Question for you T4 engine builders, Deck height way off---Too much deck ht! |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
Question for you T4 engine builders, Deck height way off---Too much deck ht! |
Borderline |
Jan 30 2007, 10:38 PM
Post
#1
|
Senior Member Group: Members Posts: 720 Joined: 8-February 05 From: San Juan Bautista, CA Member No.: 3,577 Region Association: Northern California |
I've got my case together and was checking my deck ht. My readings average from .074" to .080" for all four cylinders without any shims. The problem is I am shooting for .040" to get my compression ratio up to 9.5:1. This is my first T4 build. I have built several Vee motors in the past and never had this problem. Is it possible to shorten the cylinders? I just did a quick measure of the height of one cylinder. It is 3.62" from the case sealing surface to the top. Does this sound about right? Everything was going to well. Something had to go wrong (IMG:style_emoticons/default/mad.gif)
|
nebreitling |
Jan 30 2007, 10:56 PM
Post
#2
|
Member Emeritus Group: Members Posts: 3,314 Joined: 26-March 03 From: San Francisco Member No.: 478 |
are you using any base shims between the cylinders and case?
what are your heads cc'd at? if you can only get your deck head down to, say, 050 or 060, you could always flycut the heads at bit more. i've also seen guys machine off the tops of the cylinders. in any case, having the d.h. vary up to 006 is too much to me. it's not hard to get things down to 001. i've just been told to stop typing and go retrieve a piece of fruit for my gf. |
Twystd1 |
Jan 30 2007, 10:58 PM
Post
#3
|
You don't want to know... really..... Group: Members Posts: 2,514 Joined: 12-September 04 From: Newport Beach, California Member No.: 2,743 |
HHHmmmm...
I have a couple of questions for you. First off. Is this a bone stock piston, cylinder, setup with Mahles and STOCK rods? Are there ANY aftermarket parts in your combo? Have you measured all 4 cylinders for height? If so. What are the heights for EACH cylinder? (Top Sealing surface to bottom sealing surface) Have you checked wrist pin location to see if they are all the same? And lastly.... What device are you using to hold your cylinders to the block for deck height measurement's? Lets get through these hurdles and get on to the issue at hand. C Lets start there......... |
Jake Raby |
Jan 30 2007, 11:07 PM
Post
#4
|
Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
I answered this in depth on my forum..
The cylinder measurement you are coming up with is standard for aftermarket cylinders. OEM cylinders generally measure exactly 3.600. You'll either have to: 1- Trim the cylinders in a lathe 2- deck the case registers in a mill\ 3- Flycut the heads for a tad less chamber volume 4- Live with the difference We can help with 1-3, and don't recommend #4, that said I'd trim the cylinders. |
Borderline |
Jan 30 2007, 11:20 PM
Post
#5
|
Senior Member Group: Members Posts: 720 Joined: 8-February 05 From: San Juan Bautista, CA Member No.: 3,577 Region Association: Northern California |
the pistons/cylinders are 96mm A-A units.
the rods are stock-rebuilt by Remco, so they may be a little on the short side. I only measured one cylinder as it is getting late tonight will take more measurements in the am. I used a short piece of angle iron with some spacers to hold down cylinders using the short studs and then stacked some sockets on the long studs and tightened them up. I know it's kinda quick and dirty, but I was anxious to get some readings. I brought the cylinders up to TDC using a dial indicator and then used a dial caliper to measure down from the edge of the cylinder to the top of the piston. |
Twystd1 |
Jan 30 2007, 11:49 PM
Post
#6
|
You don't want to know... really..... Group: Members Posts: 2,514 Joined: 12-September 04 From: Newport Beach, California Member No.: 2,743 |
What Jake said... He answered your question at his forum...
