Spitfire Help me make a carb choice [Spit 1500]

[Lionheart]

I have a stock 1500 with a ZS 150 carb. It runs like crap and emits very rich exhaust. I would like to make it right, and I wouldn't mind a performance upgrade to the stock 1500.

Here are my choices:
Have my ZS rebuilt...$250 (paltech)
Upgrade to single SU HS6/manifold...$350 (paltech)
Upgrade to Weber 45 DCOE...(?$$$?) I have my eye on a DCOE 9 w/manifold.

I don't mind tuning/jetting at first, but I don't want to have to retune/rejet a carb as the seasons change. My budget is about $400. I have a header to install, if needed/desired.

Really appreciate your ideas on this one. The last time I had a car with a side-draft carb was when I was 17. ('71 Plymouth Cricket made by Chrysler UK Ltd [same as Talbot Avenger in UK]...wish I still had it.)
Thanks,
Len

 

[Bugeye58]

Len, have you considered a single HS4? It'll bolt on your existing manifold, and properly tweaked will support at least 140 HP. When I was racing a 1500 Spit, I was restricted to a single HS4, and won two club F Production championships with it installed.
Jeff

 

[aeronca65t]

I agree with Jeff....a 1.5" SU carb (HS4 or some of the other, similar versions) are a good choice on a 1500.

Right now my 1500 race engine car has a bigger (2-1/8") single, race carb on a hogged-out manifold. Like Jeff, I was limited to one carb by our club rules.
But my 1500 is likely going back in a street car by this Summer. And I'll use a stock 1500 manifold and the HS4. I had this previously when the car was streetable and it worked quite well.

A friend of mine has a 1275 race-Sprite with a single HS4 and it will pull over 110 mph.

By the way, I don't think it will slip onto the manifold without slotting the mounting holes on the carb a bit with a rat-tail file, but it's an easy job.

 

[TheAssociate]

I can't wait to get one of these. It's a Mikuni carb - brand new from Performance Research Industries in Oregon. I've emailed the rep. and they said it bolts right on to the stock manifold and includes all cables etc. and comes with a chrome or black air cleaner cover with K&N filter. They claim more power and better fuel economy.
My second choice would be the Weber downdraft, but it doesn't get me as excited. Aparently the kit sells for about $479.00 - a little pricey but I think it's slick.
Their site is down right now, but I did save this photo for some reason:


Adam.
____________________________________________________________
1973 Triumph Spitfire.

 

[Alan_Myers]

Hi Len,

I don't have quick answers for you specific to your car. Hopefully some others will. Here are some generalities to consider:

The Weber will likely be the most expensive setup of the bunch. If I were going that route, I'd want one throat per cylinder, so that would mean two DCOEs on your car.

Yes, the ideal is to tweak Webers for altitude and different atmospheric conditions, to get the last little bit of performance out of the engine. However, truth is that might be done on the race track where a half second lap time is a big deal, but for the street it's probably not often done. I ran my TR4 all over Colorado with DCOEs for years without changing the tuning, once it was set up. That might mean a slightly rich mixture at the top of a big hill, or a slightly lean mixture in some other circumstances, but it's not a huge variation in most real world street driving situations. Go slightly undersize on Webers for a bit more flexible street performance (slightly smaller venturis than a racer would use for peak rpm tuning, with jetting that's balanced accordingly).

One thing the Webers bring to the equation that neither the ZS or SU will is an accelerator pump. That will help with acceleration, but probably not fuel economy.

Just fiddlin' around with a pair of Webers to get them in tune is often frustrating and ends up being expensive. Better to put the car on a dyno, do it right, do it once and be done with it. That's what I'd recommend.

If you ever do want to tweak Webers a little, it just means having and extra set or two of some key jets and swapping them when you feel the need. It only takes a few minutes to completely swap mains and air correctors, for example. Webers are designed so that all key jets are very accessible and easily changed. Of course, you can get carried away with this and end up with a box full of various venturis, jets and emulsion tubes, if you really want to take it to that extent!

SUs might be my choice for the easiest all-around arrangement to work on myself and maintain. I'd look at a pair of smaller carbs, rather than a single one, if not restricted by racing regulations.

There is nothing at all wrong with ZS. They have about the same performance potential as SUs. It's just that there are fewer needles to choose from, service parts are a bit harder to find and the carbs are a little more difficult to work on.

Both SU and ZS are more likely to get out of tune and require some occasional attention, than Webers. That's because nearly all the metering of air and fuel in Webers is done with fixed jets and there are fewer moving parts and less to wear over time.

Depending upon the year of manufacture, your ZS carb might have some emission control limitations, may have little or no shade-tree adjustability and might even be sealed against "tampering". There were both ZS and SUs with some weird features that generally aren't good for performance, such as an anti-runon valve in the butterfly plate. So, a swap of carb models might do a lot to improve performance. Watch out though if you have to pass an emissions inspection with the car!

For that matter, Weber DCOE are not street-legal here in Calif., I don't know about New Jersey. And, of course, I'd certainly never encourage you to do anything illegal!

