Great video! M539 restoration quality for sure. I love the original finish on the intake manifolds. I will inspect a 850i next week that has been storaged in the same heated garage since year 2002. Really excited, but low expectations :)
all the plugs should be pulled for a compression test. if the head gasket has failed, compression may leak from one cylinder to its neighbor, giving a false test result. if all the plugs are out, and the compression leaks over, the result will correctly be low. edit: the starter (and batteries) will be fighting less compression and doing less work as long as the plugs are removed.
Just watched all 10 episodes on the 850i and gotta say awesome and congrats. I really enjoyed it and learnt so much. Im restoring an Aston Martin Rapide at the moment (on my channel), and since I'm not a mechanic I am having to research everything. Videos like yours have taught me so much, even If the engine is different. Looking forward to the next series looking at the body and suspension!
Nice to see more content on the 850! Looking forward to seeing what you do with the bodywork - mine in finished! (Just published the last video). I may be brave and start looking at some mechanical stuff on mine, small things i couldnt get wrong 🤣
Nice video's, I just watched all of them. I love the content, keep them coming!! I am looking forward to the rest of the video's. One tip, when you hold the camera in your hand try to keep it as stable as possible, sometimes those scenes make me nauseous. Or try to put the camera on a tripod.
Your engine seems NEW clean? I have a 92 with the left engine bank tapping AGAIN. My son put this 75k engine in as a replacement to an already rebuilt original engine 3 yrs ago. Yes it is a long $tory. He reluctantly is going to rebuild or buy (try) a next replacement engine.
Love the videos! Fair play, clearly a lot effort….but seems obvious to do this Before spending ££ in refreshing before verifying engine is strong.?! Not that I mind…love the content! Just good practice for peeps starting out 🤷🏼♂️
If you take out all the spark plugs and do a compression test without any plugs in the engine you would put a lot less load on the starter and your battery which leads me to believe that is a better way of going about the test
I did this and a leak down test on my 850 a week ago. I also scoped it. It failed miserably... The range was from 85 to 130 psi. The cam timing will change the static compression so this can be the reason why the 2 banks give different readings. Did you check the cam timing? Looking forward to more videos!
It feels like taking out all of the spark plugs would dramatically decrease amount of stress on the starter. Procedure I was taught is: - take fuel supply fuses - burn all of the remaining fuel - disable ignition system - take spark plugs out - measure compression one by one.
@@stevesbmwbarn Anyways, you are doing great job there and it looks like you enjoy it! It looks great, sounds great. I envy you having so much time, patience and, frankly, money to throw at this lovely car. I feel I missed the moment to buy this car and it is getting more and more expensive every day.
Those compression test results are too high. Borne out, I feel having seen your later instalment with problems still persisting. A shame, but you're well on the way to resolving it. Valves, or rings next imo.
Cam timing is the likely culprit. That's too much variance to be heat related in an NA motor sucking cold air. 4 degrees difference in cam timing will do that. Retarding the cam usually drops dynamic cranking hurting low rpm power while improving top end due to filling after BDC. Advancing the cam leaves the intake open longer on the intake stroke taking in more air at low speeds improving low end power and increasing cranking compression. About 300rpm shift in power peak up or down. It's easy to overlook without a lot of pushrod V8 experience. That's why it's so obvious to me. The single cam pushrod motor doesn't allow for bank to bank variations in timing. You never see that. When you first see an overhead cam motor with a bank to bank offset, it's like a glowing neon sign.
![How To Perform a Compression Test - [EASY]](http://i.ytimg.com/vi/3VmmL0YAO14/mqdefault.jpg)
![How To Perform a Compression Test - [EASY]](/img/tr.png)
Thank you for the video, from a 750il owner.
Great video! M539 restoration quality for sure. I love the original finish on the intake manifolds. I will inspect a 850i next week that has been storaged in the same heated garage since year 2002. Really excited, but low expectations :)
Great result, engine is in rude health! Looking forward to seeing the next phase of the restoration.
That's a class labouring sound before the v12 bursts into life. It reminds me of a spitfire engine.
all the plugs should be pulled for a compression test. if the head gasket has failed, compression may leak from one cylinder to its neighbor, giving a false test result. if all the plugs are out, and the compression leaks over, the result will correctly be low. edit: the starter (and batteries) will be fighting less compression and doing less work as long as the plugs are removed.
