Inlet manifold fitting.

[DMT]

I am refitting my inlet manifold. After clearing out the holes in head with a tap, I tapped my scriber in each hole and they were all clear of debris. Fitted the manifold and hand tightened each new bolt using no gaskets or washers and found 3 bottomed out before touching the Manifold.

All new bolts were the same length as the old ones.

I am not going to drill/tap the holes deeper but will cut a bit off the bolts.

Is this a normal problem.

[Wheelz]

I use extra washers or thicker washers. Are you using thinner gaskets?

[DMT]

Good idea.

I'm not sure. They are the SOC ones.

[richardthestag]

The bolts certainly shouldn't bottom out, never had that before, in fact when I lost a thread on my stag I used a carb inlet elbow bolt instead which is just a little longer as a "get me out of trouble fix" until next time I have to remove the inlet manifold, not happened in 8 years

Sounds like the bolts you are using are wrong length. is it the long ones or the short ones you are struggling with?

This is a Rover v8 from a 1970s Range Rover that I removed to fix an oil leak from the front of the gearbox. Good job that I did I guess.

A trained mechanic did this! wtaf

20220425_135838.jpg

[DMT]

Were they high tensile nuts?

It was the small bolts. I compared the new bolts to the old ones and they were the same length.

[jbuckl]

The bolts certainly shouldn't bottom out, never had that before, in fact when I lost a thread on my stag I used a carb inlet elbow bolt instead which is just a little longer as a "get me out of trouble fix" until next time I have to remove the inlet manifold, not happened in 8 years

Sounds like the bolts you are using are wrong length. is it the long ones or the short ones you are struggling with?

This is a Rover v8 from a 1970s Range Rover that I removed to fix an oil leak from the front of the gearbox. Good job that I did I guess.

A trained mechanic did this! wtaf

20220425_135838.jpg

Yeah scary.

[jbuckl]

Good idea.

I'm not sure. They are the SOC ones.

maybe they are not scrupulously cleaned threaded holes?
Maybe they were badly repaired threads ?
maybe they are metric repairs?

use a 5/16 unc bottom tap.

clean out with brake & parts cleaner…. At least twice!

Have seen helicoil repairs that are tapered because the repair thread was done with a second cut tap.

That can cause the bolt / screw to appear to bottom out.

[DMT]

Thanks

[richardthestag]

if you dont have a bottom tap you can make one fairly easily using a taper tap and an angle grinder. Chop the taper off and then grind back the first turn of the thread

If the short bolts are the same length then your issue is more likely to be crud in the hole Dave.

When using the bottom tap dunk it in some grease first as all the detritus should stick to it. Be wary of using a blow gun unless the inlet ports are protected first. Tape over them should be more than enough

[jbuckl]

Probably a teaching to suck eggs comment sorry, but if you don’t have thread pitch gauges, compare new with old by holding together & up to the light.
m8 is relatively close to 5/16 unc…. A few I saw were repaired with m8 x 1.25 pitch helicoils.

[jbuckl]

if you dont have a bottom tap you can make one fairly easily using a taper tap and an angle grinder. Chop the taper off and then grind back the first turn of the thread

If the short bolts are the same length then your issue is more likely to be crud in the hole Dave.

When using the bottom tap dunk it in some grease first as all the detritus should stick to it. Be wary of using a blow gun unless the inlet ports are protected first. Tape over them should be more than enough

It’s possible…. But to be fair for these threads a second & bottom is useful to have (both original & helicoil)

Also, a 1.5d is adequate, even a 1d. Imho 2d isn’t needed.

[DMT]

Thanks Richard. I will modify the tap and re tap them.

Dave