I got a call recently from a guy who used to live near me but had since moved out of state, we used to spend a good deal of time working on cars but he was mostly a guy who did paint and interior work, not engine and drive train related stuff.
( I wish he was still local because he was and is far more skilled in that area than I am, so Ive had to call him in the past, for advice several times in those areas)
he had recently had a machine shop rebuild his 396 bbc engine, he had installed it and got it running, but just barely, with the help of some local guys, but he said it had not nearly the same power the older worn engine had and he was really disappointed.
what many guys seem to ignore is that each minor adjustment and each sub system does effect the total results, a simple change like a few degrees in the timing curve or a 1 psi change in fuel pressure, or a couple rockers that are a bit too tightly adjusted, will very definitely effect how the car runs.
knowing your true compression ratio would help, as would knowing your converter stall speed, exhaust back pressure at peak rpms and plenum vacume reading at peak rpms and your ignition timing and advance curve.
posting clear pictures of your spark plugs labeled to match the cylinders would also be useful, as would any info on jets and power valves, accelerator pump cams , and fuel pressure etc. If you were local we could work out the testing and details far easier, things like voltage, and exhaust,back pressure, fuel pressure get over looked but they can be great indicators
Well I talked to him a bit and it became rather obvious that he was not really up on basic trouble shooting or engine tuning , so I suggested he do several things and posted him a half dozen links., to related threads and like most guys he failed to read all the links and sub links, so he called back several times and over a weeks time. EVERYONE learns by making mistakes or seeing others make mistakes much of the time, so having a check list and some experience or some experienced friends helps, and yes (you get experience from making mistakes) so its part of the learning process.
you can avoid mistakes by assuming that every possible area has been badly adjusted or put together in-correctly until you personally verify its correct!
The end result was that I had to work him thru each problem, and point out the link he had over looked, or failed to understand ,he eventually was to check a dozen areas, and with each area he found things that needed to be either adjusted or corrected, the fact was that no one area what his major source of a problem, but several were major contributors to the total problem, but eventually after checking , each the ignition timing, got set correctly, vacuum hose connections got connected, the valve cover vacuum to the carburetor ,the , firing order, the ignition timing, the spark plug reading,showed he had correctly adjusted the carburetor,the fuel pressure,was reduced to a consistent 5 psi so the carburetor was not flooding, with a quality fuel pressure regulator vs a cheap P.O.S. that allowed the fuel presure to go from 5psi to 7psi, (which made tuning the car a huge P.I.T.A., and having the caruretors floats correctly adjusted,sure helped, and once a return line and a fuel pressure regulator that was previously removed was reinstalled, he had the correct fuel air ratio, and eventiually he had the carburetor adjustments and setting the valves, correctly done, after those issiues got handled. the engine power was far better but still seamed to be a bit lower than he expected, so I had him check a few things and he eventually found that the carburetor to intake gasket he had used was preventing the carburetor secondary throttle plates from opening even 1/4, once that little screw up was corrected the car ran noticable better.
understand that there was a great deal of minor stuff that needed to be checked, adjusted and corrected, the result was probably close to 1/3rd of the cars power was not available and it ran like crap until those adjustments were made, and its far from unusual for a new engine, or even an older engine thats not been tuned recently, to not need those tweaks
( I wish he was still local because he was and is far more skilled in that area than I am, so Ive had to call him in the past, for advice several times in those areas)
he had recently had a machine shop rebuild his 396 bbc engine, he had installed it and got it running, but just barely, with the help of some local guys, but he said it had not nearly the same power the older worn engine had and he was really disappointed.
what many guys seem to ignore is that each minor adjustment and each sub system does effect the total results, a simple change like a few degrees in the timing curve or a 1 psi change in fuel pressure, or a couple rockers that are a bit too tightly adjusted, will very definitely effect how the car runs.
knowing your true compression ratio would help, as would knowing your converter stall speed, exhaust back pressure at peak rpms and plenum vacume reading at peak rpms and your ignition timing and advance curve.
posting clear pictures of your spark plugs labeled to match the cylinders would also be useful, as would any info on jets and power valves, accelerator pump cams , and fuel pressure etc. If you were local we could work out the testing and details far easier, things like voltage, and exhaust,back pressure, fuel pressure get over looked but they can be great indicators
Well I talked to him a bit and it became rather obvious that he was not really up on basic trouble shooting or engine tuning , so I suggested he do several things and posted him a half dozen links., to related threads and like most guys he failed to read all the links and sub links, so he called back several times and over a weeks time. EVERYONE learns by making mistakes or seeing others make mistakes much of the time, so having a check list and some experience or some experienced friends helps, and yes (you get experience from making mistakes) so its part of the learning process.
you can avoid mistakes by assuming that every possible area has been badly adjusted or put together in-correctly until you personally verify its correct!
The end result was that I had to work him thru each problem, and point out the link he had over looked, or failed to understand ,he eventually was to check a dozen areas, and with each area he found things that needed to be either adjusted or corrected, the fact was that no one area what his major source of a problem, but several were major contributors to the total problem, but eventually after checking , each the ignition timing, got set correctly, vacuum hose connections got connected, the valve cover vacuum to the carburetor ,the , firing order, the ignition timing, the spark plug reading,showed he had correctly adjusted the carburetor,the fuel pressure,was reduced to a consistent 5 psi so the carburetor was not flooding, with a quality fuel pressure regulator vs a cheap P.O.S. that allowed the fuel presure to go from 5psi to 7psi, (which made tuning the car a huge P.I.T.A., and having the caruretors floats correctly adjusted,sure helped, and once a return line and a fuel pressure regulator that was previously removed was reinstalled, he had the correct fuel air ratio, and eventiually he had the carburetor adjustments and setting the valves, correctly done, after those issiues got handled. the engine power was far better but still seamed to be a bit lower than he expected, so I had him check a few things and he eventually found that the carburetor to intake gasket he had used was preventing the carburetor secondary throttle plates from opening even 1/4, once that little screw up was corrected the car ran noticable better.
understand that there was a great deal of minor stuff that needed to be checked, adjusted and corrected, the result was probably close to 1/3rd of the cars power was not available and it ran like crap until those adjustments were made, and its far from unusual for a new engine, or even an older engine thats not been tuned recently, to not need those tweaks