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Feb 21, 2008 19:26:15 GMT
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The big problem with oversized SUs, which makes them REALLY useless, is that they just wont open fully! You can be blatting along at full throttle, peak rpm.. and the carb pistons are only half open. That is why the HS8s wont offer anything at all over HS6s, which are already more than big enough.
A 45mm carb on a harley isn't that silly. If we are talking 1300cc, that is the same carb to displacement ratio as an MG metro engine, which is also an antique design. Apples to oranges obviously, but it isn't apples to broken ball point pens.
An NA 4 pot that makes enough power to use a pair of hs8s would be a rare animal. Anything hot enough to make the 200+ horsepower would be enough of a monster that the last thing you would want would be the damped movement of the SU pistons. It wouldn't be wise, but it would be possible. SUs are not great for all out racing engines, they are built primarily to make civilised road engines. Besides, a modern head will have 4 ports.. So you would want 4 HIF38s instead of just two carbs!
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loon
Posted a lot
Posts: 1,092
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Feb 21, 2008 21:07:03 GMT
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Since that ford model B (I assume) 3.3 litre engine makes 40-50 horse out of the box, and road tuned ones are about 70 horse, with new head, cam, carb, and manifolds, that is still a long way short of the kind of power range the HS8s are known to cover, unless it is an extremely hot engine of some kind. Obviously, only 4ever4 can tell us what its current power output is. 114.3 BHP @ 3910 rpm (98 mph) 188.8 lBft @ 2450 rpm thanks seth you have just made the other point 188.8lbft of torque without this you will be sitting at the lights i can drive my amazon at 25mph in 4th gear (without laboring) because of the torque and it will go up to 70 ;)before i flick it into overdrive |
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what the fcuk have you done lately
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Enbloc
Part of things
Posts: 353
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Feb 21, 2008 21:20:55 GMT
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What's the carbs that currently on it ? Carbs are Stromberg 97's. They are original fitment on mid 30's Ford V8's more commonly known as flathead V8's. |
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Enbloc
Part of things
Posts: 353
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Feb 21, 2008 21:34:17 GMT
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Also, I think it's worth it to mention that 188 ft/lbs is an amazing amount, and if he were to use the larger carbs to gain more top end, he could probably afford to spare a few ft/lbs down low and still have a car with top notch driveability. I think this sums it up for me. I think its a little unfair to compare HS8's to the the current output of 114 bhp because the reason for stepping up to the HS8's is to INCREASE the power output. If I wanted to stay with the current output but run SU's, then your suggestion of HS6's is valid. I'm sure your going to tell me now that a single HS2 is the best choice! Change of subject.... Balance tubes on manifolds, yes or no? Opinions? |
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Feb 22, 2008 14:02:02 GMT
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Well, it is your car.. but do you really think new carbs are going to take your 114 horsepower to over 200? That just isn't going to happen. Even with HS6s, you will never reach their flow limit, the carbs would be sitting comfortably in the middle of their flow range even at a hugely optimistic 150 horse.
Fit HS8s if you like, but you will be kicking yourself when they never actually open fully! It isn't worth bodging at all. The rolling road setup that SUs need is going to set you back £150 at least, and you don't want to pay it twice.
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slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
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School Me On All Things SU.... slater
@slater
Club Retro Rides Member 78
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Feb 22, 2008 16:45:04 GMT
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This thread is mad!
They are definatly bigger then optimal considering you say you want economy and drivability!
No arguements from me.
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Enbloc
Part of things
Posts: 353
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Feb 22, 2008 17:31:19 GMT
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They are definatly bigger then optimal considering you say you want economy and drivability! I should have put a smiley after that orignal comment as it was a little tongue in cheek. You have to bare in mind what my current set-up is. I'm running nearly 75 year old carbs! They're very basic and very inefficent in all areas (Airflow, fuel economy, driveability, tuneability.)! Changing to SU's, even if they are, in some peoples options too large for this application, should, on paper at least, be a considerable improvement over the current set-up in all the above areas. |
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Last Edit: Feb 22, 2008 17:35:05 GMT by Enbloc
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Feb 22, 2008 19:07:17 GMT
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The SU isn't exactly a new design either! The basic concept has been in use for over 100 years, and the H series have been around since before ww2. It is a good, and robust design though.
I really don't see what the problem is.. Giving the HS8s a polish, sticking them on the 'bay, and buying a set of hs6s with the proceeds is hardly the end of the world. A pair of HS6s are no more costly. The HS4s are the ones with the scene tax on.
The difference in top end power between them, will be nil. However, the hs6s will do better in throttle response, torque, and economy. It will be a noticeable difference too. Why compromise when it is so easy to start out with the right thing? I've told you SUs are not trivial to set up. Since the needle is infinitely adjustable, it takes time, skill, and patience to get them cut right. It means a lot of time in the hands of an expensive specialist. It is worth it, no question. Add to that the cost of fabricating a manifold, and the expense and effort of getting the right carbs in the first place is minimal. It just seems wrong to spoil it.
If you don't believe me, ring the tuner who will be setting them up.
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Last Edit: Feb 22, 2008 19:07:42 GMT by rustybits
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slater
Club Retro Rides Member
Posts: 6,390
Club RR Member Number: 78
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School Me On All Things SU.... slater
@slater
Club Retro Rides Member 78
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Feb 22, 2008 21:21:29 GMT
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stick on a couple of HIF 44s and a shorrock?  |
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