Fuel Pump Pushrod with OEM Roller Cam

[zac]

Somebody gave me the short block from an ‘89 Iroc-Z Camaro. 638 2 bolt block, has fuel pump boss and is drilled for a pushrod. The cam has the fuel pump eccentric, obviously has never been used. Checked it with v blocks and dial indicator, appears to be #10066049 207/213, .415/.430@1.5. Appears to be correct for ‘89. Everything appears to be in good serviceable condition, it occurs that I could put 1.52 or 1.6 rockers on some good 462 heads I have and give it a shot, mostly for laughs. But I’m going to run a mechanical pump and I see nothing but conflicting info about the pushrod I need to use. It ranges from must use a bronze or roller tip to run a regular stock one. It seems to come down to what is the cam made of and what was the GM engineers’ intent? I did grab the distributor gear off a low perf ‘92 RS camaro but it looks like any other gear.

Any ideas?

[toolboxchev]

I have the exact same Motor someone gave me from a 88. Considering the exact same thing. What was interesting is that the heads on this one are 083 castings with a 73 stamped in them. Makes me wonder wonder if they are 73 cc chambers as they looking a bit smaller in that area.

Some say these blocks are capable of 500 ponies.

[zac]

I will qualify this by saying “I got this off the internet,” but it seems they used different heads for those years with smaller chambers and the goofy bolt holes for the intake manifold- the ones that make early intakes unusable. CR seems to have been listed around 9.3, which makes me think I would be in the 8’s with the 64cc heads, the stock dished pistons and the fat Felpro rebuilder gasket. Right where I need to be with a K20. But info is pretty scarce and I think unreliable—no doubt because this is kind of an obscure rabbit hole to go down.

[toolboxchev]

That pretty accurate there, staying away from TPI and stupid intake manifold with different heads is what I have been thinking, so far I hate the thought of dished P holes.

One local builder informed me of a oiling issue due to GM wanting to get better economy. I think it has to do with the clearances in the crank and lightweight motor oil which, of course can be changed.

Mine came equipped with the oil cooler assembly on the filter which I may decide to keep. Running a motor with a 190t-stat and oil cooler sounds like a solid idea.

[zac]

I’m thinking the GM 3704817 standard push rod is correct. That’s the one GMPP specifies for the ZZ4 crate motor with a factory roller cam.

[Tom]

Run a melonzied distributor gear to work with roller cam. Never knew there was a different fuel pump pushrod for roller cams but seeing as they never made a roller cammed carb'd engine from the factory I don't feel bad not knowing haha.

[truckster]

I bought a bronze-tipped fuel pump rod for my L31 Vortec. I figured it was cheap insurance.

[zac]

What cam are you running in the L31? I assume you can run the bronze tipped rod on anything. The distributor gear is a whole different can of worms. Melonized, composite, bronze, etc. I understand it’s all about what the cam is made of, but these cams have been around long enough that you’d think there would be less confusion. And the cam I’m looking at is from the transition twilight zone

[Tom]

Has chevy ever offered a roller cam with anything but a melonzied distributor gear? I don't know of any oem bronze gears, only melonized.

[zac]

Not that I’m aware of.....just watched a comp cams video on how to identify what material your cam is made of. It’s either cast iron, ductile iron or billet steel, apparently. Didn’t help at all. The IROC and Vortec roller cams I have don’t look like any of them in the video. I assume they are ductile iron since they are mass produced OEM

[kenn]

Hello, For my rebuild I used a Comp Cam light weight fuel pump rod that had bronze tips on it.
After starting I thought I had a bad lifter on #2, changed it out but still had the tapping.
By the time I removed the pump to check the rod the end had mushroomed to the point that I had to remove the cam to get it out.
The cam lobe was fine and is still running the stock rod.
just my 2cents. K.E.N.

[zac]

What cam are you running, kenn? I have noticed some of the GM performance roller cams appear to be billet and others ductile iron.

Here are some pics, in all of them they are IROC with fuel pump lobe, Vortec L31 and standard old cast hydraulic flat tappet, left to right.

I watched the Comp Cams video again regarding picking the correct distributor gear, and as far as I can tell the IROC and Vortec cams are billet steel. You can see the IROC cam has some different machining marks than the Vortec. It also has a little more lift and noticibly more duration. The distributor gear seems to be a somewhat lighter color as well, although that could just be staining.

As far as I can tell, no GM production car came with a carb, mechanical fuel pump and a roller cam. I think these cams with fuel pump lobes came only in Corvettes and 3rd Gen F-bodies. One board I saw was talking about SS Monte Carlos in this era, but I found no evidence of that. One guy claimed his '87 Caprice 4 door came with a factory roller cam. Unlikely.

As has been pointed out, it doesn't seem likely that any production GM car came with a bronze gear. So I assume all OEM roller cams use the melonized gear. My idea to just use the stock original Camaro gear on my HEI won't work. The shaft size on the distributors is apparently smaller on roller cammed vehicles. I guess maybe it could be drilled out (what could possibly go wrong with that plan?).

With GM cams most people seem to get along fine with the standard fuel pump pushrod. But one guy posted that he took a roller cammed 305 from a '92 Camaro and put it in his street rod with a mechanical pump and standard pushrod. Eventually the pump wouldn't move enough fuel to supply the carb. His comment was "the eccentric on the cam wasn't fully machined to drive a fuel pump." I have no idea what to make of that. Sounds like it wore down.

Discussion boards are littered with these issue, particularly the distributor gear part. I'm having a hard to figuring out why there are all these problems this far down the road with these cams. If the Holy Grail article on this is out there on the internet, I haven't seen it yet. Please post the link when you find it. Comp Cams solution is to have you buy their $100 distributor gear.

[toolboxchev]

Interesting tidbit about the distributor shaft being smaller. I wuz hopin to re-use my old HEI set up.

Looks like I will be buying an new distributor at this point, unless we have more confirmation.

[kenn]

I can't remember the number but it is a Comp Cam I have the paperwork at home if the number is needed.

[zac]

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.

[Captainfab]

For the distributor gear, I have used the melonized gear that GM sells for the .491 shaft. In the same engine we used a stock fuel pump pushrod. This is with the 14097395 cam. Granted the engine does not have a lot of miles on it, but there are no known issues. Even in a stock L29 & L31 Vortec, the distributor gears don't last as long as you think they should. They do wear out and cause issues.