The V8 Owners Forum -

I've bought one and a Performer manifold to go on my 4.6 Rover this winter and have just noticed the way the manifold is machined puts the carb downhill at the front when the manifold is level - the manual says by 2.7°
It also says "the carb face on the manifold can be machined up to a maximum of 4° extra to optimise bonnet height clearance".
Does this mean it doesn't matter if (within limits) the carb isn't level front to back or does it assume the engine'll be tilted to keep the carb level?

In most cars the engine sits slightly nose up so they are correcting for that to keep the carb level

Yes, that makes sense but if you've machined the manifold carb face to get more bonnet clearance as they say then the carb's probably ended up not being level anyway.
If mine ends up not level then what making a tapered plate to go between the carb and manifold - any thoughts?

ratwing wrote: ↑Sat Sep 14, 2024 10:55 am Yes, that makes sense but if you've machined the manifold carb face to get more bonnet clearance as they say then the carb's probably ended up not being level anyway.
If mine ends up not level then what making a tapered plate to go between the carb and manifold - any thoughts?

I'm struggling to remember the detail of mine (over 20yrs ago) but one slight issue you may find if you machine the face of the manifold is that the bolt/stud holes will no longer be true to the mount face and will try and bend when you tighten down.

When I ran a carb' (4 brl Webber which I think is an Edelbrock 500) modified it to sit true as my engine does not tilt. IIRC I faced the mount face of the manifold down (maintaining the angle) then bolted on a spacer which I machined true to the manifold mount faces hence giving a taper and re-established the mount hole patern in the spacer, I think this is correct but I'm not sure why the hole patterns wouldn't interfere, pity I don't have photo's but this was before camera phones. One thing I did do was taper the apertures in the spacer to give a smooth flow between carb' bore size and manifold bore size.

Either way I don't see any issue with a tapered spacer apart from the bolt/stud angles and as long as you don't have any clearance issues this is probably better than altering the manifold, difficult to go back then.

As you say, altering the manifold is pretty much a permanent change. I don’t want this to come back and bite me so I’ve been giving it some thought and reckon I can get around the bolt problem by using studs - make some nuts the same thickness as the spacer, run the nuts down to the manifold and bend the studs. Remove the studs, take the nuts off and refit them with high temperature locktite through the spacer and lower gasket and then, fingers crossed, the upper gasket and carb should slide down no problem.

Google Holley wedge plate and you will see loads.



I would suggest not machining your manifold but measuring it once installed.

Then add a pre-made wedge plate for the correct angle……… keep it simple

Ian

Possibly stupid comment, but how much difference does it make being at a small angle given that we still manage to drive up and down hills?

scudderfish wrote: ↑Sun Sep 15, 2024 1:06 pm Possibly stupid comment, but how much difference does it make being at a small angle given that we still manage to drive up and down hills?

I must admit I did wonder about that when I did mine but did it anyway. Because I could!

scudderfish wrote: ↑Sun Sep 15, 2024 1:06 pm Possibly stupid comment, but how much difference does it make being at a small angle given that we still manage to drive up and down hills?

Indeed.
When designing the manifold, Edelbrock chose to make the carb face down by 2.7° - I doubt they just picked a figure at random so assumed there's most likely a reason for it.
Then on the other hand, they say if you want more bonnet clearance then go ahead and machine it another 4° so if it was level to start with it won't be now.
The more I think about this the more I wonder if it really does matter so I'm inclined ( ) to just use the manifold as it is if the angle's within those limits.