?? tapping/clapping from left exhaust pipe?? - Impala Tech
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post #1 of 6 (permalink) Old 10-15-2010, 01:42 PM Thread Starter
 
 
Join Date: Aug 2010
Location: Dover, DE
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?? tapping/clapping from left exhaust pipe??

Ok. Back in business arm is healed up got stainless plate seven screws in right forearm. So started my 68 up (307) and seems to have a tap/clap coming from left exhaust tailpipe. I am not a motorhead by any stretch of the imagination, but can find my way around a engine, but I am stumped. Is it a valve issue, exhaust issue, both I don't know. When i started her up after sittin for a couple of months I fogged the neighborhood out (white smoke) which if I am right is a coolant issue, or rings, but if I remember correctly, the smoke should have a bluish hue to it. Both tailpipes spewing like crazy under choke. Turned off car cussed moaned smoked a cig and started her back up. Running rough and just puffed smoke about 12" out the pipes. So I decided to set the gap on points. Runs much better and smoother except for the before mentioned tap/clap which was there before the points setting. I plan on swappin engine out in spring as I am in the midst of nailing down a 454 to put in it. But want to drive it threw the winter just because she is bad *** and I likke it. So what's the problem???? Motor toast. Head gasket issues, valves or what? Appreciate and help. Thanks
James
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post #2 of 6 (permalink) Old 10-16-2010, 08:40 AM
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After sitting for a few months condensation will build up in the exhaust system. Depends, but it can be quite alot. When fired up it can produce white smoke till the engine warms up and burns it off. As for the noise, Could be a lifter not pumping oil or a rocker arm -push rod problem. Or if its the passenger side it could be the heat riser valve in the exhaust.

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post #3 of 6 (permalink) Old 10-16-2010, 09:37 AM
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Agreed. Most heat riser valves rusted solid in a partly open position and stay siezed up like that. I like to replace them with a cast iron open spacer that replaces the heat riser valve that are found on three quarter and one ton trucks trucks and high performance cars.

http://www.bobschevelleparts.com/195...te-spacer.html

Yours could still be flapping if it were well oiled to keep it from rusting.

As to the lifter noise. It could be from a collapsed lifter (one that was on full open when you turned off the key and it is having a hard time pumping up again). Or a few lifters clattering that are out of adjustment due to rocker arm pressed in studs pulling out of the head.

Chevy got rid of the pressed in studs in the mid-seventies as they didn't work with stiff valve springs required to run a heavier valve train or high RPM operation.

Big Dave
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post #4 of 6 (permalink) Old 10-16-2010, 10:52 PM Thread Starter
 
 
Join Date: Aug 2010
Location: Dover, DE
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Ok then looks like I can drive it till it dies and swap out in spring. Had question about 307. Have heard that some people have put 305HO heads and mild cam which turns the 307 into a stroked 283. Is this worth it. I have a chevy truck with a six and I wont want to get rid of engine just in case I decide to sell the car I can give engine and trans with it.
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post #5 of 6 (permalink) Old 10-16-2010, 11:50 PM
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The 307 is indeed a stroked 283. The only advantage to installing a set of 305 heads is the smaller 58 cc heads (a 327 head is 64cc in size). The down side to the 305 is their small valves to fit into a tiny bore. Even a set of Power Pack 283 heads will have bigger valves. If you are looking for cheap heads; a used set of SBC 400 heads have the same large intake ports as the high performance camel hump fuelie heads, but are endoweed with huge 78 cc combustion chambers that can be filled with piston domes to get your compression back up, with out spending a lot on the heads. If you are going to be buying new pistons any way they are all the same price regardless of piston dome or dish or flat top.

Everyone I know trashes the 400 SBC heads as being usless based soley upon the chamber volume, but they are decent flowing heads if you put 2.02" intake valves and 1.72" exhaust valves. If you are buying a whole new top end (heads and intake) I would recommend the Vortec heads off of a 1996-'01 350 (5.7 liter, or 5700 Vortec) pick-up truck. They are the best flowing heads with the best combustion chambers that Chevrolet ever cast.

Big Dave
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post #6 of 6 (permalink) Old 10-25-2010, 11:29 PM Thread Starter
 
 
Join Date: Aug 2010
Location: Dover, DE
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Update to issue. Well was checking for a leak on my power steering pump and move plug wires out of way and wham, damn thing smoothed out. Let go of it and back to rough idle. Well thought to have had a cam. Ha. Nope well clap went away runs awesome. New wires new plugs and its actually fun to drive. Won't smoke the tires (thanks powerglide/307) but runs and sounds better. Short lived excitment though. Radiator is now leaking. Real bummer since the thing was replace less than a year ago. (Receipt verifies) Ah the joys or owning a classic car. But she is running better. Who cares if I can't go far.
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