flooding holley carb on '67 300 hp

[William F.]

In a recent thread I thought I had a vacuum leak . May, but I definitely have carb flooding. After stopping engine ,can see gasoline accumulating on top of primary throttle valves -can't tell if coming from idle transfer slots or from leak in air horn to throttle body gasket. Also some fuel on outside bottom of carb appearing to come from primary throttle shafts.
I changed needle valve/seat and set float-no change. I haven't looked inside float bowl for dirt or soggy float. What to do next? In past on other Corvette with holley, problem was air horn-throttle body gasket.
All help appreciated,thanks,
William Ford

[Bill I.]

Re: flooding holley carb on '67 300 hp

Bill, suggest you pull the bowls and check for crap and readjust float levels. Bill

[Timothy B.]

Re: flooding holley carb on '67 300 hp

William,

I suspect your Holley needs to be carefully taken apart and the surfaces of the main body and throttle body checked and sanded flat.

I use a piece of plate glass 4" wide with 220 wet paper as this fits in the main body nicely and will work on the sides also.

The throttle body needs to be checked also for flatness, both top and bottom and after removing the throttle blades and linkage this can be done on a flat table with a piece of 220 paper..

If you find excess play in the throttle shaft bore, the teflon bushings will generally tighten the secondary throttle shafts but you may need to rebush the primary shaft bore.

The secondary metering plate also needs to be checked/sanded for flat, this is a bad problem with the 4160 holley. It's really not that bad once you do one so don't get crazy over it. Just replacing the gaskets will not cure the problem for long if at all..

[William F.]

Re: flooding holley carb on '67 300 hp

I brought bowl scres up to correct torque that that stopped 99% of problem Still have intermittent vacuum leak whistle. On 3oo hp engine does stainless steel baffle go next to carb with base gasket underneath and on manifold or other way around?

Thanks

[John H.]

Re: flooding holley carb on '67 300 hp

On 3oo hp engine does stainless steel baffle go next to carb with base gasket underneath and on manifold or other way around?

Thanks

Bill -

The base gasket goes on the manifold first, then the stainless baffle, then the carb.

You mentioned that you changed the needle and seat and adjusted the float level, but haven't seen the inside of the float bowl; a previous owner must have changed the float bowl, as a 3810 doesn't have externally-adjustable floats - you have to remove the float bowl to change the needle and seat or set the float level. Photo below of a 3810 primary float bowl.

[William F.]

Re: flooding holley carb on '67 300 hp

John Hinkley,

I certainly respect your Corvette knowledge, but my 67 300 hp is a non A.I.R. engine, supposed to be the original carb, and the '67 Chevy shop manual shows adjusting floats externally. Are you sure the carb for a "67 300 hp didn't have externally adjustable floats?

[Gerard F.]

Re: flooding holley carb on '67 300 hp

John Hinkley,

I certainly respect your Corvette knowledge, but my 67 300 hp is a non A.I.R. engine, supposed to be the original carb, and the '67 Chevy shop manual shows adjusting floats externally. Are you sure the carb for a "67 300 hp didn't have externally adjustable floats?

William,

The 67 base engine carb, list 3810 and other 67 holley side inlet carbs do not have externally adjustable floats. The engine fuel section in the 67 Service Manual is just a generic manual for all carbs and does not show the carbs with non externally adjustable floats. You have to look in the 67 Chassis Overhaul Manual to find the 67 carbs with non -externally adjustable floats.

That is one thing that always confused me, it is not in the 67 service manual

[Patrick T.]

Re: flooding holley carb on '67 300 hp

About 4 years ago, my original #3810 Holley was leaking like a sieve, so on John's advice, I sent it to Jerry MacNeish, who restored and rebuilt it to like new and it never leaked and the car ran great.

Then about 3 weeks ago, it developed a small leak where the fuel line goes into the carb, which is no good and very hazardous. Turns out the threads inside the front fuel bowl somehow got stripped and there is no choice but to replace the front bowl.

