Realized i was sort of hi-jacking other posts with my questions and there are sure to be many more.
Some of the following might be a repeat of other posts, but trying to consolidate in one place.
I have been reading Bob Hoover off and on for a few years, have the Aero-Vee manual, and most of the GP manual/reference materials. Have topped & maintained a few Continentals including a GO300 i used to own, and various 4 cyl. Continentals since. Misspent youth elbow deep in MC's & a few Brit sports cars 40 - 50 yrs ago. I'm a capable manual machinist. OTOH, VW engines are completely new to me.
Engine in question is a GP 2276 installed new sept 2013 & flown 35 hrs until June of 2017. EMPI heads. Airplane is a Sonerai 2.
Basically, i don't know what is normal for the engine, and what the tolerances and limits are for inspection.
I borescoped the cylinders and saw more rust than i was comfortable with, esp around the exhaust valve seats. So pulled the worst looking head. Most everyone else who has seen it said " You should have just run it & changed the oil, it would clean itself out."
On the bench the valve keeper lands were swaged out to the extent the valves would not slide through the guides until i used a small last-cut file to dress them all around. The intakes are essentially straight/cylindrical and there is little deviation in the guide ID's. The Manley Stainless exhaust stems are barrel shaped. "Good one" is about .0025 under at each end of travel range. Worst is a little over .003". Valve stems are .310 +/- a couple tenths in the centers, as are the intake stems "all over". Ex guide ID's are .025" & .030" over valve stem size at each end of the guide. The wear in the guides is slightly oval.
Inspecting this head compelled me to go back and pull the other, which i will dis-assemble and inspect today.
My assumption is that the exhaust guides and valves should be replaced & recut seats to match?
Should the intake valves be replaced "anyway" ?
Last night while removing the cyl 1 & 2 side head, most of the studs unscrewed. They are 8MM and the nuts are rusted or galled to the top thread area to the extent i could not hold the studs from spinning in a flat-face machine vise on one of the hangar mills, albeit it is a cheapo vise. (Not an angloc). I left them with penetrating oil and will clean up later.
Should i buy a new stud set? Despite my mention of rust, the studs are mostly clean, the rust is under the threads. My inclination is to just buy a new set, but maybe that is dumb? If i clean the studs up, can i just use new grade 8 nuts from the local jobber? How about new, cut down (OD), grade 8 washers?
I'm trying to put together an order list and get everything at once, though there's always "just one more" item found later, of course.
For a 2276 av-conversion VW, what should the cold, dry, clearance between stem and guide be, when new exhaust guides and valves are installed?
People on several forums have generously linked various online sources for reference which are much appreciated, and utilized.
OTOH, not always clear how applicable to av use some of the specs might be. Is there a good manual, like a Continental OH manual, that sets all the tolerances, limits and inspection procedures out? With focus on Av application?
Thanks!
smt
Some of the following might be a repeat of other posts, but trying to consolidate in one place.
I have been reading Bob Hoover off and on for a few years, have the Aero-Vee manual, and most of the GP manual/reference materials. Have topped & maintained a few Continentals including a GO300 i used to own, and various 4 cyl. Continentals since. Misspent youth elbow deep in MC's & a few Brit sports cars 40 - 50 yrs ago. I'm a capable manual machinist. OTOH, VW engines are completely new to me.
Engine in question is a GP 2276 installed new sept 2013 & flown 35 hrs until June of 2017. EMPI heads. Airplane is a Sonerai 2.
Basically, i don't know what is normal for the engine, and what the tolerances and limits are for inspection.
I borescoped the cylinders and saw more rust than i was comfortable with, esp around the exhaust valve seats. So pulled the worst looking head. Most everyone else who has seen it said " You should have just run it & changed the oil, it would clean itself out."
On the bench the valve keeper lands were swaged out to the extent the valves would not slide through the guides until i used a small last-cut file to dress them all around. The intakes are essentially straight/cylindrical and there is little deviation in the guide ID's. The Manley Stainless exhaust stems are barrel shaped. "Good one" is about .0025 under at each end of travel range. Worst is a little over .003". Valve stems are .310 +/- a couple tenths in the centers, as are the intake stems "all over". Ex guide ID's are .025" & .030" over valve stem size at each end of the guide. The wear in the guides is slightly oval.
Inspecting this head compelled me to go back and pull the other, which i will dis-assemble and inspect today.
My assumption is that the exhaust guides and valves should be replaced & recut seats to match?
Should the intake valves be replaced "anyway" ?
Last night while removing the cyl 1 & 2 side head, most of the studs unscrewed. They are 8MM and the nuts are rusted or galled to the top thread area to the extent i could not hold the studs from spinning in a flat-face machine vise on one of the hangar mills, albeit it is a cheapo vise. (Not an angloc). I left them with penetrating oil and will clean up later.
Should i buy a new stud set? Despite my mention of rust, the studs are mostly clean, the rust is under the threads. My inclination is to just buy a new set, but maybe that is dumb? If i clean the studs up, can i just use new grade 8 nuts from the local jobber? How about new, cut down (OD), grade 8 washers?
I'm trying to put together an order list and get everything at once, though there's always "just one more" item found later, of course.
For a 2276 av-conversion VW, what should the cold, dry, clearance between stem and guide be, when new exhaust guides and valves are installed?
People on several forums have generously linked various online sources for reference which are much appreciated, and utilized.
OTOH, not always clear how applicable to av use some of the specs might be. Is there a good manual, like a Continental OH manual, that sets all the tolerances, limits and inspection procedures out? With focus on Av application?
Thanks!
smt
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