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Camaro_Hodges
07-22-2003, 11:35 AM
7/19/03 Problem with HEI Distributor Gear Ware

Last year I purchased a 69 Camaro with a 454 out of an 89 truck and the guy did not change the lifters when he changed the cam. He said that the cam had not been broken in yet or anything. So I decided to take it apart and see what I had.

Original Description

1989 454 – date code J159=Oct 15 1989 … cast #10068286 = 90 & 91 4-bolt Gen IV .. short deck

Head – date code is J139 … Cast #14092360 = 86-88 oval port

Comp Cam – 280H – part #11-208-3

Int Ext

Gross Lift 0.52 0.52

Dur at 0.050: 230 230

Lobe Lift: 0.3063 0.3063

Lobe Separation 110

Lifters – 812-16

Springs – 911-16

Edlebrock: Performer 2.0 Intake

GM standard HEI



Rebuild #1: grind crank, replace bearings, replace cam bearings, new lifters, SAME Comp Cam 280H flat tappet hydraulic cam, different heads, new oil pump, metal oil pump shaft, water jacket plugs and cam plug, double roller timing chain and sprockets.

Parts Description

Heads --- 336781 -- 73-85 oval port w/ larger valves --- I do not know if the heads have been surfaced many times before or not!!!

Start-up after rebuild #1:

The distributor gear was wearing away. I did not look at the gear during the first rebuild, but it was warn after only 2 hrs. I went ahead and changed the 1st gear not knowing if it was already worn before the rebuild, and it did the same thing. I replaced the HEI with one from the junkyard and it did the same thing (see picture #1). I figured I had too much endplay or a bad cam, so I went for rebuild #2.

See Web Site For Image: http://users3.ev1.net/~ohodges/Camaro_Rebu...ens_Rebuild.htm (http://users3.ev1.net/~ohodges/Camaro_Rebuild/Owens_Rebuild.htm)

Picture #1: Gear #2 is pictured below after about 70 street miles. The second gear is on left hand side, and the right hand side is the new one from the junkyard. Double Click on picture below to enlarge.


Picture #2: Gear on 2nd HEI is pictured after 10 miles. Notice that the ware is pretty even. Both pictures are of the same gear at the same time.

See web site for image: http://users3.ev1.net/~ohodges/Camaro_Rebu...ens_Rebuild.htm (http://users3.ev1.net/~ohodges/Camaro_Rebuild/Owens_Rebuild.htm)

Rebuild #2: With help from Brent of Jim’s Machine Shop, I replaced cam, lifters, installed thrust button (set at about 0.005 inch end play), replaced cam channel plug to insure proper depth, bronze distributor gear.

Start-up #2

I started the car and ran it for 25 minutes at around 2000-2500 rpms. When I removed distributor and I have significant ware on the distributor gear (see pic #3 below). From the ware pattern, it appears that the distributor needs to set down about 1/8" lower. I replaced the 0.060" gasket with a 0.030" gasket and I still have the problem. I shimed the gear to take out all of the slack and when I set it in the hole it seems like it does not bottom out. I can not get a 0.006" feeler gage between the gear and the intake.

Picture #3: after 25 minutes of cam break in at 2000 rpms not under load.

see web site for image: http://users3.ev1.net/~ohodges/Camaro_Rebu...ens_Rebuild.htm (http://users3.ev1.net/~ohodges/Camaro_Rebuild/Owens_Rebuild.htm)

Request – I need suggestions on what to look at next. Some have recommended that I get a MSD Pro Billet distributor with an adjustable height. I can also try to install shims above the gear to lower it a little (done). Do you have any other ideas on things to check? Give me a call at 713-826-3213 or email at o.hodges@ev1.net to discuss further. Thanks in advance for any thought you give this tiring problem.

msdtech1
07-22-2003, 02:57 PM
Based on what I see from your photos, you have used a variety of different gears from different manufactures. I believe that the recommended gear for your application is a steel melonized gear but you will need to confirm this with the manufacture of the camshaft that you are currently using. If they recommend a steel melonized gear then I would suggest using the GM #10456413 Distributor Gear available through the GM Performance Parts Group. Here is a link to their web site.
http://www.gmgoodwrench.com/gmgoodwrenchjs...tion=ep#1104067 (http://www.gmgoodwrench.com/gmgoodwrenchjsp/perfparts/partlist.jsp?cat=9368&section=ep#1104067)
Also, it appears that you have varied the depth of the distributor by either a manifold or cylinder head change. I would recommend using our Distributor Installation Tool, PN 8599 Set up Tool. The optimal position is for the gear mesh to be centered on the distributor gear.
Thanks,
msdtech1