280 into 240 whats not needed

[ozting]

Hi All,
I'm looking for a bit of help with a 240z I've bought that has had a 280z engine put in. Its running on Jaguar 2' SU's and when I bought it it was only running from a petrol can under the bonnet. Normally I would have walked away but the amount of work that had been done well to this car swayed the balance. So I trailered it to its new home. After connecting fuel lines up as they should be I wasn't surprised it didn't start so I started checking everything from the tank to the float chamber. Although all was new under the hood and new copper fuel lines ran to the tank there was a hose from the copper lines to the tank that had perished inside and so when the pump was trying to draw fuel it was collapsing this pipe.Once this was replaced and the line purged to the carbs it started and ran really well.
Now I have had chance to look at the car more I can see certain things that are not common on the 240z like the return line from the fuel rail, Then there are lots of emissions tapings (or so it seems). The return fuel line on this car seems to be blocked or blanked. Is it needed?
The 2" SU's won't take the standard air intake as it fouls the inner wing. There are 2 spacers in the manifold that are orangey red, about 20 mm thick. Are these needed?
I will probably need to fit aftermarket air filters any recommendations?
It has a nice janspeed like exhaust manifold and has been jetted with jag 2.8 needles .

Will add some pic's as the car gets back on the road...

 

[Rob Gaskin]

My car had 2" SUs and a standard air filter when I got it.

20mm thick spacers seem excessive - I think more like 10mm is normal That could give the clearance problem. It is tight on a standard car .

Return pipe - lots of people don't use them. I think it's a good feature and keeps the fuel cooler, which is a good thing on a non-crossflow engine.

Don't know about your needles - you need a rolling road session with someone who knows how to tune SU - getting rare these days. But it has the potential to run ok.

 

[ozting]

Hi Rob, That all makes sense. It does run alright just idling fast, and I think thats due to the lack of filters. just looking at K&N.

 

[Rob Gaskin]

Idling fast wont be the lack of filters. Have you tried adjusting the carbs i.e. slacking all the linkages off?

If you can't slow it down then you have an air leak, air is bypassing the carbs. Check all the connections on the manifold/s and gasket seal.

 

[Craig_260]

yeah idle can be adjusted on the carbs and i use k&n filters on mine you can get really flat ones something like 2" the ones i have are closer to 4" and the front is a little awkward to jimmy into place. as for return I agree with Rob id keep it if its blocked its probably worth sorting it out in the long run tbh.

 

[status]

Get yourself a colour tune,could save you hundreds rather than go on a rolling road,always used them and my cars ran ok,rolling road bit much for a couple of su s,in my experiance anyway,no doubt other people on here wont agree but for wot they cost its worth a bash,a rolling road stint aint cheap

 

[ozting]

Colourtune

Didn't think about a leak on the manifold but I will check it out today and let you know.
As for the colourtune that's a great idea I have used them before and it was very successful then. I'm also going to get some K&N filters sorted as soon as possible. Apart from a fast idle are there other symptoms of air leaks? It does run very smoothly!
I am going to dig out a Jag SU drawing so I can make sure I am on the right track it has been a while since I've needed to tinker with them.
My first 260 had the same set up and it went all over to get rid of a flat spot at high revs. Never solved it. Even took it to the guy at Silverstone who had a Z place at the track. He ran it round the track and gave me an electric fuel pump to run in series with the mechanical one. Had those tuned on a rolling road in Hastings and although it made a heck of a difference come 5k rev's it still choked. Strangely that car colour was very close to this one.
Thanks again for the advice I am sure I will be bending your ears for further help.

 

[Mr.F]

K & N filters for 2" SU available in various depths - 45mm, 54mm, 63mm and 83mm - call to discuss.
240Z would have had a restricted return originally. Particularly useful in keeping fuel in the railaround the rocker cover cool when idling.
240Z manifold spacers are quite thick. You could use 260Z versions which are much thinner, but you would need to change the manifold studs as well. This would bring you another 10mm clearance.

 

[ozting]

Hi Mike,
I will have a look and see what clearance I have then give you a call.
Does it make any performance difference the size of these spacers, why are they there? ( is that a dumb question)

 

[Rob Gaskin]

Ozting, what model are your carbs?

HS8, HD8 etc I may have some info.

Check all those emission 'take-offs' for leaks and servo pipe etc.

Status - never underestimate the simple SU's capabilities

Which would give more power a set of triples set-up with a Colourtune or a pair of SUs expertly set-up on a rolling road? That would be interesting - to me anyway.

 

[Mr.F]

Spacers are there to minimise heat transfer from manifold to carbs.

 

[status]

I never underestimated anything,nothing wrong with su 's,as we know no point with a rolling road if there has been no head work,wont go into that as its been said umpteen times before ,as for which would give more power,well triples set up with a colourtune,dont knock it till you try it,i have and yes ,can be just as good,depends who is doing it,every car is different,and Ozting if i have my colourtune and you were thinking of getting one well you can have mine if i still have it also the vacum gauge i used with it,car ran perfect,i will have a look in the morning,cant promise though

 

[Rob Gaskin]

Status, I have used a Colourtune - I may still have it. Good tool.

