RD28->RB28 conversion, Offsetground crank

[Isacnr77]

Well i have 4 RD28T’s laying around, and I have wanted to build a “poor” mans Rb with them. A lot of searching and talking and yet I haven’t found what pistons and rods combo people run. There are several ways to go I guess when keeping the stock crank and block.

1• 2.8L> Stock RD stroke with Rb25/26 sized lobes. With the bored up 85mm cylinder to 86mm u can run Rb 26 pistons. But then what length rods? 

2• 2.?L same as above but with offset ground crank making it a longer stroke. I guess how much it’s offset sets the legth of the rods. Again what length rods and what offset. And what will the final volume be?

But in all, with a bored up block to 86mm and re ground crank. Is there a off the shelf forged pistons and rods combo? Simplest way is to go stock 2.8stroke and just get longer rods. 

I can just throw the engines in the bin if my Swedish ass would even attempt to do these calculations 😂 but iam happy if anyone would try to explain how to calculate it if there is no straight answer.
 

 

[T.m]

Hey I'm super interested in this, id definitely wanna learn more if you have any information or even a build thread if you're actively working on this, pretty much looked everywhere I can but cant find anything on these motors, any help is a big help, and you thinking about getting rid of any of those rd28's wouldn't mind getting my hands on one if you'd be willing. 

[Isacnr77]

I did some research! RD28 block height is same as RB30! 227mm. 

Cheapest solution is to use stock RD crank (hens u use the RD block) it has 83mm stroke. 
use the : http://www.wallaceracing.com/rod-length-calc.php

webbsite and u put in the numbers together with the specs of RB26 pistons (30mm piston to pin height). Then u get the results that you need 155.5mm length rods! 

Now to the cleaver solution, RD28 has larger big ends just like the RB30 (RD28/RB30 has same) RB20/25/26 has smaller. So u either need to grind crank so it fits 20/25/26 big end rods and find right length for the stroke(u will not if u don’t order custom)

BUT!!! SPOOL in australia offers a 155mm rod for the rb30 to be used with high comp flat top pistons (different pinheights and so on)

That rod from spool together with rb26 pistons will leave u only 1 thing left. U need to bore the block to 86mm, RD28 is 85. Well it’s in ur favor, it’s like starting with virgine block(square one) 

I have the solution and documentation for fitting rb26/25 head to the block also. That is a story in it self. Kind of a lot of modifications to get all the passages right and to get vct to work! Need to come back for that one!

This was a bitch to research, all I had to measure and figure out my self. No really good documentation on this topic.

But hey! If ur a broke horse farmer and live in sweden and don’t have access to rb30 blocks it’s good cheap Option with some custom work to it! 
I got 5 complet rd engines in sweden for 450usd so not to much to complain about!

“Ghetto stroker deluxe”

Sorry for bad English, now I need to get back to work !

[Isacnr77]

1 hour ago, T.m said:

Hey I'm super interested in this, id definitely wanna learn more if you have any information or even a build thread if you're actively working on this, pretty much looked everywhere I can but cant find anything on these motors, any help is a big help, and you thinking about getting rid of any of those rd28's wouldn't mind getting my hands on one if you'd be willing. 

Oh I for got to quote u! But I responded, see above! 
 

1more thing, this combo gets u closer to a “squared” engine, like the JZ (86mm bore and 86mm stroke) it will be different characteristics than ur 2.6 block stroked to 2.8/3.0/3.2 the bigger stroke u have without longer deckheigt get u really short rods! And iam no scientist but rod to stroke ratio supposed to change the characteristics of an engine is several ways

Edited November 4, 2022 by Isacnr77
Used wrong word

[T.m]

On 11/4/2022 at 2:53 AM, Isacnr77 said:

Oh I for got to quote u! But I responded, see above! 
 

