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Discussion Starter #1
Hi people
Is there anything we could use from this engine? block? I read some on other posts that the crankshaft can be used, what about the block? and if only the crankshaft can be used, what rods and pistons should be used with it?
cheers,

joe
 

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Discussion Starter #2 (Edited)
ok, just downloaded a rd28 service manual, and compared to the specs of the rb26, the block is still an unknown since we'd have to know the distance from the centre of the crankshaft to the deck on both blocks (rd28 and rb26) and compare BUT we know the rd28's bore is 85 and the rb26's bore is 86 so a little boring would be required if the block is gonna be used with rb26's stocker size pistons.
About the crankshaft it seems that only the journal pin would have to be grind down from about 49.9 to 47.9 to be able to use the rb26's connecting rods.
Also probably get a oil pump collar too.
Obviously pistons would have to be either stock rb26's or aftermarket.
Now I dont know about the rod/stroke ratio others compared in other posts it would be nice if someone chimmed in about it!
EDIT: the rod/stroke ratio of the rd28 crank with rb26's pistons would be 1.46 (121.5/83) so its bad so that leaves with the option of using the rd28's connecting rods but they're 140mm centre to centre so since they're longer you would need a reeally decompressed piston wich I doubt there is, we'd have to compare distance between centre of piston pin and piston crown(top) or something.
cheers,
joe
 

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Discussion Starter #4
ok, after all the reading it appears to be a reeally bad ass block, although not worth the hassle of modding if you're not going beyond 1000hp.
As stated above apparently the only good stuff is the crank, but I dont know wether the use it with stock rods? also do they use it on the 26, 30 block?
The thing is theres this rd28 at a bargain price, its in a skyline gtx2000 (adapted of course) and they're on sale for little cash. So I wanted to know if I should sell that engine or use some of its parts.
 

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Ive researched this possability a little as well.

The block requires pretty radical modifications to get the water and oil galleries to line up. It is about 20mm taller than an RB26 block. I calculated this one a while back when I found some data stating the crankshaft stroke was 83mm and the rods were 140mm, and compression height was 34 from memory. To be honest you'd be better off grout filling an RB26 block instead to make it strong enough to support over 1000HP, then look into sleeving it as well.

I have been told (unconfirmed by me though) that the rod journels on the crank are much wider than RB26 & RB30 rods. This means custom rods would be needed, or use of custom pistons with a press in gudgen so the rod is piston end guided on the crankshaft. Not an ideal way to build an engine though. Pauter or carillo would be the best aproach. If they ARE actually RB30 width then modification using RB26 rods and potentially de-stroking to 81mm would be a nice solution. That combined with some custom low compression heigh pistons would produce a 2.9lt engine that will fit inside a stock block height. There is a company in Australia that is modifying RB30 cranks to fit an RB26 block by destroking them to 83.2mm, simular to what I have described, and they are making over 400awkw easily. The beauty is they look and measure up as stock from the outside, so there is no fitment issues as well.

The RD28 rods arent designed for performance, and use very heavy 24mm gudgen pins. Too heavy for high performance. Custom rods, or RB26 ones are the go. You would definatly be using custom pistons as well for obvious reasons. Something with a 5-7cc dome would work nicely.

If you have an engine there and feel like cracking the sump off the bottom of the engine to measure the rod width I'd appreciate it. Getting real data on the internal sizes of this engine isnt easy to come by.

Cheers,
Ian
 

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A bit of a necropost, but it may answer some questions others may ask.


I've a RD28 in bits here, just the basic NA 2.8 diesel, not the Turbo RD28T which has the oil squirters, the one I have hasn't any squirters.

25mm thick conrods at the big end, journals are 25mm and a fraction wide on the crank, and the rods are 734 grams each, rather hefty. The Gudgen pins are 167 grams each. +/- normal variations in manufacture.

Identical oil pump gears as the stock RD30 drive gears in the NA RD28 oil pump, a RB26 oil pump should fit on but the crank only has the narrow drive surface.
 

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I bought an RD28 crank a few months ago too and can confirm what you've said about the dimensions.

There are two possabilities that would work with modifying the crank to fit an RB26 block that I came up with.

Option 1.... De-stroke the crank to 81-81.2mm while re-sizing the crankshaft rod journels to 48mm (from 50mm). Use RB26 rods (optionally with GTiR 19mm bearings, but with an undersize bearing to allow for more offset grind.. closer to 81mm).

