Converting My Z From Pssht To Woosh

After many days and nights of thinking about what I want to do with my Z, I have decided that its not going to be turbo anymore... or injected for that matter.

Yes, thats right. Im converting it carby. Why? Cause im a little mentally unstable. Laugh all you want. The point here is to do something a little different, and old school. Its knackered, so it needs a rebuild anyway. Might as well do something thats brave... or incredibly stupid.

I will be doing most of the build myself, so I need to source the parts myself as well. I've hit a brick wall though. I cant seem to find many places to get the internals, at least not for the single cam VG anyway.
Anyone able to point me in the right direction?
And what other cars did the VG NA go in? (knowing this will help the search)

Also, a bit more on the technical side.
I need some advice regarding an overbore. As in, I intend on over-boring, but I want to know what experiences, bad or otherwise, people have had with the VG and doing this. Am I going to run into issues, and would anyone happen to know what a (relatively) safe oversize would be for these engines?

If anyone wants to throw some ideas, advice, or experience my way, I'd be glad to hear it. Im not looking to break the sound barrier, so boost is not on the menu.

Cheers in advance.

 

If you are not technically capable, but want a project nonetheless, just swap a used NA motor into it. Budget <$ 500, and some booze for a few mates and hire of an engine hoist.

'Over-boring' an engine is not a simple task, firstly an engine builder needs to strip it, measure cylinder taper, correct and core-shift from the original casting, and then go about the cylinder bore. Add to this a line-hone on the mains, ideally new rods, rings and pistons (to account for overbore) and you are coming into the thousands of dollars range. Keep in mind the head needs to be decked, cylinder heads would need a bit of TLC, and all associated gaskets need to be sourced.

If you really wanted a carby engine, look at a transplant of an old series 1 L28 out of a 280Z. They are a solid engine, the block looks like its out of a damn truck!
Due to the shape of the Z31 though, this transplant might not even be possible.

 

L series engine sounds cool, like a full on Devil Z rebuild, L24 twin turbo

 

Why wouldn't you want an extra 400cc though? In a pre '83 car in NSW you need to meet less stringent pollution control.

I've heard people talking about a DOHC conversion for the L series engines, apparently a mercedes I6 head will line up for all but 1 oil gallery... Now THAT would be a nice conversion.

 

Do it if you want ito defected. You cant put an engine in it that doesnt meet the Pollution specs of when the car was made or the more stringent later specs.

There is NO WAY it will pass any 1989 pollution test with an old carby engine in it.

Dont care ?? put an old carby V8 in it !!!

 

Rb30s
Google it

 

Thanks for the info.

Thankfully, I have enough knowledge in my noggin to accomplish such a task. Its just the machining side of things that are out of my bounds.

My goal for this is to use the V6 in carby form, but build it to produce a better hp figure than a stocky. As in, do all the usual carby engine tricks like bigger carb, lumpier cams, head and block work, overbore, extractors (if they exist) ect. Basically, I would be doing this as a technical exercise, rather than a cheap alternative to injection.

On a side note though, im not completely sold on touching the block internals (crank, rods, and pistons). Im more swaying to just leaving it stock. Obviously, being a turbo engine, it will need a different set of pistons to bring the compression ratio back up, but apart from that, the rest is just food for thought. Rebuild it, but leave the components stock? Dunno.

 

Off memory there is a RB engine by the code of RB24S. I think it consists of an NZ RB20 SOHC head and an early Series 1 RB30E block. It is carby fed and is said to go like a rocket in an average sized Coupe or Sedan. Google it?

 

An afterthought here, and a question for someone with NA experience.

Will the pistons need to be cut to accommodate a bigger valve lift, or is there generally enough clearance there to get away with it?

 

This.

If you don't care about the legalities of it all then chevy small block is the only way to go if you like carbies.

 

Well waddya know. You learn a new thing everyday. I didnt even know these existed. Might be a good way to go. That would definitely be different.

Thanks for the idea.

 

Never heard of a RB24 being released. You can make one with a RB20 block, RB26 crank and rods and RB20 pistons with RB20 head.

Edit: Found this on Wiki:

That's pretty lame though, had about the same power in my old corolla

You could get a carby V8 approved in a Z31 easy as. Eric got his carby 350 SBC approved in a '89 Z32.

 

OK, I get where your coming from m8. This is my kind of old school thought and with a little imagination and i say go for it if your game!!

The engine part is easy. there is nothing untoward when building a 200Hp carb V6 @6500rpm.
Your stock block. Take it down to your local engine shop.
All usual clobber, bore and hone to suit next oversize. Chemical clean, replace welsh plugs..blah.
Check crank pins for taper and ovality, if in order new bearings or is no good, grind crank to next undersize.
Rods for size, ovality and twist. Close and hone if necessary.
Reciprocating and rotating parts balance.
All straightforward and easy stuff. there is a plethora of Nissan SUV's utes and cars that use the single stick VG30e and ANY engine shop will be able to supply all the bits youll need.

