General Category > Quadrajet Carb Talk and Tips
Divorced choke and headers
von:
Just FWIW I had a stock Q jet and intake on my '69 396 with the stock divorced choke and headers. The choke worked fine. The heat riser passage in the intake was open.
77cruiser:
How tight is the choke set with the engine cold? Maybe it could be adjusted a bit lighter?
Cliff Ruggles:
I suspect other issues. Even with the addition or headers and removing the heat riser valve in the exhaust manifold the intake should get so hot in less than two minutes your hand would literally melt to it if you touched the pad where the divorced choke sits.
Still using the stock intake?
Stock thickness gasket under the carburetor?
Intake gaskets open at the crossover?
If stock intake when was the last time the carbon was cleaned from the crossover?
The electric choke "conversions" that attach to a divorced choke carb are "flimsy" and complicated and I wouldn't recommend that route.
The electric divorced choke replacements are OK, but I still use and prefer the stock divorced choke coils. Might be time for a replacement if the intake is heating up quickly after start-up.......
Cliff Ruggles:
For those reading this I'll tell my first header story. It dates clear back to the early 1980's but worth the read. I purchased a 1979 K-5 Blazer with about 60,000 hard miles on it. It had the 400 small block engine, TH350 and 12 bolt locking diff. I absolutely LOVED that vehicles and decided right after the purchase to do a couple of "upgrades".
I purchased a set of full length headers for it, which required removing the exhaust manifolds, spark plug heat shields no longer fit, etc. I was certain it was going to make it a BEAST as header manufacturers advertised. I saw NOTHING for power improvement anyplace but it did sound bad-ass with the full dual exhaust and turbo mufflers that I added. I loved it to much I tossed the cast iron manifolds and all related hardware removed into the scrap heap, which turned out to be a BAD move on my part.
About a week into the header install I developed a loud "tick" at start up from one cylinder. It wasn't that noticeable at first but every morning on a cold start it got louder and louder then didn't go away and turned into a blah, blah, blah, blah even after it was warmed up. What I thought initially was a rocker arm tick was an exhaust gasket blown at one of the flanges. I replaced the gasket on that side, good to go. Then about a week later same damn thing from the other side so fixed that deal. Then a collector gasket blew out, one side then the other. Repairs were made, "improved" materials used, good to go once again.
.....continued
Cliff Ruggles:
Then we decided to take a long road trip to NC from Virginia where I was stationed at that time. It was early summer and really heating up outside. Steady cruising down the highway there was a LOT of heat coming from the floorboards, so much so that the ice cold A/C all the way up wasn't enough and my wife was picking her feet up and putting them on the seat and bitching at me most of the trip.
Then we pulled off for our first fuel stop. Topped off the tank, jumped quickly back in, turned the key and NOTHING......WTF? The starter was ceased up. I beat on it some with a hammer and made a half dozen trips to the bathroom sink at the convenience store to fetch water to throw on it. FINALLY it cooled down, groaned just a tad but started the engine.....cool....back on the road.
So we're back on the highway rolling along nicely and the engine develops a "miss". Not too bad at first then it got steady enough I pulled over to take a look. I opened the hood only to find a plug wire that was somewhat close to one of the tubes on the drivers side had spark jumping over to a header tube. I messed with the routing some and back on the road but ended up buying a new set of wires at the first opportunity and replacing it with some serious manipulating to gain as much clearance to that header tube as possible.
We finished the trip and stayed with friends on the Outer Banks of NC. Got up bright and early the next morning and loaded up for a day of beach fun and surf fishing. Cranked up the Blazer and the annoying "tick" had returned as I'd blown another flange gasket. Talk about a kick in the nuts, but I loaded up the wife and kids and off to the beach we went.
I'll shorted up the long story but over the next month or so I'd warped ALL the flanges torqueing the piss out of the bolts and replacing flange and collector gaskets a few more times. I'd also wrapped a ton of insulating heat shield material around ALL the wires where they ran near the tubes and made a heat shield for the starter, it worked OK but looked like chit when you picked the hood up.
When it was all said and done I ended up amputating the headers and putting a set of center dump factory manifolds on that vehicle and buying a new set of OEM spark plug heat shields and long wires to run under the manifolds and come up from underneath like the factory did with that set-up.
I went on to put about a zillion hard miles on the Blazer as it was my dialer driver and family vehicle for vacationing and such. NEVER had the first issue with anything else related to cooking starters, plug wires or blowing out exhaust manifold gaskets, etc. I'll add here that there wasn't the slightest bit of power difference, exhaust sound, fuel economy or anything else between the manifolds and the headers.
I repeated that EXACT same deal with two additional GM vehicles I bought years later that showed up with headers on SBC engines in them. Part of the "upgrades" to them were REMOVING the headers and going back to manifolds and factory spark plug heat shields.
....continued
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