I called Jerry and he said he could fix it but due to his heavy racing schedule now, it would take quite a while for him to get to it. So as many have said here, I sent it to Custom Rebuilt Carburetors in Middlesex, N.J. and I should get it back this week.

I swear, I don't see how the threads inside the primary bowl could be stripped all of sudden, when I have not touched that area except four years ago, when I hooked up the fuel line. PT

http://customrebuiltcarbs.com/index.shtml

[Larry M.]

Re: flooding holley carb on '67 300 hp

John Hinkley,

I certainly respect your Corvette knowledge, but my 67 300 hp is a non A.I.R. engine, supposed to be the original carb, and the '67 Chevy shop manual shows adjusting floats externally. Are you sure the carb for a "67 300 hp didn't have externally adjustable floats?

Bill:

As John and Gerry have already said, the #3810 for 1967 327 corvette engines does not have external adjustable floats. I wish it were not so......a lot more trouble for many of us.

How does the carb date match up with your car build date? Bowls could also have been changed by someone over the last 40 years who wanted the external adjustable feature.

Larry

[Larry M.]

Re: flooding holley carb on '67 300 hp

I swear, I don't see how the threads inside the primary bowl could be stripped all of sudden, when I have not touched that area except four years ago, when I hooked up the fuel line. PT

Pat:

Do you run leaded fuel?? The lead scavengers contain chlorides and bromides that can cause corrosion....especially if any moisture or water is present.

Larry

[William F.]

Re: flooding holley carb on '67 300 hp

Please educate me. How do I tell:
(1) whether I have a 3810 carb but someone in past has changed fuel bowls to ones with externally adjustable floats(my throttle linkage has the kickdown tab that I didn't have on a '66 with 3367 carb)or whether this is a 3367?
(2)How to find build date of my carb?
(3) Did absolutely no '67 300 hp's come with externally adjustable floats?

Thanks in advance!

[Patrick T.]

Re: flooding holley carb on '67 300 hp

Pat:

Do you run leaded fuel?? The lead scavengers contain chlorides and bromides that can cause corrosion....especially if any moisture or water is present. Larry

Larry, I've always run 93 unleaded fuel but it sounds like you've got a point. Thanks PT

[Timothy B.]

Re: flooding holley carb on '67 300 hp

William,

The air horn should have a GM part # stamped into it and below that the LIST # stamped should be 3810. The date code follows on the third row and should be a three digit date, year, month and week. For the month, the number 1 to 0 is January thru October then A= November and B= December.

[Patrick T.]

Re: flooding holley carb on '67 300 hp

William,

The air horn should have a GM part # stamped into it and below that the LIST # stamped should be 3810. The date code follows on the third row and should be a three digit date, year, month and week. For the month, the number 1 to 0 is January thru October then A= November and B= December.

William, here is a picture of my '67 carb. Up in the right hand corner is List-3810 and below it is 763. The 7 is (1967), the 6 is (June), and the 3 is the (third week of June).

[Gerard F.]

Re: flooding holley carb on '67 300 hp

William, here is a picture of my '67 carb. Up in the right hand corner is List-3810 and below it is 763. The 7 is (1967), the 6 is (June), and the 3 is the (third week of June).

PT,

What's your VIN and the date on your engine stamp pad, we must be pretty close. The Vin on my 67 S/B 300HP is 22049 (June 29 by the book) and my engine stamp pad date is 0626. The reason I ask is that I just acquired a 3810 with a date code of 763 as in the picture above of yours, and am getting ready to restore it.

763- 1967 third week of June is just one week before my engine assembly and I'm wondering if it is too close. I'm wondering if any one has seen any Holley later, a 764 or 771. Maybe the 763 was the last of the batch.

BTW here's the current 3810 on my car, a 751 which I restored myself, plated or colored every part on it in my garage: