Hard Starting Hot

[Rich72C10]

Got my truck back today. Short story: Carburetor is untunable and is a turd

The shop owner is good friends with another local shop owner that is a Chevy Racer/Quadrajet lover. After I get my "old" Carburetor back on, he wants me to bring this one to him on Monday. He wants to do a deep dive with the other shop owner. He wants to understand how can a supposedly rebuilt carburetor can be so horrible.

Also, zero charge - basically he feels really bad for me.

[j_cst_10]

Buy a Holley and be done with this.
Posted via Mobile Device

[Rich72C10]

That's not the point, I been on a mission to replace this '78 Carter with a matching number '72 Quadrajet. Though I didn't think it would be this problemic!

[Carl Spangler]

Wow................ this is almost like a scary sci-fi movie.

Sorry for the dark humor! Good luck with getting this carb sorted out or replaced.

[j_cst_10]

I give you credit for sticking with it. I’ve followed this from the beginning. I understand wanting to stick to a factory set up if that’s your thing.

I’ve owned plenty of vehicles with Qjets and I don’t mind them but honestly would never choose one of them over a Holley square bore for a toy vehicle. Part throttle is superior with the larger primary side. You give up some mpg but for occasional use vehicles not a big deal
In my mind. Super easy to tune and rebuild even for a novice.

Drive a Qjet engine then slap a Holley on with a cheap adapter and it will feel like a different vehicle.
Posted via Mobile Device

[HO455]

The fact is that some carburetors cannot be made to work properly.
Improperly machined at the factory, physically damaged at some point, allowed to get wet and corrode or just mismatched components. The tolerances inside are small and precise. A couple thousands here or there and the fuel and air cannot not flow as designed.
See my earlier post 162.
Any ideas on how many Qjets GM replaced under warranty?
How many of those are still floating around being resold as NOS carburetors?
I know of one very rare Pontiac Qjet that has been bought and sold a number of times for big money. A beautiful looking carburetor that simply will not work.

I wish you the best of luck finding what you want. If you can't find the problem and need a new core let me know and I can make some calls.

[ChevyGuyNC]

Originally Posted by Rich72C10

That's not the point, I been on a mission to replace this '78 Carter with a matching number '72 Quadrajet. Though I didn't think it would be this problemic!

Wow Rich so sorry about that. I'd be sick spending as much $$ and time only to find it's a dud.

If the shop can't figure/fix and you still want a correct QJet, give National Carb here in Jacksonville a try. They have one that matches the # on my truck and reasonably priced. I'll take mine there if/when I decide to rebuild.

[Steeveedee]

Originally Posted by Rich72C10

That's not the point, I been on a mission to replace this '78 Carter with a matching number '72 Quadrajet. Though I didn't think it would be this problemic!

I can understand wanting originality. I met my wife in 1980, and rebuilt the carburetor on my FiL's truck at least once, back in the day, as I was a mechanic then. Rebuild it, set it up right, FiL had no complaints. We inherited the truck in 2009. I had issues with gas drying up in it due to not driving it, but got that taken care of. In that entire time, I've not changed anything except rebuild parts. It still has the original metering rods and jets! All those mods to the circuits on yours were completely unnecessary, IMO. I'd suggest finding another unmodified carburetor with the right part number and starting over, if you are set on that. BUT, if that "wrong" carb works, I'd leave well enough alone. What is your final intent? Concourse original, or not?

[body bolt]

Enquiring minds want to know. Keep us posted. I hope your truck is running well now.

Originally Posted by Rich72C10

He wants to do a deep dive with the other shop owner. He wants to understand how can a supposedly rebuilt carburetor can be so horrible.

[Rich72C10]

Thanks guys, nice to have you alls support

I was really feeling like a idiot not being able to get this sorted out, which is why I punted to the shop. Luckily I have got a good place to go to, not sure how he could let me out the door for free...

There isn't a real reason for the matching number carb other than I started down the road getting a new carb and decided on getting one that matched the truck. This getting a new carb goes back to May 2020, since my brother wasn't 100% sure how well he would be able to rebuild the '78 one (he never worked on a Quadrajet before). So I decided to go top self and not to cheap out. Funny thing, my shop guy says the one my brother rebuilt was/is running perfectly and describes driving my truck as: "it drives like a new old truck with your old carb".

