Hello! Log in or Register   |  Help  |  Donate  |  Buy Shirts  See all banner ads | Advertise on TheSamba.com  
TheSamba.com
 
dished pistons
Page: 1, 2  Next
Forum Index -> Performance/Engines/Transmissions Share: Facebook Twitter
Reply to topic
Print View
Quick sort: Show newest posts on top | Show oldest posts on top View previous topic :: View next topic  
Author Message
walter kandetzki
Samba Member


Joined: June 02, 2003
Posts: 713
Location: Dillwyn, VA
walter kandetzki is offline 

PostPosted: Wed Sep 11, 2019 5:07 pm    Post subject: dished pistons Reply with quote

hi guys i am building a 1.7 CB type4 engine in my 68 beetle and the pistons it has are dished.would i be ok using them or do i need to have the crown shaved?i am going to use a cb performance cam and dellorto/weber carbs


Image may have been reduced in size. Click image to view fullscreen.
Back to top
View user's profile Send private message Send e-mail Gallery Classifieds Feedback
APPLEGREENVW
Samba Member


Joined: November 30, 2003
Posts: 1492
Location: Seekonk,Massachusetts USA
APPLEGREENVW is offline 

PostPosted: Wed Sep 11, 2019 6:49 pm    Post subject: Re: dished pistons Reply with quote

walter kandetzki wrote:
hi guys i am building a 1.7 CB type4 engine in my 68 beetle and the pistons it has are dished.would i be ok using them or do i need to have the crown shaved?i am going to use a cb performance cam and dellorto/weber carbs


Image may have been reduced in size. Click image to view fullscreen.


Sell your dished P&C,and buy these.
http://vwparts.aircooled.net/Piston-Cylinder-Set-96mm-x-66mm-Flat-Top-p/vw9600t4s66.htm?CartID=1
_________________
76 Beetle sedan
Back to top
View user's profile Send private message Send e-mail Gallery Classifieds Feedback
Lo Cash John
Samba Member


Joined: February 06, 2004
Posts: 2048
Location: Jacksonville, FL
Lo Cash John is offline 

PostPosted: Wed Sep 11, 2019 7:13 pm    Post subject: Re: dished pistons Reply with quote

You need more compression ratio than the dished pistons can give.
_________________
www.LoCashRacing.org
More brains than bucks...Believe it or not!!

If you actually drive your VW, you need www.AirMapp.com

My boss told me I need to work on my mutli-tasking. So now when I use the bathroom at work I surf The Samba on my iPhone.
Back to top
View user's profile Send private message Send e-mail Visit poster's website Gallery Classifieds Feedback
H2OSB
Samba Member


Joined: April 14, 2013
Posts: 599
Location: Modesto, CA
H2OSB is offline 

PostPosted: Wed Sep 11, 2019 7:40 pm    Post subject: Re: dished pistons Reply with quote

I am in the exact same boat. I have an unused set of NOS 90mm pistons and liners. They're meant for a 411 and have a 3cc dish. I have tried every which way to increase the CR to run a decent cam.

You either need to flycut the heads or shave the pistons. Fly cutting is a dicey prospect because the exhaust studs are not too far under the surface so you can't get too much reduction. If you shave the pistons, other things need to be considered, like deck height.

Apple green may be right. Cut your losses, sell the ones you have and get flat tops...or...run less compression. Ray Greenwood suggested to me, with no base shims or head gasket you can get about 8.0:1 and be at roughly 85hp all day long. That would still be really fun in a Beetle.

H2OSB
_________________
Some people should not work on engines or other machinery.
Sorry to say that you are one of them. Actually no offence intended. ~ boolean
Back to top
View user's profile Send private message Gallery Classifieds Feedback
H2OSB
Samba Member


Joined: April 14, 2013
Posts: 599
Location: Modesto, CA
H2OSB is offline 

PostPosted: Wed Sep 11, 2019 7:52 pm    Post subject: Re: dished pistons Reply with quote

Btw, which of the two cams are you wanting to use? They seem to be a great compromise betwixt Scat and Web, money wise, but I'd like more details about them like effective rev range. Also CB has a good hardening process so SEEM like they should hold up well.

Against the advice of people I respect, I'm going to run either a Scat C25 or C35(if I can get the compression up) to try to stay cheap on my 1.7. I'll use this cam with stock reground lifters(by Web). For my other 1303, I'm building a 2056 with a Web 86A.

H2OSB
_________________
Some people should not work on engines or other machinery.
Sorry to say that you are one of them. Actually no offence intended. ~ boolean
Back to top
View user's profile Send private message Gallery Classifieds Feedback
raygreenwood
Samba Member


Joined: November 24, 2008
Posts: 16109
Location: Oklahoma City
raygreenwood is offline 

PostPosted: Wed Sep 11, 2019 9:22 pm    Post subject: Re: dished pistons Reply with quote

H2OSB wrote:
I am in the exact same boat. I have an unused set of NOS 90mm pistons and liners. They're meant for a 411 and have a 3cc dish. I have tried every which way to increase the CR to run a decent cam.

You either need to flycut the heads or shave the pistons. Fly cutting is a dicey prospect because the exhaust studs are not too far under the surface so you can't get too much reduction. If you shave the pistons, other things need to be considered, like deck height.

Apple green may be right. Cut your losses, sell the ones you have and get flat tops...or...run less compression. Ray Greenwood suggested to me, with no base shims or head gasket you can get about 8.0:1 and be at roughly 85hp all day long. That would still be really fun in a Beetle.

H2OSB


Yep....the 3cc dishes ...are California 1.7L pistons. The other 48 states and most others ran the DOMED pistons that provided 8.2:1 with stock head gasket and .009" cylinder shim. Remove those and it safely subtracts about .030"ish from the normal .075"-.080" deck surrounding the dome This gives about 8.4:1 give or take.
With the dished pistons and a very light shave on the heads you can hit 8.0:1. With good tuning and cam you get 85 hp.

Flat tops are...ok. You will still have issues getting 7.8:1. If this is a bus...that might be ok.

You could order pistons from someone like Keith black or some other companies. Send them one of yours as a profile and tell them you want the dish inverted ...plus a little.
No it wont be cheap....but if you have seen the cost of a set of NOS Porsche 914/411/412 domed pistons....custom made pistons for a good set of existing used and cleaned up or NOS cylinders...are entirely affordable. Ray
Back to top
View user's profile Send private message Send e-mail Gallery Classifieds Feedback
walter kandetzki
Samba Member


Joined: June 02, 2003
Posts: 713
Location: Dillwyn, VA
walter kandetzki is offline 

PostPosted: Thu Sep 12, 2019 2:48 am    Post subject: Re: dished pistons Reply with quote

APPLEGREENVW wrote:
walter kandetzki wrote:
hi guys i am building a 1.7 CB type4 engine in my 68 beetle and the pistons it has are dished.would i be ok using them or do i need to have the crown shaved?i am going to use a cb performance cam and dellorto/weber carbs


Image may have been reduced in size. Click image to view fullscreen.


Sell your dished P&C,and buy these.
http://vwparts.aircooled.net/Piston-Cylinder-Set-96mm-x-66mm-Flat-Top-p/vw9600t4s66.htm?CartID=1






now are the cylinders ok to use?i heard (could be totally wrong as i dont know much) to take 2.0 cylinders and bore them to 96mm and just buy the cylinders only as some aftermarket cylinders are junk (like i said i could be wrong...car wont be a race car)
Back to top
View user's profile Send private message Send e-mail Gallery Classifieds Feedback
Alstrup
Samba Member


Joined: July 12, 2007
Posts: 3850
Location: Videbaek Denmark
Alstrup is offline 

PostPosted: Thu Sep 12, 2019 3:04 am    Post subject: Re: dished pistons Reply with quote

I have never seen such pistons Rolling Eyes
Optimize the deck height to 1 mm sparp. Cut heads 1,25 mm and you will get close to 8,5 cr.
OR, source some 412E euro pistons, optimize the deck height and you are around 8,5
Back to top
View user's profile Send private message Send e-mail Gallery Classifieds Feedback
H2OSB
Samba Member


Joined: April 14, 2013
Posts: 599
Location: Modesto, CA
H2OSB is offline 

PostPosted: Thu Sep 12, 2019 6:23 am    Post subject: Re: dished pistons Reply with quote

That's quite a bit more dish than my pistons have. Mine have a barely visible depression. How much can you safely reduce the CCs of a 1.7 head before you run into trouble with the exhaust studs? I'd be thrilled to get to 8.5(9.0 even better) but I'm unsure what is realistic with what I have. I'd love to find 412E pistons, but even the NAME sounds rare.

