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?
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.
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.
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.
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.
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.
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.
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.
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.
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.
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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