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brake booster delete

 
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After_Thought  



Joined: 08 Oct 2019
Posts: 24
Location: Hudson ohio

PostPosted: Fri Jan 17, 2020 5:35 am    Post subject: brake booster delete Reply with quote

Recently put webers on but didn't realized the intake i ordered doesn't' have an inlet that the brake booster needs. Is it possible to delete the brake booster? or is there another way around this problem.
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morghen  



Joined: 21 Jan 2005
Posts: 8155
Location: Romania

PostPosted: Fri Jan 17, 2020 6:11 am    Post subject: Reply with quote

Well mod the intake, non boosted brakes suck.
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 889
Location: Maysville, Colorado

PostPosted: Fri Jan 17, 2020 8:50 am    Post subject: Reply with quote

Morghen is right. Pull the manifold and tap one port ONLY for a 1/4" NPT and get fittings from the local hardware. There will probably be a stub for drilling on the #3 or#4 inlet port. Make sure you use a check valve also. I have been trying to figure out a booster delete on my track only car and it is a tough one.
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Mike
Poco a Poco, #033 '78 Vintage racer, SCCA Dp-81
'77 924
cricketdesigns.com
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TJC  



Joined: 04 Apr 2010
Posts: 742
Location: Central-ish Arizona, USA

PostPosted: Sat Jan 18, 2020 2:39 am    Post subject: Reply with quote

I wouldn't advocate a brake booster delete on any road car that came from the factory designed with it, UNLESS a great deal of thought and design is undertaken to replace it.
Obviously it can be done in a number of ways and performance cars with disc brakes were released without power assist but they were designed and engineered that way from the factory. As an example, my 1968 big block Corvette with disc brakes all around did not come with power assist. But it was designed with a properly sized master cylinder, proportioning valve, etc. to work compatibly to ensure proper braking and pedal feel and so forth.
Since it's a road car I would second Morghen's suggestion. For a race/track car only I would seriously look at using dual master cylinders with a balance bar and cockpit manually adjustable proportioning valve if the rules allowed. If not, it's time to do some research and get the calculator out if the booster is to be eliminated!
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'81 Porsche 924 Turbo...Parting!
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924-76  



Joined: 05 Jun 2006
Posts: 1411
Location: Ontario, Canada

PostPosted: Sat Jan 18, 2020 3:08 am    Post subject: Reply with quote

I believe some weber carb have vacuum port hidden under a screw on the top.
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After_Thought  



Joined: 08 Oct 2019
Posts: 24
Location: Hudson ohio

PostPosted: Sun Jan 19, 2020 3:18 pm    Post subject: Reply with quote

Thank you so much guys! I'm going to start looking into taping into the manifold. That sounds like a lot less work than the delete and probably a much smarter idea. Thanks
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After_Thought  



Joined: 08 Oct 2019
Posts: 24
Location: Hudson ohio

PostPosted: Sun Jan 19, 2020 3:41 pm    Post subject: Reply with quote

Oh and another question about vacuum. My vacuum line on my distributor isn't hooked up to anything. If I tapped into the manifold could I use that vacuum for the distributor? (Sorry if that's a dumb question I'm very new to working on cars)
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 889
Location: Maysville, Colorado

PostPosted: Sun Jan 19, 2020 11:55 pm    Post subject: Reply with quote

Leave the distributor plugged. Using Weber's the only vacuum line should go to the brake booster.

The static timing should be at about 10 deg BTDC(I put a mark on the crank pully). Tuning is quite different than using the stock CIS. Find the Weber tuning directions and make sure you have the correct ones, much of the internet published information is inaccurate and for an older generation of carbs.

There are two versions of the DCOE the later ones are identified by an air bypass screw which should probably not be touched and is typically covered with a small white plastic cap on the side of the barrel. The idle tuning is different than what is found on the old carbs. The newer idle adjust screw is a long taper instead of a short taper so the adjustment is quite different. I'll look it up and get back.









t
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Poco a Poco, #033 '78 Vintage racer, SCCA Dp-81
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After_Thought  



Joined: 08 Oct 2019
Posts: 24
Location: Hudson ohio

PostPosted: Mon Jan 20, 2020 3:39 am    Post subject: Reply with quote

Thank you. the correct jets for my carb should be coming sometime this week. I had bought the carbs used so it wouldn't even start it was way too rich. But tuning them is going to be rough considering I've never touched a carb in my life
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MikeJinCO  



Joined: 08 Jun 2010
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Location: Maysville, Colorado

PostPosted: Mon Jan 20, 2020 4:06 am    Post subject: Reply with quote

Set up the float levels first, if it is too high then fuel stats leaking back out the carb. I got mine used from someone who couldn't get them working and finally found the the set screws holding the venturis in place were loose, thightened them up and it started working. The trick is to get the idle right first don't worry about anything else to start with. The idle jet does everything up to about 3000 rpm, then the main takes over up to about 5500, then the air corrector manages it. There is typically a flat spot at the transition from idle to main at about 3000 and it can be tricky to get rid of. If it really bogs down and the accelerator pump is not really working the main is probably a bit rich . If it just really crashes when you floor it the accelerator pump is giving too much fuel and you need to increase the size of the bypass jet which is inside the float bowl.

Really the only way to get it all correct is find someone who really know them and have them set it up on a chassis dyno. But you can get the idle jet and it is the most important for everyday use.
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Poco a Poco, #033 '78 Vintage racer, SCCA Dp-81
'77 924
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After_Thought  



Joined: 08 Oct 2019
Posts: 24
Location: Hudson ohio

PostPosted: Mon Jan 20, 2020 4:31 am    Post subject: Reply with quote

Do you recommend these jets for the 924? They are the ones I ordered.

https://www.carbparts.eu/jetting_table
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After_Thought  



Joined: 08 Oct 2019
Posts: 24
Location: Hudson ohio

PostPosted: Mon Jan 20, 2020 4:31 am    Post subject: Reply with quote

But I can't find anything on where to start with the float bowl level
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 889
Location: Maysville, Colorado

PostPosted: Mon Jan 20, 2020 8:26 am    Post subject: Reply with quote

The 924 jets are probably a good place to start. I wouldn't worry about the emulsion tube as there a zillion of them and I think the F5 and F11 are sort of the general duty ones. Many were apparently developed for a specific engine. Go to Pierce Manifolds web site to tech help for the float level. If it is stamped 45DCO152 on top for the 45 or 151 for the 40 it is the new carburetor also the white cap on the side. The new carb idle mixture should be 2.5 to 3 turns out instead of the older 1/2 turn. The best explanation I have seen is at htttp://www.datsun2000.com/tech/weber_tuning_methodology.htm

Redline Weber and Pierce manifolds are good sources for information, they never updated their methodology when the new versions came out. I put some wheel bearing grease on the vibration mount O-rings to keep them in place during assembly.

I'm sending you a PM with my regular email and phone.
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Poco a Poco, #033 '78 Vintage racer, SCCA Dp-81
'77 924
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