1more thing, this combo gets u closer to a “squared” engine, like the JZ (86mm bore and 86mm stroke) it will be different characteristics than ur 2.6 block stroked to 2.8/3.0/3.2 the bigger stroke u have without longer deckheigt get u really short rods! And iam no scientist but rod to stroke ratio supposed to change the characteristics of an engine is several ways

Bunch of interesting info here thanks! In the effort of keeping cost down would running Rb25 rods and 83mm 4age 16valve pistons be a better option than boring out the block(now that im looking at it stock ca18det pistons might also fit) ? I could see that getting expensive pretty quick even if it gets us a square bore, id be interested in an as low cost rb28-30 as possible just because we can. I'm from canada where we didnt get any rb's of the sort new sold here, but i like to experiment, expensive hobby over here

Edited November 8, 2022 by T.m

[GTSBoy]

8 minutes ago, T.m said:

Bunch of interesting info here thanks! In the effort of keeping cost down would 83mm 4age 20valve pistons be a better option than boring out the block? I could see that getting expensive right quick!

83 mm piston will rattle around in an 85 mm bore like a dick is a shirtsleeve. Not to mention that a 5 valve piston will not be at home against a 4 valve head.

I think you mistook the original RD28 stroke for the bore measurement.

[T.m]

12 minutes ago, GTSBoy said:

83 mm piston will rattle around in an 85 mm bore like a dick is a shirtsleeve. Not to mention that a 5 valve piston will not be at home against a 4 valve head.

I think you mistook the original RD28 stroke for the bore measurement.

Yup, not gonna lie misread that bit, thank you, in that case guess it wouldnt be too bad then

Edited November 8, 2022 by T.m

[flying fridge]

On 04/11/2022 at 10:38 AM, Isacnr77 said:

I did some research! RD28 block height is same as RB30! 227mm. 

Cheapest solution is to use stock RD crank (hens u use the RD block) it has 83mm stroke. 
use the : http://www.wallaceracing.com/rod-length-calc.php

webbsite and u put in the numbers together with the specs of RB26 pistons (30mm piston to pin height). Then u get the results that you need 155.5mm length rods! 

Now to the cleaver solution, RD28 has larger big ends just like the RB30 (RD28/RB30 has same) RB20/25/26 has smaller. So u either need to grind crank so it fits 20/25/26 big end rods and find right length for the stroke(u will not if u don’t order custom)

BUT!!! SPOOL in australia offers a 155mm rod for the rb30 to be used with high comp flat top pistons (different pinheights and so on)

That rod from spool together with rb26 pistons will leave u only 1 thing left. U need to bore the block to 86mm, RD28 is 85. Well it’s in ur favor, it’s like starting with virgine block(square one) 

I have the solution and documentation for fitting rb26/25 head to the block also. That is a story in it self. Kind of a lot of modifications to get all the passages right and to get vct to work! Need to come back for that one!

This was a bitch to research, all I had to measure and figure out my self. No really good documentation on this topic.

But hey! If ur a broke horse farmer and live in sweden and don’t have access to rb30 blocks it’s good cheap Option with some custom work to it! 
I got 5 complet rd engines in sweden for 450usd so not to much to complain about!

“Ghetto stroker deluxe”

Sorry for bad English, now I need to get back to work !

Hey i am really interested to have a extensive talk with you about the whole rd28 topic since i try to get it working as well, since here in germany it‘s extremely hard to find a rb30 and i love the technical advantages of the rD28. 

[Isacnr7]

58 minutes ago, flying fridge said:

Hey i am really interested to have a extensive talk with you about the whole rd28 topic since i try to get it working as well, since here in germany it‘s extremely hard to find a rb30 and i love the technical advantages of the rD28. 

This is my back burner project. Got my head in a few moths back, and came up with a good solution to get the vct oil feed relocated and all the oil drain and water ports modified to fit the rd28. 

My whole goal with this is to get a “2,8” as cheaply made as possible. I don’t say it is the best way but hey, it is expensive as f**k with Rb’s in Sweden.

