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Old 06-22-2022, 09:07 PM
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Default Put my big boy carburetor on today ... I must be getting old!

I decided on a whim to try out the Holley 800 spreadbore I had laying around. Should be an easy swap right? I ordered a Holley trick kit and rebuilt the car and dropped the primary power valve down from 8.5 (original) to 6.5.

Of course my dual feed lines were to short center to center ( I knew that) so I bought a 3/8" inverted flare T and inverted flare to hose fittings for a temp "hose job" rather than go through the trouble of bending and flaring new hard lines until I was sure I liked the way it ran.

I had a Chevy Quadrajet throttle bracket to use and went to install. Started with the original mounting studs and the thick base gasket ... studs were too long and the carb studs hit the underside of the float bowls.

I picked up some shorter studs and went with a thin gasket. I tried to fiddle the locking nuts on but there still wasn't enough clearance between the top of the stud to the bottom of the float bowls. I tried short bolts (3/4" long) and of course they couldn't be angled into the holes in the carb flange without hitting the float bowls ... back to the studs. I gently wedged a flat-blade screwdriver between the gasket and carb base flange to raise the car until just a couple threads were exposed and started the nuts. Then I had to back the screwdriver wedges out a bit at a time until I could drop the carb and finger tighten the nuts.

Speaking of tightening the 4 nuts down ... that was nuts. I had to run to the hardware store and buy a bifold door bottom pivot just to get the thin, stamped adjusting wrench they come with so I could tighten the nuts as no normal wrench could work on two of the nuts..

Fired it up and was immediately overcome by the smell of gas. Shut her off to find all the hose fittings leaking like a sieve. I used Edelman fittings and found that their inverted flare fittings don't match their inverted flare distribution block. They only threaded the fittings part way and they run out of threads before the inside flare makes good contact.

I am bending new steel lines tomorrow with brake line and tube nuts that are full body-threaded right up to the underside of the nut. Honestly, I don't remember this stuff being so difficult. Hey, it's a simple carb swap, right?

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Last edited by b-man; 06-23-2022 at 03:20 PM. Reason: Removed Godzilla-size images
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Old 06-22-2022, 09:18 PM
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be interesting to see how you like it when sorted out,

i have the same carb on a iron 1968 q'jet intake going to put it on my 462 this winter

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Old 06-22-2022, 10:46 PM
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I thought you had the Slayer on your car and really liked it. Do you think the Holley will run better than the vacuum secondary Slayer? I was actually going to buy a Slayer based on a previous post you made so I am interested on how the Holley compares.

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Old 06-22-2022, 10:49 PM
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I hate the Holley mounting nuts.

George

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Old 06-22-2022, 10:58 PM
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Short time I had it running I could tell the throttle response was way better than the QuickFuel slayer that I had on it. Just starting it up it ran better cold even with no choke. Immediately settled into an idle.

Did you have to monkey with mounting studs also? I've never seen anything so basic as carb studs and nuts requiring installation precision. It was like doing brain surgery (in 90+ degree heat in the garage) just to mount the frickin' thing.

My intake is dual mount but shaped for a Qjet. I really like the idea of eliminating the adaptor plate and having the throttle bores aligned with the intake plenum shape. I think it's going to make a big difference. I've also got the feeling the mechanical secondaries and the TH400 kickdown are going to make life interesting.

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  #6  
Old 06-23-2022, 02:34 AM
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Quote:
Originally Posted by West Coast GTO View Post
I thought you had the Slayer on your car and really liked it. Do you think the Holley will run better than the vacuum secondary Slayer? I was actually going to buy a Slayer based on a previous post you made so I am interested on how the Holley compares.
Yeah, I did like the Slayer. It ran pretty well and I liked it better than the Holley Street Avenger I had before it. Bear in mind this is a spread-bore like a Quadrajet. I just thought I'd try this one out for fun which that turned out to be no fun installing so far.

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Old 06-23-2022, 02:54 AM
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Smaller pics, The originals are full screen on my monitor but others are saying they have to scroll to see the full pics.










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  #8  
Old 06-23-2022, 07:33 AM
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No pain no gain. You'd think going Holley to Holley would be easier. I like the old gold finish, hard to find new these days. I'm interested in your results.

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69 GTO 467, 850 Holley, T2, Edelbrock Dport 310cfm w Ram Air manifolds, HFT 245/251D .561/.594L, T400, 9" w 3.50s 3905lbs 11.64@ 114, 1.59/ 60'
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Old 06-23-2022, 07:41 AM
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I have in the past installed the center body on the manifold first then attached the metering plates and bowls

just makes it easier with some carbs particularly if you already have them apart prior

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Old 06-23-2022, 07:47 AM
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These carbs are a pain to mount! I have a wrench ground down to get on the nuts. I used to run one years ago. Nothing ran better. Worked especially well with a stick shift! I only switched to a Q-jet because I could slow down the secondary opening rate on launch at the track. Made my 60 foot times better and more consistent.

