cna you use a gasser block for a diesel? - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• cna you use a gasser block for a diesel? by gldgti on 02 Aug, 2005 18:00
• i hope i dont get grilled for this post by you guys, but i've gotta ask...
  
  here in aus diesels arent really easy to find.... however petrols arent so hard. infact i might be coming by one soon - a gasser 1.6 with shot bottom end bearings.
  
  sitting in shed at home, we have spare IP, head, and some other misc. extra's.
  
  what i'm wondering is..... can i use the petrol block and spare diesel head? is it do-able?
  
  i dont really know but i assume that the petrol config is same stroke but larger bore....? is this right?
  
  i have been dreaming of a ported polished head with nice new injector tips, big airbox, the the high revving ability of the 1.5's stroke with the slightly bigger bore.....a diesel screamer... can it be dome? is it worth it?
  
  what are your thoughts?
  
  aydan
• #1 by chrissev on 03 Aug, 2005 05:14
• Quote from: "gldgti"

  i hope i dont get grilled for this post by you guys, but i've gotta ask...
  
  here in aus diesels arent really easy to find.... however petrols arent so hard. infact i might be coming by one soon - a gasser 1.6 with shot bottom end bearings.
  
  sitting in shed at home, we have spare IP, head, and some other misc. extra's.
  
  what i'm wondering is..... can i use the petrol block and spare diesel head? is it do-able?
  
  i dont really know but i assume that the petrol config is same stroke but larger bore....? is this right?
  
  i have been dreaming of a ported polished head with nice new injector tips, big airbox, the the high revving ability of the 1.5's stroke with the slightly bigger bore.....a diesel screamer... can it be dome? is it worth it?
  
  what are your thoughts?
  
  aydan

  
  
  Don't know much about this, but do know that the diesel pistons protrude out of the block when they are at TDC and the gas engine ones don't do this.  Not sure if this is related to the crank design or longer rods, or bigger pistons.  The intermediate shaft on a diesel is also quite different from that on a gas engine.  Might be a few other small variations with regard to placement of threaded holes on the outside of the block.  Those are the differences I know about.
• #2 by veeman on 03 Aug, 2005 07:10
• Not sure if this helps or not, but in the last few yeas, I saw a caddy in a magazine (European Car) that was set up to do land speed records.  
  
  The interesting part is that they had to use the original diesel block (1.5?) to compete in the category, but they had converted it to run as a gasser.  I believe it had a later head (either ABA or 16V) and a few other tricks (supercharger?) to make some pretty good horsepower.
  
  I also know of another guy on the vortex who's using a diesel block to make a race motor.
  
  Does that mean that the two blocks are interchangable?  Not sure as I'm betting those motors were more than a little modified.  Perhaps someone else would have more info or perhaps a scan of the article...
• #3 by vwmike on 03 Aug, 2005 07:53
• Dimensionally the blocks are nearly identical, but I question metallurgy more than anything.
• #4 by Northboundtrain on 03 Aug, 2005 07:56
• Does the gasser engine have a vacuum pump?
• #5 by veeman on 03 Aug, 2005 08:01
• The gas engine does not have a vacuum pump.  It "makes" its own vacuum because it has a throttle body, not a wide open intake like the diesels.  On the gassers, the line for the brake booster comes right off the intake.  
  
  On the gasser, the distributor is in the vac pump hole, but I assume if you used the right intermediate shaft, the vac pump might work on the gas block.
• #6 by QuickTD on 03 Aug, 2005 08:03
• Quote

  Dimensionally the blocks are nearly identical,

  
  
  This was one of the design goals of the VW 4 cylinder engines. The gas and diesel engines blocks were designed to be machined on the same transfer lines. The bearing sizes, bore centers and bolt locations are all the same. The diesel block is of heavier construction though. The block has some added internal webbing and a more closed deck than the gas block.  
  
