Bonnet clearance 420R?

[BrettJ]

Could someone tell me if this normal, the bonnet is resting on the oil cap?

 

[ScottR400D]

It's always pretty close. Is the nose on In that shot? I guess not and the hood might be supported slightly if it were. 
 

Is the underneath of the hood marking? 

[BrettJ]

No, the nose isn't on and I hadn't thought of that. Thank you for pointing that out

[John Vine]

That intrigued me so I went to check my R400D (with the nosecone off):

The gap is pretty small, and probably less than 1mm.  But in my case the bonnet is resting on the black foam pad stuck on the front of the coil cover (just visible to the right of the filler cap).  I fitted that as the bonnet was definitely contacting the coil cover, with witness marks to prove it.

I'd guess that, when fitted, the nosecone would raise the bonnet slightly anyway.

JV

[John Vine]

Btw, are you mid-build as I don't see any hoses?  Certainly your engine is scrupulously clean!

JV

[BrettJ]

Thanks for the photo, I'm assuming mine will be the same as it currently doesn't have the coil cover on atm.

[ChrisC]

I agee, you can't compare without the noise cone and bonnet / nose cone foam, 

Have you got the new gearbox engine spacer, fitted between the gearbox and the gearbox mount?  I thought your kit was supplied before mine.  My kit wasn't supplied with one, but I have seen it on new kits. 

It's normally the coil cover corner that touches the bonnet, and need careful organisation of the coil wires below (not as delivered) and possible trimming of the cover to get it as low as possible.   The tin foil trick will give a good indicator, but its only valid with the nose cone in position.   

[BrettJ]

Yes I'm, well I'm almost finished as I've only got the engine bay plumbing and electrics to do.

[BrettJ]

I did see your blog where you used the tinfoil, which was why I put the bonnet on to check this. However, I didn't take into account that the nose cone would raise it.

I wasn't aware of any new gearbox spacer, could you please elaborate on this new spacer?

[Geoff Brown]

My 2012 R400D had the very same problems. When ticking over there used to be an annoying rattle from under the bonnet.

Solution - bespoke cut thin pieces of self adhesive foam attached to the underside of the bonnet in the appropriate places. In addition the centre plastic fastener pad of the Pipercross filter touched the bonnet. Judicious but careful use of a junior hacksaw sorted that out.

[John Vine]

Re #10:

In addition the centre plastic fastener pad of the Pipercross filter touched the bonnet.

That too, Geoff, now that you remind me.  I used your foam-under-the-bonnet trick.

JV

[ChrisC]

This is the new spacer that's been added to the Mazda gearbox mount. It's my understanding the spacer was introduced sometime 2020 / 2021 to increase clearance around the Mazda gearbox.  I wondered if it had been added to alter the prop working angle, but apparently not, so it's not on my priority list at the moment, because I am currently looking at a road speed vibration issue with my car. 

That said, if you raise the gearbox tail it must lower the front of the engine in front of the mounts.   

I will add one next time I have to remove the gearbox mount. 

[BrettJ]

Thanks Geoff, I'll keep that in mind when I fit my RB.

[BrettJ]

I really don't understand what clearance they are referring to. I do agree with you regarding the prop angle as that is still a concern of mine, did you order this or did Caterham just send it to you?
 

[ChrisC]

I got the details from another kit builder, including all the dimensions.  I spoke to CC after sales about it to see if was a possible cause of my vibration, who initially where unaware of the enhancement.  They later confirmed after checking with the factory the enhancement was for gearbox clearance and not prop working angle.  Adding that spacer would be way cheaper fix for my car, so it would have been in CC's benefit to do so, but its not even being considered. 

At the moment is doesn't even have a part number (or one that has been published), so you can't even get it from CC parts, but when you can, I will be adding one to my car (at my cost).    

[ScottR400D]

Chris, so that spacer lifts the tail of the gearbox? That would do something to correct the difference in angle of the diff and engine, assuming the angles some of us found last year during the great diff debate are typical. 

Does the engine in the 420/Mazda not already tilt down at the front a little? My R400D/6 speed certainly does. Unfortunately the diff slopes even more! From memory the engine canted down by about 1 degree but the diff did the same by 2.7 degrees or so. 

If you do fit that new mount I'd really like to know how much it alters the angle by and if you feel it makes a difference. 

[aerobod - near CYYC]

With it being about 900mm between the engine and gearbox mounts, 1.7 degrees of additional tilt would require the spacer to raise the rear mount by 27mm.

[BAZZA]

Do your coil pack connectors touch the underside of the cover?

[ChrisC]

The coil pack cover is the most likely candidate for touching the bonnet. 

The spacer is 3mm, so no where near 27mm.

[BAZZA]

Chris,

I appreciate that the cover will be the bit that touches the bonnet, I was just asking as my coil pack connectors do touch the underside of the cover and may cause some vibration related noise which I do notice.

also it does mean that the cover can't be lowered.

[ChrisC]

I have no evidence of the coil packs touching the coil cover.  I would expect some witnesses marks if it was.  It took a fair bit of effort altering the coil pack wiring, and adjusting the fit of the cover, to make clearance happen. Don't forget the nose cone foam, make sure it's in good condition and supports the bonnet fold lip to lift the bonnet a tiny bit, and foam under the side edges of the bonnet also lifts it a bit.

I would hate a painted coil cover because things are that tight any mistake would ruin the effect.

[ScottR400D]

You're right James. During 'diffgate' I did the same calculations hoping to change the diff angle to suit the engine but it wasn't possible.

I asked CC a question about the respective angles of the engine and diff but they had no idea. (That was literally the reply - no idea)

Like Chris it's not a priority for me. When I had the prop out there was no discernible wear so the assumption is that the angle is within the capability of the bearings. 

[John Vine]

Re #22:

I asked CC a question about the respective angles of the engine and diff...

A few years ago, Phil Stewart refurbed my Ford diff.  At the time, he suggested that a lot of the driveline noise in Duratecs was caused by a slight misalignment between engine/gearbox and diff, one consequence of which was rattling propshaft universals.

JV 

[ScottR400D]

#23 Yes, John, Phil told me the same but there's a couple of things that don't add up. 

One being that, according to driveline experts, the angular difference is within acceptable levels for the speed the shaft turns. 

The other, which is perhaps more significant, is that the tilt of the Duratecs actually reduces the angular difference between the engine/box and diff compared with the Sigma.

This is according to my and others findings that the diff, for whatever reason, tilts down at the front either by accident or design. so tilting the engine down at the front (to clear the hood) improves the alignment. 

Incidentally, the noise Phil is referring to is the highish pitched chatter on slight lift off. Steve Perks thinks this is the CW and P and is actually excited by firing pulses not being damped on cars with light flywheels. That makes more sense to me. 

[John Vine]

Re #24:

Interesting, thanks for that.  In my case, it doesn't bother me as I can hardly hear it anyway over the ear defenders!

JV