Thank you for the offers on other carbs ... I am not sure if I have the stomach to spend more cash on another carburetor....

PS: On the upside I can swap carbs in like 10 minutes now.... I don't even forget a clip or a vacuum hose anymore ;-)

[Rich72C10]

Originally Posted by body bolt

Enquiring minds want to know. Keep us posted. I hope your truck is running well now.

She is back to her normal self... which is starting right up and idling properly. Though they say, the grass is always greener on the other side .... until you actually get to the other side!

I'll update on any details I get.

Thanks again!

[Rich72C10]

I am back to one pump in the morning and starts right up in proper fast idle. I am soooo frustrated.

I can't believe the the response I got from Quadrajet Power. You'd think they would want to know what the F**k went wrong, if they are soooo good and experience. With other projects, when a repair has gone wrong I guess I have been lucky with people that actually care what they do. Case in point, I been working a 1948 Wurlitzer. After having the mech rebuilt and brought home it fell flat on it face within a hour or so. The repairman drove out on a Sunday, pulled the mech out and redid the job, replacing even more hard to find parts. Delivered it backed, installed it and insured it worked and I was happy. Zero charge to the travel, re-work, or parts. His opinion, it was his fault and I shouldn't have been allowed to take it home from his shop.

Then we have Quadrajet that can hardly return a email, won't offer any real advise, or even allow for a call.

Originally Posted by Quadrajet Power

I have only built a few thousand Quadrajets. How many has he seen? I’m really sorry you can’t tune it or find someone that can. We have tried our best to help.

[Rich72C10]

interesting, very recent BBB review can be found here below. I swear this guy is my twin on experience with their carb rebuild....

https://www.bbb.org/us/tx/boerne/pro...stomer-reviews

[body bolt]

I agree, they should have left it stock. It would have run fine and they'd at least have had a baseline. It's not a race car.

Originally Posted by Steeveedee

I can understand wanting originality. I met my wife in 1980, and rebuilt the carburetor on my FiL's truck at least once, back in the day, as I was a mechanic then. Rebuild it, set it up right, FiL had no complaints. We inherited the truck in 2009. I had issues with gas drying up in it due to not driving it, but got that taken care of. In that entire time, I've not changed anything except rebuild parts. It still has the original metering rods and jets! All those mods to the circuits on yours were completely unnecessary, IMO. I'd suggest finding another unmodified carburetor with the right part number and starting over, if you are set on that. BUT, if that "wrong" carb works, I'd leave well enough alone. What is your final intent? Concourse original, or not?

[Rich72C10]

I explicitly told them I was a stock truck with only a mild cam. I told them it was a truck and in no way was a racer or ever would be. I wanted a solid reliable carburetor with a balance of power on WOT and gas milage. I was mainly interested in the bushings for the throttle mod. I am not sure how I could be more clear with them. I then said I leave it to you guys, as the experts.

Live and learn. It was a expensive lesson in cash and time!

Edit: I did a review on the BBB site in Central Texas and this is their response:

Originally Posted by Quadrajet Power

We are sorry he couldn't tune it. Quadrajets are all we build and we have an 8 month backlog. Only a few return of the thousands we have build over the years for customers all over the world. It is difficult for us to tune remote for someone not willing to follow our advice. This customer went to forums for advice and would tell us what we need to do to help. We offered our help, and tried to tune it as close as possible when it was returned. He continued to tell us we knew nothing about these and the internet forums were his source of info. Again, sorry we couldn't help you. We offer support by email, and not by phone. We assist many whether they purchase from us or not and cannot do the volume by phone or our backlog would be even longer. We are thankful for all of our business and our thousands of very pleased customers. There are a few that we just cannot help with their needs.

[Rich72C10]

A bit of a update. I was reading another thread where someone recommended Cliffs High Performance Quadrajets. What a super nice fellow and seems to be crazy smart / knowledgeable about Qjets and SBC! I have gotten more information out of Cliff in a few emails then I got from Mark/Quadrajet Power in nearly a year. He also gets "repaired" Quadrajet Power carbs that Mark has messed up, so I am not the only one it seems.

