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Old 07-10-2013, 12:51 PM
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Rocker arm play, and head casting

Ok so i was looking fro my head casting numbers on sbc and they are 3973487 so does this tell me anything about motor or anything?

Also i noticed that the crane rocker arms seem to be loose maybe? I tried to wiggle them side to side and there is 1 that has a weird amount of play compared to the other ones, is there a reason for this maybe or do they do that when they need to be tightened up some?

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Old 07-10-2013, 01:02 PM
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A motor can have any number of head numbers installed by owners.

Assuming these are hydraulic lifters, there is no legitimate 'reason' for any variance in adjustment. There are several possibilities as to cause, rocker stud backing out, adjusting nut backing off, bent pushrod, cam lobe going flat, initial adjustment not correct, lifter collapse, etc.
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Old 07-10-2013, 01:24 PM
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Here's a reply from another board member on another (5-year-old) thread about these heads....

"487x heads flow the best out of all the big chamber (76cc's) medium valve heads (1.94"/1.50") these are highly sought after and would give you a small performance boost over your 624 or 882 heads.

Many classes of dirt track racing are restricted to these large chamber heads and the racers are looking for this casting number specifically.

DO NOT PORT THEM have them cleaned and checked for cracks and then sell them on ebay and put the words IMCA and WISSOTA in the title and I will gauruntee that you get $350 for the bare castings and even more if you put new valves and have a valve job done. But they may be worth more as untouched crack free originals. These are getting harder and harder to come by so you may want to hang on to them and sell them in a few years.

To boost compression use a GM performance parts 10105117 head gasket, they are advertised at .028 compressed but they are actually .021 and they are a composite with a metal core, so you don't have to worry about them leaking like a shim gasket but you get the compression boost all the same.

PM me if you want to sell those heads quick. We use them on our circle track motors."
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Old 07-10-2013, 01:48 PM
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My heads dont have the x after 487 though? Or at least i dont remember seeing it there.
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Old 07-10-2013, 02:06 PM
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Ok i did some research and apperently the x stands for 10cc larger runners and then i read that they really arent much different and the x heads are just thought to be better.
Anyways do they add any hp/tq over a stock 76 c10 bc350 motor?
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Old 07-10-2013, 02:14 PM
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Quote:
Originally Posted by chevyboy1986 View Post
Ok i did some research and apperently the x stands for 10cc larger runners and then i read that they really arent much different and the x heads are just thought to be better.
Anyways do they add any hp/tq over a stock 76 c10 bc350 motor?
I understand that your heads don't have the X, but I was simply trying to answer your question about what the heads are and if they would tell you anything about your motor. 76cc heads on a 350 street driver motor will not make a world-beater. The static compression ratio will be low (somewhere in the 8's), so there is no point trying to prop the motor up with more cam. You'll just make it worse.

If you want to go faster, sell the heads to someone who would like to circle track race them and buy a good set of aftermarket heads. None of the cast iron production Chevy heads are going to make a world-beater motor.
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Old 07-10-2013, 02:32 PM
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So are the heads off a 305 lg4 motor better then these heads? And what can i get for the heads like they are Minus my crane roller rockers?
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Old 07-10-2013, 03:16 PM
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Ok so what should i do? Now i have a few questions so here they are listed below.

1. Would buying a set of heads off an 80s or 70s sbc 350 be better then these 478 heads?

2. Would the heads off my 1986 Lg4 305 camaro motor be better then the 478 heads and other stock 350 heads.

3. My valves dont have a lot of play in them and it's like only half of them that move side to side some and the other ones have almost no play in them, and this was only checked on the one head so far.

4. Are the 478 heads on my 1976 c10 motor with a mild cam, performer intake, roller rockers, and holley 600 bad combo?

THANKS, and this black background is annoying when trying to set the typing marker lol you cant see it.
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Old 07-10-2013, 05:07 PM
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1. Performance wise. NO
2. NO
3. Valves should have no play. Must fit tightly in guide. Rocker arms will move from side to side normally. Check to see if the pushrod guide slots in the head are worn.
4. Hundreds if not thousands of this combo out there
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Old 07-10-2013, 05:42 PM
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...THANKS, and this black background is annoying when trying to set the typing marker lol you cant see it.
Change the background to white down in the lower left corner drop-down menu. Not sure what you mean though, when replying the text box is white...
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Old 07-10-2013, 05:45 PM
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Change the background to white down in the lower left corner drop-down menu. Not sure what you mean though, when replying the text box is white...
Holy crap, thanks soooo much man the black background made it a pita to see where to type lol.
Oh and my text box and background were both black, i wish the text box was white.
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Old 07-10-2013, 05:50 PM
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Originally Posted by BOBCRMAN@aol.com View Post
1. Performance wise. NO
2. NO
3. Valves should have no play. Must fit tightly in guide. Rocker arms will move from side to side normally. Check to see if the pushrod guide slots in the head are worn.
4. Hundreds if not thousands of this combo out there
Ya thats what i meant if i said it wront but the rocker arms move side to side on some of them, not drasticaly but anyways i guess it is normal.
I was offered $500-$1000 depending on it's condition he said, for the motor by a guy that does dirt track racing i guess, isnt that to much for this motor?

