modding z block to fit rb20det head

[pauly_adams]

i was just wondering if the forum has any engineers on bord. i had an idea the other night of machining the z blocks down about 1 inch or so then making a plate simerler to a adaptor plate for a carby going from the z block water ports to a rb20det head water ports, then welding it too the block, welding in the cylender walls and boring it back to normal specs (making it smooth in the bore again) would it be possible

 

cheers pauly

[NZeder]

I guess anything is possible but I guess the reason it has not been done before is the following reason - Just put a RB block in too.

 

I know that both the RB and L6 have the same bore spacing and head bolt locations but that is about it. I have also seen L6 blocks that have had all the water galleries on one site welded up (I assume due to the large bore it was running it was offset bored so the non-thrust side was thinner and this was the side the water jackets were full welded)

 

If you do put a RB head on a L6 the engine is still leaning in the stock location which is the wrong way for the intake of the RB head so you will want to make different engine mounts - then you need to sort out the gearbox angle too (you could use a 4 cylinder Z series engine bellhousing = same bolt pattern but leaned over for the crossflow head that is on these bottom ends, the Z series block is basically a L4 block) so if you have to do all this just but a RB engine/gearbox in and be done with it.

 

It is for the above that no one has done it yet = too much $$ time and engineering involved this does not mean that it can't be done just the old question why? And people said the same about building a DOHC for a L6 using KA24 heads and now someone has a car running with this hybrid head/block combo.

[pauly_adams]

thanks was somewhat expecting that but you realy do make alot of sense not so much if it can be done but the money time etc its not realy worth doing it thanks for your input

 

cheers pauly

 

[zedevan]

what are the reasons for the engine being on an angle?

[Mr Camouflage]

The engine is canted to reduce the overall height of the engine in the bay. This allowed for a lower bonnet line and more ground clearance for the sump.

 

The L series was designed and used in other Nissans before being used in the Z. So they leaned it over to make it a better fit.

 

I guess it also gives more room for the carbies/airfilter assembly, and possibly offsets some of the weight from the induction system over the to the center line of the car, maybe.

 

 

[NZeder]

All the L6 powered cars I have seen have had the engine leaned over like the 240z/260z (Skyline's, 260c, 280c, Laurels etc) but some not quite as far by the look - hard to tell as the engine bays are a different shape so that might be off putting. I am not sure about the lean and if you were to put an RB head onto a L6 if this would cause any problems but if running carbs then the manifold would have to level up the carbs so the float levels in carb would work with the carb angled down they might not full correctly = lean = boom

 

Also the other real issue is chain vs belt drive - however this could be over come as the last of the LD20 II (that is a 4 cylinder L4 style block) was belt driven so you could get one of these and see how Nissan made the L4 block a belt drive then replicate that to the L6 block. The other technical issue would be dizzy you would have to remove this as it would foul with the wider head so you would have to run a coil on plug setup/wasted spark = more $$ for ECU then if you do this you might as well run EFI = fuel changes to support the EFI pressures, surge tank yada yada so now your budget goes up again....hmm makes the RB conversion looking more and more like an option.

 

Can you tell I have thought about this too - this is why I have RB30E long block and RB26 head in storage for when my budget will allow me to complete a rebuild and replace the current L6 in the long term project 260z (it will be DE not a DET mind - NA power is enough for me)

[nat0_240_chevZ]

JESUS!!!!

 

give the fellow SOME ideas to work with.

 

the rb head could be done, not easily as in way of bolt up, but can be done.

block leaning over is no dramas for the rb head or injection (depends if youre after carbies im not sure, if you are you just need to machine half of the eqiv angle on the intake/manifold faces and the other half on the carby/intake side of the manifold)

 

the main problem with the rb to L swap is the oil and water galleries at the rear of the block. Now both L and RB have an oil drain port, problem is the rb oil drain is massive. and overlaps an L water gallery.

also the rb water galleries down the side of the block are a large curved oblong where the L's are a very small oblong.

 

I have often tempted to make a stencil for those that want to meild the 2. it would be like a head gasket but it would be somewhere in the middle ground of the metal meat needed to get them to mate better. trace the stencil on both head and block, the grind the L block with a die grinder with a tungstun carbide burr and weld up the rb head and re shape all ports with the same grinder. then test and face the head and block. (problem is when replacing the head have to do it all again)

 

as for the cam drive..... well this is not as hard as some make it sound. laser cut 2 sprockets and machine the necessary boss's and bore size to slip on the end of the cams, then fold up a sheet metal camcchain cover that bolts to the front of the rb head (like the plastic ones that the rb have). Make custom gaskets to seal the L timing cover to the sheet metal cover to enclose it fully (imagine a sheet metal plastic cover instead of the plastic ones, but totally sealed to hold oil and crankcase pressure/vacuum).

