351w only running on 4 cylinders
01-22-2011, 10:28 PM
#11
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Join Date: Jul 2006
Location: San Diego, CA
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I ended up having to go down to Grover Beach to get a full rebuild kit, I called a bunch of stores and know one had just the gasket kit. I'll just give everything a once over I guess. I have everything soaking in some heavy duty carb cleaner now.
Getting the thicker carb base gasket is one thing that slipped my mind though. I'll see if I can make it over to get one but that means borrowing a car again. I may reuse my old thick one or just put on the thin one, we'll see. I also got a new filter so everything should be good once it's all reassembled tomorrow.
Getting the thicker carb base gasket is one thing that slipped my mind though. I'll see if I can make it over to get one but that means borrowing a car again. I may reuse my old thick one or just put on the thin one, we'll see. I also got a new filter so everything should be good once it's all reassembled tomorrow.
Last edited by 4reboy; 01-22-2011 at 11:38 PM.
01-23-2011, 01:49 AM
#15
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Location: Elk Grove, CA
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Bending a pushrod on every single cylinder supplied by that side of the intake is really long odds. Unless something on the exhaust side is messed up, pushing exhaust gases back into the intake runners during the intake stroke. But usually that results in a nice loud popping sound out the carb. Really distinct sound.
01-23-2011, 02:17 AM
#16
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Location: California
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I'd put my money on it being ignition if it's running a box. What box is it using? Most of the aftermarket units like MSD/Crane etc are set up to run on 4, 6 or 8 cylinder engines, commonly by having a cylinder selector wire that is either non connected(8 cylinder setup), connected to 12v power(6 cylinder) or grounded(4 cylinder) for instance.
What ignition box and how is it set? If you have a multi engine deal like most boxes, double check the setup for 8 cylinder firing. If something happened and it's set to 4 cylinder then it will only fire every 180* of crank rotation instead of 90, so it will not fire every other cylinder in the firing order.
What ignition box and how is it set? If you have a multi engine deal like most boxes, double check the setup for 8 cylinder firing. If something happened and it's set to 4 cylinder then it will only fire every 180* of crank rotation instead of 90, so it will not fire every other cylinder in the firing order.
01-23-2011, 12:54 PM
#18
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Join Date: Feb 2010
Location: Ohio
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is it possible you have a 302 firing order instead of a 351W firing order?
i went thru this issue years ago. put a new cam in my 289, wired it up with the firing order on the cam card (289/302) and it would only run on about 4 cylinders. rotate the distributor 180 and the other cylinders would start firing. it would backfire, push flames out the carb and everything. it took a couple weeks of screwing around with everything.
finally it was determined that the cam was actually ground on a 351W firing order. swapped the wiring around and it ran beautifully.
i went thru this issue years ago. put a new cam in my 289, wired it up with the firing order on the cam card (289/302) and it would only run on about 4 cylinders. rotate the distributor 180 and the other cylinders would start firing. it would backfire, push flames out the carb and everything. it took a couple weeks of screwing around with everything.
finally it was determined that the cam was actually ground on a 351W firing order. swapped the wiring around and it ran beautifully.
01-24-2011, 02:00 AM
#20
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I didn't realize this got so many replies today, so let me clear everything up.
It was indeed the carb as frdnut and Starfury pointed. I rebuilt the whole carb today and got it back on the car and it runs better than ever. The problem is gone, and I feel like the car gained a significant amount of power (even with my basic tune). The throttle response is very sensitive now, putting down a lot of power right off the bat.
And no, I don't have a ignition box, it is the Pertronix module that sits inside the stock distributor. I've had a problem or two with those in the past which is why I initially suspected that. And I definitely didn't have the wrong firing order, as I originally stated the problem happened after I got off the freeway, it was running fine before that.
So for all of those who find this threadlater on, if you loose a lot of cylinders check to see if they are the cylinders that one of the planes on a dual plane intake lead into. It is most likely that side of the carb that is not supplying enough fuel at idle. Luckily, if this happens two cylinders will be out on each side, so the engine is still balanced and the internals shouldn't get banged up provided you don't keep driving it like that.
The carb rebuild wasn't too difficult, it's just all about remembering where everything goes and making sure it is very clean. The exploded view diagrams that edelbrock provide came in handy. In a way I'm glad this problem happened, because now after the rebuild my car runs great. It may have only been 4 years old but it definitely needed a good cleaning.
It was indeed the carb as frdnut and Starfury pointed. I rebuilt the whole carb today and got it back on the car and it runs better than ever. The problem is gone, and I feel like the car gained a significant amount of power (even with my basic tune). The throttle response is very sensitive now, putting down a lot of power right off the bat.
And no, I don't have a ignition box, it is the Pertronix module that sits inside the stock distributor. I've had a problem or two with those in the past which is why I initially suspected that. And I definitely didn't have the wrong firing order, as I originally stated the problem happened after I got off the freeway, it was running fine before that.
So for all of those who find this threadlater on, if you loose a lot of cylinders check to see if they are the cylinders that one of the planes on a dual plane intake lead into. It is most likely that side of the carb that is not supplying enough fuel at idle. Luckily, if this happens two cylinders will be out on each side, so the engine is still balanced and the internals shouldn't get banged up provided you don't keep driving it like that.
The carb rebuild wasn't too difficult, it's just all about remembering where everything goes and making sure it is very clean. The exploded view diagrams that edelbrock provide came in handy. In a way I'm glad this problem happened, because now after the rebuild my car runs great. It may have only been 4 years old but it definitely needed a good cleaning.