  I'm not sure how well the gas block would handle the stresses of diesel operation.
• #7 by VWRacer on 03 Aug, 2005 08:22
• I'm with QuickTD on this one. Furthermore, in SAE papers about the early VW diesel engines thee are statements to the effect that certain parts of the diesels are simply "picked" parts out of the gasser parts bin. If you can make the pistons work I'll be it would work fine, so long as you're not thrashing it to within an inch of its life!
  
  FWIW, the GM V-8 diesel engines of the '80s that were so unpopular in passenger cars are VERY highly sought after for drag race engines. New (gasser) heads are installed along with a new intake and a carb, but other than that the engines are run with all their diesel parts. I know that's the exact opposite of gldgti's question, but it goes to support the idea in principle.
• #8 by vwmike on 03 Aug, 2005 11:32
• Quote from: "QuickTD"

  Quote

  Dimensionally the blocks are nearly identical,

  
  
  This was one of the design goals of the VW 4 cylinder engines. The gas and diesel engines blocks were designed to be machined on the same transfer lines. The bearing sizes, bore centers and bolt locations are all the same. The diesel block is of heavier construction though. The block has some added internal webbing and a more closed deck than the gas block.  
  
  I'm not sure how well the gas block would handle the stresses of diesel operation.

  
  
  I think this brings up enough question of how wise this woujld be to make me not want to attempt it....Are you sure you can't find a diesel block? It would be expensive, but I'm sure someone would be willing to ship one to you.
• #9 by Josh on 03 Aug, 2005 15:46
• I don't think the fact that diesel blocks are being used in/as gassers says anything about the likelihood of the reverse working; it may just be that the diesel blocks are metallugically speaking much better and stronger blocks, and that the gas folks recognize and wish to capitalize on this fact.  
  
    I think it's dumb as heck to experiment with the reverse, unless you've got lots of extra time and money on your hands.  To attempt it as a money saving idea is not logical, I think.  
  
     -Josh
• #10 by jtanguay on 03 Aug, 2005 17:41
• didn't GM convert gas engines to run as diesels in the 80s??? and didn't the motors suffer from premature failure after around 100'000km? (or miles)
  
  A gasser engine should be able to take the heat from a diesel no problem... it should just be a matter of the extra pressure around 8:1 compression compared to... 23:1 - my guess is it would work at first, but eventually the block will just crack (on a nice cool morning, or a really cold winter day)
  
  converting diesel to gasser would be awesome.   Would be extremely hard to blow head gaskets. no matter how hard you'd drive it
  
  Only way I could see a gasser block taking the added abuse, would be to build up the sides with some welds... by the time thats done a diesel block would be cheaper.
• #11 by gldgti on 03 Aug, 2005 18:11
• well, thanks everyone,
  
  my concern was really about the metallurgy of the block - i didnt know if they were the 'same' block, or if the blocks were just dimensionally the same.
  
  the use of diesel blocks for gasser engines is far more plausible and common than the reverse - i know peugeot nuts have done things with peugeot diesel blocks, multi-camshaft heads and turbochargers that could frighten the most enthusastic vw gasser tuner in the hp department.
  
  evidently, my interest in making a diesel from a sub strength block is extremely limited - thus my original question. even if i could do it, there'd be little point wasteing my efforts on something that wouldnt be as good as the original.
  
  as far as my research has taken me, 1.6 blocks are just about unheard of in aus, and 1.9's are rare to say the least. there are quite a few mk4 diesels driven around here but the availablility of a spare engine is limited. this is why i was interested in the petrol-diesel conversion.
  
  ahh well, i'll just have to wait till i can afford to ship an AAZ over...
• #12 by jtanguay on 04 Aug, 2005 03:58
• do you know of any wrecked mk4's ?  
• #13 by VWRacer on 04 Aug, 2005 07:31
• I guess I'm just a racer at heart, and willing to try just about any reasonable idea when it comes to engines. The man has a gasser block and a diesel top end...and diesel parts are rare and expensive in his neck of the woods. If you really want to chart new territory, give it a try. Of course, the safe bet is to import an AAZ...  :wink: