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Old 07-08-2018, 10:13 PM   #15
zac
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Join Date: Jul 2008
Location: louisville, ky
Posts: 500
Re: Fuel Pump Pushrod with OEM Roller Cam

I guess my question is, what did the installation instructions say, if anything, about what pushrod to use if you choose to run a mechanical fuel pump? Since the cam had the eccentric for it, seems there would be pretty explicit instructions about it. You were obviously concerned about it. Just seems weird that they would leave us trolling discussion boards trying to figure it out.

I came across many discussions concerning going non-electronic on 87-92 Camaros, etc. Not once did I see anything concerning the distributor drive gear. "Put an old large head HEI in and run it." Most of their concerns had to do with wiring to defeat the ECM etc and dealing with ramping down the fuel pressure to the carb. I found one article on an aftermarket parts website about it, same deal. Never mentions changing the gear. Eventually I came across a discussion on a board where a guy was building a truck motor with one of these cams. He did ask about it, and a couple guys were very insistent that you don't have to worry about it. Just run the regular HEI with whatever gear is on it.

So I went out and pulled the gear off one of my spare old HEI's and compared it to the one I pulled off the '92 Camaro. The car was at the local pull and pay. It was a run of the mill RS with a TBI 305. I'm sure it had a roller cam because I pulled the timing cover off and made sure. Look at the pics I posted and see if you can tell a difference. They are identical other than the fact the Camaro one has a step down where it goes on the smaller shaft. The bottom of the hole is the same where the oil pump drive fits in. I checked.

I also looked up what the hell melonizing is. From what I can tell it's just hardening the surface of the gear with a very thin coating. Whatever coating was on the Camaro gear, the normal wear had clearly gone through it. The pics don't show it well, but you can clearly see a bright steel wear pattern. It's in the foreground in the last pic. And the regular old HEI gear looks the same to me. I realize that GM sells a melonized gear for the old-school large shaft (.491) HEI, but part of me suspects the gears have been hardened on OEM cars for a long time. It's just a matter of deciding if I want to be the guy to test that theory.
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