However I have also had 2" SUs set-up by an expert - fine tuned the needles with emery paper etc etc. Never touched them after that as far as mixture goes. They were superb.

Same goes for triples of course, it's all down to the guy doing the changes/adjustments.

So Ozting with a Colourtune or an Expert with a Rolling Road? However, genuine Experts are very hard to find. My Rolling Road session cost £90 - the guy is no longer on this earth unfortunately.

 

[RIDDLER]

Took mine to a highly regarded rolling-road tune-up expert who told me he charged £150 an hour. Said he would probably get it done in an hour - I told him he ruddy well better had! Car ran superbly afterwards and has done ever since.

 

[rallymanDP]

As Rob has said, the 2" SUs are excellent for power and driveability once they have been adjusted properly for the mixture to be correct at all parts of the Rev range.
The needles need to be carefully modified at several points to do this, and only the older Rolling Road guys are prepared to do this ( and know how to actually do it ) - as has been said before, they are a dying breed nowadays.
If you would care to make the bold move to travel over the Pennines to the right side of the Country with your 'Z', we have the very Bloke located not far away from the Thirsk area to do the job properly.
All the local Historic racers use him - he doesn't advertise and doesn't need to do so, and he doesn't charge a lot, but gives a thorough report on the Engine, Ignition, etc., at the same time.
He can't use a Computer and writes the report by hand, and even Amocrace uses him, so he must be good.

If interested, send me a pm for his phone number.

And No, I don't get Commission....

 

[ozting]

Well no rolling rd for the moment busy concentrating on the basics.
Bought a colourtune kit and that's the way I'm going.
Just tuned by ear today and its running better & the idle has dropped. There are a couple of places related to possible air intake issues but I'm happy with the run for now.
Took it for a test run and lovely but a serious clonk related to rotation getting worse. So stopped and eased back to workshop, jacked up the front to find all the wheel nuts are loose. Glad I didn't go to far!
Still happy it's a simple fix.

 

[morbias]

They look like HS8 carbs, there are tuning and adjustment instructions on the burlen website: SU Carburetters Technical

I think KL needles are the recommended needles for HS8 carbs on a L26, part number AUD 1536, might be suitable for a L28 too

[EDIT] Also this needle comparison tool is good for working out what needle to go for if you're running lean/rich at certain revs: http://www.mintylamb.co.uk/suneedle/

 

[status]

emery cloth,been there good results,old school mechanics are usually the best,one of my old mates uses his ears ,no colourtune or rolling rd,perfect every time and yes 2 inch su's,good bit of kit.Quetion, are they the equivalent to a set of triple 40's when used on a worked head? anyone know the answer to that ?

 

[Rob Gaskin]

Status, I'm sure on a high performance engine a well tuned set of triple twin-choke carbs can give a power increase over SUs. It's probably down to airflow through the carbs and manifold though rather than mixture.

My point is that to get the best out of any modification a GOOD rolling road session will do that. A Colourtune is better than nothing but you will not be simulating driving under load, taking power readings, ignition under the same conditions etc If the car is only going to be used for touring that's fine but in my case I wanted every single bhp I could get out of what I had on the car. My rolling road session was worthwhile to me and was very interesting.

I'm usually the one who suggests taking the simple, cheap option on these simple old cars but my Rolling Road session was money well spent - but I had had the engine fully rebuilt/modified so I was starting from scratch.

On my current standard car (as Datsun built it) simple servicing and tuning have transformed the driving experience and I don't think there would be much gained from a Rolling Road session. I might just try a Colourtune on it though

 

[ozting]

HI All,
Thanks for the for the SU link I will look at that later. I did set up yesterday by ear and as I said was running fine but not under load. I bought the colour tune kit and will use that to just get it so it is nicely balance. It has the Janspeed looking manifold and custom exhaust so with these carbs set up right should give it a nice boost over the stock car. I have also ordered the K&N filters to suit and they will be with me tomorrow. (Did try calling you Mike but no answer) I totally agree with the logic of the rolling road as described by Rob. On my other 240z with the V8 4.1 engine in that will be getting a rolling road tune up for sure and the guy to do it is Rick Wood I am told but as I am planning to sell the standard car I just want it nice with no issues. Its a really pretty car and had loads done to it so deserves to be finished off. I am toying with the idea if fender flares because I have a really nice set of JDM wheels I could put on but they are wide. Its hard to sell a car like this though because after having zed's for so long and hunting parts that are hard to find for them this one has them all on (or 99%) so maybe the V8 has to go. One way or the other I can't keep both. At the moment the V8 is more likely to stay after its refurb a year ago it really is an amazing drive. Could keep both and get rid of the misses I suppose!

It has Wolfrace wheels on at the moment but as I mentioned the nuts were loose ( just hadn't been tightened by previous owner) Do these still use stock nuts or should they be using a tapered aftermarket nut, Does anyone know?