Does anyone know the bolt size ......

[mk1fan]

..... for the overrun valve on a 3.5 RV8? It is a flapper EFI so NOT stepper motor.

Need to swap the cap head bolt for button or socket as it is fowling the throttle cable.

Thanks.

[v8s4me]

mk1fan said:

..... it is fowling the throttle cable....

It is because it's a flapper that it's fowling?

[mrzigazaga]

Hi mate

I think this is it...

Overrun valve Bolt 5/16" UNC x 2.1/4 inches long

Cheers


Ziga

[KKson]

mrzigazaga said:

Hi mate

I think this is it...

Overrun valve Bolt 5/16" UNC x 2.1/4 inches long

Cheers


Ziga

All, no sure that's right? The over run valve on mine has quite short bolts (set screws) as they only just go through the plenum wall. 2.5" would take the bolt all the way into the plenum. If I get a minute tonight I'll try and measure them.

[phillpot]

you'll obviously know the length from the existing bolt.

Diameter can be measured easy enough

Thread is unlikely to be metric as these engines are of American origin so that leaves unf or unc. threads into alluminium are usually unc.
It's fiddly but thread pitch can be counted (if you don't have a thread gauge), unc will be 18tpi whereas unf is 24, a very distinguishable difference.

[mrzigazaga]

KKson said:

mrzigazaga said:

Hi mate

I think this is it...

Overrun valve Bolt 5/16" UNC x 2.1/4 inches long

Cheers


Ziga

All, no sure that's right? The over run valve on mine has quite short bolts (set screws) as they only just go through the plenum wall. 2.5" would take the bolt all the way into the plenum. If I get a minute tonight I'll try and measure them.

I found this info on a Rover V8 forum....So apologise if its wrong!

[v8s4me]

I have a 3.9 EFI plenum in the loft. If the overrun valve goes in the same mounting hole I can get it out this evening and measure it for you.

[mk1fan]

phillpot said:

you'll obviously know the length from the existing bolt.

Diameter can be measured easy enough

Thread is unlikely to be metric as these engines are of American origin so that leaves unf or unc. threads into alluminium are usually unc.
It's fiddly but thread pitch can be counted (if you don't have a thread gauge), unc will be 18tpi whereas unf is 24, a very distinguishable difference.

I am away from the car ATM and wanted to order some in ahead of my return. I was going to pinch one of them but forget.

[mk1fan]

v8s4me said:

I have a 3.9 EFI plenum in the loft. If the overrun valve goes in the same mounting hole I can get it out this evening and measure it for you.

Thanks Joe. No rush though as I need to go to Spain this weekend so this 'quick fix' job will have to wait!

[phillpot]

mk1fan said:

I am away from the car ATM and wanted to order some in ahead of my return. I was going to pinch one of them but forget.

Order a selection!



........... can't have too many spare bolts

[mk1fan]

phillpot said:

Order a selection!



........... can't have too many spare bolts

There's already a large selection of metric 'spares'. Really don't want to start an imperial one too

[KKson]

Isn't metric. Pulled one off my plenum. 20mm thread length and my old 5/16" tap runs up the hole. Allen head set screws. My tap is quite old so couldn't see if UNC or UNF.

[eesbad]

KKson said:

Isn't metric. Pulled one off my plenum. 20mm thread length and my old 5/16" tap runs up the hole. Allen head set screws. My tap is quite old so couldn't see if UNC or UNF.

Looks like UNC to me and the thread length 3/4"

[eesbad]

Just checked and we only carry 1 1/2" long hex head in that thread size at work. Oh well.

[mk1fan]

Thanks.