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Old 02-18-2006, 04:32 PM   #1
R@nger
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TH-350 vacuum question

I just got my edelbrock #2701 manifold and my Holley Street Avenger 570cfm carb from summit yesterday but today when I went to install both of them I ran into a problem.

The problem is the holley fuel bowls are so long that they only leave a 3/4 inch gap between the bottom of the fuel bowl and the 3/8 vacuum port on the manifold. The way things are hooked up on my truck now this won't work. Currently a line is coming up from the modulator on my TH-350 trans and connects to a barbed fitting that screws into the vacuum port on my manifold...this barbed fittings sticks straight up so it won't work at all.

I tried buying a 3/8 male to 3/8 female 90degree fitting but it's still to tall.

Can I do away with that vacuum port and use one of the ones off my carb? I have 4 vacuum ports on the carb, #1 Power brake(using) #2 vacuum advance for distributor(using), #3 PCV(using), #4 Full manifold vacuum port(not using) Can I use that one?

How can I make this work?...how have some of you made this work?

I know I'm not the only person to ever use this combo so there has got to be a way to do it.

Thanks for the help!
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71 GMC Fleetside C15(cab), 3/4 ton, 350, Holley Street Avenger 570cfm carb, TH350 trans, Leaf-springs, 2WD.

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Last edited by R@nger; 02-18-2006 at 04:49 PM.
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Old 02-18-2006, 04:49 PM   #2
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Re: TH-350 vacuum question

can you get a spacer for the carb to solve the clearance issue???
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Old 02-18-2006, 04:50 PM   #3
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Re: TH-350 vacuum question

One of the companies make a special fitting for just that situation.
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Old 02-18-2006, 05:04 PM   #4
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Re: TH-350 vacuum question

I had the same problem when I switched to a holley, I just put a plug in the manifold and used the manifold vacuum port on the carb for the trans. Works great.
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Old 02-18-2006, 05:07 PM   #5
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Re: TH-350 vacuum question

I found it.

Edelbrock makes the special low profile fitting that clears underneath Holley fuel bowls.

http://store.summitracing.com/partde...5&autoview=sku
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Old 02-18-2006, 05:28 PM   #6
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Re: TH-350 vacuum question

Awesome, thats the exact part I was trying to find all morning and everyone said they don't make a part like that.

Personally I like the idea of using that low profile fitting as opposed to plugging the hole and using the vacuum off the carb...although Wink_tim I don't doubt for a second that it works just fine.

I was really trying to get this project done by the weekend but I think I'll just take my time and order that part...plus it's like 15-20 degrees outside and the wind is blowing and my truck won't fit in the garage, soooo ya it's a bit chilly today.

I really appreciate the help guys...I was feeling like I was stuck between a rock and a hard place...thanks so much for the help.
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71 GMC Fleetside C15(cab), 3/4 ton, 350, Holley Street Avenger 570cfm carb, TH350 trans, Leaf-springs, 2WD.

"Peter are you sleeping on the job? No I have a bug in my eye and I'm trying to suffocate him." - Family Guy

Last edited by R@nger; 02-18-2006 at 05:30 PM.
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Old 02-18-2006, 06:32 PM   #7
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Re: TH-350 vacuum question

isnt it strange that edelbrock has a fix for a problem with a holley
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Old 02-18-2006, 07:05 PM   #8
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Re: TH-350 vacuum question

That's why it took me so long to find the part for him. I looked at all of the obvious sources like Holley, transdapt. Mr Gasket, Earls, etc, first. Who would have thought it was Edelbrock who made the part?
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Old 02-18-2006, 07:45 PM   #9
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Re: TH-350 vacuum question

Ya no kidding...lol it would have taken me ages to find that darn part.
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"Peter are you sleeping on the job? No I have a bug in my eye and I'm trying to suffocate him." - Family Guy
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Old 02-18-2006, 08:12 PM   #10
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Re: TH-350 vacuum question

I got a real fast connection here at work in my office. I can have 4 or 5 pages going at once looking for something.
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Old 02-18-2006, 09:17 PM   #11
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Re: TH-350 vacuum question

Heres another question I have...it's a bit off topic but here it goes.

I bought some summit pipe plugs to plug one of the temp sender holes in my new manifold. When I screw it in it gets to the point where it seems like it can't go in anymore...problem is it's still got about 1/4 of an inch of threads stickin out, is that normal. I have never used pipe plugs before so I haven't a clue, I just assumed they would go down almost flush.
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71 GMC Fleetside C15(cab), 3/4 ton, 350, Holley Street Avenger 570cfm carb, TH350 trans, Leaf-springs, 2WD.

"Peter are you sleeping on the job? No I have a bug in my eye and I'm trying to suffocate him." - Family Guy
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Old 02-18-2006, 09:54 PM   #12
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Re: TH-350 vacuum question

That's normal.

The threads are 1/2 N.P.T. which is "national pipe thread"

They are not straight threads like a normal bolt has. They are tapered. The further you tighten, the tighter it gets. Be careful though, only tighten enough and stop. Too much can, and will, crack the manifold or fitting.

Use a sealant on pipe threads too. I use teflon paste. It will make the seal better without having to tighten it so damn tight and risk damaging something.
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Last edited by Tx Firefighter; 02-18-2006 at 09:54 PM.
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Old 02-18-2006, 10:06 PM   #13
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Re: TH-350 vacuum question

Oh ok good deal, thanks.

Although I must say it would be much more aesthetically pleasing to have them flush...ah well my truck is no show truck so it really isn't important that it looks good.
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Last edited by R@nger; 02-18-2006 at 10:08 PM.
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