Building a GMC 702 V-12
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== Hydraulic Tappets == | == Hydraulic Tappets == | ||
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| + | This was sort of fun. I went to all the old fleet repair engine shops, you know the ones that have been there since the 20's and have the old time engine mechanics who have actually worked on this stuff in the day. I also scoured the internet and parts books. Not to mention I do have the GMC heavy truck maintenance manual. Armed with all that I was started with the notion that the Chevy six-cylinder passenger car from 1950-52 with the power glide had the same lifters. That is supposedly identified as an HT-761 but the first ones had that hand written on the boxes. Not even worried yet as I needed 24 and only had two, seven months of e-bay (these things are expensive too, just looked and saw someone asking $499 buy it now for a six cylinder set)netted me a large collection in excess of 50. All of them for six chevy motors. Now look at this, | ||
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| + | [[File:A variety.jpg]] | ||
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| + | On the left is the one marked for 50-52 there are HL-16, HL-18 and HL-31. The one laying in front has no such designation but carries the same part number as the HL-16. The HL-18 and HL-31 are different part numbers. | ||
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| + | [[File:Variation Topr.jpg]] | ||
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| + | From a top view you can see the differences in the push rod cup. Note too that the non HL designated lifter has seemingly larger ID bore from the outside looking in. Anyway, the V-12 has solid push rods and there is not any hole in the cup so I focused initially on the HL-18 and the HL-31. Problem is however that I only have 5 of the HL-18s and a dozen or so of the HL-31. I am forced to dissect them to see what I could do. | ||
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| + | [[File:Variation body.jpg]] | ||
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| + | My plan is to have at least all new bodies and from the above picture you can see that two of the types have grooves and two don't. My research indicated that these grooves are intended to help keep oil in the lifter bore for longer life. I am not going to worry about that, if I get 1000 miles a year on this I will be smiling from ear to ear. Note the large galley hole in the one on the far right it has the same PN as the HL-16 but these are major variations. | ||
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| + | I will start by taking the HL-31 apart and comparing it to a used V-12 lifter. | ||
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