SBC 350 will it be mismatched much? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 06-06-2010, 09:28 AM
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SBC 350 will it be mismatched much?

My dad gave me the 350 he swapped out of his truck. it dropped a cylinder but has good compression so it's probably just a head gasket.. anyway he took everything off it and put it on the crate engine. so no carb, intake or distributor. I'm trying to put it togther cheaply. so I spent $28 on a used Holley 1850-3 600 CFM and I'll rebuild it. also got a Weiand 7546 intake for $45 which was made b4 it was called the X-celerator. but from what I can tell it runs from 1,500-6,000 RPM even tho it's a single plane, at least that's what the 7546 X-celerator is listed for.. I'm going to buy a used OEM HEI, and I will probably use some sort of headder, but I'm not sure what's going to fit my hotrod yet

the engine is a 1972 Chevy truck 350 4 bolt. 260hp/ 8.5:1 compression rated on the emissions tag of the original truck. as far as I can tell the engine is stock.

will this at least run ok?

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Old 06-06-2010, 10:43 AM
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whattya mean should "run" fine a stock 350 in a truck with a single plane though? ebay it and get a stock cast iron 4bbl and home port it with a carbide on a (dont gasket match)put new gaskets in it check for copper showing on the bearings put it all together with a fresh coat of paint and drive'er
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Old 06-06-2010, 11:48 AM
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you can cheaply rebuild a 350 these days, you should check the bottom end, and the heads for guide wear and what shape the valves are in, by the time you go in the bottom end of the motor, you mite aswell rebuild it! the machine work ant that expensive, and the machinest can get you a good set of flat tops for around $100.00, and a good cam for what you want for around the same price... the single plane wouldnt be a good, they kill the bottom end power, for the street stay with a high rise dual plane, like the performer RPM, or Stealth, or mayb the AirGap, the 600 1850 should be fine, if you use any kind of good bump cam you mite want to use a 4.5 or less power valve... with the stock heads, have a valve job done, if they the open chambers with flat tops that should get you 9.1 CR with .41 head gasket...
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Old 06-06-2010, 11:57 AM
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I'm not going to rebuild it right now, I don't have time or the budget. it didn't knock, always had good oil preassure. just dropped a cylinder 1 day, and my dad parked the truck and ordered a crate engine... the engine he took out has been sitting in dry storage with oiled cylinders for about 3 years now. which is the engine he gave me..
I'm sure the valves may have some wear, but I don't think that is why it dropped the cylinder, as the compression is good on all cylinders. most likely it's got a head gasket problem, even tho it wasn't running hot when the cylinder went down
the engine is not going in a truck, it's going in my hand built hotrod which should weigh less than 2,500 lbs
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Old 06-06-2010, 01:02 PM
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thats cool, my first 350 i bulit i left it std bore, std mains and rods, hell the short block costed $30, it had melted pistons.. it still runs good to this day, 10 years later!!
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Old 06-06-2010, 02:53 PM
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Your going to have to confirm which cylinder it dropped. If the problem isn`t obvious you`ll be removing one piston after the other trying to find the issue.
Was there another reason why it dropped a cylinder? Possibly a dead cam? broken rocker? rocker backed off? burned valves? dead rings? broken piston? Fouled plug? bad plug wire? the list goes on and if the problem lies in the rings you won`t know which cylinder it is since there not visable. If I had to take a engine most of the way apart to find the problem I`d rebuild it, may as well when it`s that far down.
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Old 06-06-2010, 03:02 PM
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I'm wondering what you mean by "dropped a cylinder".

