Gday gday i need help as the numbskull so called carby "GURU" led me way up the garden path "they wont like anything over 2 psi" at this idles fine driving on the other hand is a different story, surges flat out so thought id turn it up and tried it several times. now at limit of reg but have a bigger one ill fit tomoz as it only does it a little when its slightly loaded and at about 2500 to 3000 I'm guessing as tach isnt fitted yet. Sorry they are 1 1/2" in size and press is now 5.5psi. thanks

I'm also running an electric pump.

stu.

Edited October 7, 200620 yr by kickn5k

When i was having my 1.5" SU's tuned, i was advised that SU's generally do not need more than 3PSI. Anymore pressure than that, and it can ruin the needle and seats. Higher pressures (7-10psi) will overpower the float mechanism in the carburettor and cause flooding. I believe 2.5PSI is optimal. Most articles also recommend a fuel flow rate of 15gph.

 

The damper oil is very crucial too. I found that engine oil (20w/50) worked well for street use. ATF oil was too thin and allowed the piston to rise up too soon. Make sure the oil levels are topped up too.

 

I can recommend a bloke in Cheltenham that i used in the past. Very helpful and more than happy to help out. He also has a carb balancing tool. Let me know if you find a Dyno tune shop that are confident in tuning SU's. I called numerous shops, and unfortunately they only deal in Holleys, Webers etc.

 

Sandringham Automotive Engineers

303 Reserve Rd

Cheltenham

9553 4939

 

This link is for an article that i found to be very informative, and helped me out more than once.CLICK

 

Some Links Of Interest:

Balancer

Tuning Tips

Needle Chart

Edited October 7, 200620 yr by kangaroosa

I concur.

 

Anything over 3 psi is bad. As Kangaroosa said, needle and seat damage will occur if you keep pumping more in. If these are on a decent 5K, they may be a bit small for the engine. I had a 1360 race motor, and the 1.5's were borderline too small.

 

I used ATF in the pots. Worked for me. Get them dyno'd and see what happens.

Rob, i'm gunna dissagree with ya here....OMG I KNOW! lol

 

Having had twin 1.5" SU's on my 5K for a while and having it on the dyno a couple of times i can clearly see that with the right needles and a bit of trial and error these should go pretty bloody hard....it's just getting the time and money to get them tuned.....I shall let you know how i go with these after next weekend, as i am getting a carby guy that loves SU's to have a look at them.

 

I've only had a little eletronic pump in the car, never had an issue.

Edited October 8, 200620 yr by Xany

just backed them off now, my carby tuner will V8 man has dyno and we might get him to chuck her on with a sniffer to see what she is actually doing. The needles and main jets were purchased through a MG guy and had same setup on a reasonably strong street MG 1500 no probs. Was just trying to get a drive tune as have next size richer needle may try them on dyno, until then might try a ricker base idle tune to get her regoed thanks heaps for info keep updated.

I'm running 1.75 su's on my ke20 with holden turbo'd 202

an finding the engine oil in the damper to be hell of alot better ,more responsive , i run my fuel pressure at 4-5psi max an no problems there , did have a slight leak when i first played with them but that was due to the float pin got stuck leaving the needle an seat to stay open.

ive got my mate at work to photo copy his su tuning guide book (the pages i most needed) and it goes through needle sizes for the application which is needed,

what to look for , tuning of singles an doubles, there is alot of information in there which helped me a lot as i was in total blank when it came to these carbys :n: .

if i remember i try to get the name of the manual for you next time i see him at work. its a pretty decent thick little manual may be worth grabbing youself one . :2thumbs:

 

cheers adam

I'm running 1.75 su's on my ke20 with holden turbo'd 202

a what the what the on the what size did you say and in huh? nothing exceeds like excess i spose, rip a mean skid though. i didint mean carby size either.

Seriously though i backed it off as i said to 3psi wound the main down almost a turn again(3 and a bit turns now) and drives and pulls great not reving it to hard as bedding in gapless rings. fix front end and reg then off to dyno to just power run it with the sniffer on then take it from there.

Thanks for all your information guys its been a great help!!!

stu.

Edited October 9, 200620 yr by kickn5k

Gday gday i need help as the numbskull so called carby "GURU" led me way up the garden path "they wont like anything over 2 psi" at this idles fine driving on the other hand is a different story, surges flat out so thought id turn it up and tried it several times. now at limit of reg but have a bigger one ill fit tomoz as it only does it a little when its slightly loaded and at about 2500 to 3000 I'm guessing as tach isnt fitted yet. Sorry they are 1 1/2" in size and press is now 5.5psi. thanks

I'm also running an electric pump.

stu.

 

Hi.

I ran a pair of 1.5" Hitachi SUs (off a Datsun 1600) which look like a copy of the HS4 1.5" SUs used on MGBs etc. on my 5K engined race car for a while. I put rebuild kits into them and left the standard needles in place. I used an electric pump and regulator set to 2.5 psi. They ran very well after road tuning and balancing them, a little rich in the mid range but no flat spots and good throttle response. I used 10W30 oil in the dampers. I'm sure I could have got them better on a dyno and exhaust sniffer Cold starts were not as easy as with the old webers.

When I put the rebuilt Webers back on there was a performance gain but not that much. I'd be happy with a well tuned set of 1.5" SUs on a warm 5K.

I got mine tuned and balanced today and far out what an incredible difference that made. The guy who tuned them recommended a regulator with 2psi fuel pressure otherwise it damages the needles and seats. I highly recommend getting your su's tuned as it makes one hell of a difference. :y:

Edited October 10, 200620 yr by Corolla_Kid

I've actually been trying to hunt around for some air filters for my HS4's.....you think i can find anyone that can help me.....grrr

I've actually been trying to hunt around for some air filters for my HS4's.....you think i can find anyone that can help me.....grrr

 

Hi.

I used Ramflow filters made in Australia. Search "Ramflow" and you can (or could) order on line. They work and fit very well and the replacement filter elements are cheap. The air filter bodies are made with a range of different mounting off sets to suit any clearance problems. Its a while back but I think they cost about $40 each. There is an ebay seller that stocks them too. Look under MG in the car section.

I've actually been trying to hunt around for some air filters for my HS4's.....you think i can find anyone that can help me.....grrr

 

What sort of mounts do you have? I got mine from carbitz and they were to fit a borg warner or something like that. Try taking your filters in and say match these. :y: good luck mate.

I've actually been trying to hunt around for some air filters for my HS4's.....you think i can find anyone that can help me.....grrr

 

 

I used Ram tubes and socks. Purchased them from Hardiman Auto Supplies.

Hi.

I used Ramflow filters made in Australia. Search "Ramflow" and you can (or could) order on line. They work and fit very well and the replacement filter elements are cheap. The air filter bodies are made with a range of different mounting off sets to suit any clearance problems. Its a while back but I think they cost about $40 each. There is an ebay seller that stocks them too. Look under MG in the car section.

 

Sorry mate but i would NEVER EVER use a ramflo air filter again after i saw one ignite.....those things should be bloody illegal. I'm thinking about the ramtubes and socks idea.....i've been trying to get some cheapies...lol.....failing that i could probably get some more unifilters (looks at empty wallet).

Simon, what happened to the finer filters that were on it?

 

I may still have one ram tube and the socks, too........