Pin End Dia: 0.9447
Pin End Thks: 1.100
Rod Material: Steel
Lube: 90898
Stretch: .004-.006
Torque: 45 lbs.
They promised me 8-10 weeks delivery; they came in 6 weeks. How's that for under-promising and over-delivering!
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erstwhile owner of just about every 924 variant ever made
Last edited by ideola on Wed Dec 09, 2009 11:00 pm; edited 3 times in total |
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PwrGTOGuy
Joined: 23 Jun 2007
Posts: 194
Location: Middletown, PA
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| Posted: Thu Sep 06, 2007 5:45 am Post subject: |
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Pretty....  |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11723
Location: PacNW
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| Posted: Thu Sep 06, 2007 5:46 am Post subject: |
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Yikes, that's a pile of dough! Dey pretty tho.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Thu Sep 06, 2007 6:29 am Post subject: |
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| Quote: | | Yikes, that's a pile of dough! |
Considering the alternatives...
- Pauter rods @ $1200 per set
- Oliver rods @ $1200 per set
- Notching the block ~$500 + another hot tank trip
...I felt that the Crower Rods were the best approach. The original plans were to just use stock rods. However, we were given bad info when investigating the stroker build, and found out after the cranks were done that the stock rods cannot be used with a stroker unless the block is notched. The benefit to the custom rod is added strength and reduced weight. So, yeah, it ended up costing ~$800 more than I was originally planning to spend, but in the end, I have a better build. In the grand scheme of things, ~$800 is less than .5% of the total project budget, so just a drop in the bucket.
Incidentally, Tom Cooper deserves all the credit for doing the leg work, finding Crower, ordering the first set, and verifying fitment. Thanks Tom!
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erstwhile owner of just about every 924 variant ever made
Last edited by ideola on Wed Dec 09, 2009 11:01 pm; edited 1 time in total |
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endwrench
Joined: 07 Dec 2002
Posts: 1631
Location: Victor, Montana
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| Posted: Thu Sep 06, 2007 6:49 am Post subject: |
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You'll never be sorry with Crower quality. Nice stuff.
Did you ever give consideration to using small journal SB Chevy rods? I seem to remember researching this at one time. They're slightly longer at 5.7" but you needed custom pistons any way. For others it would be a way of raising the compression slightly in a 924. Just one of those things kicking around in my head.
Todd
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'79 924NA. Rebuilt 9.5:1, MSDS header, Mega Squirt Injection, MJLJ-EDIS Ignition, 1.6L Whipple Charger and Intercooler, 10lbs Boost, 944 Trans, Custom HD Clutch.
"simsport" said....superchargers are better than turbos its official!.... |
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Thu Sep 06, 2007 6:49 am Post subject: |
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And here are the custom 931 pistons I had made up some time ago:
Custom on the left, stock on the right:
These are designed to be non-interference 931 pistons, retaining a similar squinch area, but made to avoid the valves. These particular pistons were designed at 8.0:1 CR. The wrist pins are offset so that the pistons can be used with stock rod length in combination with a stroker crank (increased stroke from the stock 84.4mm to 90.75mm, or .25 in). The tops are ceramic coated for better heat resistance, and the skirts are teflon coated for reduced friction.
Here are the specs:
Bore: 3.4550 (87.5mm)
Compression Height: 1.610
Effective Volume: -4.17
Top ring: 1.5m
2nd ring: 1.5m
Oil ring: 3.0m
Lock ring desc: spirolox double
Lock ring part #: 01-5104
Wrist pin dia: .945
Wrist pin length: 2.500
Piston weight: 377 grams
Total cost was in the neighborhood of $800. Unlike Crower, Diamond Pistons were a PITA to deal with. They were late by over two months delivering the order. They also delivered the wrong wrist pins and didn't include the spirolox. To be fair, after a bit of wrangling on the phone, they did deliver everything I ordered. But I was less than impressed with their attention to detail and customer service. I think things would be better the next time around, so I would still order from them. But just want to be straight up about the experience I had with them.
