Bonnet and cam cover problem

PostPost by: William2 » Wed Apr 22, 2015 12:39 pm

Just when I thought I was on the home straight, I hit a problem on my S4 restoration!! When I carried out a trial fit of the bonnet it hits the top of the cam cover and won't close to the line of the bodywork by at least 1/2". The car has the original chassis and body so nothing has changed in that area. I have fitted new Dellorto variant engine mounts and all the nylon screw heads at the bonnet hinge point are set to the correct height. When I lowered the body back onto the chassis it fitted on the chassis correctly and all the holes lined up. The body did not require any spacers at the rear end or on the bottom chassis rail which is desirable as the chassis spreads the load more. At the front 2 mounting points it needed about 5mm worth of penny washers to fill the gap. It seems strange that the engine is at least 1/2" too high. I have checked everything and the engine is canted over at the right amount and there is about 1" of clearance under the left hand carb. Not sure what to do about it. If I remove all the body/chassis mounting bolts and put spacers in at every point to raise the body enough to cure the problem then the front turret bobbin holes won't line up any more.
If only there were a way of lowering the engine it would seem a simpler solution. Ideally a set of replacement engine mounts that lower the engine enough would be great but I assume there is nothing on the market.
I did wonder whether a machine shop could somehow modify the engine mounts. All thoughts would be most welcome.

William
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PostPost by: andywatts » Wed Apr 22, 2015 12:55 pm

I had a similar issue with my +2, as a result of replacing the chassis. I fitted the engine (and gearbox) without checking the location and alignment, and then had to re align it, both vertically and forward/backward, to get the bonnet to close and the gear lever central in the body. To adjust the engine I was able to drill additional holes in the very substantial engine brackets (Spyder chassis) and get it exactly right.

From what you say the only difference has to be the engine mounts, so an obvious option would be to revert to the standard mounts (pic attached). You might be able to oval the holes a little, but there is not enough 'meat' to be able to drill new holes. You could also look at the chassis bracket and see if there is any leeway there.
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PostPost by: RotoFlexible » Wed Apr 22, 2015 2:36 pm

In addition to checking and possibly reverting the engine mounts, make sure that the transmission mount is not lower than previously. That would raise the front of the engine.
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PostPost by: William2 » Wed Apr 22, 2015 3:13 pm

The only other point I forgot to mention is that the engine mounts I have fitted are the Tony Thompson uprated type which possibly means that the engine hasn't dropped as much as it would with the standard mounts.
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PostPost by: Certified Lotus » Wed Apr 22, 2015 5:11 pm

I just ordered the TT engine mounts. Is this a common situation with them, that it raises the engine by 1/2 inch?
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PostPost by: lotusfan » Wed Apr 22, 2015 5:15 pm

Have you fitted the spacers at the gearbox mounting?
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PostPost by: William2 » Wed Apr 22, 2015 6:43 pm

No, I'm not suggesting it is necessarily a problem with uprated engine mounts but until I try fitting standard ones I won't know how much the engine lowers.
Mike, I have fitted the correct height gearbox mounting spacers.
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PostPost by: marklowe » Wed Apr 22, 2015 8:16 pm

If you have fitted Dellorto variant engine mounts to an S4 that was originally fitted with Stromberg carbs this will lift the carb side of the engine.
Have you recently converted to Dellortos?

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PostPost by: elansprint71 » Thu Apr 23, 2015 6:52 am

1" of clearance between the left-hand carb and top of the foot-well? On my S4 the gap is less than 1/2" between the air-box and the top of the foot-well; on the Sprint even less!
When we changed the Sprint chassis I had to put packing pieces between the chassis and body to achieve the clearance for the bonnet; fortunately I had made a jig before removing the engine and chassis so I knew where the cam cover had to sit in relation to the body-shell.

I suspect the (excellent) TT engine mounts might need to be modified to allow adjustment of engine height. Good luck.
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PostPost by: ericbushby » Thu Apr 23, 2015 11:17 am

William,
The gap between the rear end of the square type airbox and the top of the footwell on my 1967 S3 is 1/4".
This might be a bit close as it used to tap there when it was running rough but it is OK now.
Eric in Burnley
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PostPost by: elanner » Thu Apr 23, 2015 2:40 pm

William,

I agree with the previous replies that 1" seems too much (from the bottom of the airbox, at least, whereas you mention left hand carb). What's the gap under the heater valve? My unscientific estimate is that you should be able to run your fingers under both, but only with a snug fit.

Take a look at:
lotus-twincam-f39/heater-valve-clearance-t31580-15.html

The picture I posted there shows the distance between the top of the chassis and the top of the exhaust side footwell to be about 6 3/4" (on my Elan, which is a looooong way from being the final arbiter, but presumably about right).

Using that measure, if the distance is smaller the implication is that the body is too low and needs spacers. If the distance is the same (or larger) the implication is that the engine is too high. Is that right? Following this logic, if the distance is right, and the gap between airbox, heater valve & their footwells is a snug finger fit, then the implication is that the engine is angled upwards, which brings you back to the gearbox mount (is it possible that a new gearbox mount is the wrong size?).

Of course, having never rebuilt an Elan my comments need to be taken with plenty of salt. ;-) ;-)

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PostPost by: William2 » Thu Apr 23, 2015 3:37 pm

Thank you for the replies. Sorry for the confusion, but when I mentioned there was about an 1" of clearance under the carb, I meant under the carb body itself. I currently am awaiting an airbox to arrive in the post as the car didn't have one.
The gearbox spacers are definetly the correct height as I purchased them from Miles. I am in the process of swapping the engine mounts for standard ones to see if this helps.
Should the engine be horizontal or raised slightly at the front?
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PostPost by: ericbushby » Thu Apr 23, 2015 6:10 pm

William
The gap under the carbs is inaccessable with the airbox fitted.
My engine is raised slightly at the front. Using a spirit level on the cam cover it slopes 1/16" in 9" (the length of my level). I suppose many things could affect this but I can't find a suitable datum to measure from. However the car seems to stand correctly and my garage floor is level. Someone else measuring theirs might help.
Best of luck,
Eric in Burnley
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PostPost by: William2 » Fri May 01, 2015 4:54 pm

I was considering raising the gearbox slightly by increasing the height of the mount spacers by a few mm. As suggested, this should lower the cam cover height very slightly which would help in my bonnet clearance problem. Has anyone else done this? I can't think of any problems in going down this avenue. My current spacers are about 10mm high.
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PostPost by: ericbushby » Fri May 01, 2015 6:43 pm

For what it's worth, and using a drill as a feeler guage the spacers on mine are just over 12mm, so probably ?".
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