Spitfire Spitfire 1500 1-Z-S to 2-SU's ...some issues...

[IanF]

Howdy all.

For the past week I've been in the process of converting JerseyGirl's Spitfire Baldrick from his single Z-S (with a stuck water choke) to a pair of SU HS4's purchased from Carlisle a couple of years ago and recently rebuilt (as well as finally installing the Bell header to go with the rest of the Bell exhaust). After some initial problems and some great help from Ben Pender, I finally got the car to start and run reasonably well. However, I have a couple of problems that are plaguing me.

1. The engine has horrible pick-up and won't rev much past 3500 rpms. My first thought is to change the damper oil to something lighter, but I also think the cable may not be pulling on the linkage correctly. So tomorrow/Monday I plan to fab up a new stop plate for the linkage similar to a car I found in the BCF classifieds. (a white '79 w/ what appear to be the exact same carbs).

2. The engine has developed a terrible oil leak. Like really bad... Oil is practically pouring from the rear of the block... I'm not 100% sure if its from the engine or the transmission. After doing some searching, I found the page on Teglerizer where he talks about a similar issue. My concern is we had the leak when the vent was disconnected entirely while I was still sorting the carbs out. The port for the crankcase vent on the valve covers was simply open and we were still getting this leak. This leads me to believe the engine "wants" to be under vacuum to prevent leaks? There is a threaded port on the intake manifold for the OE PCV valve, but I don't see me being able to get one soon... besides the fact it cost no small amount of money... I'm wondering if an adapter, some hose and an inline PCV valve could work.

Thoughts? Suggestions? We're in somewhat panic mode right now as we really wanted to take the car out to Carlisle this year... :frown:

Ian

(p.s. I won't be able to check this thread again until Sunday afternoon, but please keep ideas coming! )

 

[poolboy]

Re: Z-S to SU conversion... some issues...

I experienced leaks when I left the valve cover vent on my TR6 just open to the atmosphere. It needs just a little vacuum (not manifold vacuum) that the ports on the 175CD provide.
I bet the same applies to the Spit.

 

[foxtrapper]

Re: Z-S to SU conversion... some issues...

Virtually every racing Spitfire (and TR6 for that matter) uses a simple oil catch-can off the rocker cover. You do not need vacuum, and they do not simply leak because of a disconnected line. But, if the top of the cover is blocked, you build up pressure, and then you squirt oil most remarkably.

There's a fair chance you've got the needles so far off that the mixture is too far off for the engine to rev up well. Many of us who've done the conversion have been there. Make sure also that the manifold is truly seated against the head and not against the exhaust manifold.

 

[tomkatb]

Re: Z-S to SU conversion... some issues...

Ian

My son and I made the same change last summer.

We had the same issues with performance.

1-With the heat shield etc. there are 8-10 gaskets that need to be tight on the intake,. We had several vacuum leaks. We used carb cleaner and patience. Oil in the carbs is a minor item. On our car the air cleaner being on the car made it run better. With 100% more air going in you need the air cleaner for vacuum.

2-1 bad float valve.

3-The car ran well with the mixture off. It was set according to the book. Another small issue. Ours was rich.

4-I assume the vacuum advance works properly.

Hang in there. It took me 3 weeks to get it 100%. You will be amazed at the improvement.

Larry

 

[IanF]

Re: Z-S to SU conversion... some issues...

Yes, the idea of "needing" vacuum seems odd to me... but at this point I wouldn't put anything past this car... Nothing is blocking the valve cover that wasn't there before... the engine dripped a bit, but not what I would consider excessive for an engine of its age and mileage.

Part of the problem is there is no inlet port on these carbs in a similar position to the old Z-S. So my choice is to either drill and tap a hole into the back plate of her fancy, custom made air filter housings, or rig up some sort of PCV set up to connect to the existing port on the manifold... with the hope of not creating a massive vacuum leak...

I guess the question is, if it's NOT vacuum, then what else could cause the engine to all of sudden start spewing oil when simply open vented?

The jets and needles worry me some... I ordered a basic rebuild kit and new jets and needles... I remember seeing some charts that showed various needle sizes... Maybe I can find them and gain some insight to whether or not they are right for a 1500.

 

[IanF]

Re: Z-S to SU conversion... some issues...

