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Old 03-07-2017, 12:11 AM   #1
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Motorhome timing chain and gear question

I wasn't sure whether to post this under the mechanics section, Argosy section, or here, but figured this was a place to start.

We have a 1978 Argosy motorhome (mileage 83,000). Does any know if the 454 V-8 engines of that era had a plastic (bakelite) timing chain gear? We are replacing the water pump and since we are few steps away from the timing gears, we thought we would change those now if it are plastic. One service manual says that the V8ís had the Bakelite gear but on-line I read where the P-30 / motorhome chassis had all-steel gears. Does anyone know or have had their timing chain / gears changed? Thanks.
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Old 03-07-2017, 01:59 AM   #2
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I think it may have been plastic coated in some way. Brad or Martin are sure to know. I'd PM them if they don't reply (which is unlikely)!

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Old 03-07-2017, 02:20 AM   #3
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Not sure my 5cents is relevant because although we just had the timing chain replaced on Bella, she has the small block 350 not the big block motor.

The feedback I have from the shop is the one installed probably was not original as it was all metal (the original gears were meant to be nylon coated) and didn't appear to be heavy duty (maybe the reason it wore out?). But there is a replacement heavy duty chain and cog set that replaces even the original MH version - that's what went into Bella.

So my suggestion would be disregard what was originally fitted and go with the uprated modern version if there is one.
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Old 03-07-2017, 02:28 AM   #4
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All timing chains can fail, just some are more prone too than others. If your worried about it inspect it and find out if it needs addressed.
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Old 03-07-2017, 02:32 AM   #5
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I posted a 1978 light truck repair manual in the sticky. Look at the P section for Motorhomes. You'll probably find the answer there


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Old 03-07-2017, 03:53 AM   #6
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💡. I'm so kicking myself that I didn't think to do the timing gears/chain while in there doing the cooling system. Dang!

Cheers Richard
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Old 03-07-2017, 05:15 AM   #7
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You are that close. Do it and you can relax in the future. A failed timing chain on the road will not be any fun.
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Old 03-07-2017, 06:33 AM   #8
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Should I be worried about the metal timing chain on my 1991 250 classic?


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Old 03-07-2017, 07:32 AM   #9
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Quote:
Originally Posted by Boom Sounds View Post
I think it may have been plastic coated in some way. Brad or Martin are sure to know. I'd PM them if they don't reply (which is unlikely)!

NR x
I'm afraid I can't help here. The 454 in my Argosy was missing when I bought it back in 2007. I pulled a 454 from an 81 Chevy 1-ton dually and used that engine instead.


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Old 03-07-2017, 10:59 AM   #10
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Keyair has posted extensively on this subject. If I recall correctly, the older 454's had the plastic/Bakelite gears and the newer ones have longer lasting metal gears. I took timing chain off of my preventive maintenance list after reading his posts and concluding that my '84 probably has metal gears.
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Old 03-07-2017, 11:45 AM   #11
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I would suggest doing the gears and chain
I would replace the distributor as well if it where mine
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Old 03-07-2017, 12:46 PM   #12
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I would replace them, my 454 had about that many miles, and the chain seemed to be stretched. Very sloppy movement, don't think that was normal? Sold that engine to a rebuilder.
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Old 03-07-2017, 03:34 PM   #13
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I think you can test slackness by removing the cap and rotating the distributor.

I've done some digging and think they used the nylon coated sprocket at least until the TBI in 91. I'm going to check the oem part number in my 91 coach, find out if it was entirely steel and report back. Can anyone report a steel sprocket on a pre 90 carb coach?


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Old 03-07-2017, 06:45 PM   #14
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Tis a simple answer - most likely - yes, plastic. But even if by chance it's commercial market roots resulted in a steel version, replace is the only wise course of action for a power plant of that age. And an RV grind cam with new bearings is not that far beyond the scope of a timing gear replacement. Worth considering. Pat
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Old 03-07-2017, 09:29 PM   #15
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This may be a record: 14 views with 13 replies! Thanks to all. Looks like the consensus is to replace regardless of whether we are dealing wit metal or plastic. It's just "one more thing" to have to deal with. But better now when the radiator and other parts are out of the way than on the road somewhere.

BoomSounds/Nick: I'm still digging through the Stickys for the 1978 P30 Service Manual link...do you have it handy?
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Old 03-07-2017, 11:01 PM   #16
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If you have had a plastic sprocket strip teeth you know you were dead in the water. A new metal sprocket, chain, and harmonic balancer are a must. The sudden jerk on the harmonic balancer when the sprocket fails can cause the balancer to go out of position so the end result is a lot of roughness. Been there done that in old Mexico, no less. Had to borrow a vehicle to get back to a US parts house.
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Old 03-07-2017, 11:47 PM   #17
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If you have had a plastic sprocket strip teeth you know you were dead in the water. guskmg
Happened to us in my '71 Monte Carlo (had that car for 3 decades) and 'dead in the water' is a very good description. Fortunately we were only about 40 miles from home, but a tow home was still the order of the day. A tow for the Argosy wouldn't be as easy (or cheap).

Unless we knew for sure that we were dealing with plastic, in this case, we figured 'why fix it if it isn't broke?' Hence the question regarding what was OEM at the time. But looks like regardless, we'll be getting new parts.

Thanks for the reminder...
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Old 03-08-2017, 05:43 AM   #18
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Post 94 in the sticky for the service manuals


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Old 03-08-2017, 06:06 AM   #19
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Post 94 in the classic motorhome section. It will be the first post


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Old 03-08-2017, 09:20 AM   #20
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Post 94 in the classic motorhome section. It will be the first post
Thanks Nick. But just my luck, the link to the 1978 pdf isn't working. The 77 and 79 come up, but not the 78. It doesn't matter though as I believe we have a hard copy of the 78 manual anyway. The cover of ours is the same as for the 77 except for the date and the color.
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