Just watched all 10 episodes on the 850i and gotta say awesome and congrats. I really enjoyed it and learnt so much. Im restoring an Aston Martin Rapide at the moment (on my channel), and since I'm not a mechanic I am having to research everything. Videos like yours have taught me so much, even If the engine is different. Looking forward to the next series looking at the body and suspension!
Loving the series and great to see the 850 on camera again, such a rare beauty! Looking forward to what's coming next.
Starting up an M70 V12 always gives me the chills. Congrats to the results, Steve. Fabulous machine.
Testimony to how great these cars are. Great work Steve.
Nice to see more content on the 850! Looking forward to seeing what you do with the bodywork - mine in finished! (Just published the last video). I may be brave and start looking at some mechanical stuff on mine, small things i couldnt get wrong 🤣
I really like your series. That's great work. Greetings from Munich
Good results. Next time, all plugs out at once, but also throttle is best held wide open
Excellent professional video 👍
That´s one beautiful clean engine bay! :)
great job man
nice videos
you deserve more subs
Compression tests are best done with all the plugs out.
Nice video's, I just watched all of them. I love the content, keep them coming!! I am looking forward to the rest of the video's. One tip, when you hold the camera in your hand try to keep it as stable as possible, sometimes those scenes make me nauseous. Or try to put the camera on a tripod.
Your engine seems NEW clean?
I have a 92 with the left engine bank tapping AGAIN. My son put this 75k engine in as a replacement to an already rebuilt original engine 3 yrs ago. Yes it is a long $tory. He reluctantly is going to rebuild or buy (try) a next replacement engine.
Love the videos! Fair play, clearly a lot effort….but seems obvious to do this Before spending ££ in refreshing before verifying engine is strong.?! Not that I mind…love the content! Just good practice for peeps starting out 🤷🏼♂️
If you take out all the spark plugs and do a compression test without any plugs in the engine you would put a lot less load on the starter and your battery which leads me to believe that is a better way of going about the test
Again great video Thanks Steve :)
I did this and a leak down test on my 850 a week ago. I also scoped it. It failed miserably... The range was from 85 to 130 psi. The cam timing will change the static compression so this can be the reason why the 2 banks give different readings. Did you check the cam timing? Looking forward to more videos!
Oh really, was it a decent tester? What's the mileage on it? M70?
@@stevesbmwbarn 165k km but crazy blowby. I am swapping the engine for a s62 as the m70 is too far gone
It feels like taking out all of the spark plugs would dramatically decrease amount of stress on the starter. Procedure I was taught is:
- take fuel supply fuses
- burn all of the remaining fuel
- disable ignition system
- take spark plugs out
- measure compression one by one.
Yep thats probably the best way to do it, I always intended to split the job over two days so just did it one by one.
@@stevesbmwbarn Anyways, you are doing great job there and it looks like you enjoy it!
It looks great, sounds great. I envy you having so much time, patience and, frankly, money to throw at this lovely car. I feel I missed the moment to buy this car and it is getting more and more expensive every day.
Those compression test results are too high. Borne out, I feel having seen your later instalment with problems still persisting.
A shame, but you're well on the way to resolving it. Valves, or rings next imo.
You replace half of the engine and you masseur compression on the end. Absolutely ridiculous.
I like these videos, but footage is way too shakey to stick with…
Cam timing is the likely culprit. That's too much variance to be heat related in an NA motor sucking cold air. 4 degrees difference in cam timing will do that. Retarding the cam usually drops dynamic cranking hurting low rpm power while improving top end due to filling after BDC. Advancing the cam leaves the intake open longer on the intake stroke taking in more air at low speeds improving low end power and increasing cranking compression. About 300rpm shift in power peak up or down.
It's easy to overlook without a lot of pushrod V8 experience. That's why it's so obvious to me. The single cam pushrod motor doesn't allow for bank to bank variations in timing. You never see that. When you first see an overhead cam motor with a bank to bank offset, it's like a glowing neon sign.
Your synopsis is likely bang on, thanks for the input!
@@stevesbmwbarn Your workmanship is second to none. I can't wait to see that beast in better than new condition.