Home  |  Forums  |  914 Info  |  Blogs
 
914World.com - The fastest growing online 914 community!
 
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.
 

Welcome Guest ( Log In | Register )

2 Pages V  1 2 >  
 Reply to this topicStart new topic
> ARRRGGGGGGG! KB p/c's, New pistons are too small for slightly used cylinders...
ptravnic
post Sep 7 2006, 01:00 PM
Post #1


Senior Member
***

Group: Members
Posts: 1,231
Joined: 27-May 03
From: Chicago, IL
Member No.: 747
Region Association: None
the shop honing my ~10k mile old 96mm cylinders is telling me the brand new pistons are going to be loose in the cylinders! WTF, the original KB set of p/c's is what was in the original engine. I've been planning re-honing the cylinders and using a new set of KB pisons w/new rings...

WHY does God hate me? Is boring out 93mm or 94mm pistons & maatching them up to the pistons the only way to go?

HELP!!!
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
tdgray
post Sep 7 2006, 01:10 PM
Post #2


Thank God Nemo is not here to see this
*****

Group: Members
Posts: 9,705
Joined: 5-August 03
From: Akron, OH
Member No.: 984
Region Association: None
Dumb question.

Can you get Oversized Rings for them?
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
ptravnic
post Sep 7 2006, 01:17 PM
Post #3


Senior Member
***

Group: Members
Posts: 1,231
Joined: 27-May 03
From: Chicago, IL
Member No.: 747
Region Association: None
I dunno but don't think so. Probablly want the rings holding the compression as little as possible.

Anyone else know?

-pt
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
McMark
post Sep 7 2006, 01:33 PM
Post #4


914 Freak!
***************

Group: Retired Admin
Posts: 20,179
Joined: 13-March 03
From: Grand Rapids, MI
Member No.: 419
Region Association: None
Bad idea. Piston to cylinder clearance is important.

PM me if you end up needing a set of cylinders to re-bore.

Perhaps the cylinders were too large the first time around, so now they're even bigger? (IMG:style_emoticons/default/confused24.gif)
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
ptravnic
post Sep 7 2006, 02:17 PM
Post #5


Senior Member
***

Group: Members
Posts: 1,231
Joined: 27-May 03
From: Chicago, IL
Member No.: 747
Region Association: None
That is what I was afraid of... This is only for a street car. Jake thought the old cylinders should be OK but just need rehoned. Then again he's also said the cylinders that come w/the KB p/c set were not very good to begin with.

McMark - I may take you up on the offer. I'll take a look at the set when I pick it up tomorrow. The shop has been around for 20+yrs and I tend to trust their judgement (KOS Motorcars in Lyndhurst, NJ).

I'm PISSED b/c after a 2 week delay I thought this w'end I'd be able to get the damn engine together & the car back on the road.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Mark Henry
post Sep 7 2006, 02:31 PM
Post #6


that's what I do!
***************

Group: Members
Posts: 20,065
Joined: 27-December 02
From: Port Hope, Ontario
Member No.: 26
Region Association: Canada
Have Mark send them to Rimco (in CA) for boring. Measure the slugs first before they bore.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
ptravnic
post Sep 8 2006, 06:12 AM
Post #7


Senior Member
***

Group: Members
Posts: 1,231
Joined: 27-May 03
From: Chicago, IL
Member No.: 747
Region Association: None
QUOTE(Mark Henry @ Sep 7 2006, 04:31 PM) *

Have Mark send them to Rimco (in CA) for boring. Measure the slugs first before they bore.



I'm just amazed that the almost new (only 10k miles) cylinders that came w/the pistons as a MATCHED SET (from Keith Black ) are already shot. They should require a simple honing fore reuse w/a new set of pistons.

But since when does "should" mean "is"...

-pt
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Jake Raby
post Sep 8 2006, 06:19 AM
Post #8


Engine Surgeon
*****

Group: Members
Posts: 9,394
Joined: 31-August 03
From: Lost
Member No.: 1,095
Region Association: South East States
Keith Black doesn't make cylinders.

Where did you buy the set up from??

Our spec for skirt clearance is .0018-.0030 at max. Looser than .003 with KBs and they'll rattle and burn oil
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
ptravnic
post Sep 8 2006, 06:35 AM
Post #9


Senior Member
***

Group: Members
Posts: 1,231
Joined: 27-May 03
From: Chicago, IL
Member No.: 747
Region Association: None
QUOTE(Jake Raby @ Sep 8 2006, 08:19 AM) *

Keith Black doesn't make cylinders.

Where did you buy the set up from??

Our spec for skirt clearance is .0018-.0030 at max. Looser than .003 with KBs and they'll rattle and burn oil



I'd have to dig up the receipt but I bought them ~ 4yrs ago from a place out in California. From memory, they were advertised as a set and the pistons were the genuine article - same as the ones you sell (and just sold me last week...). It is possible the jugs were inferior quality.

BTW, Thanks for the skirt clearance #'s. I'll find out later this morning from the shop what readings they are getting w/the micrometer.

-pt
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Jake Raby
post Sep 8 2006, 06:40 AM
Post #10


Engine Surgeon
*****

Group: Members
Posts: 9,394
Joined: 31-August 03
From: Lost
Member No.: 1,095
Region Association: South East States
Yep- They are made in Mexico

Now you see why saving a buck initially isn't really "saving a buck" in the end.

The issue is that the cylinders were not made specifically for the KBS when they were honed- all the off the shelf kits I found were too large for the KB piston. Most KB pistons measure 3.77780 and most of those Mexican cylinders start off at 3.7805 at minimum giving loose clearances from the beginning for the KBs.

