Post mortem on a 13B with low compression
03-25-08, 08:00 AM
#1
Post mortem on a 13B with low compression
Coles notes: Bought an engine, tore it apart, was rebuilt wrong. Mistakes to avoid. Long post, but worth reading I think.
I recently bought a 13B from a list member for $150. At first, I thought I was buying a blown engine, but was later informed that the engine had weak compression, and may not be blown. I was buying the engine just for screwing around, learning to inspect, measure, and try some porting, so I didn't care if it was blown anyway. I will PM the seller (I have no idea who rebuilt the engine) so any future mistakes can be avoided (maybe he knows who rebuilt it).
There are a few good threads in the archive, and other rotary sites. If you're attempting to rebuild a rotary, you'll do well to refer to all info available along with the FSM (see sig.). I'm no expert (I've rebuilt only around five engines successfully), so I have a few questions and am looking for advice and constructive criticism and thoughts from those who know (keep reading).
I took the engine home (with some help), and removed some items that were still on it. Quite a bit of oil around the front cover, but I didn't check for a cause thoroughly, although it wasn't the front seal. Maybe from a metering oil pump seal.
I noticed gasket maker (silicone) oozing from all over, especially the oil pan. Was the blue stuff and didn't look original at all, so at this point I knew the oil pan had come off. Noticed the front cover had cracked and had been fixed, well, sort of. As is sometimes the cause, I noticed that the bolt nearest the crack didn't have the thin washer between the water pump and the front housing. Always make sure these thin washers are used in their original places - I believe there are two of them - where the gasket does NOT go. Loosened the flywheel nut (see my other thread), front hub nut (seemed damn tight), and unbolted front cover.
Upon removing the front cover, I noticed two things. The washer behind the nut for the oil pump had been re-bent at a different location, so this was proof at least the oil pump had come out. It started to look like the engine was rebuilt. The other thing (advice neede) was I noticed the oil passage between the front cover and the housing had the usual o-ring, but also the gasket with the bigger hole and the white plastic washer - which I thought was used only in the newer front covers - but I may be mistaken. Either way, everything stayed in place.
Didn't check if the CAS sensor was aligned when I took it out. All the parts behind the front cover were put in properly (CAS gear, spacer, torrington bearings not jammed, etc.). Didn't check end play before removing front hub nut (damn!).
Let me post this before I loose the text...
I recently bought a 13B from a list member for $150. At first, I thought I was buying a blown engine, but was later informed that the engine had weak compression, and may not be blown. I was buying the engine just for screwing around, learning to inspect, measure, and try some porting, so I didn't care if it was blown anyway. I will PM the seller (I have no idea who rebuilt the engine) so any future mistakes can be avoided (maybe he knows who rebuilt it).
There are a few good threads in the archive, and other rotary sites. If you're attempting to rebuild a rotary, you'll do well to refer to all info available along with the FSM (see sig.). I'm no expert (I've rebuilt only around five engines successfully), so I have a few questions and am looking for advice and constructive criticism and thoughts from those who know (keep reading).
I took the engine home (with some help), and removed some items that were still on it. Quite a bit of oil around the front cover, but I didn't check for a cause thoroughly, although it wasn't the front seal. Maybe from a metering oil pump seal.
I noticed gasket maker (silicone) oozing from all over, especially the oil pan. Was the blue stuff and didn't look original at all, so at this point I knew the oil pan had come off. Noticed the front cover had cracked and had been fixed, well, sort of. As is sometimes the cause, I noticed that the bolt nearest the crack didn't have the thin washer between the water pump and the front housing. Always make sure these thin washers are used in their original places - I believe there are two of them - where the gasket does NOT go. Loosened the flywheel nut (see my other thread), front hub nut (seemed damn tight), and unbolted front cover.
Upon removing the front cover, I noticed two things. The washer behind the nut for the oil pump had been re-bent at a different location, so this was proof at least the oil pump had come out. It started to look like the engine was rebuilt. The other thing (advice neede) was I noticed the oil passage between the front cover and the housing had the usual o-ring, but also the gasket with the bigger hole and the white plastic washer - which I thought was used only in the newer front covers - but I may be mistaken. Either way, everything stayed in place.
Didn't check if the CAS sensor was aligned when I took it out. All the parts behind the front cover were put in properly (CAS gear, spacer, torrington bearings not jammed, etc.). Didn't check end play before removing front hub nut (damn!).
Let me post this before I loose the text...
03-25-08, 08:23 AM
#2
Some pics.
Noticed the front cover had dimpling on the gasket surface...haven't seen this before (???).
Took the tension bolts off. Took apart housings. Looks like all rotor seals were installed right (lost an apex seal side piece, but am sure it was there), but noticed a couple of major errors in regards to the coolant seals (main reason I say this engine was rebuilt).
The inner coolant seal was not installed with the seam in the proper location (I believe 3 out of 4) and the outer seal had the white strips placed against the housings.
Noticed most of the seals were very stiff as far as movement is concerned, especially the oil control seals. Don't know how long the engine was run after rebuild. I will be measuring seals and housing wear in the near future. It *looks* like the side housings have quite a bit of wear, and also the rotor housings, although no major chrome flaking. The rotor and main bearings are showing copper, and believe should be replaced. I'm looking for second opinions on the housings and bearings. The rotors look pretty good, will post pics. once they're cleaned up. Not in a hurry (I want to street or bridge port this thing), so I just did a decent cleaning for now, oiled all the parts I took apart and saran-wrapped them for the meantime.
I hope this thread will produce a good informative discussion. More pics. to come.
Noticed the front cover had dimpling on the gasket surface...haven't seen this before (???).
Took the tension bolts off. Took apart housings. Looks like all rotor seals were installed right (lost an apex seal side piece, but am sure it was there), but noticed a couple of major errors in regards to the coolant seals (main reason I say this engine was rebuilt).
The inner coolant seal was not installed with the seam in the proper location (I believe 3 out of 4) and the outer seal had the white strips placed against the housings.
Noticed most of the seals were very stiff as far as movement is concerned, especially the oil control seals. Don't know how long the engine was run after rebuild. I will be measuring seals and housing wear in the near future. It *looks* like the side housings have quite a bit of wear, and also the rotor housings, although no major chrome flaking. The rotor and main bearings are showing copper, and believe should be replaced. I'm looking for second opinions on the housings and bearings. The rotors look pretty good, will post pics. once they're cleaned up. Not in a hurry (I want to street or bridge port this thing), so I just did a decent cleaning for now, oiled all the parts I took apart and saran-wrapped them for the meantime.
I hope this thread will produce a good informative discussion. More pics. to come.
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