mfg Posted October 18, 2018 Report Posted October 18, 2018 Why are mechanical fuel pumps found on Chevrolet V8's (as used in '65-'85 Avantis) more susceptible to failure than the mechanical fuel pumps used on Studebaker V8's ('63-'64 Avantis)?
r1lark Posted November 8, 2018 Report Posted November 8, 2018 (edited) Well, I was going to say that there was no built-in filter on the Chevy pumps, but remembered that the R-series pumps didn't have a built-in filter either! How about closer to the exhaust manifold, so it sees more heat? I have never worked on a Chevy smallblock so this is a wild guess. Edited November 8, 2018 by r1lark
mfg Posted November 8, 2018 Author Report Posted November 8, 2018 58 minutes ago, r1lark said: Well, I was going to say that there was no built-in filter on the Chevy pumps, but remembered that the R-series pumps didn't have a built-in filter either! How about closer to the exhaust manifold, so it sees more heat? I have never worked on a Chevy smallblock so this is a wild guess. Good thought!...however the problem lies with very poor oiling to the upper fuel pump parts (arm and pin)..........This issue is common to all small block Chevy V8's. Replacement Chev fuel pumps normally come with instructions to pack the fuel pump lever (arm) cavity with wheel bearing grease prior to installation to help with long term lubrication. Studebaker V8 fuel pumps never had any problem with lubrication.
brad Posted November 10, 2018 Report Posted November 10, 2018 (edited) The recommendation to pack the area with grease (for lubrication)is absolutely not true. What they ARE recommending is to pack the push rod hole with grease so the rod stays in place while installing the pump. They do not have the arm riding on the drive eccentric like some cars, but in actuality have a drive push rod. The only reason it MIGHT have a oiling problem is if non stock gaskets were used between the first mounting plate, and the block. There should be no gasket overlap between the pump body opening, where the pump actually bolts to the adapter plate. I have worked on May SBC engines, and NEVER saw ANY oiling problems ate the fuel pump. They simply do not exist. Edited November 10, 2018 by brad
mfg Posted November 10, 2018 Author Report Posted November 10, 2018 (edited) As many Avanti/Avanti ll owners are driving cars powered by small block (i.e. 305, 350, 400 ) Chevrolet V8 engines, I feel it's important to get the correct information pertaining to potential problems "out there"! Brad Bez is unfortunately completely incorrect when he says there is no lubrication problem regarding the stock mechanical fuel pump used with the above mentioned engines. As a matter of fact, replacement fuel pump manufacturers have recognized this 'lack of lubrication' issue for quite some time now, and most pack a note with the pump asking the installer to fill the fuel pump 'arm' cavity with grease before installation. I myself changed out a mechanical pump on my '83 Avanti 'everyday driver' back in June of this year.....a pump I installed back in 2013....I hadn't heard of this lubrication problem back in 2013, and sure enough after I removed this pump I saw that the arm and the pin it pivots on were extremely loose in the casting...the pin had actually started to move up and down in the fuel pump casting following the up and down motion of the arm....this from insufficient engine lubrication..............NOT GOOD! Edited November 10, 2018 by mfg
mfg Posted November 12, 2018 Author Report Posted November 12, 2018 (edited) For those not familiar with the Chevrolet 'small block' fuel pump operation (as compared to the Studebaker V8 and several other engines)....The Stude V8's fuel pump operating arm rides directly against an eccentric located ahead of the timing gear....the operating lever and pin receive plenty of lubrication from splash off of the timing gear. On the Chevy, the fuel pump is bolted onto a 'chamber' located on the side of the engine block, with a 'go between' push rod, riding in a machined bore in the engine block, connecting the camshaft lobe to the fuel pump arm. Other than whatever little bit of oil that may seep down that push rod onto the fuel pump operating lever, the Chevy fuel pump arm and pin receive hardly any (if any at all!) lubrication.....Hence the packing of the fuel pump arm cavity with grease. Edited November 12, 2018 by mfg
mfg Posted November 13, 2018 Author Report Posted November 13, 2018 Please take a minute to read my last (today's) post on the "Fuel Pump Lubrication Issue" thread elsewhere on this forum.
mfg Posted November 15, 2018 Author Report Posted November 15, 2018 I find it kind of interesting how a simple trivia question such as this can bring to light something fairly important, and that apparently many mechanics weren't aware of! Pretty 'cool' stuff really!
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