If the compression is the same (+/- 10 PSI) on all 8 cylinders, then it's not likely a mechanical (piston, rings, or valve) issue, right?
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Old 06-06-2010, 04:25 PM
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Quote:
Originally Posted by DoubleVision
Your going to have to confirm which cylinder it dropped. If the problem isn`t obvious you`ll be removing one piston after the other trying to find the issue.
Was there another reason why it dropped a cylinder? Possibly a dead cam? broken rocker? rocker backed off? burned valves? dead rings? broken piston? Fouled plug? bad plug wire? the list goes on and if the problem lies in the rings you won`t know which cylinder it is since there not visable. If I had to take a engine most of the way apart to find the problem I`d rebuild it, may as well when it`s that far down.
my dad was driving on the interstate when it developed an intermittant miss, and eventully by the time he got home, it was firing on 7 cylinders... compression across all 8 cylinders was perfect and oil down the cylinder did nothing for it, no broken rockers and the cam isn't flat ( ran it w/ valve covers off and there was nothing out of the ordinary ). so it's probably just the head gasket.. I'm going to pull the heads in any case and check things out.. if I rebuild it, I will buy a 383 rotating kit, but I can't afford that right now, so the engine may be just a mock up engine for now, if it does need any internal attention, but I really don't think it does... my dad just wanted a shiny new fresh engine. that's why it got swapped
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Old 06-06-2010, 05:19 PM
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If you have got good compression in ALL cylinders there is nothing wrong with the head gasket. Could be intake gasket leak, burnt valve, bad plug wire, cap, rotor, but NOT the head gasket.

The 7546 intake works much better if you can find or fab the divider for the plenum. The slot it fits into should already be machined into the plenum. I have seen dyno reports of 60 ft lbs and 40+ hp disappearing when the divider was removed on a mild engine.

Last edited by ericnova72; 06-07-2010 at 05:08 PM. Reason: spelling
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Old 06-07-2010, 12:42 PM
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I'd have to agree that the head gasket is OK if the compression was good.

Even if a valve was burned, that cylinder wouldn't pump as high- so you might only be looking at a secondary ignition problem, like cap, wire or plug.

Good luck!
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Old 06-07-2010, 01:16 PM
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I'm doing a similar truck (71/72 Chevy Stepside)with a 350. (To clarify, it has parts from 71 and 72 thus the 2 yr models, but only one truck.)
First things first....if it has been sitting for a couple of years....tune it up. For $40-$50, it'll save you a lot of headache and wasted time troubleshooting something that may be nothing. New plugs, fluids, cap, rotor, etc. You may find your intermittent "miss" is now missing.
Your set up sounds like it will run fine, it won't be peeling the rubber off the tires, but it will work for the time being. I intend to turn mine into a 383 also, so I understand not wanting to put much into it only to have to undo it later. I would go ahead and get the better intake though (less $$$ later).
Have fun with it and be proud of your thriftiness, not everyone has the budget to get exactly what they want when they want it. And sometimes its more fun that way.
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Old 06-07-2010, 01:28 PM
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Quote:
Originally Posted by ericnova72
...The 7546 intake works much better if you can find or fab the divider for the plenum. the slot it fits into should already be machined into the plenum. I have seen dynoreports of 60 ft lbs and 40+ hp disappearing when the divider was removed on a mild engine.
I forgot.... I believe Brothers Trucks has the divider for a reasonable price, you can do a search for them. I agree the divider would be a great idea.
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Old 06-07-2010, 07:38 PM
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i beleave they are rite the head gaskets should be good if the cyl presser is good!!!!!!!!
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Old 06-10-2010, 11:00 AM
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I got the intake, and it was made before the X-celerator name came out. just says WEIAND 7546 on it.. it also does not have the provision for the divider.. so I could effectivly assume, the engine should make 240 hp. given reoprts of this manifold producing -40 hp on mild builds when not used with the divider... that's still enough to power the 2,500 lb car

Last edited by matt167; 06-10-2010 at 11:05 AM.
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Old 06-10-2010, 11:15 AM
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Unfortunately, the best thing that can be said about the #7546 is that it doesn't weigh much. I had gotten this one in trade, we ran it twice and found it to be sorely lacking- no bottom end to speak of- which could be understood. But it didn't run that well up top, either.

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