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aribert

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About aribert

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  1. I was surfing to harvest expansion tank / plumbing images when I came across my own thread from years ago. I figured I would close the loop as to what the problem was, how I found it and how I solved the problem. The Country bearings were not the issue. The block had been line bored for the Spit cam bearings. The block had been lined bored very poorly. the inner most bores were 0.010 undersize. It appears that the machine shop simply honed the cam bearings to suit. The engine never had good oil pressure. The only consolation is that the "reputable" machine shop went out of business in 2010. My bore gauge only reached in to the second journal so I machined a stub of a shaft in 0.002 inch steps progressively undersize and used that as a go/no go gauge. I studied Truimph-V8's excellent posting above, I made concept sketches but I was too scared to try to do my own line boring - in part because my mill has a table that is only 36 inches across. To get adequate travel, I would need to bore from both ends of the block - this just seemed to be an accident waiting to happen. And I am not a machinist - just someone who plays around with the big tools. I resolved to modify the cam bearing shells. I made a mandrel to fit the ID of the bearing shells in their free state with a very light press fit. I superglued (cynoacrylate adhesive (sp)) the shell to the mandrel and then used a toolpost grinder to remove stock from the OD of the shell. Each shell was ground as needed to achieve 0.001 to 0.002 greater press fit as would a stock bearing in a properly sized journal. The bearings were installed and then I took a junk cam and turned the first journal down (from memory) about 0.005, the second journal 0.004, ... I cut a groove perpendicular across each journal. My junk cam was now a stepped reamer. Since the outer journals were correct to size and the 2nd journal not too much smaller my cam was entering the 3rd journal before it began its first light cut as I rotated the cam. As the cam was inserted to the next journal the process began all over, but now light cuts on 2 journals. I inserted the cam from both ends of the block. Lots of cam rotation will the slightest of (manual) feeding in of the cam. I took a 2nd junk cam (I have a habit of hoarding junk parts) and cut the perpendicular groove across the journal but leaving the journal dia as is. This cam did more burnishing of teh bearing surface than material removal. The end result is that only a few thou were removed from the bearing surfaces. The newcam installed in the block required a bit more force to rotate than similar cams in other 6 cyl engines. After 10,000 miles of use, oil pressure has never been better.
  2. Thanks for the replies. Nick: How long ago did you buy the Country bearings? I received a response to a similar question on a US based list and the individual bought his Country cam bearings 3/4 year ago (and had no issues). Triumph-V8: Do you have any pictures of the line boring tool you made or of it in use that you would care to share? Were you able to line bore end to end in one pass or did you set up and bore from each end of the block? I also have a mill but it does not have quite enough travel to bore on a single pass (plus I lack the creativity in imagining how I would fab a boring tool and hold concentricity to the axis of the camshaft).
  3. Greetings all: I tried to search for my cam bearing problem but came up empty. My Spit6 has a 2.5L engine. Back in the mid '90s my engine suffered an oil starvation issue at one of the cam journals and damaged the bore. I had the block line bored and installed early Spit cam bearings (lined up the oil holes and pressed them in, cam slid right in, correct clearance,...). I recently pulled and dismantled the engine for some maintainance and thought I would replace the cam bearings while replacing the cam shaft. It appears that the only cam bearings available in the USA currently are Country brand, made in India. When I install the bearings (now much more difficult to press in) the cam shaft will not install. Some quick measurements lead me to believe that the bearing shell on the new bearings is 0.001 thicker and the OD is 0.002 to 0.003 larger. I was told by someone in the Triumph business to have the bearings line honed after installing into the block - that just seems wrong - to remove the soft bearing plating on the ID of the new bearings. Instead I bought a small diameter bore gage, measured a new bearing in the block (0.0045 too small), and removed the new bearing. I machined an aluminum bar so that the bearing would fit over it, bonded the bearing to the mandrel and removed stock on the OD of the bearing. Now with the modified bearing in the block, the clearance to the camshaft is good but there is not enough interferance for the cam bearing to remain pressed in place in the block. My old cam bearings have a noticeable wear on the bottom qtr of the circumference. I could reuse my old cam bearings. I could drill new oil galley holes in the old cam bearings so that the worn area would face up, but then the bearing seam would be face down in the high load area. I dont't like this idea. I have been monkeeing around with these cam barings for the last 4 Saturdays! Anyone else aware of Spit cam bearing issues? Solutions? I can't be the only one with this issue. THanks for reading this far.
  4. There is a guy in the US currently doing something like this. I have not paid close attention as I already have a Mazda diff in my car. I think he was going to make a couple of spares and I ***think*** he mentioned somewhere in the $700-$800US. Do a search for a Spitfire group on Yahoo groups.
  5. Gt6 Gearbox Reassembly Issues

    I'm new to the forum, live stateside near Detroit and have owned my Spit bodied GT6 Mk3 for 23 years. First two years of ownership as a stock coupe then I rebodied. Replaced the motor w/ a TR 2.5L & added DCOEs. After breaking 2 differentials in 4 years, I emulated the Mazda differential built by GrassRoots Motorsports (US based magazine) in their Ro-Spit project car. So the reason I am posting instead of lurking: Seven or eight years ago I took the gearbox apart to replace some worn synchros (baulk rings) - I did not appear to have any issues on reassembly. This time I took it apart to replace 1st and 2nd gears, the 1-2 shift hub and the synchros. I posted the same question to a US based Yahoo Spitfire list (NASS). I did all the gap / tolerance checks per the Bently manual. Between the split ring and the miserable 3rd gear circlip the main shaft asm is in tolerance. From the split rings rearward to first gear the axial gap is 0.001 out of tolerance (spec is 0.00 to 0.002) - no big deal. But when I asm the main shaft in the gear box housing, there appears to be an excessive gap of approx 0.150 between the 3-4 shift hub and 4th gear. First pic is of the main main shaft asm in the housing: http://i290.photobuc...xreassembly.jpg THe second picture is a composit of where the gap is and how it looks when sliding the 4th gear synchro back and forth. http://i290.photobuc...eassembly-2.jpg I am convinced that the problem is not on the mainshaft from the 3rd gear circlip to the split washers to the rear mainshaft bearing (I have had all the bushings and thrust washers on the shaft to check the axial play). I don't have any pcs left over and the mainshaft bearings are fully seated in the gearbox housing. I'm lost on this - I know the 4th gear synchro can not have 0.150+ of axial play - it would get chewed up. Your thoughts? Since intitally posting, I once again removed the shaft asm from the housing and measured the distance from one retaing ring face to the opposite end of the gearbox housing. I locked the vernier "calipers" and then measured the distance from inside edge of retaining ring to opposite side. the main shaft asm appears to be 0.088+ shorter than the fore/aft length of the gearbox housing. housing measurement: http://i290.photobuc...ph/IMAG0375.jpg The next picture shows the "caliper up against the inside edge of the retaining ring and on the opposite end the caliper extends beyond the retaining ring. http://i290.photobuc...ph/IMAG0376.jpg I had both of the shift hubs dismantled and have attempted to asm w/ both of the hub inner parts reversed. Reversing the 1-2 hub left me with a 0.150 gap on the mainshaft adjacent to the split washer. Reversing the 3-4 hub left me with a gap on the opposite end. As I mentioned earlier - I am flat out lost. TIA
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