Custom pistons with a 10cc dome, profiled to suit an RB26 and with a 27mm compression height would be used. This would give a positive deck of around 0.65mm, which you would combat with thicker head gasket, minimum 1.6mm to provide a 9:1 compresison ratio.

The pistons would also be designed to guide the rods, so the gudgens are shimmed to support the conrod small end side clearance of about 8-12 thou.

Rod ratio would be 1.5 which would limit your maximum safe rev limit by piston speed to about 8000 rpm. Provided its all balanced very nicely that is, and you have the supporting mods to suit.

Add a pair of 2860-5's and rev to a maximum of 8000 rpm and you'd have a very responsive 2850-2890cc engine. (86.5 or 87mm bores)

Option 2.... Basically as above, but using RB20 rods to allow a further decrease in the crankshaft stroke. 79-80mm is more possible then, and that in turn allows you some variation with the choice of other components.

Either allowing a 0 thou deck or use of more common 28mm compression height pistons, eg: HKS step 2 RB28 pistons. The 14cc dome profile would increase the compression a little to ofset the stroke decrease, and you could always use that to help optimse for running E85 fuel too.

Destroking the crankshaft to using a 45mm rod journel doesnt weaken the crankshaft as much as you might think, as the material overlap area between the mains and big ends is retained in a de-stroke. You would also reduce the rotating diameter of the crankshaft to be about 3mm above the rod journel, and consider knife edging it while your at it to reduce the rotating mass a little.
 

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Ive seen an RD28 crank offset ground in an RB25 which stroked it to 2.9 ....
Worked well,except for how exposed the pistons were at bdc, still went well though.
 

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diesel blocks are only good because they are stronger because they need to tolerate higher in cylinder pressure ..... unless you wan to build an engine with a big twin on high boost fed with enough methanol to satisfy an alcholic on an open bar night it aint worth it
 

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I agree, I just can't see the point in messing around when its so easy to build a 26 or 30 to handle well over 1000hp with plenty of rpm if required.

Nothing wrong with having a play if you've nothing better to do but doing something like this thinking its developing something where there is an actual need due to short commings of conventional builds is misguided IMO.

Rob
 

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also. dont diesel engines have muuuch smaller water passageways as they dont produce as much heat?

a petrol engine with high horsepower could easily overheat.

simon
 

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Here's an Rd28.
When you drop an Rb30 head gasket onto this block you'd have to be crazy to try to mate them up.
Water jackets, head studs, oil drains, way too much work.
BTW oil pump gears may be the same as Rb30, but the housing is unique to the Rd28.
Nissan must have been on drugs when they dreamed up the cylinder head for this poor engine.

 

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Good to see im not the only one out there having a go and trying new things with RB engines. I agree the RD28 is a bit of a dead end as far as development goes, but it was interesting to investigate for the excercise. For the moment Rb30 components and sleeve kits are the only well proven options to increase displacement.

I forgot that I came across this data as well... it may answer a few more questions.

New Page 1
 

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....... There is a company in Australia that is modifying RB30 cranks to fit an RB26 block by destroking them to 83.2mm, simular to what I have described, and they are making over 400awkw easily. The beauty is they look and measure up as stock from the outside, so there is no fitment issues as well.

Cheers,
Ian
do you have a weblink for the company, or any contact info?
 

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do you have a weblink for the company, or any contact info?
I believe they are primarily a machine shop and engine reconditioning firm working with all differnt kinds of engines. One of the fitters and turners that works for the company developed the 2.9lt kit for his own car and they have since made quite a few bottom end kits for other people.

Rhemac
 

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I believe they are primarily a machine shop and engine reconditioning firm working with all differnt kinds of engines. One of the fitters and turners that works for the company developed the 2.9lt kit for his own car and they have since made quite a few bottom end kits for other people.

Rhemac
cheers :thumbsup:
 

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Sorry to rehash, but does anyone know the Dia. of the BE journal or con rod BE measurement without bearing installed?
Near on close enough to 50mm, same as an RB30. But they are about 25mm wide, not 21mm (rb30) or 22mm (RB26/SR20).

I investigated Remac's offset grind RB29, and they only way they can make it work is to use RB20 sized con rods, which use a 45mm (honda size) rod journel. This allows the offset grind to go back as far as 81mm (from 85), and still have a light rod. This also maintains quite reasonable crankshaft strength too as the cross-section overlap between the mains and big ends is maintained pretty well.

If you want exact measurements on the RD28 crank let me know. I still have one in the workshop.
 

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Yeah if you could confirm BE Size and Width that would be awsome.

Im not sure that I would want to try and stuff it into anything other then an RB30 block
 
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