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2.1 MV rebuild
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90weekender
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PostPosted: Mon Sep 14, 2020 8:14 pm    Post subject: 2.1 MV rebuild Reply with quote

Hello Samba Friends,

This was an "MV rebuild with DJ pistons, 1.25 ratio rockers and HP cam"

The Incident:
6 months ago, the intake-throttle boot was loose so the engine behaved like switch at part throttle. As I pulled over in traffic to check it out the engine made a distinct ďPINGĒ sound when I lifted off the throttle in 2nd gear. A few weeks later on the way to Joshua Tree it started blowing white smoke at start up and felt like the ignition was missingĒ at highway speeds. With 130k on the odometer, I knew this might mean trouble...head gasket at least, so I opted to remove the whole engine and go deep.

We do most of our camping in the sierras above 6000 ft. so I am taking this opportunity to see what my options are to make it: stronger, faster, more reliable and more efficient. (Iím can dream). After studying many options from typical vendors of aftermarket pistons and kits my initial build spec was:

DJ Pistons and Liners
Rebuilt Stock or NOS Connecting Rods
1.25 Ratio Rockers
AMC Heads
Vintage Speed exhaust

Potential upgrades:
CB Performance Eagle 2252 Hydro cam

After interviewing several people who've put DJ pistons in an MV engine, I've discovered the 10.3:1 DJ pistons require;

A knock sensor: http://www.jandssafeguard.com/VampirePage/Vampire.html

And crank case breathing apparatus: Mann Provent 100 for example. Although the virtues of the Provent were lauded, no photos or detailed reports of a VW WBX with the Provent installed were shared on this forum. So I can only guess the add cost and complexity are unlikely to result in a reliable power increase.

The last expert confirmation with first hand experience putting DJ pistons in an MV engine was from David Clymer who's engine threw a rod after 2 years. He advised using breathing(bigger valves and exhaust), volume(bigger pistons) and ratio rockers to gain reliable power. And most critically to keep compression below 9.5:1.

I'm still researching my options including big valve heads from Marco Manci and checking the health of my original engine. So far it looks like my engine has plenty of life left and so I may keep stock.

Rick


Last edited by 90weekender on Thu Oct 29, 2020 12:05 pm; edited 1 time in total
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sanchius Premium Member
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PostPosted: Tue Sep 15, 2020 6:42 am    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

Nice, we look forward to watching and learning as you do your build. Naturally, the more pictures the better.
Many times I looked at other's rebuild photos when I was uncertain about placement details

Here's my rebuild costs & links spreadsheet from my recent WBX rebuild:
(I didn't need to do any machining, so that's not in the spreadsheet)
https://docs.google.com/spreadsheets/d/1PbKUEuZ2gIhlpH_aPEz7npEssnABy_-I/edit#gid=1637704663

Here's my (unfortunately unindexed) list of WBX & aircooled rebuild links that I looked at along the way:
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goldtooth
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PostPosted: Tue Sep 15, 2020 7:28 am    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

Maybe a silly questions but what are DJ pistons? Higher compression?
nate
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Bulli Klinik
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PostPosted: Tue Sep 15, 2020 7:30 am    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

You will need to clay the tops of the pistons and run the valves through a cycle to be sure. It may play out on paper but you will need to check.

I believe that you will need at least .040" clearance to the valve, though I'd have to refer to my old Berg book to be sure.

Sounds like a solid, somewhat simple build. I look forward to seeing the results.
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Howesight
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PostPosted: Tue Sep 15, 2020 11:34 am    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

A Samba poster who goes by the handle JBerger did a build similar to your plan and you might benefit from sending him a PM for particulars. He has, IIRC, listed out a number of the parts and specs in his DJ-pistoned engine.

Two critical parts of his build that I recall were installing a knock control system and a proper Mann Pro-vent PCV system. Excess oil in the combustion chamber increases the probability of knock, so the upgraded breather system is a must. Proper crankcase ventilation also helps the compression rings seal better - - a win-win.

Since you will be operating at altitude a lot of the time, a higher-compression engine (especially with knowk control), is viable.

