DCOE mounting

[inchoate]

I have reason to believe that the sandwich plates on my carbs have seen better days. I got a new set of sandwich plates and grommets and I'm getting ready to swap everything out. My Weber carburetor book says to spin the mounting nuts down until everything is in contact and then tighten a further 1 1/2 turns. Does that sound right? If someone has a better idea I'm open to the opinions of those with more experience in the matter.

[bball7754]

Think I read the same advice. My recollection is that doing that left them looser than I was comfortable with.

 

Have you you taken them off yet? If not, maybe get a feel for how much you can wiggle the carbs up and down, and aim to replicate that. You can also take a measurement of the gap between the plate and the carb, or the plate and the manifold (although they should be the same).

 

I decided that the important part was that they be able to move-but not fall off.

 

Steve

[fastg]

Year ago I remember using a feeler gauge to make sure the plate was not fully compressed and evenly clamped down, not I cannot remember what size feeler gauge.

 

Graham

[MoBoost]

I preferred the steel spring isolators. Less compression set and no heat aging, unlike rubber.

[inchoate]

I preferred the steel spring isolators. Less compression set and no heat aging, unlike rubber.

 

I've heard references to "Thackeray washers". Same thing?

[JohnCh]

I used Thackeray washers on all my cars that ran DCOEs. As I recall the procedure was to tighten the nut until the washer fully compressed and then back off one turn. The key is that the carbs can rock without breaking the seal.

 

-John

[Kitcat]

A possibly relevant side note: As I have posted before, when the engine mounts on Cats of this vintage wear, the engine starts moving about excessively. It can be so excessive that the air cleaners poking though the bonnet slam against the bonnet cutout causing the seal between the carbs and the engine to leak. This was the very first (of many:)) mystery issues that I had to trouble shoot on my original Cat. I think BBall had the very same issue. In fact he may be the one who solved it for me? The other tip off that something is amiss, other than power loss, is abnormally loud metallic noises when hard cornering. Since the engine mounts can be shot after 5-8K miles, this is a maintenance issue worth keeping an eye on.

[TheDingo8MyBaby]

The sandwich plates are referred to as "soft mounts." I highly recommend purchasing a set of the high-quality misab plates as they don't tend to have the o-ring displacement issues the plastic ring and groove plates have.

 

In order to allow the carbs to flex to prevent frothing of the fuel in the bowl, you'll want to use either rubber grommets or thackeray washers. Dave bean recommends using the rubber on top and the thackerays below since fuel soaks the rubber and the thackerays tend to fatigue on the bottom. I've found the thackerays to be just fine, but I do check them often. One note - the thackerays sold most places (pierce manifolds, etc) these days seem to be different than the original thackerays that required a coil spacing of 0.04". I tend to use 0.02" as it is apprpoximately the same spring rate as the original thackerays at 0.04" coil spacing.

 

The best option (to keep the carbs better sync'd) is to use nissan (nismo) mounts for mikuni 44's on Datsun roadsters. These are NLA from Nissan and are expensive, but can be found if desired.

[m wirth]

In reference to Kitcats post, on my vehicle with side drafts I had the same problem with engine torque and carbs hitting what they shouldn't, I installed a rubber mounted torque rod using chevy rubber engine mount to frame and solid mount to engine, no more banging filters on frame, this vehicle has over 550,000 miles running DCOE 40, 20R Toyota pickup.

[Joe Petty]

Be sure to check the rubber part!

I had a soft mount with a tear in the raised o-ring and a sliver of rubber would flop around and occasionally jam the butterfly part way open.

After many return springs and cable/ linkage inspections, I finally found it when I had the carbs off.

The mount looked normal, you had to rub over it to find the loose section, apparently the inlet vacuum was enough to get the sliver out in the venturi.

3K idle when you don't expect it is quite a thrill!

[inchoate]

I have new Misab sandwich plates and rubber grommets from Burton in England and they look to be high quality. Of course the weather here has deteriorated so I haven't had a chance to work on the car, maybe next week.

 

The info about the engine mounts is interesting. My car has spent most of it's life sitting and it wasn't particularly well looked after, I've had to replace quite a few rubber bits. I'll give the engine mounts a good hard look the next time I have the hood open.