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Guest Message by DevFuse

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nixing the hitachi and going to a dual SU, need advice

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4 replies to this topic

#1 Alex C

Alex C

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Posted 09 January 2005 - 07:01 PM

I am getting rid of the hitachi, its worked, wont say good or bad, just worked for many many years. Anyway, I need something better. I found a pair of SU's off a older volvo of similar displacement. These are 44mm side draft cv with external float bowl. Are there any things i should do with the manifold to make these work better? any worries I should have? What vacuum lines do I need to keep? should i make a plate for the vacuum lines? If I hack the manifold what water goes through it and how should I reroute it?

Thanks in advance.


#2 kingbobdole


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Posted 09 January 2005 - 08:05 PM

I'm intrested on where exactly you plan to place side drafts in the small confines of the ru. 2 things of note. First on the stock air box, usually they use a style of built in velocity stacks, do your best to keep those around, they help. Secondly, from my experances with old Datsun 240Zs, dont worry about that coolant line. In the Z the lines run through the intake manifold to heat it, but its not a very efficent way of doing things, so it really doesnt seems to matter if you use it or not. Also check old 240s intake air boxes for those velocity stacks, they have them too.
Good luck and keep us up to date

#3 Alex C

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Posted 10 January 2005 - 01:34 PM

I am thinking of getting an extra manifold and hacking it, then making two L's so the carbs can sit side by side inbetween the manifolds and in front a bit. these are fairly small in width and legth, but not so tall as they would hit the hood. I also guess I need to find some air filters that will work. Maybe Ill make an airbox for the carbs and run a tube to the non battery side and put a filter there.

Has anyone hacked there manifold before? EA81 or 82? Do any of the rogue roo's have a spare manifold they would be willing to part with?



#4 swiftt


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Posted 10 January 2005 - 02:46 PM

I've a lot of experience with S.U.'s since I've owned british cars all my life. If those carbs are used, be sure to closely inspect the throttle shafts. The throttle shaft is steel and the carb body is aluminum. They are prone to wear and cause vacuum leaks. If they are worn, you can either buy oversized throttle shafts and have the carb body machined to accept them or you can have the carbs machined and insert a brass bushing for the shaft to mount in. The latter is the preference as it will provide longer life and can be easily serviced into the future with the replacement of the bushings.

FYI, I'm guessing, but it sounds like you have HS6's. If you want to run dual carbs, these are pretty large for a < 2.0litre application. It's definately do-able, and even preferred, if you have a hot motor. It may be difficult to tune with a stock engine though. You may want to consider running only a single HS6. If you go to the later, HIF4's, they have the brass bushing already installed. In a dual application, the size of these is more appropriate for a stock 1.8 application too. HIF4's also have an attached float bowl which may prove an advantage when mounting...?

Also note that twin S.U. carbs are not the same as twin DCOE carbs. While DCOE's can be setup and almost forgotten, be prepared to continually tinker with your S.U.'s to keep them synced and running efficiently. This could prove a pain if it's your daily driver.

Some trivia: HS2, HS4, HS6, HIF4, etc are all S.U. carb models. The number in the model represents the throat size, in 1/8ths of an inch + 1.

For example: HS2: 1 + 2(1/8)=1.25" throat
HS4: 1 + 4(1/8)=1.5" throat
HS6: 1 + 6(1/8)=1.75" throat

Have fun with it!

#5 Alex C

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Posted 11 January 2005 - 12:45 AM

I know its a 44mm throat, or 1.75 inches, and they have external floats, and they came off a 1.4-1.8 volvo engine(the pair that is). so i am assuming it is an appropriate amount of carburation for what I have (EA81 with an aftermarket torque cam). I am not sure which cam I have though, just that it is higher torque. Ill look at the shafts and see whats going on tomorrow at work. I do know for 30$ for the pair I dont think i should run away.



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