See this thread by JBerger:

https://www.thesamba.com/vw/forum/viewtopic.php?t=563283
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90weekender
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PostPosted: Tue Sep 15, 2020 4:47 pm    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

Wow! Thanks Guys.

Sanchuis...those rods on ebay with NSBolts look cheaper than a rebuild.

Howesight...I've read JBergers post and have contacted him to get more detail on his engine specs. Cam, Rockers...etc.

goldtooth...YES...DJs are a high compression piston offered in Europe by VW as an OEM option...about 10.3:1 Compression Ratio.

Bulli Klinik...That clay technique looks good. Is this a special builders clay? Do you simply put it top of the piston and torque up one piston/head stack to check?

I'm also guessing that if the recesses in the piston crowns are the same depth on DJs and MV pistons, then shouldn't these components work together without interference?

R
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90weekender
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PostPosted: Tue Sep 15, 2020 4:52 pm    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

Could this be the source of the loud "PING" incident?


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


This ring was broken off but still embedding in the groove until i separated the liner from the piston...then it fell out.

Progress so far:

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


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


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


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


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mbwesty
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PostPosted: Tue Sep 15, 2020 6:04 pm    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

Hi Sanchius:

Very nice and organized info.!!!

So from the Googlesheet I see that you had used RJ's 95.5mm sleeve/cylinder set, and the stock conn rods. Do you mind letting me know how did the deck height checked out and how's the engine power and etc.?

I am currently in debate between the AA and the QSC piston/liner set. My understanding was RJ's set was from QSC before.

Thanks and appreciate your info.!

Tim

sanchius wrote:
Nice, we look forward to watching and learning as you do your build. Naturally, the more pictures the better.
Many times I looked at other's rebuild photos when I was uncertain about placement details

Here's my rebuild costs & links spreadsheet from my recent WBX rebuild:
(I didn't need to do any machining, so that's not in the spreadsheet)
https://docs.google.com/spreadsheets/d/1PbKUEuZ2gIhlpH_aPEz7npEssnABy_-I/edit#gid=1637704663

Here's my (unfortunately unindexed) list of WBX & aircooled rebuild links that I looked at along the way:
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Viva.Sabata
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PostPosted: Tue Sep 15, 2020 7:16 pm    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

When I did my build I ended up going with the GW piston and liner set for a 2.2l. I wanted to go with a cheaper alternative but was never sure if they would squish properly as many have the wrist pin cast too high. 10c was getting ones that were cast low and was machining the tops to get the clearance set correctly, something beyond my current shop capability and I canít find a machine shop I would trust with that job.

In the end though the GW (forged) units work just fine (but pricey) and donít noticeably slap at cold start up as feared.

A listing of vendors selling cast pistons with the correct wrist pin offset would be very helpful. And specifically where are you sourcing your DJ pistons?

Watching this post intently as I already installed the antiknock system and am contemplating another build!
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Last edited by Viva.Sabata on Sat Sep 19, 2020 4:49 am; edited 1 time in total
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MarkWard
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PostPosted: Wed Sep 16, 2020 3:58 am    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

10.3 to 1 compression is pretty high. Youíll be running premium fuel and that may not be enough. As mentioned a knock sensor or octane boost may be required.

Itís not special clay. We do composite work and we get clay from our local fiberglass supply business. You donít need the rings on to clay the squish area or the pushrod tubes. For it to be accurate and repeatable your going to need a way to disable the hydraulic lifter. A solid lifter would be ideal. You also need to pay attention to how the rocker tip rides on the valve stem while you rotate the engine through. Lots of videos on that.

Should be a decent boost in power if you can get it to work reliably. Good luck.
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PostPosted: Wed Sep 16, 2020 8:14 am    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

mbwesty wrote:
So from the Googlesheet I see that you had used RJ's 95.5mm sleeve/cylinder set...

I don't want to hijack 90's nice build thread here, so I've moved my reply to the Sanchius & Tuna thread:
https://www.thesamba.com/vw/forum/viewtopic.php?p=9460106#9460106
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90weekender
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PostPosted: Thu Sep 17, 2020 11:06 am    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

VivaSabata...I like the GW 2.2 pistons but want to see if I can get more power AND fuel economy from the 2.1 DJ.