Direct Quote from Cliff after he asked a bunch of question about my engine:

Your problems are two fold here.

993 heads are EXCELLENT for flow but have 76cc chambers.

You used “builder” 350 pistons which are dished and typically around .025-.035” in the holes at TDC. The head gaskets were most likely from a standard “kit” so would have been at least .040” and possible even .050-.060” thick. So quench is far from ideal and in the .055-.095” range someplace instead of .035-.038”.

Then you put in a larger “RV” cam, most are 204/214/112LSA.

The original engine had the pistons .015-.018” below the deck at TDC and .020” steel shim head gaskets for .035-.038” quench. This yielded about 8.2 to 8.5 to 1 compression with the factory dished pistons. Cam was 194/204 duration so it made great vacuum, butt loads of low end power and strong mid-range power.

The pistons and head gaskets used for your “build” LOWERED the compression ratio quite a bit. Not your fault, even the most skilled machine shops do this ALL THE TIME. They don’t know about all that stuff, they just machine engine components and sell parts to go with them. It’s probably down around 7.5-7.7 to 1 or so. Add a larger cam and it will be “soft” at lower RPM’s, but still shine pretty decent from about 2500-4800rpm’s or so.

The lower compression deal REQUIRES more timing and fuel to keep things happy.

Then you trumped the entire deal with “remanufactured” carburetors. Cripe, I can NOT make them work well without considerable effort as they are “butchered” all to chit and not using stock specs anyplace.

After telling him that I got my Rochester Quadrajet 7042208 from USA Carburetors he told me this:

USA carburetors is BOTTOM of the barrel and probably why Mark couldn’t do anything with it either, they are “hacked” pretty hard and often butchered up enough difficult to get working correctly.

This is what he told me about Quadrajet Power / Mark:

Mark wasn’t able to get it done, and he’s better than most. I still get a few of his carbs in here on occasion with fundamental issues. Did two last month one was leaking under the seat due to a “crater” where the gasket seals. Another one for a stout 355 SBC in a 1970 Nova just wasn’t calibrated close enough for the larger cam the guy decided to install in it.

After all this is still thinks he can get my Rochester Quadrajet 7042208 running properly but does think I should just start over (because it came from USA Carburetors but I don't know where to find a good 7042208 core). Heck his cost is only like 1/3 of what Quadrajet Power charged me and 5 months faster to get to it too. I wished I'd find this guy before even starting the rebuild of my SBC 350!

So I am going to give this a try .... like I told him, in for a penny, in for a pound LOL

Edit: though it seems the piston installed look like the ones that came out of my engine.

[ChevyGuyNC]

Originally Posted by Rich72C10

A bit of a update. I was reading another thread where someone recommended Cliffs High Performance Quadrajets. What a super nice fellow and seems to be crazy smart / knowledgeable about Qjets and SBC! I have gotten more information out of Cliff in a few emails then I got from Mark/Quadrajet Power in nearly a year. He also gets "repaired" Quadrajet Power carbs that Mark has messed up, so I am not the only one it seems.

Direct Quote from Cliff after he asked a bunch of question about my engine:


After telling him that I got my Rochester Quadrajet 7042208 from USA Carburetors he told me this:


This is what he told me about Quadrajet Power / Mark:


After all this is still thinks he can get my Rochester Quadrajet 7042208 running properly but does think I should just start over (because it came from USA Carburetors but I don't know where to find a good 7042208 core). Heck his cost is only like 1/3 of what Quadrajet Power charged me and 5 months faster to get to it too. I wished I'd find this guy before even starting the rebuild of my SBC 350!

So I am going to give this a try .... like I told him, in for a penny, in for a pound LOL

Edit: though it seems the piston installed look like the ones that came out of my engine.

Hey Rich, I found Cliff too, and you're right, he really knows QJets and SBC's. I actually called him and we spoke for about 45 mins, and I decided to get his kit and do the rebuild myself... Haven't done it yet, but plan to, and knowing he's a quick email or call away made it a good choice.