Question. Is this a 2.0 block? If so... I just had to deck my block to get it dead nuts flat and parallel to the bore. Guess what... All my decks are even at 30 thou now...... Kewl...!!!! (Thanks Joe J!!!!!) C |
Borderline |
Jan 31 2007, 12:00 PM
Post
#7
|
Senior Member Group: Members Posts: 720 Joined: 8-February 05 From: San Juan Bautista, CA Member No.: 3,577 Region Association: Northern California |
I found the problem:
The AA cylinders are .020" longer than stock. The AA pistons are .030" shorter pin-top |
rhodyguy |
Jan 31 2007, 12:11 PM
Post
#8
|
Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,080 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
bummer.
k |
drewvw |
Jan 31 2007, 12:23 PM
Post
#9
|
new england car guy Group: Members Posts: 1,631 Joined: 24-February 06 From: Boston, MA Member No.: 5,630 Region Association: North East States |
this thread is real interesting to me, as I was looking at those pistons/cylinders. |
rhodyguy |
Jan 31 2007, 12:30 PM
Post
#10
|
Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,080 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
find a good set of 94mm oem cyl opened up for 96mm. next get a 96mm KBs with the correct pin heigth and be done with it.
k |
drewvw |
Jan 31 2007, 12:38 PM
Post
#11
|
new england car guy Group: Members Posts: 1,631 Joined: 24-February 06 From: Boston, MA Member No.: 5,630 Region Association: North East States |
That was my initial approach....but i heard recently that the aa pistons and cylinders can work out well if you use Jake's rings or something to that effect.
Jake...any comment on that? |
Brando |
Jan 31 2007, 03:57 PM
Post
#12
|
BUY MY SPARE KIDNEY!!! Group: Members Posts: 3,935 Joined: 29-August 04 From: Santa Ana, CA Member No.: 2,648 Region Association: Southern California |
|
Aaron Cox |
Jan 31 2007, 04:01 PM
Post
#13
|
Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
brandholio...
you know machinists.... have em lathe em down a bit (IMG:style_emoticons/default/smile.gif) |
Jake Raby |
Jan 31 2007, 04:22 PM
Post
#14
|
Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
Unfortunately these variances are what come with the economy cylinder/piston sets- I don't like it, but there isn't much wew can do about the issues and eep the price down..
My Keith Black arrangement is the better solution. |
Brando |
Jan 31 2007, 08:19 PM
Post
#15
|
BUY MY SPARE KIDNEY!!! Group: Members Posts: 3,935 Joined: 29-August 04 From: Santa Ana, CA Member No.: 2,648 Region Association: Southern California |
randholio... you know machinists.... have em lathe em down a bit (IMG:style_emoticons/default/smile.gif) Yeah but... Last thing I want to spend double money on. If I had access to a lathe I would just do it myself... Maybe I can call the resident german-ator... |
914werke |
Feb 1 2007, 12:54 AM
Post
#16
|
"I got blisters on me fingers" Group: Members Posts: 10,070 Joined: 22-March 03 From: USofA Member No.: 453 Region Association: Pacific Northwest |
I found the problem: The AA cylinders are .020" longer than stock. The AA pistons are .030" shorter pin-top .03 shorter pin to top? (IMG:style_emoticons/default/blink.gif) So by cutting a set of OE 94 Mahles and using the AA Pistons your back to .01 ? what would that theoretical CR be? |
Brando |
Feb 1 2007, 01:00 AM
Post
#17
|
BUY MY SPARE KIDNEY!!! Group: Members Posts: 3,935 Joined: 29-August 04 From: Santa Ana, CA Member No.: 2,648 Region Association: Southern California |
Actually 0.05" difference in height than stock without gasket or shims. The piston is 0.03" shorter, the cylinder is 0.02" longer. Add the two...
So you either need different pistons and machined cylinders, or lose the CR. |
Aaron Cox |
Feb 1 2007, 01:07 AM
Post
#18
|
Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
or longer rods (IMG:style_emoticons/default/smile.gif)
|
Twystd1 |
Feb 1 2007, 01:17 AM
Post
#19
|
You don't want to know... really..... Group: Members Posts: 2,514 Joined: 12-September 04 From: Newport Beach, California Member No.: 2,743 |
Or...
Off set bush the small end of the rods......... Hee... Hee.. Then re-balance the whole assembly...... Naw...... Just cut the cylinders Brando. OR: Sell em on samba. Cut your 1.8s and buy KBs.!!!!!!! C |
r_towle |
Feb 1 2007, 09:37 AM
Post
#20
|
Custom Member Group: Members Posts: 24,574 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States |
I have a question.
Is there a reason that these set are manufactured like they are? I assume that a run was made, and that needs to be sold off. Can input be provided to the manufacturer/distributor to change the specs for future runs of these parts? Seems like it should happen if tha parts are just wrong...or are they correct for a BUS motor and wrong for a 914??? Rich |
Lo-Fi Version | Time is now: 18th May 2024 - 02:00 PM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |