GU engine Conversion : RD28 out and RB25DET in

[to4zgtr]

I thought i might post up a pic of my engine conversion. After picking up a 2.8L GU for a good price i quickly got bored with the rd28's lack of any sort of acceleration . There wasn't any decent factory GU engines to consider so i pulled it out and put a rb25det in it from a r33 skyline . They have 185kw stock and with exhaust and some boost more like 250kw. So heres a couple pics. As you can expect its alot brisker now. I tried to make it look as factory as possible . The intercooler piping will be painted black this week to make it look more factory.

[revhead307]

Very neat looking conversion!

Would be interesting to drive i imagine.

Jeff

[chunderlicious]

awsome. i considered an RB26 before i did my 5.0W conversion and thought it might be missing some low end.... from real world experience. how does it drive?

[to4zgtr]

Low end power is fine. Its not as good low down as my old td42 gq but once this gets on boost it blows it away and loves to rev.

[adamj1300]

There wasn't any decent factory GU engines to consider so i pulled it out and put a rb25det in it from a r33 skyline

nice conversion but don't nissan make a 4.5 v8 for the infinity?

[tuf045]

what gearbox did you use? as in how did you adapt it to the gearbox?

[to4zgtr]

There wasn't any decent factory GU engines to consider so i pulled it out and put a rb25det in it from a r33 skyline

nice conversion but don't nissan make a 4.5 v8 for the infinity?

The vh45 4.5L v8 didnt come out in a patrol and the conversion would have been alot more diffucult and expensive . On top of that the low down torque on the vh45 is nothing special and theres no easy way to get more power out of them .

Also the rb25det bolts straight up to the rd28 gearbox with no modifications.

[blackmav]

I think I heard that the ricer boys were useing the RD deisel blocks with the twin cam heads on top. ????????

[to4zgtr]

I think I heard that the ricer boys were useing the RD deisel blocks with the twin cam heads on top. ????????

Ricer boys ? I think thats the term given to honda civics etc not rb engines.

And you use the rd28 crank in the rb25 block to make it a 2.8L twin cam.

[D2MUCH]

Nice conversion very neat
What computer did you use ?

Oh yeh wheres the blow off valve

[tna racing]

great conversion there. bet it goes well

[blackmav]

I think I heard that the ricer boys were useing the RD deisel blocks with the twin cam heads on top. ????????

Ricer boys ? I think thats the term given to honda civics etc not rb engines.

And you use the rd28 crank in the rb25 block to make it a 2.8L twin cam.

So the only advantage is 300cc?

[to4zgtr]

Its running the stock rb25det computer but will put a nistune rom in it soon so i can tune it .No blow off valve as i cant stand them. Yeh the extra 300cc helps a bit down low but if your gonna go to that much trouble you might as use the rb30 bottom end and bolt the rb25 head on, something i may do in the future.

[blackmav]

I found a little about putting the twin cam head with VCT onto the RB30 bottom end. Mainly about the differences in galleries but I will just bung it in here for future reference. Would be a great upgrade for the old RB GQ.

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Stolen from another forum.

-----------------------------------------------------------------------------------

ok here's what ya do.

you will need a brass or stainless T piece with two female and one male entry points, the diameters and thread should match that of the thread and diameter on your oil pressure sender unit located under the intake.

you will need to 1/4 inch steel or similar hose fittings with the same thread and diameter.

a tap and die set with the tap to match the fittings you choose to use.

two hose clamps 1/4 inch

600mls of 1/4 highpressure hose....fuel line will do.

some gasket glue or thread tape.


number all your hydraulic lifters I1 I2 I3....I12 and E1 E2 E3...E12

pull them all out and turn your head up side down so you are looking at the face that bolts to the block.

stand at the front of the head , the exhaust ports should be on your left
the intake ports on your right.

at the front right of the head on the corner there is a water jacket and also a small round oil gallery very near each other.

you will note on the front left(intake side) of your rb30 block that there is no small oil gallery near the water jacket.....this is why at the momment the head is incompatible with the 30 block as these two overlap and will mix oil with water.
standard_rb30_face.jpg ( 30.08K ) Number of downloads: 48



with the head still upside down and you standing at the front of it circle the small round oil gallery on the head's face, next to the front right water jacket with a pen and take it to a work shop and get them to tig weld up the hole.. ..

rb25devvl_head_gasket.jpg ( 64.48K ) Number of downloads: 22


now when it is bolted to the rb30 block the oil and water gallery wont over lap.
you can now use a wider range of rb series head gaskets.

at this point you can choose to bolt the head on now leaving the VVL redundant or do what i did below.

whilst your head is still off now is the time to set up the head for a new oil input for the vvl hydraulic lifters.

