RB20DE head on an RB30 bottom with RD28 crank.

[kiwi303]

A thread on small ports on L6 engines got me thinking. I picked up an RD28 diesel engine for pennies recently and have a RB20DE head. With a bit of work an RB20 head will fit on a RB30 block to provide an RB30DE, which is one way to make the RB30DET motor before RB25 and RB26 heads were common enough to be used as much as they are now.

 

This is the thread on small ports in the L6, and the effects on low end torque.

http://forums.hybridz.org/showthread.php?t=143259

 

What I am wanting is a torque-y engine to re-power my 2L 4-cyl petrol Toyota Hilux Surf (4-runner in the states) that will enhance the offroad power.

 

Given what was said about small port = torque, I'm wondering about swapping the head off the RD28 for the RB20DE head, and changing the pistons/rods for RB30 rod and pistons. I'd need to have the bore machined out 1mm, but i believe the deck height is the same between the RB30 and the RD28, meaning a 2mm shorter stroke with the RD crank. whether the smaller chambers in the RB20 head is enough or I will have to get the block decked down slightly is the question...

 

Given machining costs... would it be more cost effective to pick up a RB30e bottom end complete with crank, pistons and rods for about $200 and just fit the rb20de head on that?

 

Having the RB20 size ports on an RB30 bottom end should increase the low end torque for the 4x4, which is what I want in a offroader,

 

would it work? and is it worth doing?

[Z24O]

i would have thought that an rb20 head on an rb30 bottom end would be too restrictive

the best bang for buck for offroad torque would be a turbo rb30e (ie na rb30 with a turbo kit added)oodles of off boost low end torque due to high compression with the added boost when under load

not sure about kiwi land but in oz this combination could be thrown together for under $1000,proven to work well as long as you don't go over 1 bar of boost,very streetable with basement torque

[kiwi303]

Hmm, about $350 for a RB30e in running condition with ECU and loom, about $400 to $500 for a RB30DET aftermarket top mount manifold, which would fit an RB30e as well. and a second hand turbocharger about $400.

 

Given the Exchange rate between aud and nzd, probably close to $1000aud as well. Doable.

 

 

 

I ended up with the RD28, at such a price I just couldn't resist getting it, I'm sure others on here have gained "Bargains" like that which makes one want to do more, which means getting more parts, which makes things expensive

 

Anyhow the RD crank fits the RB block, and can have RB rods fitted, so i was thinking of a RB29DETT... RB30 decked 2mm with a RB25DE head with log style TT manifold and 2 turbos and the RD28 crank which is 2mm less stroke than an RB30.

2mm isn't much, but I was hoping it would be enough to make things a little revvier than the stock RB30 crank. but then I found this RB20DE head, again at an unmissible price... and got thinking about the small port thread... and my hilux needs a better motor than an anemic 3Y 2.0L petrol 4cyl.

[RIPSNZ]

What alot of messing round for not alot.

 

IMO, get a N/A RB30e and turbo it as is or get a RB30 bottom end a R32 RB25de head, use a stock RB20 exhaust manifold and a small turbo.

 

If your doing things on such a tight budget I wonder how you expect to get all this in and running in a hilux?

[kiwi303]

If your doing things on such a tight budget I wonder how you expect to get all this in and running in a hilux?

 

mostly by being mates and attending the same church as a local mechanic, so mount alterations and gearbox to motor adaptor plates are mates rates or roll up and borrow the tools sort of things. Boring at decking and other block work is the expensive bit since he doesn't have the expensive boring and honing machinery.

 

An RB tacked onto a Hilux Gbox and transfer case isn't really much different to a holden 202 onto a hilux Gbox which is what a different garage where I used to livehas done several times on Kingswood Utes.

 

Certification would be the complicated bit.

[NZeder]

There is a website in Japan that shows a RB20DE/T head that is modified to for a RB30 bottom end (aka Tommy Kaira M30 first gen engine) and I can tell you it is a lot of work, welding, welding and more welding that water jackets so the head could then be worked for air required to feed a RB30 bottom end.

 

So I would bin that idea and get a RB25DE/T or RB26DETT head.

 

Re the RD crank. Why? If you have a RB30e bottom end why? Rob of RIPSNZ can rev his stockish bottom end to 9500rpm with no problems and 1000+ HP with the longer stroke so why change it 2mm is not worth all the extra effort and custom parts required.

 

Maybe if the RB30e bottom end is hard to get (which here in NZ and OZ is not an issue.....might be one day when the supply dry's up) then you do the RB/RD hybrid and build a RB28/29 like others have already done. However this is using the RB25 bottom ends and a raiser plate I believe.

[kiwi303]

welding water jackets? hmm... my ali welding sucks, so I guess goodbye to that idea.

 

Thanks for your advice everyone. I'll just grab a RB20e bottom and a RB20DET manifold and fit together a RB20DET as I find parts. A 20e is only about $60 for a short block looking at trademe...

[kiwi303]

Well, just for yucks and "Because I CAN" I'm playing around with the RB20DE head I have and the RD28 block.

 

I've read on here that the RB20DE head flows comparable to the L28 head, having 2 smaller valves each on intake and exhaust to the L28's large single valves but coming to similar flow rates. This should mean a RB28 hybrid should manage reasonable if not masterful performance.

 

Looking further into things since this thread was started, it looks like the thick faced diesel pistons can be milled down 1 to 2 mm so rather than finishing flat against the face of the former diesel head and protruding through the former head gasket, they can be set to whatever depth is needed to fit the compression ratio desired.

 

It's something to keep me occupied in the evenings