Bob_Spidell
Yoda
Offline
Denizens of the Forum,
I need to replace the clutch in my BJ8, and I've decided to pull the engine and gearbox together and do an engine rebuild while I'm at it (the engine has 110K miles +/- on it since last rebuild). Even with low compression, the engine runs like a proverbial 'Swiss Watch'--and just gave another 3,427 miles of flawless performance over 10 days--but it's noticeably lacking in power and runs out of breath pulling up a grade at high altitudes (and will barely rev over 4K RPM at sea level). So, I'm looking for suggestions from the cognoscenti on how to:
- get at east a little more power at the top end (I'm thinking getting compression up around 10:1 would help)
- keep a reasonably smooth idle (I do spend quite a bit of time stuck in traffic)
- still be able to run without detonation on 91-octane (R+M/2) pump gas (or 90-octane when that's available, usually at higher-altitude pumps)
- continue to be bullet-proof (I venture where a lot of people wouldn't even consider taking an old LBC, and almost never see even modern exotics in such places)
The cylinders were bored 0.030" over some time before I bought the car--at 64K miles--and the block was painted black so a PO must have done an overhaul for some reason. I plan to have the cylinders bored--only by the minimum necessary--and to use Denis Welch's Omega brand pistons (3-ring). With nearly 200K miles on the engine I feel it's time to spring for uprated studs and bolts (head, crankshaft, rod). Beyond that, I am considering:
- Cam. The cam was reground at the last rebuild by Crower. My dad specified their mildest grind without asking me--smart man--which, as far as I can tell is very close or identical to stock BJ8. The engine idles nicely around 750 RPM with just a slight lope. I have a Lempert 3.54:1 rear end and do most of my motoring between 2,000 and 3,000 RPM (I usually downshift when I get below 2,000 RPM, which works well in my Mustang as well). I'm leaning towards staying with the stock grind--or a new cam if it can't be ground again--but would consider a hotter cam if I can still get a similar idle but a little more top end.
- Pistons. As mentioned, I'll probably use DW's because I believe only 2 compression rings are necessary and they look to be top quality (BTW, has anyone else ordered DW's new catalog? It is absolutely a work of art, printed in full color on glossy, heavy (photo?) paper and the list of parts now available is incredible. What a resource.)
- Lifters. Leaning towards bucket lifters (just because).
- Rocker shaft. Leaning towards a roller-tip unit from Rocker Arm Specialists (anyone know if they're still in business and still providing quality?). The stock one's ratio is a little under 1.5:1 but the RAS ones claim true 1.5 which I think (hope) may give a small boost in performance (David at DMD--can't remember his last name and I believe he passed away a few years ago--told me this should give a bit more 'grunt').
- Flywheel. I toy with the idea of getting the flywheel lightened--or exchanged--but with the 3.54 getting off the line is a little touchy as it is
- Rear main seal. We put one on our BN2 and it still leaks, but I think that may be due to crankcase pressure (I think the draft tube may be at least partially blocked). I bought a seal years ago and never installed it but am considering DW's Al rear engine plate and seal so I don't have to modify the stock engine plate.
- Head. Would love to have DW's Al head for the weight loss if nothing else, but it's an awful lot of jack and I don't know what I would gain with an otherwise stock setup. Would also consider getting the stock head worked over by someone who knows what he's doing (not me).
- Headers. See 'head.' DW claims "The twin carb manifold will make the single most increase in power and torque possible for the money spent to a standard car." I'm concerned about installation issues and, though I've never run any car with tubular headers I have seen issues with tubular exhaust manifolds cracking (the Jeep I6 engine is notorious for this). I also wonder how an exhaust can be installed without the flex tubing found on stock down pipes--won't vibration wear on the headers or exhaust? If I don't go with headers, I will have the manifolds ceramic coated--would do to headers as well--if for no other reason than to (try to) prevent the stumbling due to vapor lock on hot starts due to ethanol in fuel (had the opportunity to buy ethanol-free premium gas in Oregon this trip, and didn't get the stumbling so I'm convinced ethanol is causing the problem).
All other wear items--bearings, etc.--will be replaced. The crankshaft is still stock, but will do a regrind if necessary. My dad has a friend/former student who owns a racing engine shop and Dad says he has a New Zealander machinist working for him who is an absolute perfectionist, so they will do the work (I'll do final assembly).