if you look where the hydralic lifters sit there is a gallery that runs the lenght of the head on both sides

this feeds the hydraulic lifters, you need to feed this gallery again with oil.

with the head in the same position as above, you will note to the right of where the intake cam seal on the front of the head is there is a vertical rib running down from aforementioned welded hole on face to
just below the cam.

place the rear cam cover on(before you would put the cam pulleys on). this will give you a accurate estimate of how much space you have and at what angle the fitting needs to be at to clear everything.

take the brass T junction with two female and one male fittings with the same thread as your oil pressure sender unit.

you will also need two qauter inch hose fittings , one to fit the T piece and one to screw into the side of the head

screw the oil pressure unit into one of the holes on the T piece and then screw in a qauter inch fitting to the other. screw the whole assembly into the block where the oil pressure sender was.

ensure the Brass hose fitting on the T piece is facing up and forward to the front of the engine once tight in the block.

drill a hole (slightly smaller than thread on the second Hose fitting) into the aforemention oil gallery running up the front of the head near the intake cam. with the tap and die set thread the hole to match the thread on the 1/4 inch fitting.

ensure when drilling that you allow for your rear cam cover to go back on. including room for the hose clamp.

screw in the fitting to the head, link the two via the hose and clamp each end.

now you vvl will operate normally as if it was on its orginal rb25 block.

may i add the series one r33 engines had a oil gallery seperate to that of the series two

the series two shared the right front head bolt hole(larger diameter above the thread) to flow oil up to the head. this is why on the series one gasket the hole is seperate yet on the series two head gasket the head bolt hole is tear shaped.

[to4zgtr]

some good info there

[blackmav]

Yeah, I guess you would still have to upgrade pistons etc so the only real advantage would be more capacity and no need to muck around with engineers / rego etc.

[McJeff]

This is awesome idea!

Does the motor bolt up stock mounts?

How do you go into engineer it?

Wouldn't you be using RB30 patrol g/box and t/case mated to the motor? Or use the original RD28 combo?

You still running standard computer?

Cheers

Grant

[stool]

The rb30s and rd28t have the same running gear.

[brad-chevlux]

I found a little about putting the twin cam head with VCT onto the RB30 bottom end. Mainly about the differences in galleries but I will just bung it in here for future reference. Would be a great upgrade for the old RB GQ.

------------------------------------------------------------------------------------

Stolen from another forum.

-----------------------------------------------------------------------------------

ok here's what ya do.

you will need a brass or stainless T piece with two female and one male entry points, the diameters and thread should match that of the thread and diameter on your oil pressure sender unit located under the intake.

you will need to 1/4 inch steel or similar hose fittings with the same thread and diameter.

a tap and die set with the tap to match the fittings you choose to use.

two hose clamps 1/4 inch

600mls of 1/4 highpressure hose....fuel line will do.

some gasket glue or thread tape.


number all your hydraulic lifters I1 I2 I3....I12 and E1 E2 E3...E12

pull them all out and turn your head up side down so you are looking at the face that bolts to the block.

stand at the front of the head , the exhaust ports should be on your left
the intake ports on your right.

at the front right of the head on the corner there is a water jacket and also a small round oil gallery very near each other.

you will note on the front left(intake side) of your rb30 block that there is no small oil gallery near the water jacket.....this is why at the momment the head is incompatible with the 30 block as these two overlap and will mix oil with water.
standard_rb30_face.jpg ( 30.08K ) Number of downloads: 48



with the head still upside down and you standing at the front of it circle the small round oil gallery on the head's face, next to the front right water jacket with a pen and take it to a work shop and get them to tig weld up the hole.. ..

rb25devvl_head_gasket.jpg ( 64.48K ) Number of downloads: 22


now when it is bolted to the rb30 block the oil and water gallery wont over lap.
you can now use a wider range of rb series head gaskets.

at this point you can choose to bolt the head on now leaving the VVL redundant or do what i did below.

whilst your head is still off now is the time to set up the head for a new oil input for the vvl hydraulic lifters.

if you look where the hydralic lifters sit there is a gallery that runs the lenght of the head on both sides

this feeds the hydraulic lifters, you need to feed this gallery again with oil.

with the head in the same position as above, you will note to the right of where the intake cam seal on the front of the head is there is a vertical rib running down from aforementioned welded hole on face to
just below the cam.

place the rear cam cover on(before you would put the cam pulleys on). this will give you a accurate estimate of how much space you have and at what angle the fitting needs to be at to clear everything.

take the brass T junction with two female and one male fittings with the same thread as your oil pressure sender unit.