Good luck with yours, I'm sure Cliff will do it right.

[body bolt]

"Then you trumped the entire deal with “remanufactured” carburetors. Cripe, I can NOT make them work well without considerable effort as they are “butchered” all to chit and not using stock specs anyplace."

I like this.

Your carb in factory original form should work fine so I don't understand why the other place was tweaking it.

[Rich72C10]

FYI: My truck didn't come with the factory original but one from O'Riley's that is a '78 carb. Which was done by the previous owner of my truck.

The idea was to get a numbers matching Rochester Quadrajet 7042208 and when it took 3 to get one that seem right (long story on that), I decided it have it professionally worked on.

Needless to say, epic fail on my part. Live and learn. Perhaps my pain will help someone else make a better informed decisions. If that happens, I'd would actually feel a lot better about this whole thing.

[body bolt]

Years ago I bought what was supposed to be a rebuilt 7041211 for my '71. It worked OK but when I had to rebuild it I found it had a primary choke valve that was impossible for it to open completely. I don't know why I never noticed that but I don't drive with my foot in it. Also, the choke pull-off and rods were wrong.

[lil hoodlum]

Originally Posted by Rich72C10

FYI: My truck didn't come with the factory original but one from O'Riley's that is a '78 carb. Which was done by the previous owner of my truck.

The idea was to get a numbers matching Rochester Quadrajet 7042208 and when it took 3 to get one that seem right (long story on that), I decided it have it professionally worked on.

Needless to say, epic fail on my part. Live and learn. Perhaps my pain will help someone else make a better informed decisions. If that happens, I'd would actually feel a lot better about this whole thing.

I've had quadrajet issues as well with my 1968 C10 with 327. Years ago I bought one from classicindustries with a numbers matching quadrajet carb. Actually ran pretty well out of the box. Since then I have bought carburetors from O'reillies auto parts, Summit Racing, and National carburetors out of Florida. The classic industries worked the best for me and the National Carburetors is what I'm running now and does ok, not great, but ok. The O'reillies one had issues that I couldn't over come and the Summit one just wouldn't work at all.

I'm no carburetor guru but it seems to me it is just the luck of the draw at this point with these old carbs...


I would love to have Cliff rebuild my carb or sell me the rebuild carb kit, but I'm limited on time as my truck is my daily driver and I count on it to get me back and forth to work nearly everyday.

[Rich72C10]

Well, my carb is re-boxed up and ready to go to Cliff. I really love his communication skills, so responsive!

His last bit of information on my pistons, which is a REAL bummer. It's not like I am going to be opening up my engine to correct this.

NEVER put dished pistons in a SBC rebuild. The 76cc heads are already reducing the compression ratio to 8 to 1 with them and that’s if you use a .020” thick OEM type head gasket. Adding a “builder” gasket just drops the compression into the 7 to 1 range and they don’t run for chit anyplace, low on torque and inefficient at low RPM’s.

Sadly very few folks know this, not even skilled machinists and engine builders. The quench distance on an SBC engine needs to be at or close to .035” for best efficiency and power. It will also use less fuel, and take less timing to make best power. Another side benefit is running much cooler, and requiring less octane........

[LNP]

I hope everything works out for you in the end. Sounds like Cliff is the answer to your issue.

[pjmoreland]

If your block was decked and your heads resurfaced, then maybe the use of "builder" head gaskets just made up for the removed material without reducing the compression or increasing quench.

[Rich72C10]

Well, there is big chance he'll tell me that I just need to cut loose my Rochester Quadrajet 7042208 and keep on with my Carter Quadrajet. Which is the recommendation of my local shop mechanic. Which he thinks I am nuts as my truck "runs like a dream" as it is. I suppose I am glutton for punishment. Heck I am already bouncing in my head, what would it actually take (cost) to switch out my pistons and use the correct gaskets to have this proper "quench distance" - which until Cliff brought it up I never heard of (no suprise there as I don't know sh*t about SBC). Just when I thought I didn't need to really do anything more to my truck LOL

Hopefully at the very least someone will stumble on this tread and get something out of it before they make their decisions on which path to take on things. That is what this all about, learning and sharing.