H2OSB
_________________
Some people should not work on engines or other machinery.
Sorry to say that you are one of them. Actually no offence intended. ~ boolean
Back to top
View user's profile Send private message Gallery Classifieds Feedback
raygreenwood
Samba Member


Joined: November 24, 2008
Posts: 16109
Location: Oklahoma City
raygreenwood is offline 

PostPosted: Thu Sep 12, 2019 6:41 am    Post subject: Re: dished pistons Reply with quote

Actually Alstrup makes a good point.
I was thinking the same thing but just blew it off as optical illusion.........the pistons in your pictures......do not "look" anything like any dished piston I have found in any 411, 412 or 914 versions of a type 4 engine.

Can you post the part # of your piston and cylinder set?

Ray
Back to top
View user's profile Send private message Send e-mail Gallery Classifieds Feedback
mark tucker
Samba Member


Joined: April 08, 2009
Posts: 20982
Location: SHALIMAR ,FLORIDA
mark tucker is offline 

PostPosted: Thu Sep 12, 2019 6:57 am    Post subject: Re: dished pistons Reply with quote

force feed it a little.....
Back to top
View user's profile Send private message Gallery Classifieds Feedback
buguy
Samba Member


Joined: November 17, 2003
Posts: 3769
Location: Port Orange, FL
buguy is offline 

PostPosted: Thu Sep 12, 2019 7:58 am    Post subject: Re: dished pistons Reply with quote

If a little is good....
Back to top
View user's profile Send private message Gallery Classifieds Feedback
nextgen
Samba Member


Joined: August 19, 2004
Posts: 4228
Location: CONGERS, N.Y.
nextgen is offline 

PostPosted: Thu Sep 12, 2019 8:52 am    Post subject: Re: dished pistons Reply with quote

30 years ago I used 2.0 dished pistons they were not so deep as my memory tells me, but we are talking 30 years ago, ha. Had new 1700 heads with a steep in them . I took it to hot rod machine shop and the guy ask what conpression do you want, I said high as you can got safely. He did some measurement and said 8:5 would be perfect. Just by removing the steep and a sight bit more. Same Engine in my car 30 years later no problem.
_________________
site: www.nextgen-usa.com
email: [email protected]
or
[email protected]
The Type IV Upright Conversion Manual
Back to top
View user's profile Send private message Send e-mail Visit poster's website Classifieds Feedback
nextgen
Samba Member


Joined: August 19, 2004
Posts: 4228
Location: CONGERS, N.Y.
nextgen is offline 

PostPosted: Thu Sep 12, 2019 10:12 am    Post subject: Re: dished pistons Reply with quote

OK that said in my last post -- the car is running great for the last 30 years.

But never i ask this question---

Is there a performance difference with everything else the same , if you achieved the 8:5 with flat top pistons or the dished.

Does the dish change air flow???
_________________
site: www.nextgen-usa.com
email: [email protected]
or
[email protected]
The Type IV Upright Conversion Manual
Back to top
View user's profile Send private message Send e-mail Visit poster's website Classifieds Feedback
raygreenwood
Samba Member


Joined: November 24, 2008
Posts: 16109
Location: Oklahoma City
raygreenwood is offline 

PostPosted: Thu Sep 12, 2019 12:54 pm    Post subject: Re: dished pistons Reply with quote

nextgen wrote:
OK that said in my last post -- the car is running great for the last 30 years.

But never i ask this question---

Is there a performance difference with everything else the same , if you achieved the 8:5 with flat top pistons or the dished.

Does the dish change air flow???


Yes. I do not know about the dished because its damn hard to get decent compression with dished. But flat tops to domes at the same compression in a 1.7L.....the domes have cleaner more complete combustion and better throttle response.

The 1.7L head was well designed. That dimple on the edge of the quench area mirrors the edge of the dome shape and helps steer the mixture into the quench area.

I have rebuilt several 1.7L engines with flat tops modified for stock 8.2:1....running with D-jet. They run great....far better than dished at,7.3 amd flat top at 7.8.....but not,quite as good as domes at 8.2. Ray
Back to top
View user's profile Send private message Send e-mail Gallery Classifieds Feedback
nextgen
Samba Member


Joined: August 19, 2004
Posts: 4228
Location: CONGERS, N.Y.
nextgen is offline 

PostPosted: Thu Sep 12, 2019 1:33 pm    Post subject: Re: dished pistons Reply with quote

Ray you lost me on the " damn hard to get decent compression with dished"!