Mark...I hear you, and I've spoken to 16CVs about his MV engine with DJ pistons. He reports no issues with detonation associated with higher compression.

Does anyone know how to definitively answer the question of DJ pistons detonating in and MV engine?

I am not interested in purchasing...and attaching a $500 electronic box to my engine for this project. I'd rather buy a RJE or GW 2.3 kit...which is basically throwing in the towel wrt my "Do more with less" approach.


Last edited by 90weekender on Thu Sep 17, 2020 2:03 pm; edited 2 times in total
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Steve M.
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PostPosted: Thu Sep 17, 2020 11:21 am    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

goldtooth wrote:
Maybe a silly questions but what are DJ pistons? Higher compression?
nate


Same engine with higher compression pistons as you said. Takes it from 90 hp up to 112-115 hp., but you need to use premium gas.
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90weekender
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PostPosted: Fri Sep 18, 2020 5:27 pm    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

Let's talk cams for a sec...yeah right.

I'm looking for power to get up highway mountain passes, and don't feel a need for low speed truck-like grunt to go off roading.

Here's nice dialog about carious cams...CB 2252, 2254, 2280

https://shoptalkforums.com/viewtopic.php?f=37&t=122471&hilit=cooler

I think the 2252 is the best option (in conjunction with the 1.25 ratio rockers).

R

BTW - CBP is out of stock for the 1.25 ratio rockers with no restocking date. Anyone have opinions on quality of the SCAT 1.25s? They are available.
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PostPosted: Fri Sep 18, 2020 5:58 pm    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

When looking at and comparing cams, you really need to see hp and torque curves. That will give you a comparison and you can overlay the rpm range you will be operating at.
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90weekender
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PostPosted: Fri Sep 18, 2020 10:22 pm    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

MarkWard wrote:
When looking at and comparing cams, you really need to see hp and torque curves. That will give you a comparison and you can overlay the rpm range you will be operating at.


I agree...where are these charts. I checked the CBP website and the Samba with no results.
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Viva.Sabata
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PostPosted: Sat Sep 19, 2020 4:53 am    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

90weekender wrote:
MarkWard wrote:
When looking at and comparing cams, you really need to see hp and torque curves. That will give you a comparison and you can overlay the rpm range you will be operating at.


I agree...where are these charts. I checked the CBP website and the Samba with no results.


They are usually available from the cam vendor, but Iíve never been able to find any either and CB stated they had none a couple years ago. You just need to look at the cam specs very carefully and verify clearances upon assembly.

I can verify, just as many others can, that the 2252 with 1.25 rockers is daily drivable and very enjoyable combination.
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Viva.Sabata
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PostPosted: Sat Sep 19, 2020 5:08 am    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

90weekender wrote:
MarkWard wrote:
When looking at and comparing cams, you really need to see hp and torque curves. That will give you a comparison and you can overlay the rpm range you will be operating at.


I agree...where are these charts. I checked the CBP website and the Samba with no results.


They are usually available from the cam vendor, but Iíve never been able to find any either and CB stated they had none a couple years ago. You just need to look at the cam specs very carefully and verify clearances upon assembly.
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MarkWard
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PostPosted: Sat Sep 19, 2020 5:53 am    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

My advice is to not stray too far from stock. You are already adding ratio rockers which are increasing lift. Mathematicaly, since the valve has to open and close in the same rotation the duration is also affected.

These are not sports cars. They are non aero pigs and add the load of the camper. Out of the hole is where you need power and torque. The vw engineers had a good idea of where the power should be. You donít want to end up with a rough idle and slipping the clutch to get moving up a hill from a dead stop.
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90weekender
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PostPosted: Sun Sep 20, 2020 10:51 pm    Post subject: Re: 2.1 MV rebuild With DJ pistons, 1.25 rockers and HP cam Reply with quote

OK...so 2252 with 1.25:1 ratio rockers seems like a valid direction. I like that the flexibility of deleting the 1.25 rockers if there is interference.

Next I'm concerned about the need for "Mann Pro-vent PCV system" from JBerger's build.

I will PM him.
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