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SU question


zguitar71

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I just ordered ZTherapy SU's to replace my SU's that are going on over 20 years untouched. I am planning on doing some head work on the car this winter. I have an L28 with and E31 head and will be running stock SU's with SM needles (so I guess that part is not stock). As far as I can tell the pistons are dished (I have never had the head off and the person that owned the car before took that knowledge to the grave). I would like to know what the limit of the SU's are. In other words how far can I go on the head work before I surpass the SU's abilities. I would like to go with a cam about the equivalent of the MSA stage 3, port and polish the head and go to larger valves and raise the compression to 10:1 or so. So the motor should stay at or below 7K when autocrossed or any other time it is driven hard. Do you think the stock SU's are capible of that or should I not go as far with the head? I really could not get a straight answer from the ZTherapy guys. Are they capible of making 225-250 HP with an L28? I do not want to go to tripples, I just like the SU's (can't give a good reason, I just do). Thanks for any help.

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Making 225 -250 with a 2.8 -- will be difficult enough, with or without SU's

To give you some idea how difficult.

I have just spent 5 months and a zillion pounds, designing and building a custom individual 40mm throttle body injection system with fully mapped ECU, distributorless ignition with a custom flowbenched head, 40 cc chambers and stainless big valves sitting in 3 angle seats and a big duration cam.

The engine has custom flat top pistons machined and lapped to 8 thou under deck, ARP bolts, lightened flywheel ACT big clutch, balanced everything, total seal gap-less rings, state of the art exhaust, running a static compression of nearly 11.1

We mapped it the other day on the rolling road and 4 hours later I was pleased with the 230 HP (flywheel) we achieved, I could possibly get a little more with cold air induction and a differant exhaust config but not much say another 10 or so at best.

I would be suprised if SU's flowed as well -- still we live and learn, who knows, there are people who have made big HP on SU's but with some seriously serious engine mods.

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Your wish is my command sir

I have just uploaded some to my gallery dont know how long it takes to approve

I will scan in the dyno sheet tonight (its 14:30 here) the torque curve is interesting its more like a set of peaks and troughs than a curve but thats work in progress and hopefully that will flatten out with a new exhaust set up

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I'm with you zguitar71, I just like the SU's but these triple webers in the shed may be put to the test one day. Anyways, ZTherapy can also up the size of nozzle jets, (I'm running .101 Nozzle Jets with SM Needles-no problems) also they can do some trick things to the SU bore, pistons, butterfly shafts and a few other machining processes too. Won't make them legal in certain stock race classes, if someone knows what to look for. Possibly some street driveablity may drop some due to running rich in stop & go traffic, but in W.O.T. conditions these SU mods could boost your "seat of the pants" ride!

Hey BeanDip, I'm interested in the info. regarding the SM needles too.

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