You are not talking loss of compression, right !

Sealed chamber is a sealed chamber??
_________________
site: www.nextgen-usa.com
email: [email protected]
or
[email protected]
The Type IV Upright Conversion Manual
Back to top
View user's profile Send private message Send e-mail Visit poster's website Classifieds Feedback
raygreenwood
Samba Member


Joined: November 24, 2008
Posts: 16109
Location: Oklahoma City
raygreenwood is offline 

PostPosted: Thu Sep 12, 2019 6:10 pm    Post subject: Re: dished pistons Reply with quote

nextgen wrote:
Ray you lost me on the " damn hard to get decent compression with dished"!

You are not talking loss of compression, right !

Sealed chamber is a sealed chamber??



What I meant....is that its Damn hard to get a decent compression RATIO...for a 1.7L type 4 (maybe for a bus...but who drives a brick shaped POS like that Laughing ).....with dished pistons.

You cannot just willy nilly start fly cutting. You only have so deep you can go...and you are also shaving out the dimple (with no domes it probably does not matter). Or you will have to trim the cylinders.

Compression on type 4's...especially with any of the stock EfI...and especially on a 1.7L....matters a great deal. Its a big chunk of hp left on the table with low compression...along with most of the throttle response...and it tunes poorly with stock injection with low compression.

Anything less than 8.0:1 compression on a type 4 engine with good high ratio final drive gears...meaning not a bus....is a hot running mess. Ray
Back to top
View user's profile Send private message Send e-mail Gallery Classifieds Feedback
nextgen
Samba Member


Joined: August 19, 2004
Posts: 4228
Location: CONGERS, N.Y.
nextgen is offline 

PostPosted: Fri Sep 13, 2019 7:56 am    Post subject: Re: dished pistons Reply with quote

Totally understand, thanks!! I agree that is why I like the fact I had the Material in the Step in the 1.7 head to get the 8:5.
_________________
site: www.nextgen-usa.com
email: [email protected]
or
[email protected]
The Type IV Upright Conversion Manual
Back to top
View user's profile Send private message Send e-mail Visit poster's website Classifieds Feedback
H2OSB
Samba Member


Joined: April 14, 2013
Posts: 599
Location: Modesto, CA
H2OSB is offline 

PostPosted: Fri Sep 13, 2019 10:50 am    Post subject: Re: dished pistons Reply with quote

Ray--
In your opinion, do you think it's possible to shave out the 3cc dish on my pistons, with the understanding they are NOS pistons, (and I plan to have the case machined to get .040 deck height)?

H2OSB
_________________
Some people should not work on engines or other machinery.
Sorry to say that you are one of them. Actually no offence intended. ~ boolean
Back to top
View user's profile Send private message Gallery Classifieds Feedback
raygreenwood
Samba Member


Joined: November 24, 2008
Posts: 16109
Location: Oklahoma City
raygreenwood is offline 

PostPosted: Fri Sep 13, 2019 5:39 pm    Post subject: Re: dished pistons Reply with quote

H2OSB wrote:
Ray--
In your opinion, do you think it's possible to shave out the 3cc dish on my pistons, with the understanding they are NOS pistons, (and I plan to have the case machined to get .040 deck height)?

H2OSB


Sure...is possible....but think about that for a minute. You are taking 3mm out of the area above the ring lands. I just do not know how much strength and heat conduction metal that will remove.

Then...you still will have to have the cylinders turned/trimmed to now get rid of that huge 3mm deck. New pushrods (probably good anyway)....everything changes.

Hey...check this guy out. He is in Houston and has numerous sets of new 90mm 1.7L domed pistons for sale. Thinking about buying a set myself.
https://www.thesamba.com/vw/classifieds/detail.php?id=2212478

Ray

https://www.thesamba.com/vw/classifieds/detail.php?id=2212478
Back to top
View user's profile Send private message Send e-mail Gallery Classifieds Feedback
Display posts from previous:   
Reply to topic    Forum Index -> Performance/Engines/Transmissions All times are Mountain Standard Time/Pacific Daylight Savings Time
Page: 1, 2  Next
Page 1 of 2

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

About | Help! | Advertise | Donate | Premium Membership | Privacy/Terms of Use | Contact Us | Site Map
Copyright © 1996-2018, Everett Barnes. All Rights Reserved.
Not affiliated with or sponsored by Volkswagen of America | Forum powered by phpBB