A carb swap by itself, without other matching engine improvements, won't give all that much performance boost, might just get the car back to where is was when the car was new and the carbs were in top working order. You really need to add a hotter cam, perhaps increase compression, do some porting, install headers and a freer flowing exhaust system, etc. before you will start to realize the full potential of the carbs. Of course, some of this can be done in steps and a carb swap might just be the starting point (they would need re-jetting/retuning once other mods are done).

p.s. Yes, I'd forgotten about PRI. I've seen their one-carb-per-cylinder setup on a GT6 at a car show. It looked really neat and sounded like a demon! I didn't get to drive it or even a ride, though, so can't say how well it actually performs. It seems like it should really go, though! https://www.prirace.com is their website

 

[Trevor Triumph]

What about the twin HS4s with the European manifold? TSI sells manifolds and SUs. That would change to car to European spec. I understand to get the most from the Webers the header and other engine mods might be in order. T.T.

 

[Lionheart]

Hey, thanks for all that input!

I have emailed Jeff at Paltech to see how much he wants for an HS4 carb. I also have a bid in on the Weber 45 DCOE 9 on Ebay...but that may not last.

I am not concerned with emissions, as I am switching the reg to 'collector' in the spring (limited to 3000 miles/yr...no inspection). I will also NOT be racing the Spit, just tooling around the local area or down to LBI, so that's not a problem.

In the back of my mind, I think anything that I can flog on Ebay is an OK investment. The Weber setup seems infinitely re-saleable.

I'll see how the Weber 45 auction goes...if that doesn't work out, I'll go for the HS4. (The Weber definitely gets 'cool-points'.)

Thanks Again,
Len

 

[tdskip]

I went with a dual carb Euro set up from Ted.

Here is his store; https://www.tsimportedautomotive.com/

These are the ones I bought;

https://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=220057506015&ssPageName=ADME:B:EF:US:2

He was good to deal with, but be aware that the carbs still need an overhaul.

I haven't installed them yet....

 

[CaptDon01]

Anyone have some pictures of the single SU on the stock 1500 manifold?

Don

 

[Lionheart]

Anyone have some pictures of the single SU on the stock 1500 manifold?

Don

Eventually.

I lost the Weber DCOE 45 auction on Ebay, so I'm going to order an HS4 from Jeff at Paltech. $200

 

[Lionheart]

OK, so I haven't ordered the HS4 yet. Did some looking around and found this:
https://www.webercarbsdirect.com/product_p/wk054-34.htm
I must say the price is very attractive vs other conversion kit options.

Anyone have any experience using a DGV/DGC carb on the 1500 motor?

Any reason this wouldn't make a good reliable street carb?

Thanks,
Len

 

[heliguy]

My 80 Spit came with the single Stromberg. It was "acceptable". I found a used Webber DGV, re-built it and installed it on a cannon manifold. Much better performance than the Stomberg and easier to tune ( once it was jetted correctly) Used that for about 2 years and came across a set of HS4's. Looked great, ran great and out performed the webber hands down!
For the money you are going to spend, go with the SU's!

 

[eejay56]

My 78 Spit has a Weber DGV and I'm real happy with it. Tuneup is a breeze. I plan to add a header and expect I'll need to rejet it.

 

[Lionheart]

I just had to have a DCOE.

OK, so here's where I'm at now:
Got a like-new 40 DCOE carb on Ebay (~$185 shipped)
Got a Cannon manifold from Jam Engineering (~$120)
Got the Braden Weber carb book on Ebay (~$14)

Now I figure I'll spend about $100 on chokes and jets.
(Any input on sizes for these would be appreciated.)

Wish me luck!

Len

 

[Lionheart]

For the record, here is how it came out:

Installed the single DCOE 40 and header.
Fired up with no problem.
Idle much improved.
Acceleration much improved.
Sound much improved.
...and it's just such a COOL carb!
(Installed a homebrew heat shield to ensure the above statement remains true.)

Here's the specs:
Idle jet: 45F9
Main jet: 125
Emulsion tube: F11
Chokes: 27
Accel pump jet: 50
Air corrector: 160

I bought a Carter electric fuel pump, but decided to try it with the stock mech pump...works fine! Now I'm debating whether to install the bloody thing or not.

Have another matched pair of DCOE 40's awaiting install now. Maybe next year.

Take Care,
Len

 

[DNK]

I'll take the carter for a song!

 

[Jerseygirl]

Lionheart, where in Jersey are you? Just curious to know if there's another Spit "in my neighborhood" and I don't know about it. I'm near Princeton.

We're going to be converting my 1500 from it's ZS carb to a pair of HS2's sometime this spring. Can't wait. I've got the same problem you had with the ZS. The car runs really rich right now.

Glad to hear your conversion went well.

 

[Lionheart]

Lionheart, where in Jersey are you?

I'll give you a hint:
It's the ultimate gated community.

Answer: McGuire AFB

Princeton is not too far away.

 

[hondo402000]

Mikunis for sale, I have 3 that I was going to put on my tr6, I am selling them for 400 each including the adapter to bolt to the manifold and a KN filter, you will need to get a cable from PRI, Chris says he has life time support on the carb he sells no matter who you get them from
PM me if you are interested, also have a goodparts triple manifold for strombergs(sp)