Ian

Hang in there. It took me 3 weeks to get it 100%. You will be amazed at the improvement.

Larry

Thanks... I hope so... Right now I want to put the Z-S back on... which we didn't really have a problem with, all things considered... it usually started easily... it just had a sticky choke so it ran rich all of the time... to the tune of around 18 mpg... and the car was downright painful to follow behind...

Unfortunately, I don't have 3 weeks... I have 3 days... No, I don't know why we wait until the last minute to do these installs either... Should have just left the poor car alone and lived with the crappy gas mileage... ...or maybe opened the water choke up and see if that could be fixed...

 

[poolboy]

Re: Z-S to SU conversion... some issues...

Virtually every racing Spitfire (and TR6 for that matter) uses a simple oil catch-can off the rocker cover. You do not need vacuum, and they do not simply leak because of a disconnected line. But, if the top of the cover is blocked, you build up pressure, and then you squirt oil most remarkably.

I have to take issue with you on this foxtrapper. I'm not making this up. I've tried venting to the air, in fact the PO had the V/C vented to the air with a heater hose. The block was coated w/ oil.
I routed the V/C vent to where it was designed to be, no more leaks except the rear crank shaft seal.
If the vent line does become blocked, sooner or later oil will blow out the dip stick tube as well
BTW, the vacuum line at the ZS carbs that are there to vent the V/C is no where near as strong as the 18 or so in-Hg at the manifold; it's closer to 5 in-Hg.
I just measured it yesterday for the benefit of another thread on another Forum.
Perhaps if the V/C does not have a baffle behind the vent nipple the pressure may not be as trapped as in the original valve cover with the baffle and may not need that little extra suction that the carbs provide to relieve the pressure. That's just speculation on my part though.

 

[foxtrapper]

Re: Z-S to SU conversion... some issues...

Where at the back of the block is it leaking? For I'd rather suspect you've got something broken that's now leaking. Be it a damaged valve cover gasket to a fallen out blanking plug.

I have seen crankcase lines run to the front of the air filters. I can't say I'm impressed, but some folks just love it. There's very little vacuum inside the air filter, and it can make a mess of the front of the pistons.

The haystack program is darn handy for figuring things out. Free from the web, scions of lucas as I recall. But don't discount the vacuum leak. These manifolds seem to love hiding vacuum leaks under the bottom side where it's embarassingly difficult to locate.

 

[tomkatb]

Re: Z-S to SU conversion... some issues...

My 77 is piped the same as the European models in the Rimmer brothers catalog. I never saw the oil leakage that I have heard about before. A 3/8” hose runs from each carb to a t that connects to the valve cover. However mine uses more oil than seams normal. My kid put synthetic 10W40 in it that can be an issue. My carbs are actually from Europe.

My carbs did not do well with the air cleaner off.

Last week my son resurrected a Honda Magna with four similar carbs. It would not act right until it had the resistance of an air filter. It requires vacuum to move the pistons to move the needles. It was night and day.

My carbs had an odd set of needles that came with the carb. It runs so well I am afraid to change them. My engine is newly rebuilt but, stock except for higher compression.

Larry

 

[poolboy]

Re: Z-S to SU conversion... some issues...

If you are running at a steady pace, there isn't all that much draw fron the vacuum ports on the carbs that vent the valve cover. But, if you accelerate sharply or let off the throttle at speed, then there is a little more vacuum in those ports. That's when the carbs really draw in a good portion of the oil vapors floating around in the valve cover.
Oil consumption adds up if you drive like that.

 

[eschneider]

Re: Z-S to SU conversion... some issues...

re: fuel problems

1) are you experiencing the 3500rpm limit with the stock air filter assemblies installed? If not, that may be your problem. One way to test this theory is: try pulling the choke lever while driving the car down the road (warm). If the extra fuel helps the problem, you either have a vacuum leak or need to restrict the airflow. If you don't have a stock arir cleaner assembly, try restriciting the airflow using duct tape around part of the air filter.

2) were the carlisle carbs stock for a spitfire? Do they have the stock spitfire needles?

3) the stock 1500 euro-spit dual HS4 breather setup is pictured here: https://www.rimmerbros.co.uk/spitfire/images/47d.gif

Rimmer brothers has a decent breakdown of the stock HS4 setup on the 1500 spit here: https://www.rimmerbros.co.uk/rimmer/triumph/spitfire/fuel

Hope this helps.

