1970's BMW 2002 poor high end performance
07-05-2006, 06:00 AM
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1970's BMW 2002 poor high end performance I've gotten a lot of great help here at this site so I thought I would throw another question at you guys. Its not f-body related but it is engine performance related.
I am posting here because my uncle's bimmer isn't doing so well at top end. He has restored his BMW 2002 and it looks awesome. He also restored his MG B. But anyway. He bought a custom head (for the bimmer) and had it tuned from some engine expert in NC. When he first got it home, it ran great. He put a couple hundred miles on it and it seems to have lost its power in the higher rpms. He pulled the brake booster off and instead of hearing a constant sucking sound, it was a phhht phhht phhht phhht sound. Its an inline four cylinder engine so I don't know if thats the sound you're supposed to hear but it didn't sound normal to me. Last night we pulled the head off and checked it for cracks. There was nothing obvious. The cylinders also looked pretty good. It was the fourth of july and we were getting ready to see fireworks so I only spend about 10 minutes looking at it and talking to him about it. Anybody here know have any ideas?
He claims that he checked everything and he's been working on cars ever since I can remember.
I thought maybe he had lack of fuel pressure at high end but he said that he checked that. He also said that all of his valves seemed be adjusted properly. I briefly checked for a bad lobe on the cam but didn't see anything obvious. With that brake booster sound, its almost like a valve isn't opening or closing properly. They open and close with rockers.
I am posting here because my uncle's bimmer isn't doing so well at top end. He has restored his BMW 2002 and it looks awesome. He also restored his MG B. But anyway. He bought a custom head (for the bimmer) and had it tuned from some engine expert in NC. When he first got it home, it ran great. He put a couple hundred miles on it and it seems to have lost its power in the higher rpms. He pulled the brake booster off and instead of hearing a constant sucking sound, it was a phhht phhht phhht phhht sound. Its an inline four cylinder engine so I don't know if thats the sound you're supposed to hear but it didn't sound normal to me. Last night we pulled the head off and checked it for cracks. There was nothing obvious. The cylinders also looked pretty good. It was the fourth of july and we were getting ready to see fireworks so I only spend about 10 minutes looking at it and talking to him about it. Anybody here know have any ideas?
He claims that he checked everything and he's been working on cars ever since I can remember.
I thought maybe he had lack of fuel pressure at high end but he said that he checked that. He also said that all of his valves seemed be adjusted properly. I briefly checked for a bad lobe on the cam but didn't see anything obvious. With that brake booster sound, its almost like a valve isn't opening or closing properly. They open and close with rockers.
07-08-2006, 03:37 PM
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BMWs are weird cars... I dont know about something that old or anything about the engine(s) in those, but since the mid 80s and up to the late 90s (at least) the engines will idle a bit rough (normal) and with mileage start to sound like a diesel (ticking, cam(s) and supporting hardware need to be replaced). As far as the vacuum system, if you pull the dipstick or open the oil cap the engine will surge (it will almost die), this is also pretty normal. I have a feeling that the vacuum is going to act like that, but could be wrong.
