Summit Carb Install Gone Very Wrong

[da_raabi]

My new Summit-brand 750cfm carb showed up this week, so I decided to work on the install yesterday.

I will say this looked like a really nice carb. Simple design, looked like it was made well. The DVD instructions were helpful.

The install was fairly simple. All went well until I went to tighten down the mounting studs/nuts. Just a little bit of torque and I heard this... sound. I was working from the other side of the engine, so I could not see what was happening, but I figured it was just the gasket on the stud threads. No biggie. So I kept going. Heard the same thing on the back stud. Weird right? Well on I went. Hooked everything up and had the wife hop in and crank it over. Crank crank crank crank RUM... die. OK. Weird. Did it again and same thing.

Ok... Vacuum leak? So I started checking all the hoses etc. Then I saw this... Suffice it to say there was a vacuum leak of relative significance.

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There was nothing under the carb. The carb and the intake flanges were nice and straight. The ONLY thing I could find that was even remotely off was the included carb gasket. It's about 1/4" thick and very stiff, and it was warped. I did not think much of it because I could flatten it out with my fingers but that is literally the ONLY thing I could find that could cause this.

Fortunately Summit is warrantying the carb without issue, but how odd is this? I'll report back when I get the new one tomorrow.

 

[GXPWeasel]

Fuel lines causing the carb not to seat? They look a bit stiff, and MAYBE what could have caused the cart to not want to sit down completely on the gasket/intake...

 

[da_raabi]

Fuel line was floating completely free and I use a flex hose to connect to it, so nope. This is seriously weird dude!

 

[idahovette]

Got a cowl hood for Grandson's s10 from Summit and had a good sized dent in it, called 'em and they had another one on the way in 30 minutes. Wasn't a shipping error it was put in the box that way. Anyway good service from Summit.....maybe we were both just lucky?

 

[SquareRoot]

ahhh.....the age of Chinesium!

 

[da_raabi]

Got a cowl hood for Grandson's s10 from Summit and had a good sized dent in it, called 'em and they had another one on the way in 30 minutes. Wasn't a shipping error it was put in the box that way. Anyway good service from Summit.....maybe we were both just lucky?

More than likely. I've generally been happy with Summit-branded stuff. The headers I've got on my truck now are theirs and I'll be honest - they are sweet.

ahhh.....the age of Chinesium!

I'm thinking this is 99% of the problem right here. Too bad too because it is a nice looking carb. I just wish I could have afforded the more expensive US-made brands. I had to do something though. I've had it up to here with the Q-jet. I just can't get it right and it hates the (relative) cold weather we've had here in FL recently. So F it.

 

[Snoots]

How much you want for the Q-Jet?

 

[Knight84]

My new Summit-brand 750cfm carb showed up this week, so I decided to work on the install yesterday.

I will say this looked like a really nice carb. Simple design, looked like it was made well. The DVD instructions were helpful.

The install was fairly simple. All went well until I went to tighten down the mounting studs/nuts. Just a little bit of torque and I heard this... sound. I was working from the other side of the engine, so I could not see what was happening, but I figured it was just the gasket on the stud threads. No biggie. So I kept going. Heard the same thing on the back stud. Weird right? Well on I went. Hooked everything up and had the wife hop in and crank it over. Crank crank crank crank RUM... die. OK. Weird. Did it again and same thing.

Ok... Vacuum leak? So I started checking all the hoses etc. Then I saw this... Suffice it to say there was a vacuum leak of relative significance.

You must be registered for see images attach

You must be registered for see images attach

There was nothing under the carb. The carb and the intake flanges were nice and straight. The ONLY thing I could find that was even remotely off was the included carb gasket. It's about 1/4" thick and very stiff, and it was warped. I did not think much of it because I could flatten it out with my fingers but that is literally the ONLY thing I could find that could cause this.

Fortunately Summit is warrantying the carb without issue, but how odd is this? I'll report back when I get the new one tomorrow.

Engine masters on motortrend used the same one on an episode recently. They had to use a spacer because the circled parts of the carb hit the intake on all the ones they tried.

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[da_raabi]

Got the new carb. Inspected it, the intake, and the gasket and all were flat. Test fitted it about 4 times and verified it sat flat with no rocking.

Bolted it down without a hitch.

Friggen weird right?

Anyway all went well with the install. It fired right up, and from what I can tell I don't think it needs much tuning beyond knocking down the idle and fast idle settings. Dunno yet. Runs good though.

My only complaint was the included fuel rail. It was kinda flimsy and took a heck of a lot of torque to tighten it enough not to leak. As in enough to start to bend the tubes. Not cool man.

Other than that this thing is pretty cool. I grabbed a different throttle cable bracket too - although the jury is out on that one. The springs on it are STUPID stiff, which is not great when driving.

