Recently I had to take of the head of my M20B25 off (its in 1988 e34 tho) due to the fact that the head gasket had corroded and one of the rings collapsed causing pressure to escape to the cooling system... I ended up getting another head anyway because the valve seats were heavily worn. Got done everything I could:
head cleaned and a bit shaved but so slightly I didn't need the thicker HG
valves got lapped and few of them changed
somehow machine shop fixed the valve stems or valve guides because theres no movement anymore there
valve stem tops cut off a bit so theyre flat
rocker arms sanded so theyre smooth again
got another cam because mine was worn
The cam I put in was from M20B20 but according to this link the only difference was that it was 6 degress advanced. We even checked ourselves and they really seemed to be almost the same. Since this cam was near perfect we decided to put it in.
The car now has been running great and quiet for almost 200km and it does feel like it has more power in low range which is ideal for city driving but the idle is rough. I also put in M52B25 injectors since I had a refurbised set laying around and my original ones were dirty and one wasn't really closing. Also Im running first gen LPG and that also seems to have rough idle, maybe a little better, but still rough.
Vacuum lines all have been replaced including the vent hose that comes from the head cover. Dipstick oring is the same, but I inspected it and it seems ok, when putting back it felt like it went in there pretty snug. So far I haven't replaced only oil filler cap, dipstick orings, and throttle body gasket and the gasket of the thing that goes on other side of the manifold opposite the throttle body.
Yesterday I measured the vacuum and it read 52kpa. Somewhere I found that it should be 57-72kpa according to bentley. Before rebuild it was somewhere about 60kpa I think. Now after more research it found that cam advancing can decrese the idle quality and decrease the vacuum. Is that true or theres still a vacuum leak somewhere?
If I really need to change the cam I would rather get adjustable cam gear and just retard it 6 degrees. Are any of the ebay options that are usable?
head cleaned and a bit shaved but so slightly I didn't need the thicker HG
valves got lapped and few of them changed
somehow machine shop fixed the valve stems or valve guides because theres no movement anymore there
valve stem tops cut off a bit so theyre flat
rocker arms sanded so theyre smooth again
got another cam because mine was worn
The cam I put in was from M20B20 but according to this link the only difference was that it was 6 degress advanced. We even checked ourselves and they really seemed to be almost the same. Since this cam was near perfect we decided to put it in.
The car now has been running great and quiet for almost 200km and it does feel like it has more power in low range which is ideal for city driving but the idle is rough. I also put in M52B25 injectors since I had a refurbised set laying around and my original ones were dirty and one wasn't really closing. Also Im running first gen LPG and that also seems to have rough idle, maybe a little better, but still rough.
Vacuum lines all have been replaced including the vent hose that comes from the head cover. Dipstick oring is the same, but I inspected it and it seems ok, when putting back it felt like it went in there pretty snug. So far I haven't replaced only oil filler cap, dipstick orings, and throttle body gasket and the gasket of the thing that goes on other side of the manifold opposite the throttle body.
Yesterday I measured the vacuum and it read 52kpa. Somewhere I found that it should be 57-72kpa according to bentley. Before rebuild it was somewhere about 60kpa I think. Now after more research it found that cam advancing can decrese the idle quality and decrease the vacuum. Is that true or theres still a vacuum leak somewhere?
If I really need to change the cam I would rather get adjustable cam gear and just retard it 6 degrees. Are any of the ebay options that are usable?
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