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Old 02-13-2019, 01:35 PM
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Blown head gasket or other problem

I am looking at a very nice 1984 Buick with a 307 Oldsmobile V8. It has low miles, but has been sitting for a long time. It will start and idle, but quickly runs out of fuel when you give it any gas at all. It seems to have a dead miss on two adjacent cylinders 4 and 6 and there is valve clatter coming from that area.

There is no antifreeze in the oil and no steam coming from the tailpipe. My guess is stuck valve lifters, worn rocker arms or a blown head gasket between cylinders.

Has anyone encountered this kind of problem?

The previous owner said it ran fine when his dad parked it in the shed years ago.

I know the fuel tank and probably the carburetor will need to be replaced, but am wondering what else I might be getting into.

Thanks for any help.

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Old 02-13-2019, 01:49 PM
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Quote:
Originally Posted by Rocketengine View Post
I am looking at a very nice 1984 Buick with a 307 Oldsmobile V8. It has low miles, but has been sitting for a long time. It will start and idle, but quickly runs out of fuel when you give it any gas at all. It seems to have a dead miss on two adjacent cylinders 4 and 6 and there is valve clatter coming from that area.

There is no antifreeze in the oil and no steam coming from the tailpipe. My guess is stuck valve lifters, worn rocker arms or a blown head gasket between cylinders.

Has anyone encountered this kind of problem?

The previous owner said it ran fine when his dad parked it in the shed years ago.

I know the fuel tank and probably the carburetor will need to be replaced, but am wondering what else I might be getting into.

Thanks for any help.
What do you mean "runs out of fuel"? If you mean the engine stumbles and stalls, that's not running out of fuel.

First, your 307 has the Computer Command Control system - called CCC. This system uses the ECU to control both timing and mixture ratio on the primary side of the Qjet. The system also controls the EGR valve, the vacuum break diaphragm, the evap system purge solenoid, and the torque converter lockup. The CCC system is based on 1970s computer technology, so it is not particularly smart about detecting failures and given the limited number of sensors, it frequently flashes error codes that are at best misleading and at worst flat wrong. Worse, the system has about ten miles of vacuum lines, and any cracked, missing, improperly connected, or mouse-chewed hose will cause the system to go apoplectic. If the carb is ever rebuilt or replaced, you MUST adjust it following the procedure in the factory service manual exactly, or you'll just end up chasing your tail. When everything is adjusted properly, these systems run pretty well, but any hiccup or shortcuts and they run like crap.
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Old 02-13-2019, 04:24 PM
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That vintage of 307 Olds is also well known for overheating and tuliping the exhaust valves, and deeply sunken exhaust valve seats on those center cylinders due to the exhaust crossover passage going to them.
IIRC it has to do with the exhaust flapper failing shut, running all the exhaust from one side of the engine to the other through that passage, even when fully warmed up. Only supposed to re-route exhaust like that during warm up, then valve in pipe opens and all exhaust goes out normally. Often as low as 50,000 miles or less.

From any performance standpoint, engine is also a total loser....it has an oddball head and nobody makes a aftermarket intake for it. Pure boat anchor, not worth the cost of rebuilding it for sure.

Compression check may reveal a lot if info, a leakdown test even more.
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Old 02-13-2019, 04:24 PM
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It is just getting enough gas to idle. Any attempt to rev it up causes it to die. I poured a few ounces of gas into the carburetor through the vent hole and it ran and revved up until the gas was gone.
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Old 02-13-2019, 04:35 PM
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Thanks, You may be on to something. I am well aware of the lack of performance of these engines, but this is a very low mileage car that has always been stored and is in excellent condition except for the current problems. If I go back to look again, I will take tools including a compression gauge and will look at the flapper valve.

Have you ever encountered rocker arms so badly worn that they created misfire? (Hoping for the best!)
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Old 02-13-2019, 04:44 PM
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Quote:
Originally Posted by ericnova72 View Post
From any performance standpoint, engine is also a total loser....it has an oddball head and nobody makes a aftermarket intake for it.
While I agree that the easiest way to upgrade a 307 is to jack up the air cleaner and slide a 350 or 403 Olds under it, your info on the heads is wrong. The OP's 84 still has the flat tappet cam and the 5A heads that have normal small block Olds ports. You are thinking of the 1985-90 roller cam 307s that have the 7A heads with the oddball peanut ports.

I've had five 1980s Oldsmobiles with this motor and never had an overheating or valve problem. One eventually spun a rod. The other four are still running just fine. That pavement-ripping 140 HP is neck-snapping.
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Old 02-13-2019, 04:49 PM
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Quote:
Originally Posted by joe_padavano View Post
While I agree that the easiest way to upgrade a 307 is to jack up the air cleaner and slide a 350 or 403 Olds under it, your info on the heads is wrong. The OP's 84 still has the flat tappet cam and the 5A heads that have normal small block Olds ports. You are thinking of the 1985-90 roller cam 307s that have the 7A heads with the oddball peanut ports.

I've had five 1980s Oldsmobiles with this motor and never had an overheating or valve problem. One eventually spun a rod. The other four are still running just fine. That pavement-ripping 140 HP is neck-snapping.
Thanks for the clarification ...my brother had two of the '87-88 years, both had that valvetrain problem.
My mistake thinking the '84 was the same. Still may be same problem though.

Some investigation by the OP is going to be necessary.
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Old 02-14-2019, 01:32 AM
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If this has a good body, interior, and underpinnings and you're not interested in a restoration as much is an enjoyable period car, I'd just stuff the engine room with a Chevy 350 or mild build 383 to get some torque, plant a decent built 700r4, bring the rear axle up to a 3.36 gear, get rid of all the computer stuff. Just build it simple, durable, and reliable then enjoy. This can be done with all factory parts.

Bogie
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Old 02-14-2019, 01:37 AM
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Do those heads have the shaft rockers that use those plastic inserts poked into holes to keep the rockers centered on the valves? Or was that Buick who did that. If so I have seen those break off and the rocker walk sideways off of the valve. Kind of a bad design.

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