you will also need two qauter inch hose fittings , one to fit the T piece and one to screw into the side of the head

screw the oil pressure unit into one of the holes on the T piece and then screw in a qauter inch fitting to the other. screw the whole assembly into the block where the oil pressure sender was.

ensure the Brass hose fitting on the T piece is facing up and forward to the front of the engine once tight in the block.

drill a hole (slightly smaller than thread on the second Hose fitting) into the aforemention oil gallery running up the front of the head near the intake cam. with the tap and die set thread the hole to match the thread on the 1/4 inch fitting.

ensure when drilling that you allow for your rear cam cover to go back on. including room for the hose clamp.

screw in the fitting to the head, link the two via the hose and clamp each end.

now you vvl will operate normally as if it was on its orginal rb25 block.

may i add the series one r33 engines had a oil gallery seperate to that of the series two

the series two shared the right front head bolt hole(larger diameter above the thread) to flow oil up to the head. this is why on the series one gasket the hole is seperate yet on the series two head gasket the head bolt hole is tear shaped.

the first one (RB30/25head) that i built, we didn't worry about running the external oil feed the variable cam timming. this one was a basic conversion that still used the factory turbo and computer. with the extra 500cc the engine was making usefull boost at stupidly low RPM anyway, so there was always plenty of torque on hand.

once into 3rd and 4th gear you could realy notice the power fall away at about 6000rpm (turbo being to small for the engine) but in a 4by it would be the perfect combo.

kept simple and short the intercooler setup from the above patrol and the stock turbo on an RB30twincam would have very good responce and awsome low end torque.

the only real problem is finding a piston to use if you want a forged item.
the RB30T piston has a huge dish that leaves you with about 7.8:1 compression when used with an RB25 head. and the compression hight of the RB25 and 26 pistons is shorter then the RB30

[to4zgtr]

They only drop down into 7.8:1 if the use the vl turbo bottom end. If you use the naturally aspirated 3L bottom end you get a perfect turbo cr of 8.5:1 with the twin cam head. With the right tuning these pistons will still handle up to 400rwhp. Its all about the tune and not letting it detonate. Forged pistons in my opinion are only worth there weight if pushing for 400+ hp .

[j-top paj]

conversion
very tidy

[brad-chevlux]

Forged pistons in my opinion are only worth there weight if pushing for 400+ hp .

or if the customer wants them.. the customer gets, what the customer wants.

but yeah, in a 4by application with mild boost and rpm the cast N/A piston would be good. a slight skim of the head and a nice 35thou head gasket would see a nice 9:1. the higher comp would help keep the engine responsive off boost and help with economy

[nzdarin]

There wasn't any decent factory GU engines to consider so i pulled it out and put a rb25det in it from a r33 skyline

nice conversion but don't nissan make a 4.5 v8 for the infinity?

The vh45 4.5L v8 didnt come out in a patrol and the conversion would have been alot more diffucult and expensive . On top of that the low down torque on the vh45 is nothing special and theres no easy way to get more power out of them .

Also the rb25det bolts straight up to the rd28 gearbox with no modifications.

You're right just over 300nm at 2000 rpm isn't very good!!!!
Perhaps you are getting a Lexus V8 mixed up as they have very poor low down torque?

[Jimbo]

When you get sick of the power in the GU, can u sell it to me for the gq??? heehehehee

[to4zgtr]

Its a easy conversion into a gq if you have a 3L patrol to start with. I have a spare engine for sale if anyones interested. Im in Perth though.

[to4zgtr]

Just a quick update. I decided to build a rb30det in the meantime. I hooked up a external line to keep the VCT and the thing is very torquey now even with a HKS gt-rs turbo . Will post a few vids and pics .















A few more pics. has a front mount intercooler now hidden behind the grill.

few vids from today

http://www.youtube.com/watch?v=mFCCaHBc-BU

http://www.youtube.com/watch?v=Myj0SagdDn0

http://www.youtube.com/watch?v=tR0OhK8JOM0

http://www.youtube.com/watch?v=vhWw9Y6k3iA

http://www.youtube.com/watch?v=ufVJuAFH8-o

http://www.youtube.com/watch?v=kVWRQ9I3zUo

the videos dont really do it justice but these are pretty steep dunes that i had no chance of climbing with the old 2.8.

[lewie]

thats nice i love it, wouldnt mind doing something like that to my GQ 1 day, you still have the old 2.8 motor??

[to4zgtr]

i sold it mate

[shw337]

this thing is an animal. what kinda hp are you making

[lewie]

i sold it mate

ahh no worries just chasing an intercooler for my 2.8, done exhaust, upd boost and had pump done by a dyno shop and it goes alot better but keen to get temps down. The gq 2.8s suck balls for plumbing a cooler into so im scratchin my head atm