greggome

Need to replace my Holley 6210 650cfm spread bore carb on my 68 327/350. Any opinions on replacing it with the same vs a Rochester quadrajet? The car is overall stock and I'll be using it for kicking around town and for some short highway runs. Holley is real familiar to me for working on if need while but Q jets seem more complicated. I'm thinking a Q jet might be more fuel efficient and peppy around town but Ive always liked the Holleys.

roadblock69

I need to ask why you feel that you need to replace the existing carb as opposed to simply rebuilding your existing?

gerry72

All you will get are opinions, some favoring the Holley, some the Quadrajet. Neither has substantial merit over the other. People who have done the Quadrajet to Holley or vice-versa (this is with otherwise functioning carburetors on either side) will tell you they notice no difference in fuel economy or performance or that the differences are too slight to have any clear cut advantage. The triple venturi in the Quadrajet does make a difference in throttle transitions since it is more sensitive to manifold signal but how that translates to it being better is more likely an application-dependent advantage. The Quadrajet is more complicated that the Holley but not really any more difficult to work on. The ways it goes about metering air and fuel are different but that's not beyond the realm of some DIYer work if you have some background knowledge.

greggome

thanks for the info. My Holley is probably 30 years old and was not used for some time. I rebuilt it via a kit and have been having low vacuum and idling issues. i have taken it on and off 4 times so far to check on possible issues. all port/vents flow clear. Just replaced my power valve with another one which seemed to help my idle but stopping at a light the RPM drops down occasionally to almost stalling unless I feather the pedal. Vacuum still is low about 10. I have checked the manifold carb/ mounts via propane to pickup on possible leaks areas, checked hoses, vacuum connections etc. with no luck. Local mechanic feels problems probably stemming from carb and suggested I just replace it. he favored quadriajet over Holley for around town responsiveness but felt either was okay. I know opinions vary just checking to see others experiences running one vs the other.

marshal135

Greg,
I went with the edelbrock 1401. It mounts the same as 68 stock set up.
You can find them for sale here and eBay.
I put the edelbrock on and cleared up a bunch of issues related to the carb.
I made the mistake of buying a commercial rebuild quadrajet off ebay. It was a mistake.
No regrets with the 1401.
Marshal

7t9l82

hard to beat a new in the box carb. definitely Holley over edelbrock.

johnt365

It's a tough choice.

You probably already have a box of Holley tuning parts and you are already familiar with the Holley.

I have had both Holley and Quad on my car and have a Qjet on it now. If I did a Qjet I would recommend one with the APT feature. I installed a wideband O2 gauge and found that using the APT screw really allows you to dial in your part throttle A/F ratio.

On the Holley I had, the accelerator pump shot was very tunable and parts are locally availible but fine tuning a part throttle cruise was not near as easy as with a Qjet equipped with APT.

The Qjet I have required reducing the size of the air bleeds to get the calibration right. Cliff Ruggles sells these little "tap in" reducers for this purpose.

694speed350

greggome

hard to find spread bore carbs that are new. Holleys all seem to be reconditioned eg. 6210 and edelbrock doeskin seem to have spread bores on their site either. cant locate a new 1401 either.

Karsten

How about taking a look at Quick Fuel Carbs. From what I understand they are a modernized version of the Holley.

I bought a QF 680 for my 375 hp 350 as that is what ATK recommended but I believe QF also offers a 650 CFM as well.

Karsten

terrys6t8roadster

Running a Holley 650 spreadbore DP mechanical secondaries on the 69 L48. Runs and starts great. It's still available. Combined MPG 22, 3.08 screws and 200r4. T

cardo0

The 6210 holley is a mechanical secondary carb. For a better street carb u could try the Holley 0-80555C which has vacuum secondaries. A vac sec carb wont be as punchy as a double pumper - smoother acceleration. Holley, Summit and Jegs sell those carbs (as well as the 6210) new for the same price (all of them are $470 new). Changing to a Qjet will require changing back to stock throttle bracket. Your 6210 uses a divorced choke and u may want to consider an electric choke.

Best deal for u would be a Summit M2008, 600cfm square bore, vac sec carb with electric choke - has leakfree body and other upgrades over original style Holleys. This requires new fuel inlet tubing, square bore intake and possible throttle cable bracket. But it is a modern version of a carb that Holley designed and sold for a few years. Only $280.

If u want a modern carb then try a new Demon 1900 for $313 summit/jegs. Electric choke and has an air vlv like the qet for air metering and something called a "goggle vlv" - leakfree body also. Requires a square bore intake. Its marketed by Holley as a Holley product now.

https://www.holley.com/products/fuel...mon/parts/1900

Too many choices for a new carb. Good luck.

greggome

anyone have experience with rebuilt units?

cardo0

Let us know when actually know what u want or are looking for.

Tom454

The throttle shaft bore is probably worn out. An unpredictable idle in the absence of any other defects is the symptom. It can be fixed. Try the propane specifically around the throttle shaft.

greggome

I'd like to stick with what I have for an easy swap. Holley 6210 650 CFM.

I'll try the propane again as suggested around the throttle shaft. Would this also create a vacuum problem? Mines running at 10. Ive checked all over the place with no success. Even did the smoke test out of despiration but smoke just comes up out of carbs primary and secondary bores. Hoping a carb replacement will fix problem.

jb78L-82

Holley 4175 650 CFM vacuum secondary Q-jet replacement has been on my car since 1985.Easy to tune, easy to rebuild, Electric Choke, little to no difference in fuel economy versus the OEM Q-jet. A great simple Holley carb that is very street able. Changed the main jet to a bigger jet for the L-82 355 I just built and I was surprised that the engine ran so well with the AFR aluminum 180 64 CC heads, roller cam, and 10.2:1 compression. The carb is not dialed in yet but not a stumble from cold start, smooth at idle, tremendous power and perfect transitioning to the secondaries above 3,000 RPM-nothing…not a hiccup. I was very surprised.

Tom454

Yes... a very worn throttle shaft/bore will cause low vac. Give it s shot. You can't lose anything.