N1. What you need to do to be able to use the Rd block and crank as cheaply as possible is to acquire some Spool import 155mm Rb30 rods. The Rd28 and Rb30 has the same big end diameter, unlike rb20,25,26 rods. First problem! Rd 28 crank has wider rod journals, so the rods won’t be able to self center on crank. My ghetto solution is to make some piston pin spacers to locate the rod against the piston. (Common thing to do in redblocks) 

N2. Get ur self some RB26 pistons. Iam going to run a s1 rb25 head with vct, and the reason why is that they have the same domes on the pistons as the rb26, and if I would have run a neo rb25 head I wouldn’t be able to run rb26 pistons because of the lower dome the heads use. And now why rb26 pistons ? Because of the 30mm pin to crown height. Rb25 has 31,5 and that would make the pistons be 1mill above the deck. I would rathe use the 26ones and be able to deck block and head and use a normal gasket, instead of a thicker one. (All my measurements for this is lost on my old phone, I don’t have time to write and research everything again right now) this shit post is just by memory while I try to cook food. 

N3, bore ur block to spec for the 86mm pistons, the RD28 is 85stock and if ur cheap as me and don’t want to order custom shit, do this. ( I will some day update this with the water canals/ oil feeds and oil drain mods nesseseryto the block) ps, there’s some mods to be done, but no hard task.

N4. The head needs to be modified to, “kind of eazy mods” ( will upload the way to do it when I have time) the time I never have.

In the end I will have to run a PRP dual head rain for both water and oil.

N5 put a crank collar on the crank, all rd’s I have seen have the short nose one. 
 

N6 figure out a good way to tension ur longer cam belt.

the shit above is just from memory, right now I don’t have time to explain it better and in detail.

!NOTE!

I ain’t saying this is the right way to do a 2.8Rb ( actually 2.892cc ) the cheap way. the diesel crank? I have no idea if it is any good. Piston pin locating bushings? Works in other engines! This shit redneck? ueas.

There is a lot of wierd shit I do in life, but this is the way to make the cheapest Rd in sweden. I don’t care what people say, a rb25 is an arm and a leg in my country,m. And I bought 5 rd28 engines for 400usd $. The head cost me 550usd$ (really good condition. The rods brand new from Fb marketplace (dirtcheap) and the pistons was used (150usd$ )

Yes Iam a farmer, yes Iam cheap

 

I really need to learn English better, sorry for the ones that read this shit and got an aneurism. 
 

[GTSBoy]

7 hours ago, Isacnr7 said:

I really need to learn English better, sorry for the ones that read this shit and got an aneurism. 

Nah. You're good mate.

[Butters]

8 hours ago, Isacnr7 said:

piston pin spacers to locate the rod against the piston

Love to see some pictures or more info on this ?

 

Also thanks for the post, interesting info.

[Isacnr7]

13 hours ago, GTSBoy said:

Nah. You're good mate.

🤟🏻

[Isacnr7]

12 hours ago, Butters said:

Love to see some pictures or more info on this ?

 

Also thanks for the post, interesting info.

I will update when I get the time. Right now Iam packing my clothes and going on vacation to Finland. Drifting, beer and women are waiting for me

[PLYNX]

Must  . . . go . . . . to . . . . Finland ! 

[Isacnr7]

23 minutes ago, PLYNX said:

Must  . . . go . . . . to . . . . Finland ! 

It’s where the magic happens! 😂

[flying fridge]

I think about Offset boring the crank Rd28 rod journal diameter from 50mm down to 45mm, from there the Mitsubishi Evo rods are usable with 45mm big ends… 

how much stability will remain in the crank? -5mm is a lot

+ rod journal width has to be widened about 1,5mm to fit the evo cranks in, they have quite large rod bearings so therefore the force will have more surface to work on. 

stroke will be 88mm so that‘s a 3.1ltr then

What are your thoughts guys??

 

 

[vladKraft]

Hi, really interested, in Russia(sorry for my english) there is no rb30 at all, may be 30 in all country, of course not for sale. Also a problem with swap, because if i swap rb30 and engine got checked i lose registration. So i want to say a little words about ability of conversion.

