369 replies to this topic

[warrenm]

You'll get a 12 with those carbs without giving it a spray.

[Dave6179]

Whats the heat shield made of, whats it fixed too, and how effective is it at keeping the carbs cool(er)? Have you radiused the carbs piston leading edge? 

[SA EH]

It's an out of the box ACL heat shield, fairly weighty & solid in its construction. I held it in place with some short lengths of solid wire tied to the head & carbs, other than that it almost holds itself in if you cut it around the manifolds like I did.
My original problem was that I kept cooking the fuel in the su's & the heat soak into the manifolds was huge (this was more a dyno issue) causing dramas when tuning. The difference while stationary tuning is significant & much, much better. It was well worth doing, even for knowing the su's won't get SO hot, but as you know they still get hot.
Never heard of the radiused piston Dave, hence I haven't done it, only took all the dags & edges from the bodies. Any more info on that one??

[Dave6179]

Take the aircleaner off, where you see the bottom edge of the piston needs a 10mm radius...  to smooth the airflow into the carb. I pulled them out, removed the needles, put it in a vice... with rags etc and threw a file at them. Okay, used a file gently. Then some wet and dry paper to make the radius smooth. Refit needles, install pistons into carbs... no tuning needed, and drive. I was surprised at the difference, considering it cost nothing but 20min of my time. Hope this is clear enough, there was pics of someone elses job here recently.

[Dave6179]

Found it. Pretty good read.

http://www.gmh-toran...+su#entry727143

[SA EH]

Good stuff Dave, looks like I might be giving that one a go. No matter how much you think you've done, there's always something else you haven't... Cheers
By the way, nice job on the air cleaner piping. I'll be looking to do some kind of cold/cooler than hot air intake on mine but the EH is a bugger of an engine bay, unless I cut holes in the guard.

[gad05]

What sort of fuel pump are you using Jonesy?
Cheers Graham .

[SA EH]

It's a small block chev pump (holley) pushing 6-7 psi to the nitrous & 3-4 psi through the regulator to the su's.
Cheers

[SA EH]

Hey just throwing it out there, have you guys running 2" su's, or descent 1 3/4 su's, found it better to run no oil in the dash pots?? or springs?? or is it just whatever suits your particular motor combo that determines what you run.

[greens nice]

I run rover 2000 2 inch carb's, standard spring's. 

The design in the dashpot makes them slow to respond compared to the normal jaguar carb's.

No oil in the dashpot but my aim is to get the slide up fast, probably not ideal for the street.

I've modified them recently to be more like the jaguar carb's, havent tested them yet.

 

Where's the video's !?!!

[SA EH]

Ha, coming. All mods are done now, just finished off the carb piston chamfer, dyno booked for 16th. Re done tappets, re torqued head gasket, would love to swear here but geez this thing is responsive & loves to rev...

[warrenm]

When I was using the 1 3/4", I would drive to the track with springs & ATF in the pistons, then remove the springs & damper piston.

With the 2" on petrol, ATF in the damper & springs(Rover springs, which are light) on the road & non treated track, these carbs were Rover P6 altered similar to the Jag piston. On a treated surface I think I used engine oil in the damper, but really needed heavier springs to get rid of the bog off the line. The current carbs came of a Jag which have heavier springs, but I've never raced them with petrol.

[Dave6179]

I use a teaspoon of atf and the lightest springs (blue). Throttle response is instant.

I've tried no oil, but it got rattly, with the pistons crashing against the nylon stops, and one is now buggered.

[SA EH]

Cheers guys, just thought I'd see if there was a tried & true combo that worked for these things. Ive got the tune done for now but there's still a cough off idle when u flatten it. Will wait & see what the dyno brings...
I've got the red springs in but no oil in the dash pots, wasn't sure if I needed a bit of dash pot oil to get rid of the cough, or take some fuel out, or give it some more.

[warrenm]

Try a bit of ATF in the damper, the oil slows the rate at which the piston rises & works similar to an accelerator pump.

[Dave6179]

A cough is a lean mix. You know anyone with a ColourTune? Takes me 10 minutes to tune all three now, not the half to one hour... plus fuel, it used to cost when reading plugs after a run.

And, after a shop 'tuned' it once... not by my request, they obviously jammed a sniffer up the tailpipe. One carb was doing almost nothing and another was waaay too rich. Dickheads!

Edited by Dave6179, 02 December 2013 - 02:18 PM.

[SA EH]

Spot on fellas, put 2 1/2ml of ATF in each dashpot & she revs like a bought one! I started out tune by measuring each jet down with a micrometer so each one was level, then set throttles with one of those vacuum gizmos that goes over the carby intake. Got them pretty spot on - I hope.
I've never had a bad su tuning experience, that ive had to pay for that is...
Anyway, got the best man for the job. Can't wait to see what it does.

[Dave6179]

For some reason a lot of people reckon it's a hard job tuning SU's. Probly not trying hard enough.... I've been doing my own since I was 19.

[SA EH]

Just checked the piston spec sheet I got when they were made...
Minimum thickness at top of flat top 0.180"
Then bear in mind that each piston had 0.022" removed from the top when I had the block decked to remove o-rings. A quick check still gives me 0.158" up top so hopefully no issues arise - provided the spec sheets are somewhat correct...
Good to know though, cheers.

[N/A-PWR]

and some go as far as .017

[SA EH]

I SHOULD have left them out, for sure. There was plenty of piston/valve clearance. Once again I need one of those bloody time travel machines.

[SA EH]

Alrighty then.

So I got the tune up done today, super impressed with the work that went in to making it perform. Had to modify the springs in the dizzy & reset timing again, check & set all carby jets, idle, dashpot oil etc etc. Fitted a richer - read WAY richer - set of needles. Went from my old faithful TP set to RH.
Anyways, got 152.7kw n/a out of it. A bit over 200hp at the wheels in the old scale.
Now let me tell you that was nowhere near the 7k+ rpm I was expecting, it was 32 degrees & we were spraying water over the su bowls to keep them cool.
So on account of it being so f-ing hot, things were against us for running the gas without worrying about everything, so we finished up. Might give it another go in the new year on a cooler day, but for now, time to clock up some km's.