 

[IanF]

Re: Z-S to SU conversion... some issues...

Ok... this may be part of the problem: we don't have 1 1/2" HS4's... we have 1 1/4" HS2's... So while the jet's & needles may be "correct" for the carbs, they may be wrong for a 1500...

The HS2's on the car don't have any inlet ports for venting hoses as shown on the Rimmer Bros site.

Given what I'm reading here... I don't have time to make these carbs work properly between now and Thursday, so I'm leaning towards "punting"... swapping back to the Z-S and coming back to the SU conversion when, a) I am sure these carbs can actually work, and b) I am not being quite so rushed to make them work.

 

[eschneider]

Re: Z-S to SU conversion... some issues...

While my first instinct is to play cheerleader and encourage you that it CAN be done.....

This is a process that should be ENJOYED rather than rushed. The results will reflect the grins invested.

Using the H2's will require custom needles, either from someone who's been down this path before, experimenting with off-the-shelf needles, or by shaping your own. Shaping your own is a trial and error process, best done with the counsel of a air/fuel meter - but not required.

The easiest way to go is to duplicate the stock setup with the HS4's.

If you're gonna play with needles - it allows you to get the most out of a low-restriction air filter setup - I'd do it with the bigger carbs anyway. (oooo...... H4's and velocity stacks.....) Maybe someone here has even done something with a cam and H6's? (ooooo... more POWER.....)

It's easier than it sounds, as long as you smile when you're doing it.

 

[myspitfire]

Re: Z-S to SU conversion... some issues...

In my opinion duel carbs(whatever brand)are a pain in the you know what to have any kind of confidence in.I've heard nothing but problems from owners of these carbs .Personally i'd put the ZS single back on & install a manual choke.I've owned ZS and have never had a problem of any kind.
Good Luck
Ken

 

[aeronca65t]

Re: Z-S to SU conversion... some issues...

Re: The oil leak...

My racing 1500 (Midget...with Spit engine) leaks oil like sieve when there is no vacuum to the crankcase. I can fill a one-quart catch can in a 20 minute practice. It's been rebuilt several times...that didn't make any difference. The older (948, 1147) engines probably didn't displace so much air inside the crankcase (due to the smaller bore/stroke) and could survive with a road draft tube. But pushing oil is pretty common on de-smogged 1300 and 1500 engines...especially when driven hard.

When I rigged up a system to apply very slight vacuum to the crankcase, the leak went away completley. No other changes.
My car has run a 4 Hour enduro with average RPMs of about 5500 with no oil used at all after I set up a positive crankcase vent system.

My system is pretty primitive and looks like~THIS~
I use a threaded dipstick to hold off any other leaks, but for street use, you won't need that.

I have seen condition with other 1300-1500 Triumph engines too (including my brother's old street Spitfire). It's pretty common to see some form of positive crankcase vacuum on the various vintage Spitfire racers I see too.

As for the carbs, when the throttle is "floored", did you look to see if the thottle plate is wide open? (obviously, you'll have to lift each carb piston to see the throttle plates).
And look to see if both float chambers are filling.
If floats are OK, while the float covers are off, remove the piston chamber and slide. The blow down the main jet (not too much pressure....maybe 10-15 psi). This will blow back any dirt or clogs into the float chamber (watch your eyes, since some gas may spray about).
If all this looks OK, have a look at the ignition timing. Somewhere in the area of 10 to 15 degrees BTDC at idle should at least be close (and make sure it's advancing when you rev it up)

When my car was on the street, I had great luck running a single HS4 carb on the stock ZS manifold.

Not that I'm opposed to twin carbs.....my street MGB has a single (Weber) carb (from the former owner) and I just bought a set of twin SUs to convert it back.

And eschneider is right! Above all, have fun!

 

[foxtrapper]

Re: Z-S to SU conversion... some issues...

HS2's work just fine on the 1500. A number of us are running them. I've screamed mine up past 6000 rpm quite routinely with them.

I well understand placing the ZS back on for the time being, and fiddling with the SU's at a later date.

 

[eschneider]

Re: Z-S to SU conversion... some issues...