Btw: I think im a "Thanks Whore" lol
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Old 07-10-2013, 05:59 PM
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Originally Posted by chevyboy1986 View Post
3. My valves dont have a lot of play in them and it's like only half of them that move side to side some and the other ones have almost no play in them, and this was only checked on the one head so far.
If you're talking about the rocker arms moving some or being loose, that's normal after the engine has sat for a while. This is if there's no valve train noise w/the engine running (ticking or clacking) that would indicate a problem. The rockers loosen up when the engine is off because there's no oil pressure to keep the lifters pumped up. The valve spring pressure bleeds oil out of the lifters as the engine sits- thus the loose rockers.

Quote:
4. Are the 478 heads on my 1976 c10 motor with a mild cam, performer intake, roller rockers, and holley 600 bad combo?
Not a terrible combo as long as the cam matches the compression ratio. At this point you don't know the cam specs or the static compression ratio (SCR) so everything else is a guess. The SCR w/those heads can vary from somewhere around 8.5:1 w/12cc dished pistons to about 9:1 w/flat top (FT) pistons having 5cc valve reliefs. These figures assume a quench figure of 0.040"- it's likely you have more than that so these figures are on the high side of what you prolly have. The only way to know what you have for CR is to pull a head and measure the bore, stroke, chamber volume, the piston dish or valve relief volume, the piston deck clearance (how far the top of the piston is down the hole at TDC), the head gasket bore diameter and HG thickness.

But the bottom line is there's a direct correlation between the cam specs and the SCR. This relationship is sometimes expressed as the dynamic compression ratio (DCR). Too much CR w/a small cam is not good- it will rraise the cylinder pressure and cause the engine to damage itself by detonation. Also not good is too much cam w/not enough CR- this lowers the cylinder pressure too much and it'll run like ****.

SCR:
SCR calculator
Static compression ratio calculator

DCR:
Kelly DCR calculator
Wallace Racing DCR calculator
KB/Silvolite DCR calculator

Other:
•Various calculators from Wallace Racing.

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...this black background is annoying when trying to set the typing marker lol you cant see it.
Using a white crayon/tire marker to highlight the lines may help.
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Old 07-10-2013, 07:18 PM
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Well it was rebuilt at a shop so i doubt they put a bad cam in it, the guy doesnt ing about it oher then that the cam wasnt for hp it was for tq and should add 50# tq over stock he said, and it was sitting for the last year in a storage shed
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Old 07-10-2013, 07:24 PM
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Quote:
Originally Posted by cobalt327 View Post
If you're talking about the rocker arms moving some or being loose, that's normal after the engine has sat for a while. This is if there's no valve train noise w/the engine running (ticking or clacking) that would indicate a problem. The rockers loosen up when the engine is off because there's no oil pressure to keep the lifters pumped up. The valve spring pressure bleeds oil out of the lifters as the engine sits- thus the loose rockers.

Not a terrible combo as long as the cam matches the compression ratio. At this point you don't know the cam specs or the static compression ratio (SCR) so everything else is a guess. The SCR w/those heads can vary from somewhere around 8.5:1 w/12cc dished pistons to about 9:1 w/flat top (FT) pistons having 5cc valve reliefs. These figures assume a quench figure of 0.040"- it's likely you have more than that so these figures are on the high side of what you prolly have. The only way to know what you have for CR is to pull a head and measure the bore, stroke, chamber volume, the piston dish or valve relief volume, the piston deck clearance (how far the top of the piston is down the hole at TDC), the head gasket bore diameter and HG thickness.

But the bottom line is there's a direct correlation between the cam specs and the SCR. This relationship is sometimes expressed as the dynamic compression ratio (DCR). Too much CR w/a small cam is not good- it will rraise the cylinder pressure and cause the engine to damage itself by detonation. Also not good is too much cam w/not enough CR- this lowers the cylinder pressure too much and it'll run like ****.

SCR:
SCR calculator
Static compression ratio calculator

DCR:
Kelly DCR calculator
Wallace Racing DCR calculator
KB/Silvolite DCR calculator

Other:
•Various calculators from Wallace Racing.

Using a white crayon/tire marker to highlight the lines may help.
Man this post has me not wanting to waist more money on installing it, and to just sell the thing. So are you saying it might end up with under like 200hp and be slow as *** then blow up possibly?
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