I'll post pics of the setup in a bit.

Oh, and I do miss the Q-Jet secondary surge. WOT just doesn't give you that "Woah!" moment. Oh well.

 

[MikeB]

Looks like simply a bad casting. As for the carb, a buddy of mine has run the 600cfm version for around 8-10 years now. It worked great out of the box, and all I had to do was adjust idle mixture and speed.

It's based on the old Holley 4010 series, with supposedly a few improvements. I used to have the 4011 spread bore version many years ago on a stock GM Q-jet manifold.

 

[SirRobyn0]

Don't beat yourself up on this. If there is something you missed and it cracked oh well, it might be a rather expensive mistake but it happens, believe me, I'm a careful mechanic to, and things break. I think thermostat housings are the most popular thing to break, but carbs happen to. Yes it could have been a bad casting. When you start changing throttle return springs just remember that having the throttle stick open because of to light of a spring really sucks. Conversely really stiff springs are hard on the throttle plate bushings over long periods of time.

 

[78C10BigTen]

My new Summit-brand 750cfm carb showed up this week, so I decided to work on the install yesterday.

I will say this looked like a really nice carb. Simple design, looked like it was made well. The DVD instructions were helpful.

The install was fairly simple. All went well until I went to tighten down the mounting studs/nuts. Just a little bit of torque and I heard this... sound. I was working from the other side of the engine, so I could not see what was happening, but I figured it was just the gasket on the stud threads. No biggie. So I kept going. Heard the same thing on the back stud. Weird right? Well on I went. Hooked everything up and had the wife hop in and crank it over. Crank crank crank crank RUM... die. OK. Weird. Did it again and same thing.

Ok... Vacuum leak? So I started checking all the hoses etc. Then I saw this... Suffice it to say there was a vacuum leak of relative significance.

You must be registered for see images attach

You must be registered for see images attach

There was nothing under the carb. The carb and the intake flanges were nice and straight. The ONLY thing I could find that was even remotely off was the included carb gasket. It's about 1/4" thick and very stiff, and it was warped. I did not think much of it because I could flatten it out with my fingers but that is literally the ONLY thing I could find that could cause this.

Fortunately Summit is warrantying the carb without issue, but how odd is this? I'll report back when I get the new one tomorrow.

It is a good lookin carb! And holy crap!, i havent seen you around in a bit!!

 

[78C10BigTen]

Don't beat yourself up on this. If there is something you missed and it cracked oh well, it might be a rather expensive mistake but it happens, believe me, I'm a careful mechanic to, and things break. I think thermostat housings are the most popular thing to break, but carbs happen to. Yes it could have been a bad casting. When you start changing throttle return springs just remember that having the throttle stick open because of to light of a spring really sucks. Conversely really stiff springs are hard on the throttle plate bushings over long periods of time.

I always liked harder return springs for a stiffer pedal. My square is like that now. But you raise a point about the bushing i haddent thought of!

 

[SirRobyn0]

I always liked harder return springs for a stiffer pedal. My square is like that now. But you raise a point about the bushing i haddent thought of!

I'm like you I always like a stiffer pedal. My wifes van the gas pedal is so light that I have to avoid putting the full weight of my foot on it, so I end up with a stiff leg from holding the weight of my foot off the pedal all the time. It's worse when I have my boots on. So far I have not had any problem with throttle plate bushings wearing out prematurely on my carbs, so I think it depends on how over board a person goes. But I have seem it at the shop, so it is something to keep in mind. I always figure if I were to wear out a bushing it was worth it for my driving pleasure. Just don't go using brake return springs, or screen door springs or anything so strong that it torques the shaft when you hook the spring up. That's my way of thinking anyway.

 

[78C10BigTen]

I'm like you I always like a stiffer pedal. My wifes van the gas pedal is so light that I have to avoid putting the full weight of my foot on it, so I end up with a stiff leg from holding the weight of my foot off the pedal all the time. It's worse when I have my boots on. So far I have not had any problem with throttle plate bushings wearing out prematurely on my carbs, so I think it depends on how over board a person goes. But I have seem it at the shop, so it is something to keep in mind. I always figure if I were to wear out a bushing it was worth it for my driving pleasure. Just don't go using brake return springs, or screen door springs or anything so strong that it torques the shaft when you hook the spring up. That's my way of thinking anyway.

Mine has 2 springs, one inside the other. Theyre stiff enough when cruisin i can let off the gas and tap my foot on the pedal with the beat of a song. Stiffer keeps me from tryin to burn out lol. When i got my s10 i had a hell of a time adjusting to the pedal! A 2wd with a 4.3L and a soft pedal... i still unintentionally lay rubber at a stop sign or light.