Also, to be clear, the pistons are completely custom and are based on my specific build, so don't just assume that these would work for any old 931. However, Diamond can make anything you need. They were really good about working with my machinist (Holbrook Racing) to sort out the final compression height. I'm definitely glad I was working with local resources for this part of the build.
I'll post pix of the stroker crank later on. Next step is to have the block o-ringed and to have a custom crank scraper made up, now that I have the custom rods to work with.
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erstwhile owner of just about every 924 variant ever made
Last edited by ideola on Wed Dec 09, 2009 11:07 pm; edited 2 times in total |
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Thu Sep 06, 2007 6:57 am Post subject: |
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| endwrench wrote: | | Did you ever give consideration to using small journal SB Chevy rods? |
Yes, absolutely, we looked into that, but unfortunately there was something about them that wouldn't work. I don't remember if the crank journals were wrong, or if the thickness of the rod would have required too much modification to make it feasible. But when we had the strokers made, our crank guy investigated this at some length and finally determined that while the chevy rods were close, they weren't close enough to be feasible. Also, bear in mind, initially, we were planning to use stock rods. When we discovered the stock rods would interfere with the block, it was back to the drawing board.
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erstwhile owner of just about every 924 variant ever made |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11723
Location: PacNW
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| Posted: Thu Sep 06, 2007 7:20 am Post subject: |
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Wow, those are thexthy!
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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Cedric
Joined: 27 Aug 2004
Posts: 2608
Location: Sweden
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| Posted: Thu Sep 06, 2007 7:36 am Post subject: |
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Nice !
Thats a very good price for both rods and pistons. Wish i could have those prices here. Stuck with original internals..
Seems like an intresting project. Do you have more info about your engine plans ?
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1980 924 Turbo
www.instagram.com/garagecedric/ |
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Thu Sep 06, 2007 7:40 am Post subject: |
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| Cédric wrote: | | Do you have more info about your engine plans ? |
Heheh! Do I ever! Here's the Turkey Shoot thread...
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erstwhile owner of just about every 924 variant ever made |
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morghen
Joined: 21 Jan 2005
Posts: 8879
Location: Romania
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| Posted: Thu Sep 06, 2007 8:58 am Post subject: |
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holy crap...goodies !! cant wait to see these goodies at work !
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Paul
Joined: 02 Nov 2002
Posts: 9491
Location: Southeast Wisconsin
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| Posted: Thu Sep 06, 2007 9:22 am Post subject: |
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Do those rods have the oil squirters?
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy. |
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endwrench
Joined: 07 Dec 2002
Posts: 1631
Location: Victor, Montana
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| Posted: Thu Sep 06, 2007 2:08 pm Post subject: |
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Maybe I'm missing something or have forgot something but just judging by the pictures of the pistons I would have to say they are not non-interference. They look to be a zero deck height quench style piston like the original. The rim is too thick to miss the valves. It would have to be less than 2.8mm wide with stock sized valves. The outside spread on stock 40mm x 35mm valves is just under 82mm. "Assuming" this is centered it would only allow for 5.5mm futher to the edge of the bore or 2.75mm on the radius. You may want to check this out during assembly. The only way I can see these may be non-interference is if the piston actually sits .250"-.300" below the deck.
Todd
_________________
'79 924NA. Rebuilt 9.5:1, MSDS header, Mega Squirt Injection, MJLJ-EDIS Ignition, 1.6L Whipple Charger and Intercooler, 10lbs Boost, 944 Trans, Custom HD Clutch.
"simsport" said....superchargers are better than turbos its official!.... |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11723
Location: PacNW
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| Posted: Thu Sep 06, 2007 2:50 pm Post subject: |
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_________________
Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Thu Sep 06, 2007 10:20 pm Post subject: |
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When I had the pistons made, I brought the head in and they scanned it so they could make sure the combustion chamber was correctly sized. I specifically asked for a non-interference design. However, you may be right, and they may in fact interfere with the valves. I won't know for sure until I get the head back and put it all together. In the end, it's not the end of the world if there's interference...after all, it was an interference motor to begin with.
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