Where's the logic in this, (technicaly)?
Discussion
.Set cold so they are all the same... Do a spot check of one or two at the most when hot and adjust your cold settings if neccessary. Ignore the rubbish about trying to set hot, no way can you get equalized clearances as the engine cools on the RV8 EFi setup - it requires a lot of patience to get adjustable pushrods right cold.
More likely the pushrods catching on the heads or rocker arm play ~ something other than valve clearances though I would have thought. If the arms move sideways pythagoras dictates the clearances will grow as well as if you lose oil film in the shaft to arm.. I'd make up spacers & spring shims to replace the springs on the rocker shafts as well as checking carefully the fit of rocker arms on the shafts then resetting checking the valve clearances. I also prefer to run a spot check of clearance around the base circle in case there are any abnormalaties (grind or muck / grease / lube) as well as pushing the pushrod down to make sure to seat the follower on the cam.
More likely the pushrods catching on the heads or rocker arm play ~ something other than valve clearances though I would have thought. If the arms move sideways pythagoras dictates the clearances will grow as well as if you lose oil film in the shaft to arm.. I'd make up spacers & spring shims to replace the springs on the rocker shafts as well as checking carefully the fit of rocker arms on the shafts then resetting checking the valve clearances. I also prefer to run a spot check of clearance around the base circle in case there are any abnormalaties (grind or muck / grease / lube) as well as pushing the pushrod down to make sure to seat the follower on the cam.
Tappets were set at 7 thou. What should they be at hot?
Spend, I understand what you are saying about the sideways movement as I always thought that the spring method of spacing was a bit "adequate".
What do you think of the Century Performance method of adjusting clearances, it's slightly different to JE's method?
Spend, I understand what you are saying about the sideways movement as I always thought that the spring method of spacing was a bit "adequate".
What do you think of the Century Performance method of adjusting clearances, it's slightly different to JE's method?
Exhaust should be on the base circle all the time from inlet closing until the exhaust begins to open - that gives you plenty of points to check. The inlet is the same from closing until the exhaust starts opening. You can check the accuracy of the base circle along those arcs if you want, as well as the accuracy of your measuring ~ thats why I'd rather take several measurements to not only check my own work but also to get a feel of the tolerances in measurement. Measure twice, cut once also applies even with accurate tools like DTI's / verniers / feeler gauges, particularly when you can see manufacturing tolerances plus & minusing.
Introducing hot >>> cooling into the problem is just plain stupidity IMHO, as I said set them as uniformly as possible at constant room temperature (cold) and cross check 1/2 when hot to confirm is the only way to get reasonably consistent hot clearances. Measuring changing expansions due to cooling is impossible to avoid unless you can set them whilst the engine is running, which is not feasible with the EFi plenum or adjustable pushrods. Anyone that tells you they have set them hot on an Rv8 Efi can only be fooling themselves as far as I can see
Introducing hot >>> cooling into the problem is just plain stupidity IMHO, as I said set them as uniformly as possible at constant room temperature (cold) and cross check 1/2 when hot to confirm is the only way to get reasonably consistent hot clearances. Measuring changing expansions due to cooling is impossible to avoid unless you can set them whilst the engine is running, which is not feasible with the EFi plenum or adjustable pushrods. Anyone that tells you they have set them hot on an Rv8 Efi can only be fooling themselves as far as I can see
i would check your feeler gauges, if they are anything like alex's were some of those where 40thou!, pete set the rockers so they are on the rock, ie both inlet and exhaust are at the same height, then set the opposing cylinder tappets to 10thou, so get 1 on the rock and set 6, 8 on the rock set 5 etc... 1843
6572 hope this helps, ps i did reply on your last thread about the way you set them and i was very confused, they will allways expand about 10thou when the engine gets warm, they never close up.
6572 hope this helps, ps i did reply on your last thread about the way you set them and i was very confused, they will allways expand about 10thou when the engine gets warm, they never close up.
You did check valve - piston clearance with your cam didnt you?
There are all sorts of minor variations you can't really plan for: slightly different fly cut depths / positions in the piston, different seat heights, valve lengths (seating cut/eroded/lapped, stem worn..), crank angle offsets (seen over .5degree off the 90deg crossplane at big ends!), block deck height (parallel?), head skim (parallel?), gasket thickness, and not least the estimation of TDC using dead stop with offset gudgeon pins!
If you have a cam where the valves get close I would advocate checking all 16 due to the possible minor variations mentioned above.
Remember some of these things that get done in 'tuning' are actually going beyond the bounds of normal 'service' tolerances that allow for many of these variations.
There are all sorts of minor variations you can't really plan for: slightly different fly cut depths / positions in the piston, different seat heights, valve lengths (seating cut/eroded/lapped, stem worn..), crank angle offsets (seen over .5degree off the 90deg crossplane at big ends!), block deck height (parallel?), head skim (parallel?), gasket thickness, and not least the estimation of TDC using dead stop with offset gudgeon pins!
If you have a cam where the valves get close I would advocate checking all 16 due to the possible minor variations mentioned above.
Remember some of these things that get done in 'tuning' are actually going beyond the bounds of normal 'service' tolerances that allow for many of these variations.
v8 racing said:
i would check your feeler gauges, if they are anything like alex's were some of those where 40thou!, pete set the rockers so they are on the rock, ie both inlet and exhaust are at the same height, then set the opposing cylinder tappets to 10thou, so get 1 on the rock and set 6, 8 on the rock set 5 etc... 1843
6572 hope this helps, ps i did reply on your last thread about the way you set them and i was very confused, they will allways expand about 10thou when the engine gets warm, they never close up.
Rob, I checked the feeler with a vernier gauge and set them on the rock as you desribed, (which is different from the artical slideways highlighted), I also set them to 7 thou.6572 hope this helps, ps i did reply on your last thread about the way you set them and i was very confused, they will allways expand about 10thou when the engine gets warm, they never close up.
haircutmike said:
..fly cut the pistons for me ..
If the pistons have been on/off the rods a few times it wouldn't be the first case of interference fit pins not interfering in the way you want?Isn't it a JE method that uses that weird 7thou at xdeg rather than anywhere on base circle, ISTR a hazy description of such a procedure advocated from those quarters?
spend said:
If the pistons have been on/off the rods a few times it wouldn't be the first case of interference fit pins not interfering in the way you want?
Isn't it a JE method that uses that weird 7thou at xdeg rather than anywhere on base circle, ISTR a hazy description of such a procedure advocated from those quarters?
Yes Isn't it a JE method that uses that weird 7thou at xdeg rather than anywhere on base circle, ISTR a hazy description of such a procedure advocated from those quarters?
.haircutmike said:
v8 racing said:
i would check your feeler gauges, if they are anything like alex's were some of those where 40thou!, pete set the rockers so they are on the rock, ie both inlet and exhaust are at the same height, then set the opposing cylinder tappets to 10thou, so get 1 on the rock and set 6, 8 on the rock set 5 etc... 1843
6572 hope this helps, ps i did reply on your last thread about the way you set them and i was very confused, they will allways expand about 10thou when the engine gets warm, they never close up.
Rob, I checked the feeler with a vernier gauge and set them on the rock as you desribed, (which is different from the artical slideways highlighted), I also set them to 7 thou.6572 hope this helps, ps i did reply on your last thread about the way you set them and i was very confused, they will allways expand about 10thou when the engine gets warm, they never close up.
If they never close up, why set at 10 thou, set at 0 thou then as the expand when hot, they will be 10 thou. Am I missing something?
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