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Old 06-23-2022, 07:59 AM
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Good looking result. Despite saying i prefer the Q-JET, my 68 GTO still has the 1050 Holley for regular Street use.

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Old 06-23-2022, 08:24 AM
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When purchased new the Holley spreadbore carbuetorts came with four thin mounting nuts that used a 7/16 wrench.

This is why I always tell folks when they want to test a part at the track to install it before hand and then switch back to the original parts they know will fit.

I always liked the way the spreadbore Holleys looked.

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Old 06-23-2022, 10:14 AM
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Quote:
Originally Posted by Formulas View Post
I have in the past installed the center body on the manifold first then attached the metering plates and bowls

just makes it easier with some carbs particularly if you already have them apart prior

Yeah, that thought flashed through my hard head for a moment, but hard heads do things the hard way sometimes.

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Old 06-23-2022, 11:16 AM
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Since the newest Holley I ever installed was a haystack Holley on a 1956 Ford, I have no personal experience with your issue.

But from the posted pictures, I think after I tried the first one; I would have gone back into the shop, turned on the A.C., measured the O.D. of the nut, pulled out a piece of hex brass the next size smaller, and fabricated 4 new nuts from the smaller O.D. hex on the lathe. Take about 10 minutes.

If these things are that much trouble, someone somewhere probably has them for sale.

Jon.

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Old 06-23-2022, 11:29 AM
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Quote:
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Since the newest Holley I ever installed was a haystack Holley on a 1956 Ford, I have no personal experience with your issue.

But from the posted pictures, I think after I tried the first one; I would have gone back into the shop, turned on the A.C., measured the O.D. of the nut, pulled out a piece of hex brass the next size smaller, and fabricated 4 new nuts from the smaller O.D. hex on the lathe. Take about 10 minutes.

If these things are that much trouble, someone somewhere probably has them for sale.

Jon.
You're a different breed of cat. I am a house cat that downsized to a condo after retiring. I can literally carry my shop down the stairs to the garage in a tool bag. I don't even own a vise these days because I swore off working on my car ... you see how that worked out.

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Old 06-23-2022, 11:29 AM
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If you use a proper thickness Holley spread bore gasket, there is rarely ever any need to
find/use reduced height nuts to go on the studs. The thin paper gaskets are basically worthless.
That slight increase in carb height rarely ever changes any hood clearance dimensions.
I guess I will have to do a Spreadbore Carb thread in the carb knowledge topic.

The carb coloring on the carb looks like a rebuild shop coloring or a poor Holley coloring.

Tom V.

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Old 06-23-2022, 12:31 PM
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Based on Tom's answer above, I may have misunderstood the issue.

It looked like the issue was the sides of the nuts were too close to the side of the carburetor, in which case my solution would work well.

If, as Tom suggested, a mounting gasket of incorrect thickness is being used, easy solution; use the proper gasket.

As far as the lathe is concerned; I have several that are portable.

Other than a set of wrenches, screwdrivers, and pliers; a small machine lathe, and a small milling machine (doubles as a drill press) are difficult to do without; and they are NOT expensive.

A few years ago, I was restoring a 100-year old lamp, and needed a pair of brass number 2 by 56 thread screws 7/8 inch in length. Talk about unobtainium! Took about 10 minutes on the lathe to fabricate perfect reproductions.

Jon

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Old 06-23-2022, 01:11 PM
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The problem is that a standard 1/2" wrench doesn't get in the spot very well. The gasket thickness is really irrelevant. The studs need to be the right length for the gasket used. The studs need to just pass through the nut when tightened down. The key is to start all of the nuts a couple of threads first. Then run them down evenly, with your fingers, until snug. Then tighten them down a LITTLE more with a wrench. I ground a wrench down and it fits in no problem. I think the worst one is the rear passenger side because of the accelerator pump arm. Not sure as it has probably been 15+ years since I had it on. Be careful not to overtighten the nuts. It's easy to put the rear throttle shaft in a bind. Then it will want to hang open very slightly and cause idle problems. I even wound the secondary spring a little tighter and re-bent the end of it. This is for double-pumper carbs obviously. Mine is an 800cfm marine model.

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Old 06-23-2022, 02:56 PM
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Can we get a Moderator to FIX THIS THREAD??????????????????

Tom V.

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Old 06-23-2022, 03:13 PM
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Quote:
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Can we get a Moderator to FIX THIS THREAD??????????????????

Tom V.
Lol Tom, I usually just by-pass these, when they are dimsionally messed up

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