How can you tell the difference between a 350 head and 305?

I just pulled the heads on my dads 350 blazer and I was wondering if the new heads are off a 305. The bolts for the rocker arms don't thread down as far
as the old ones. And there is allot of play for the valves. I don't think that it will fit. Is this the same kind of head or what?
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What is the casting number stamped where the rockers are located? I'll give ya the specs on them thar' heads...........
Doc
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think
give
It is hard to read but I think that it says 8888882 and right next to it k12 on the other side it has what appears to be 21 or 12 and there is a bunch of number further down towards the firewall that I can't read.
Used parts suck sometimes.
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That ain't the cylinder head casting number dude.
Doc

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bunch
I looked between the rocker arms and there were those numbers. Maybe I am looking in the wrong spot. Can you tell me where I might find them.
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I bet the number is 333882. See the following: SMALL BLOCK CHEVY HEAD CASTING NUMBERS
Casting Number CID Year Application Comments
330545 307, 350 73 Pass, Camaro, Chevelle, Nova All, Medium Perf 333882 350, 400 73-76 Pass 333882 350 74-76 Camaro, Z28 All w/o Steam Holes 333882 400 74-76 Chevelle, Monte Carlo w/ Steam Holes 333882 350 74-79 Truck Light Duty, w/o Steam Holes 333882 400 75-79 Blazer 4X4 Models, w/ Steam Holes 333882 400 76-80 Truck Light Duty, w/Steam Holes 340292 350 MID 70's Replacement Over the counter Hi-Perf Turbo Head 354434 262 75-76 Monza, Nova Light Castings 354434 305 76-79 Truck Light Duty, Light Castings 354434 305 76-85 Pass, Camaro Light Duty, Light Castings 358741 305 76-79 367450 262 75-76 Monza, Nova 376445 350 77-85 Truck Heavy Duty 462624 350 71-79 Camaro, Corvette Hi-Perf, Extra Manifold Bolt Hole 462624 400 75-80 Truck Light Duty, Extra Manifold Bolt Hole 462624 350 75-86 Truck Light Duty, Extra Manifold Bolt Hole 462624 350 80-85 Truck Heavy Duty, Extra Manifold Bolt Hole 462624 350 80-85 Corvette All, Extra Manifold Bolt Hole 468642 350 71-79 Truck Heavy Duty, Small Plugs 468642 400 75-80 Truck Light Duty, Small Plugs 468642 350 75-85 Truck Light Duty, Small Plugs 468642 350 80-85 Covette Small Plugs 468642 350 80-85 Truck Heavy Duty 517513 267 79-82 Pass, Malibu, Monte Carlo 3703523 265 55 Corvette 195 HP 3703523 265 55 Pass 4 BC 3725306 265 56 Corvette 2 Bolt Exhaust Manifold, 210 HP 375306 265 56 Pass 4 BC 3725306 265 Early 56 Corvette 2 Bolt Exhaust Manifols, 225 HP 3731539 283 57 Pass 4 BC & Fuel Injection 3731539 383 57 Corvette 283 HP Fuel Injection 3731539 283 57 Truck 3731554 283 57 Pass 2 BC 3731762 265 56 Pass 2X4 BC 3731762 265 56 Corvette 3 Bolt Exhaust Manifold, 240 HP 3731762 265 Late 65 Corvette 3 Bolt Exhaust Manifold, 255 HP 3740997 283 57 Pass 2X4 BC, 250 HP, Fuel Injection

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Thanks for typing all that out. I hope it wasn't to much trouble?
So then going by what you wrote here for me. The 333882 is only for 350 and up? It couldn't go on the 305, it has to be 350. When I compared the 2 heads together while it was off I had them side by side and nothing really stuck out like the valves being different sizes so unless they are really similar to the naked eye they should be the same.
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"D.L. Man" wrote:

305 and 350 heads are the same except for combustion chamber size. My guess on the stud thread length may be the difference for head that were on a engine with factory rolled lifters or not as chevy switch them over to this style lifter some time ago the the lifter is longer/taller than a flat bottomed hyd one.
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I checked the lifters off the new head and they are the same size as the old ones the push rods seem to be the same size too. And I know that they were on the lobes when I put the intake on. they seemed to fit the old engine but not my dads.
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Lifters rest in the lifter valley in the block, not the head. Lifters are shared amongst 1st Gen SBC's at .842" diameter. 1st Gen 350's generally have 76cc open chamber heads, 305's from the same era used a dished piston and 58cc closed chamber heads with a very restrictive exhaust port and smallish valves. Pushrods are also shared at 7.8" length, unless the block or heads have been decked.
Locate a set of similar heads to the ones you are replacing and be done with it.
--
Mad-Dog
'79 Chevy K-10
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were
with
I have found heads that are identical to the ones I'm taking off. Except the threaded post that adjusts valve lash don't seem to be threaded down as far as the old ones. As it turns out I don't know if I can set the rockers arms tight onto the pushrods. I was wondering if it could be different heads because of this little threaded post problem. I could just tap the post down farther if I need to. I don't know the pitch for those but it should be easy enough to figure out if I just get the big tap and die set from autoplace.
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Oh, you're dealing with variations on the rocker stud.........it should be fine in your case. Unless the lifter(s) has collapsed you wont have to run the adjuster nut down very far to achieve zero lash.
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Mad-Dog
'79 Chevy K-10
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350 and 305 and 327 and 307 heads are relatively the same head except for combustion size and valve size. If chamber size and valve match, run them. Does not matter unless you go into vortec or roller heads. Also on engine notorious for lower compressions, 307 and 305 you will find larger chambers, which does not hurt with today's fuel.

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"D.L. Man" wrote in message

new
far
Ok I have an update of what happened. I decided to see what would happen if I tried to set the lash. I got the 1 piston to TDC and I turned the crank over 90degrees and I started to set the lash. I got it down to the pushrod and it got very tight. I was relieved too. I backed it off until there was a little drag. I moved on to all of them and then I did it again to handle the other valve on the intake stroke. I set them loose to kind tough drag. But I didn't over tighten them so I didn't think that I would get any backfiring. I then put the alternator, power steering and misc brackets back on and I attempted to start it. I had to tighten the gas line but other then that it was very smooth. It took some trouble to get it going and I notice it was backfiring but I didn't set the timing so I advanced it a little and it seemed to stop back firing. I couldn't get it to idle though. I think it maybe the EGR? It sounded real smooth running although it wouldn't idle.
I was getting allot of smoke off the exhaust too. But it could be left over stuff that is burning off. I didn't see the valve cover leaking and adding anything new. I was so close to getting it back together tonight. I couldn't figure out a few vacuum lines so I thought we should pick it up in the morning.
I want to thank all of you again for helping adding the technical input that Chilton's and Haynes don't bother with. Thanks.
David
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The easiest way to set the lash is rotate the engine to TDC and adjust available valves at zero lash...no drag...just zero lash, then rotate the crank 90 degrees and do some more....another 90 and some more until after 2 complete revolutions of the crankshaft which equals 1 complete revolution of the camshaft..... once your sure you have set all the valves at zero lash then you can tighten each rocker nut another 1/2 turn without having to rotate the engine over. When it backfires it means that either the timing is retarded or the rockers on the intake side are to tight........this is assuming of course that you don't have a burnt, bent valve or stuck valve.
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Mad-Dog
'79 Chevy K-10
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