Some measurements: (rd28/rb30) block height same, stroke 83/85, piston compression height 46.5/32.5, conrod length 140/152.5(6 inches), bore 85/86, diam of crankpin 50/48, bottom width of conrod 24.77/21.8.  Head bolt holes are in the same spots.

No problem to grind down rd28 crankpin to get 85 stroke(and it also make crankpin diam same as rb30), but there is problem in conrod width, but exists technology to fix heavy duty cranks with plasma spraying, its hard, but posible to get all rb30 sizes on rd crank to fit conrods. About another variants of stroke and rod length dont checked, want to build n/a rb30de, with my calculations using stock rb25det pistons and head i`m get near 11,5 compression.

Also about heads, they have different oil drain and some little differences in coolant galleries, this oil drains is the biggest problem of this conversion because cast iron is really hard to weld with saving durability, its unloaded part but can have some issues. Another way is to weld new oil drains to head and connect it to sump with hoses, this variant is much more easier, but now headgasket is problem.

In conclusion, need to weld block surface to fit rb head(hardest part), need to plasma spray and grind down crank to fit rb30 conrods, for example maxpeedingrods, they are affordable(700$ for set) and easier to find 

Edited June 25, 2023 by vladKraft

[flying fridge]

15 hours ago, vladKraft said:

Hi, really interested, in Russia(sorry for my english) there is no rb30 at all, may be 30 in all country, of course not for sale. Also a problem with swap, because if i swap rb30 and engine got checked i lose registration. So i want to say a little words about ability of conversion.

Some measurements: (rd28/rb30) block height same, stroke 83/85, piston compression height 46.5/32.5, conrod length 140/152.5(6 inches), bore 85/86, diam of crankpin 50/48, bottom width of conrod 24.77/21.8.  Head bolt holes are in the same spots.

No problem to grind down rd28 crankpin to get 85 stroke(and it also make crankpin diam same as rb30), but there is problem in conrod width, but exists technology to fix heavy duty cranks with plasma spraying, its hard, but posible to get all rb30 sizes on rd crank to fit conrods. About another variants of stroke and rod length dont checked, want to build n/a rb30de, with my calculations using stock rb25det pistons and head i`m get near 11,5 compression.

Also about heads, they have different oil drain and some little differences in coolant galleries, this oil drains is the biggest problem of this conversion because cast iron is really hard to weld with saving durability, its unloaded part but can have some issues. Another way is to weld new oil drains to head and connect it to sump with hoses, this variant is much more easier, but now headgasket is problem.

In conclusion, need to weld block surface to fit rb head(hardest part), need to plasma spray and grind down crank to fit rb30 conrods, for example maxpeedingrods, they are affordable(700$ for set) and easier to find 

- why do you think someone would notice? All rb and rd blocks look very similar.

- Rd28 and RB30 both have 50mm rod journal, only difference is the width, rd28 has 25mm and rb30 has 22mm. 
-> so if you want to use rb30 conrods you cant grind the rd28 crank

- what about grinding the rd28 rod journal from the 50mm down to 45mm where you can use Mitsubishi Evo 4g63 150mm rods?

[vladKraft]

4 hours ago, flying fridge said:

- why do you think someone would notice? All rb and rd blocks look very similar.

- Rd28 and RB30 both have 50mm rod journal, only difference is the width, rd28 has 25mm and rb30 has 22mm. 
-> so if you want to use rb30 conrods you cant grind the rd28 crank

- what about grinding the rd28 rod journal from the 50mm down to 45mm where you can use Mitsubishi Evo 4g63 150mm rods?

-in cases of my friends they noticed 20/25 block difference, because they`re want to find difference if you drive interesting car. For what? For make plan of catched, or just bribery 

-yeah, troubles with measurements i found

-interesting, but 45mm journal can make crank weaker, for long engines it`s problem. I think it can be usable in what i want to do(N/A) and also get more stroke, need to make calculations, because 3.4 liters rb strokers already exists, so i think it can fit in block

[GTSBoy]

Just buy billet crank?