The other fact is that in 10K miles they can wear enough to be out of spec, they guy that made them only got paid 5 bucks a day for doing the job, so you can't ask for too much!

I quit selling them, they are still listed on the site, but thats just because I keep forgetting to remove them.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
ptravnic
post Sep 8 2006, 06:58 AM
Post #11


Senior Member
***

Group: Members
Posts: 1,231
Joined: 27-May 03
From: Chicago, IL
Member No.: 747
Region Association: None
We've learned a lot in the last 4yrs... Thx again for sharing your info Jake.

-pt
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Jake Raby
post Sep 8 2006, 07:18 AM
Post #12


Engine Surgeon
*****

Group: Members
Posts: 9,394
Joined: 31-August 03
From: Lost
Member No.: 1,095
Region Association: South East States
Unfortunately the guys selling those parts haven't leaned in the last 4 years that they are junk! either that, or they just don't care!
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Mueller
post Sep 8 2006, 07:41 AM
Post #13


914 Freak!
***************

Group: Members
Posts: 17,146
Joined: 4-January 03
From: Antioch, CA
Member No.: 87
Region Association: None
I'm not recommending this at all since I have no experiance with it, but in one engine rebuild book I had thumbed thru, they mentioned knurling the pistons to bring them back to spec. (IMG:style_emoticons/default/blink.gif)

User is offlineProfile CardPM
Go to the top of the page
+Quote Post
ptravnic
post Sep 8 2006, 08:09 AM
Post #14


Senior Member
***

Group: Members
Posts: 1,231
Joined: 27-May 03
From: Chicago, IL
Member No.: 747
Region Association: None
QUOTE(Mueller @ Sep 8 2006, 09:41 AM) *

I'm not recommending this at all since I have no experiance with it, but in one engine rebuild book I had thumbed thru, they mentioned knurling the pistons to bring them back to spec. (IMG:style_emoticons/default/blink.gif)



I just learned a new word
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Mueller
post Sep 8 2006, 08:32 AM
Post #15


914 Freak!
***************

Group: Members
Posts: 17,146
Joined: 4-January 03
From: Antioch, CA
Member No.: 87
Region Association: None
QUOTE(ptravnic @ Sep 8 2006, 07:09 AM) *

QUOTE(Mueller @ Sep 8 2006, 09:41 AM) *

I'm not recommending this at all since I have no experiance with it, but in one engine rebuild book I had thumbed thru, they mentioned knurling the pistons to bring them back to spec. (IMG:style_emoticons/default/blink.gif)



I just learned a new word



glad to have helped (IMG:style_emoticons/default/smile.gif)

here is more on the process....knurling
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Leo Imperial
post Sep 8 2006, 08:44 AM
Post #16


Do you have to use so many cuss words?
***

Group: Members
Posts: 906
Joined: 29-November 04
From: 914 Roadshow - Glen Cove NY
Member No.: 3,192
Region Association: None
Knurling

Pretty cool process. Makes for a nice grip on a hammer or screw driver.

I know your not recommending the process. I just want to second the motion to not knurl. I cant see how it could be good. I can see how it would raise the surface and I also could see how it would make it rough. The process pushes the material out of the way. I actually would like to know more. Who, how and results.

I'm going to agree with Jake when he said - Now you see why saving a buck initially isn't really "saving a buck" in the end." I'm not saying dump crazy money into the engine. It's a learning process. Pete and his father have a good approach to working on their 914's. I like them am learning by working on this engine.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Leo Imperial
post Sep 8 2006, 08:46 AM
Post #17


Do you have to use so many cuss words?
***

Group: Members
Posts: 906
Joined: 29-November 04
From: 914 Roadshow - Glen Cove NY
Member No.: 3,192
Region Association: None
Ahh I see in your link (IMG:style_emoticons/default/idea.gif)
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Mark Henry
post Sep 8 2006, 08:48 AM
Post #18


that's what I do!
***************

Group: Members
Posts: 20,065
Joined: 27-December 02
From: Port Hope, Ontario
Member No.: 26
Region Association: Canada
QUOTE(Jake Raby @ Sep 8 2006, 09:18 AM) *

Unfortunately the guys selling those parts haven't leaned in the last 4 years that they are junk! either that, or they just don't care!


That's the problem with "cheap" parts.

They don't care and will blame the builder for the failure.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
ptravnic
post Sep 8 2006, 09:10 AM
Post #19


Senior Member
***

Group: Members
Posts: 1,231
Joined: 27-May 03
From: Chicago, IL
Member No.: 747
Region Association: None
Yeah, 4yrs ago when I bought them there wasn't the same depth of research available as there is today. I'll likely be boring out 94mm cylinders to get the skirt clearance within acceptable range.

So, this engine will be ready by, say, Fall 2007.....
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
ptravnic
post Sep 11 2006, 11:06 AM
Post #20


Senior Member
***

Group: Members
Posts: 1,231
Joined: 27-May 03
From: Chicago, IL
Member No.: 747
Region Association: None
The skirt clearance ended up being within range. That was good news. The mechanic was looking at the gap between the crown of the piston and the cylinder. For some reason, the KB's measured ~ 95mm at the crown of the poston, and ~ 96mm at the skirt.

I guess thats just the way the KB's are...
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
« Next Oldest · 914World Garage · Next Newest »
 

2 Pages V  1 2 >
Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 

Display Mode: Standard · Switch to: Linear+ · Switch to: Outline

Track this topic · Email this topic · Print this topic · Subscribe to this forum

- Lo-Fi Version Time is now: 17th May 2024 - 08:57 PM
Invision Power Board v9.1.4 © 2024  IPS, Inc.
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 ...