Heads: Assuming there is not undue valve seat recession get a mild "street" port done which amounts to de-dagging, radiusing of any sharp corners (and there are plenty of those in a single stick VG!) and match port inlet and exhaust manifolds.
Spring for a 3 angle valve job as well. Well worth the money in terms of low lift flow.
This is on top of a standard street head reco so budget around 1500 on heads.

Id get a couple of cams ground on the stock sticks to about a "1/2 race" level which will be fairly similar to a Holden XU-1 type grind. This will suit the 2 valve heads and give a nice, rolling "cammy" note on idle, a strong mid-range and run out of puff around 6500rpm or so which will keep your engine alive for hundreds of thousands of street K's. It will also be nicely streetable at low revs.

Now, the tricky part. Carbs and manifolds. Id say you are going to be on your own here and have to get funky and fabricate something up.
I dont ever recall the VG's coming with carbs is all.
Like the later twin cam motor, the early single sticker uses a lower manifold and a bolted on upper plenum.
All the ports at the top of the lower plenum line up more or less longitudinally along the motor and I doubt the setup would work well with a single carb atop a boxed plenum. Youd have a lot of dramas with doughey throttle response off idle, gasping and hiccups when stabbing the throttle and mixture distribution issues from such a long line of ports and larger than useful plenum volume. Itd be a pig actually.

To use this lower manifold arrangement, Id set up a divided plenum to carry 2 x 40mm DFAV downdraft Webers (non-progressive type off a V6 Capri or something like off an older XF Ford carb six shooter) or some 500cfm 2bbl Holleys with both throats feeding 3 inlet runners each and mounted one behind the other with the butterflies lined up ACROSS the motor. NOT inline!

The lower manifold does not carry any cooling water galleries so doing away with the lower inline plenum altogether opens up your options and you can use.. say a smaller double pumper or progressive Holley 4bbl on a box again with the 6 tapered runners feeding from each side of the plenum. Pretty big bit of kit to get working on a small v6 tho and very small 450cfm 4bbl Holleys are pretty rare.
Even a single smaller 2bb 500cfm Holley or 40mm DFAV weber will work nicely on this arrangement and will breath well for a 3 litre V6.
Mixture distribution will be OK due to relatively short runner lengths and add a simple "W" plate under the carb butterflies to interrupt and distribute the accelerator pump jets for that extra touch!

You could fabricate what looks kinda like a twin turbo "wing" style manifold with the three ports from each side crossing over and terminating in a small plenum and a pair of Weber DCOE's sidedrafts.

Better still for simplicity, street performance and tuneability would be a pair of 45mm SU's!! No plenum box needed due to single throat and just merge the 3 runners at the carb flange....Niiiiiice!
This setup works well due to nicely straight runners looking directly into the inlet ports so no pesky corners to cause fuel condensation and pooling, especially when cold.

To go the whole hog and look seriously trick and work real well, I would fabricate a wing style manifold crossing over and terminating in 6 opposed and individual flanges and then source and attach 6 x 40mm square slide CD Mikuni carbs off a Suzuki GSXR1000!
Any bike wreckers and prolly 3 to 400 dollars per set of 4.
These carbs come in gangs of 4, all linked together with throttle shafts so fitting would be an easy affair!
To reduce the issues of carb balancing, Id valance the 2 "wings" of 3 runners behind the carbs with a 19mm dia tube.

The whole show could easily and effectively be made from some profile cut 12" steel plate flanges and some exhaust pipe beginning at the 40mm carb end and tapering back to the inlet port diameter!
Or go ally for the real trick look.
Again low down and cold running will be pretty good due to relatively short and virtually dead straigh runners shooting durectly down the ports.

With this last arrangement, Id confidently predict easily getting as much horsepower or possibly even more than using the single stock throttlebody and plenum EFI setup.

Might not "carburate" quite as well as the EFI down low and especially when cold but once on song would look trick, sound insane and be well worth the effort!!!!

Cheers
E

 

Whoa. Your ideas are mind blowing. I like it.

You've given me alot to think about, just on carbs. I was just going to cut and shunt the manifold and drop a holley on it. You have confirmed my theory that it wouldn't work to well.

All this talk of multi-carb setups and crossed over manifolds, has seriously got me thinking now. If im going to dick around by putting a carb on it, might as well do something special with it hey.

The only issue I foresee, is the valley manifold. I could almost swear it has coolant jackets running through it, along each runner. Also has the turbo coolant return (thats easily deleted though). Correct me if im wrong.

Mmmmmm..... opposed side drafts. The more I think about it, the more im convinced!

Thanks for the mind fuel!

 

Oh yes! Mikuni flatslides! Awesome carbies

Wouldn't be that hard to do.

 

Hahaha yer its the kind of stuff that goes thru my head most of the time. Its a curse... it never ends!
Nah Crisp, would be no harder than making up headers...eeeasy!
Ive got an old VG engine up there with one head still on it. Im almost certain that no water passes from the heads to the manifold but Ill have to check tomoz.

Cheers
E

 

I reckon it would be easier than headers, that's a PITA!

 

Well when thinking about yours, then yup!!! Sheesh!

 

why dont you just put a 3.8l ecotech in if your mentally unstable

 

The thought had crossed my mind, but that would be blasphemy.