Your thoughts and suggestions are appreciated (probably by others as well). I've floated these ideas here and on the (now defunct?) mailing list before, but this time I'm serious
- Bob
I need to replace the clutch in my BJ8, and I've decided to pull the engine and gearbox together and do an engine rebuild while I'm at it (the engine has 110K miles +/- on it since last rebuild). Even with low compression, the engine runs like a proverbial 'Swiss Watch'--and just gave another 3,427 miles of flawless performance over 10 days--but it's noticeably lacking in power and runs out of breath pulling up a grade at high altitudes (and will barely rev over 4K RPM at sea level). So, I'm looking for suggestions from the cognoscenti on how to:
- get at east a little more power at the top end (I'm thinking getting compression up around 10:1 would help)
- keep a reasonably smooth idle (I do spend quite a bit of time stuck in traffic)
- still be able to run without detonation on 91-octane (R+M/2) pump gas (or 90-octane when that's available, usually at higher-altitude pumps)
- continue to be bullet-proof (I venture where a lot of people wouldn't even consider taking an old LBC, and almost never see even modern exotics in such places)
The cylinders were bored 0.030" over some time before I bought the car--at 64K miles--and the block was painted black so a PO must have done an overhaul for some reason. I plan to have the cylinders bored--only by the minimum necessary--and to use Denis Welch's Omega brand pistons (3-ring). With nearly 200K miles on the engine I feel it's time to spring for uprated studs and bolts (head, crankshaft, rod). Beyond that, I am considering:
- Cam. The cam was reground at the last rebuild by Crower. My dad specified their mildest grind without asking me--smart man--which, as far as I can tell is very close or identical to stock BJ8. The engine idles nicely around 750 RPM with just a slight lope. I have a Lempert 3.54:1 rear end and do most of my motoring between 2,000 and 3,000 RPM (I usually downshift when I get below 2,000 RPM, which works well in my Mustang as well). I'm leaning towards staying with the stock grind--or a new cam if it can't be ground again--but would consider a hotter cam if I can still get a similar idle but a little more top end.
- Pistons. As mentioned, I'll probably use DW's because I believe only 2 compression rings are necessary and they look to be top quality (BTW, has anyone else ordered DW's new catalog? It is absolutely a work of art, printed in full color on glossy, heavy (photo?) paper and the list of parts now available is incredible. What a resource.)
- Lifters. Leaning towards bucket lifters (just because).
- Rocker shaft. Leaning towards a roller-tip unit from Rocker Arm Specialists (anyone know if they're still in business and still providing quality?). The stock one's ratio is a little under 1.5:1 but the RAS ones claim true 1.5 which I think (hope) may give a small boost in performance (David at DMD--can't remember his last name and I believe he passed away a few years ago--told me this should give a bit more 'grunt').
- Flywheel. I toy with the idea of getting the flywheel lightened--or exchanged--but with the 3.54 getting off the line is a little touchy as it is
- Rear main seal. We put one on our BN2 and it still leaks, but I think that may be due to crankcase pressure (I think the draft tube may be at least partially blocked). I bought a seal years ago and never installed it but am considering DW's Al rear engine plate and seal so I don't have to modify the stock engine plate.
- Head. Would love to have DW's Al head for the weight loss if nothing else, but it's an awful lot of jack and I don't know what I would gain with an otherwise stock setup. Would also consider getting the stock head worked over by someone who knows what he's doing (not me).
- Headers. See 'head.' DW claims "The twin carb manifold will make the single most increase in power and torque possible for the money spent to a standard car." I'm concerned about installation issues and, though I've never run any car with tubular headers I have seen issues with tubular exhaust manifolds cracking (the Jeep I6 engine is notorious for this). I also wonder how an exhaust can be installed without the flex tubing found on stock down pipes--won't vibration wear on the headers or exhaust? If I don't go with headers, I will have the manifolds ceramic coated--would do to headers as well--if for no other reason than to (try to) prevent the stumbling due to vapor lock on hot starts due to ethanol in fuel (had the opportunity to buy ethanol-free premium gas in Oregon this trip, and didn't get the stumbling so I'm convinced ethanol is causing the problem).
All other wear items--bearings, etc.--will be replaced. The crankshaft is still stock, but will do a regrind if necessary. My dad has a friend/former student who owns a racing engine shop and Dad says he has a New Zealander machinist working for him who is an absolute perfectionist, so they will do the work (I'll do final assembly).
Your thoughts and suggestions are appreciated (probably by others as well). I've floated these ideas here and on the (now defunct?) mailing list before, but this time I'm serious
- Bob
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