Tappet Screw Thread

[isuzutoo-eh]

Hi all,
Before I go and destroy some threads, can I get confirmations that the rocker/tappet screws are indeed 5/16th UNF? I know later rockers are M8 but the earlier ones definately aren't.
-Mark

[JDNSW]

I can't confirm that - I would not be surprised if they were 5/16 BSF, although they could be UNF. The engine was designed right at the time the changeover was in progress, and because the thread is cut in a special part (tappet), if they started making them BSF, they would have stayed that way. Unfortunately I have none readily accessible to check. If you have an adjuster out, count the threads per inch - in 5/16 UNF is 24, BSF 22.

John

[isuzutoo-eh]

Thanks John,
That would explain why my newly purchased 5/16th UNF tap doesn't quite run through the locking nut easily, on comparison the tappet screw/adjuster and tap are very slightly different in thread count.

[JDNSW]

Thanks John,
That would explain why my newly purchased 5/16th UNF tap doesn't quite run through the locking nut easily, on comparison the tappet screw/adjuster and tap are very slightly different in thread count.

Sounds as if they are BSF. You can get BSF taps and dies - any tool supplier will get them in for you, or Brian Hjelm on this forum can probably supply.

John

[Bigbjorn]

Get yourself a set of screw pitch gauges. Absolutely essential. They come in British, US, Metric, and BA systems.

I have BSF taps and dies in stock.

[peterg1001]

Hi all,
Before I go and destroy some threads, can I get confirmations that the rocker/tappet screws are indeed 5/16th UNF? I know later rockers are M8 but the earlier ones definately aren't.
-Mark

Mark, just out of curiosity - what happened to bugger up the threads on the tappet adjusters? I wouldn't have thought rust would be a problem . . .

Peter

[isuzutoo-eh]

Long story!
After frigging around for ages with crappy parts, local motor rebuilders and engineering firms...I bought a set of rockers assembled on a shaft from Turners in the UK. When fitting, two of the tappet screws wouldn't screw in easily enough. Turner's supplier had mixed some metric rockers into their parts bins, so I ended up with a mixed up set. After a few emails and a midnight phone call from the UK, Turner's rectified it quickly by sending two M8 tappet screws, but it turned out one was BSF and just wasn't a clear thread, that has now had an M8 co-erced part way into it through frustration, ruining the thread further. I am pretty peeved at all the problems and delays these seemingly simple parts have given me, but much of it is my own inability to do anything properly the first time...


(PM sent to Brian)

[THE BOOGER]

Isnt it fun owning older cars:D the good thing is by the time you get her back on the road you will be able to completly rebuild the engine with a shifter and one screwdriver :o

[isuzutoo-eh]

yeah, I ah grrrrr ee...and by the time i'm finished i'll just about have a second vehicle's worth of mistakes too :p

[isuzutoo-eh]

In case anyone else has the same problem...the thread is indeed 5/16th UNF, not BSF-so now I have a spare 5/16th BSF tap...

Thread gauges will be ordered shortly.

Thanks all