Carb body warping...

[cjshaker]

With the recent threads on carbs and some of their issues, I thought I'd post these pictures of my current rebuild of my 3310 for my truck.

I've been fighting an idle issue that I'm sure is carb related. I had purchased a new Holley 4150 750 vacuum secondary, so instead of going through the whole process of finding the issue, then tuning the carb, I just dug out my old trusty 3310 750 that I had ran on my previous 390 for nearly 25 years. It had just started to develop a couple of issues after all those years, which I knew it obviously needed a rebuild. After I initially tuned it, I hadn't had to touch this carb in that entire time. It was just dead nuts reliable.

The hardest part was getting those old nasty gaskets off the metering block. That alone took about 5-6hrs of careful scraping with a blunt non-metallic scraper so that I didn't gouge or damage them. After that I went to check the surface straightness. It's obvious by the pictures that there were significant issues.

This was after about 5 minutes with a large fine tooth metal file.



It would have taken forever to get them right at that rate, so I upped the ante a little to speed things up. I used a fairly worn piece of 60 grit sanding belt cut to fit under the file.



I only went that route until I started to see uniform scratches across the majority of the surface. After that I went back to the file alone to smooth things back up and take out the bigger scratches left by the 60 grit. That cut the filing time down significantly and the file easily smoothed things back up.







In the end, you can still see some minor low spots, but nothing that the gaskets can't easily handle. We're only talking about .0005-.00075 at this point.

I just posted these to show people how easy it is to take care of these common issues without costing them a hundred dollars, if not well over that, by taking them to a machine shop or sending them off for weeks on end. Warpage is a common problem, especially on well used carbs. It's one of the first things a person should look for when rebuilding or refreshing a carb. And to be honest, it should be checked on new carbs also.

[jgkurz]

Interesting thread. I'm guessing you saw my BC/BD post.. 

I will probably pull down my carbs and either rebuild them myself or take them to a local "trusted" professional. They would probably run without a rebuild but I'd really like to hedge my bet and make sure they run well out of the gate.

Did the carb you rebuilt above fix the idle problem? What 2x4 carbs do you run on your 427?

[cjshaker]

I did see your post, but there have been a few lately about having some issues with carbs, so I thought this might give people a heads up to a common problem with many older carbs AS WELL as new ones. You'd be surprised how many new carbs are warped right out of the box.
I've been laid up the last few days with a bad fever so I haven't gotten it on yet, but this carb ran perfectly for over 20 years before it developed a couple issues, which I'm 99% sure was warpage related along with deteriorated gaskets. There wasn't any trash in the carb and all passages were clear. The engine it was on before is very similar to the one I got from Blair, so I don't expect to have to do much to it as far as tuning. I'll try to get it on tomorrow since I'm feeling a bit better today.

I use the BJ/BK carbs on my MR 427. They were jetted on the dyno, so after some shooter and power valve tuning (my engine has very low idle vacuum) they have been working great. It's hard to beat the factory designed carbs, they usually just need your basic tuning procedures to work well on typical street engines.

[My427stang]

Good pics!

I don't even mess around anymore, one pass with the file, if I see a dip, it gets cut at the machine shop.  Once I got a machinist trained to what I wanted it's quick and they go together nicely

[cjshaker]

I don't even mess around anymore, one pass with the file, if I see a dip, it gets cut at the machine shop.  Once I got a machinist trained to what I wanted it's quick and they go together nicely

Machining is definitely a better route to go, but this saves me a bunch of money and still gets the job done. A friend of mine owns the only local machine shop, and he's really good with his modern equipment. Unfortunately, it's just him and his boy and one other younger fellow, and they bust their butts trying to keep up with contracts with businesses. It usually takes him awhile to do any machine work when I throw him something auto related or some other project job. I know he'd REALLY like to tell me "NO!", but like I said, we're friends

The first thing I learned from him is that there is no such thing as "scrap". So of course every time I need any piece of metal for my projects, I go to him and say "I need to look in your scrap pile for........"  I always get the evil eye

And jgkurz, I did get the old 3310 installed today, and it did cure all the idle and surging problems I was having with it towards the end. It needs a little transition tuning, but otherwise runs perfectly now.

Ross, now I've got to go completely through this NEW carb to get rid of the 5-6 issues I was having with it! One of which was a steady miss that was driving me nuts (how often does a carb cause a steady miss on one cylinder?! )!! Yes, the old carb cured it and the miss is completely gone! Next time I think I'm going to try a Quick Fuel.

[My427stang]

Cool stuff, and I have no issues with a file in a good hand, nice work!

As far as carbs, my favorite has been AED for a long time when I have to buy a new one, unfortunately, they only sell double pumpers, but they do work so nice.

I am not a Quick Fuel fan, but not because of their carbs, because when I talked to their tech guys they seemed like at best, Summit guys and didn't seem to know their own stuff.  I guess I sort of judged them based on a couple of phone calls asking about their metering block emulsion design, not the carbs themselves.  That being said, a lot of people are having good luck with them

[cjshaker]

The day I call a tech line and actually get someone who can answer technical questions, I think I'd have to hang up out of pure shock..lol

[Falcon67]

Good pics!

I don't even mess around anymore, one pass with the file, if I see a dip, it gets cut at the machine shop.  Once I got a machinist trained to what I wanted it's quick and they go together nicely

I just bought a 2 1/2" 90 degree face mill to do this kind of work. 

[Falcon67]

Cheap Grizzly face mill with decent Enco inserts - test pass on scrap body

[turbohunter]

Envy meter pegging.

[fekbmax]

I got one of the Grizzly 3 way combo machines back in the late 90's. Sure it's not the best thing out there but as long as you know what you got and take your time with set up and don't try and take massive chunks it's a pretty decent home shop machine. I have gotten my moneys worth from it many many times over.

[Falcon67]

Griz (china) Square column mill - not a BP/knee mill by any stretch but still a good tool to have.  I've done a lot with it and would not even use the word "machinist" and my name in the same sentence.  I have a matching 12x36 lathe that is a nice tool also. 

[Nightmist66]

Oooh, something shiney! 

[Qikbbstang]

are carb bowl faces really machined at the factory or are they simply cast (flat) that way?............... I wonder HOW would a typical pot-metal carb base, metering plate or bowl warp?..... When you think about temps it's doubtful carbs in use ever get past 160F or there'd be no fuel left in them. Is a swing of a measly -10F to 160F enough heat to warp a bowl. At 160F will a casting warp?.... Is the torque of the bolts on bowls enough to warp a carb castings?
   The other side is carb gaskets are pretty thick the "out of true" pictured in this thread looks to be at most what three-four thousandths?............ Seems a gasket would just do the job of that clearance

[Falcon67]

They are just cast and I don't think whoever casts the parts for Holley takes much time with them.  I've never sen on that looks machined.  Compared to a ProForm or Quick Fuel replacement body, the Holley stuff looks like high school ceramic shop output.  I've done the file thing on just about every Holley I've ever owned.  I switched to using the mill recently because "tool".    Even with the good blue gaskets, I still have problems with fuel bleed over between a stock metering block and body under the gasket if the body face isn't trued up.  And you can warp a metering block trying to seal the thing to a crappy casting.  I prefer the QF blocks even on a stock Holley casting as they seal better. I have a couple of stocker Holleys that run well, but it's hard sometimes - I have a 600 that just about won't clean up at idle unless you lightly spray the metering block gaskets with HiTack.