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#1
05-18-2010, 07:41 PM
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Push Rods
I am getting ready to swap the heads on my 67 Full Size wagon. It has the original 143 casting heads, and I am replacing them with 1974 46 heads off of my 74 GTO to lower the compression and run cheaper gas. My question is, I understand that the early engines had shorter push rods than later ones. I think they changed them in 67, but I am not 100% sure....Will my 67 push rods be the same as the 74?
Thanks, Importsmasher |
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#2
05-18-2010, 10:09 PM
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1967 was a transition year. The valve angle changed from 20 to 14 degrees on only some of the 1967 heads, the large-valve performance-oriented heads such as the 670 and 061 had 14 degree valve angle and the longer pushrods (9.145").
Your 143 heads are the older-style 20 degree heads and should take shorter 8.715" pushrods. You will need the longer 9.145" pushrods to use the #46 heads. |
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#3
05-18-2010, 11:00 PM
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Ahhhh.....I thought I had heard something to that effect once upon a time....thanks for the info. I will get my hands on some later style push rods....
That being said, are there any valve to piston clearance issues using the later heads? I have a stock replacement cam in it. Thanks, Importsmasher |
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#4
05-18-2010, 11:19 PM
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Even though the piston valve reliefs will be in the wrong place you'll be fine with the .407" lift stock cam. The #46 heads have deeper combustion chamber than the #143 heads and that feature adds more piston to valve clearance.
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#5
05-19-2010, 01:58 PM
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That's what I figured, but I thought I would ask. Again, thanks!!
Importsmasher |
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#6
05-19-2010, 07:37 PM
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OK, so I pulled the heads off the car and (as expected) you were correct on the push rod length, b-man. But this got me thinking to an engine I built 12 years ago when I was young and ignorant (now I'm old and ignorant!). I had a tired 67 400 (actually I still have it....it is identical in every way to the one in my wagon...same block code, same heads, etc.) in a 73 Ventura, and in 1998 I rebuilt a 455 for the car. I know for sure that I wasn't aware of the push rod difference in 67 (I thought it was 66 and earlier), and I am fairly sure I pirated the push rods from the 67 400 and installed them in the 455. I still have both engines (I wrecked the Ventura; the 455 is in my 74 GTO now), and the 455 has always had some valve train clatter. I have BBC style adjustable valve train on the 455. What would happen if I did put the shorter push rods in the 455? They are like 4/10ths of an inch shorter; wouldn't that make the valves not open fully? Would it have been so obviously wrong I wouldn't have run the shorter push rods? Or is it conceivable that I could run an engine for years without noticing? I am trying to remember. The push rods are missing off of the old 400, so I think I used them. I may have to pull a push rod and measure it. I have only put a few thousand miles on the 455, but most of those were 1/4 mile at a time.
Again, thanks for your help! Importsmasher |
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#7
05-19-2010, 08:48 PM
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If the pushrods you used in the 455 were indeed the shorter ones you probably wouldn't have been able to get the rockers to adjust properly, and even if you did manage to the valve lift would be close to the same. Rocker geometry would be off with the shorter pushrods, negating some of the valve lift (not equal to the pushrod length difference though) due to the incorrect geometry and increasing valve guide wear.
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#8
05-19-2010, 09:12 PM
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B-man, that makes sense; I figured it couldn't negate 0.4 inches of valve lift (my cam is only .480), and it makes me think that I must have used the right push rods, but it's been 12 years and I can't remember. All I know for sure is that the push rods were removed from the old 400, and I know I didn't take them for any other engines. I guess I will just have to check!!! Once I get the wagon back together, I will pull a push rod and measure it and report back what I find in a couple of weeks.
Once again, Thanks!!!! Importsmasher |
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#9
06-02-2010, 08:27 PM
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OK, so apparently I am old and senile and my memory fails me....I pulled a push rod out of my 455 and it is the correct length. The push rods in the engine look new, so I obviously didn't pirate the shorter ones from my 67 400...
That being said, the correct longer push rods seem to short for my new heads on my wagon...I started a new thread asking about that. Thanks again for the responses, b-man! Importsmasher |
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