free hit
counters
Lotus 907 motor - how to turn motor by hand - Engine & Ancilliaries/Gearbox - The Lotus Forums - Lotus Community Partner #ForTheOwners Jump to content


IGNORED

Lotus 907 motor - how to turn motor by hand


Recommended Posts

I have a 74 Jensen Healey with a 907 motor set up with the stroker upgrades. I bought the vehicle in the "not running condition". I have been told that the car was not running for several years. I would like tp know what is the best way to start troubleshooting the engine prior to determining if engine removal and majr component replacement is required. In preparation to troubleshoot I have regularly taken out the spark plugs and added kroil and marvel mystery oil into the cylinders.  I have tried to move the main crankshaft by attempeted clockwise torquing the pully nut with a wrench.  The nut tightens(hard) but the pully does not turn.   I have not put on a tourque wrench while attempting to turn the pully. I got to the point of "afraid to do more damage" and stopped. Since I would rather own up to being ingnorant than make matters worse I am soliciting your input and suggestions.  Thanks in advance.  RA

Link to comment
Share on other sites


Upgrade today to remove Google ads and support TLF.

Pete, I was hoping that it would be simple like ring sticking.  Localized corrosion bonding?  If it were that do you think it would break free via trying to hand turn the engine? or is there some straightforward method? It would be nice to get to that point and do some compression checks and see how that shakes out.  So any ideas on getting it to turn without further damage if it is ring sticking?

And thanks for replying

Link to comment
Share on other sites

Welcome to the forum by the way!!  The main problem with the rings sticking is the danger of breaking them.  The stroker engines - depending on the supplier of the parts - often use more modern pistons with narrow rings.  Do you know much about it's history?

Pete

Link to comment
Share on other sites

Thanks for the welcome and I appreciate the kind response.  Luckily the car came with a very complete set of receipts and info. Here is what I have as a list, but would have to do more digging to find the year done:

10:1 oversized JE pistons and wrist pins

107 cams

Dave Bean aluminum flywheel

oversize exhaust valves and 3 angle valve job by West Coast Racing

New main and rod bearings, new piston rings, new rod bushings 

machined piston liners

I was told but can't yet find the receipts to verify: that the work was done in the 2008-2-12 time frame.

 

Link to comment
Share on other sites

I've never measured the torque required to turn the engine over but I'd have thought less than 20 ft.lb.  What leads you to believe it's also a stroker?  Or has it just been over-bored?  Let us know what torque you feel you got up to before you thought you might break something!  I think I came across West Coast Racing when I built the LS1 for my Excel.

Pete

Link to comment
Share on other sites

Be careful that the cam belt hasn't slipped and you are pressing the pistons against the valves!

It might be worth taking the cam belt off ( you will need a new belt if it has been left standing)  and checking the cams move, look down the spark plug holes and see where the pistons are....top of the stroke could mean contact with the valves.

  • Like 1
Link to comment
Share on other sites

If you take the belt off don’t try and move the crank as you will get valves into the pistons.

You must also take the carriers off to allow the valves to close. I would endoscope the cylinders before doing anything, however if things are so tight I would think that you need to strip the engine

Link to comment
Share on other sites

  • Gold FFM

With the plugs out, the engine should turn without too much torque. Unless the rings or such are stuck of course. I'd put a breaker bar on the pulley bolt and try shock loads in both directions, without resorting to really brute force. With penetrating oil in the cylinders that usually does the trick, if not a strip down is the only way forward I fear.

I have made many mistakes in my life. Buying a multiple Lotus is not one of them.

 

Link to comment
Share on other sites

All, thank you for the responses. They are much appreciated.  I was on business travel and now can work through some of your suggestions.  Again, the responses are appreciated. And the cautions even more so.  I will send along an update as to my progress and if that creates more questions.🙂 Ron

Link to comment
Share on other sites

  • 1 month later...

Thank you again for answering my earlier questions.  Christmas and Covid have caused delay.   I have just taken apart the spare engine I have so I can rebuild that at the same time as working on the engine once out of the car.  It is clear from your kind responses and from the tear down of the spare that I will have to: 1) extract the engine, 2) remove timing belt, 3) tear down to determine what needs to be replaced.  From what I can see the spare engine will require a bore of the cylinders. Can you recommend the best combination of piston/ring sizing and rod bearing sizing to achieve a bit more HP at reasonable value?    The engine in the car is "supposed" to be a stroker with documentation that I believe confirms that.  The extraction and tear down will confirm that.  My plan is to work on the spare and learn from that as I tackle the other engine.  Willing to accept guidance and suggestions.

 

Link to comment
Share on other sites

Assuming the JE pistons are forged you'll be looking at about 0.0030" - 0.0035" piston to bore clearance measured 2" from the top of the liners - do you have the measurement equipment to determine this?  Piston ring gaps are covered in the Service Notes, but I'd get in touch with JE and get their recommendations if they also supplied the rings.  If the pistons are over-size and the cylinder liners are not useable as they are then your only option is to buy new liners and get them honed to suit the pistons, or buy new pistons to suit new standard liners.  If you keep the pistons there is nothing you can do to increase performance beyond careful building of the engine.  If you have a stroker crank you will not have factory conrods but you can use the factory specs for bearing clearance - mains and big ends.

Post up some photos of your progress!

Pete

Link to comment
Share on other sites

  • 2 weeks later...

With respect to Pete, the 900 series con rods remained constant ( other than pin oiling reliefs ) from the 2.72" stroke of the 907 on through the 910/912 series with their 3.00" stroke. The difference was accommodated by change of compression height in the pistons, the principal reason pistons sold for either crank differ. That said, when the crank is further stroked in pursuit of 2.4 - 2.5 capacity then it will be necessary to source alternative rods. So it will depend in this case what Ron finds when tearing down.

Welcome Ron! 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...