HS2's work just fine on the 1500. A number of us are running them. I've screamed mine up past 6000 rpm quite routinely with them.

THERE we go!!!!! So which needles are you running? How is your breather configured? Doesn't get any better than the voice of experience!

Had another thought - you could tap the cross tube on the manifold as a source of vacuum for the crankcase breather.

 

[IanF]

Re: Z-S to SU conversion... some issues...

After a fair amount of debate (on a different site), it's been agreed upon the needles are wrong. The rebuild kit I bought was for HS2's mounted on a 1300 engine and the consensus is they won't flow enough fuel for the 1500.

I also suspect the throttle linkage is an issue as well, as "foot to the floor" barely nets 50% at the throttle plates. So I'll be looking for a correct linkage set-up at Carlisle this weekend. Otherwise, I may end up fabricating one (would rather not...).

So tonight I'll clean up the Z-S's water choke and reinstall it with the cracked exhaust manifold (since the Bell header and the Z-S intake interfer). This is the second time I will be "un"installing that header...

Foxtrapper mentioned earilier that he just vents the v/c to a catch can... which while that works for his car, may not be a universal condition. By the time I get around to attempting this swap again, I'll probably aquire the correct PCV valve that screws into the manifold plenum (something else to look for at Carlisle... and Robyn was jsut hopign to find a decent, chrome front bumper...).

Unfortunately, everyone I had asked prior to this debacle told me I wouldn't need to do anything... "just rebuild them, bolt them on and go! You'll love the SU's!" Obviously, I didn't ask the right people or the right questions. Honestly, the ONLY reason we wanted to do this is to make the car get better gas mileage... if the water choke can be fixed and properly adjusted, I'd almost skip installing the SU's altogether... if it wasn't for the damned cracked exhaust manifold and the fact the Bell header wasn't designed to fit with the Z-S manifold (not entirely surprising considering it's an UK-market item).

So that's where I'm at right now... if anyone has soem additional Z-S info, I'd love to read it... I have a bunch now, but as typical for these cars, it's disjointed and/or incomplete, and sometimes conflicting...the Haynes manuals don't diagram the exact carb on the car, only a similar one but the diagrams for adjustment are different. FWIW, this carb has a non-adjustable jet, so it appears that all of the adjustments are done at the idle and choke.

As my signature may hint... we have seven cars (six currently running)... all of them need something... our newer cars don't go to the dealer for service... I do it all... from simple oil changes and brakes to suspensions and timing belt changes... The TDI needs an intake manifold replacement and the serpentine belt is on borrowed time... and the '95 Dodge has a laundry list of needed repairs and fixes... and I won't even go into the Volvos... so after awhile, wrenching on the Spitfire becomes NOT fun... I just need the car DONE. Not "done, but..." Just DONE.

 

[foxtrapper]

Re: Z-S to SU conversion... some issues...

This is a darn usefull series for understanding the ZS carburetor.
https://web.archive.org/web/20020911155505/www.buckeyetriumphs.org/technical/Carbs/CarbsI/CarbsI.htm
I'd highly recommend reading through the whole thing, all three parts, as well the adendums.

Yes, there is a complication with the throttle cable and the SU conversion. You can rotate the cam arm on the shaft, gaining more throttle plate opening. I also bent the throttle pedal, raising off the floor somewhat. I wouldn't recommend that, as the high pedal is a pain. A half open throttle is not exciting, and may well be the basis of almost all your troubles. Quantum Mechanics will be there at Carlisle, usually down on the bottom row of the vendors. He will have the cable and bits to solve your carburetor linkage problems.

How nice a set of bumpers are you looking for, and what type? I've got about a dozen chrome bumpers in the shed that I should sell. I really don't need them.

And for the record, I am not running a catch-can at the moment. The top of the valve cover is sitting there, breathing freely.

 

[eschneider]

Re: Z-S to SU conversion... some issues...

So tonight I'll clean up the Z-S's water choke and reinstall it with the cracked exhaust manifold

So that's where I'm at right now... if anyone has soem additional Z-S info, I'd love to read it...

www.paulbunyan.net/~jasko/choke/

Here's a good article on ZS chokes. make sure the vacuum ports are clear on the carb body when you pull the choke off. The vacuum port to the throttle plate gets clogged sometimes.