 

Now this would also require a custom headgasket, (same as the stencil) but hell they are not hard to get. i can put you onto a number of companies willing to do so.

 

Also if there is anything i have missed just throw it at me and ill try and explain.

 

cheers nato

[pauly_adams]

i was thinking the same thing with the oil ports and whith the cams etc i would love too do it but the $ factor is holding me back but if some 1 was to donate a rb20 head would make 1 less thing to get lol can get the welding done and maybe able to get some maching for nothing so if some 1 has a rb20 head would epresiate it

 

cheers pauly

[NZeder]

anything is possible just time and $$. Most have one and not the other or you might be like most of us and have neither of both 

 

I like the idea and I think if someone can make a L31DETT using 2/3 KA24DE heads then using a RB head should be do able too.

 

I believe one of the problems with the RB engine is too much oil getting to the head and hence the large return/drain in the block. I guess this could be over come with an external return - I believe this is what some of the RB guys do anyway. Here is a pic of my block when I had the head off replacing the head gasket - you might see that all the water galleries on one side of the block are no longer there  this engine was build by a well know Nissan guy here in Auckland (he knows lots of tricks apparently) and my car has no cooling issues (does have a 5 core radiator, head gasket blew due to lean out at higher RPM = detonation) So do this and now you only have one side of the head to deal with  - the bright circles in the pic on the header side are the fulled/welded up water holes.

[pauly_adams]

cheers any pics help and if the block can stay cool with only 1 side of the water ports it does make things more simple. as for the time money situation i have the time at the moment due too no job currently its the money holding me back any way send me more pics gives me more ideas does any 1 have pics of a rb 20 head having trouble finding some

 

 

cheers pauly

[NZeder]

I have a RB26 head that I could take a photo of when I get a change to clear some stuff out in the garage and get to it again. I think I have a RB26 head gasket and L28 (both metal) here too that I could take photos of for you.

[nat0_240_chevZ]

yes give us pics, and ill see what i can do.

 

can you also have a ruler laid over the pics, one in each direction.

 

take pics perpendicular to gasket.

 

allows me to dxf the photo, and ill see what i can come up with.

 

nato!!!

[pauly_adams]

yeh what nato said that sounds good

 

cheers pauly

[NZeder]

does any 1 have pics of a rb 20 head having trouble finding some

I will do the pic thing later this week or in the weekend (will try and do it after work this week one night)

 

Re the finding of RB20 head here is an idea - given that people put the RB25de or 25DET head on a RB30 block (the early 25DE no mods just bolt on - later vvt head needs mods to work and the 26 head works with no mods too) so pickup a RB30E head and work with that (guys that upgrade don't want the RB30E head so you can pick one up for next to nothing). Then once you have a plan and if it going to work then pickup the more costly DOHC head

[nat0_240_chevZ]

here is a rough rb sketch in cad.

 

not scaled anywhere near what it should be (7850mm long hahahaha)

 

but i think you get the idea.

ill get the L6 block deck done soon, then superimpose ans match the scales of the 2.

will give a good idea on what needs to be done

 

also note the 2nd pic off hybridz, an l6 gasket on an rb head, as you can see bolt and bore spacings are bang on.

oil and water galleries need a tickle on both head and block, more so on head.

 

also note my sketch is from an rb26 not a 20/25 etc as they are slightly different in areas.

 

nato

[nat0_240_chevZ]

bump!!!

[pauly_adams]

lol got the pics ive got a l28 head gasket aswell it doesnt look to hard to change the water and oil ports but im yet to see a rb head with a l series gasket on it but will try too get a rb head sometime in the next couple of weeks so at the moment im stuck staring at pics

 

cheers pauly

[nat0_240_chevZ]

lol got the pics ive got a l28 head gasket aswell it doesnt look to hard to change the water and oil ports but im yet to see a rb head with a l series gasket on it but will try too get a rb head sometime in the next couple of weeks so at the moment im stuck staring at pics

 

cheers pauly

 

see previous page with the pic of the rb head with l28 gasket on top of it!!!!!

[pauly_adams]

yeh i seen that pic fits quite snug but with a actual head i can see how to mod it better, im just like that i can think bettter if its right infront of me

 

cheers pauly

 

[NZeder]

The only problem for me to get my RB head out to take pics - I first need to move one of my L28's that is in front of it and the engine crain is not here at home anymore (l28 is just on the floor) I will see if I can drag it out of the way in this weekend - you see this weekend I was putting my zed back together (still working on it) so let say this is not high on the agenda - when my zed has been down for 3 months (ok a few of them I was not home but OS on business)

[pauly_adams]

thanks will be waiting patiently

 

cheers pauly