Cam Bolt Material

[Mad Mart]

I can't remember but what material are the cam bolts made from? The two 1/4"-28 x ½ that hold the sprocket on.

[marshman]

They are just a standard high tensile steel setscrew, nothing special. Part No. HU704. The originals were unplated.

[Mad Mart]

Thank you.

[80Sprint]

Someone put mild steel in mine many years ago. It wasn’t a pretty ending .

[Mad Mart]

Someone put mild steel in mine many years ago. It wasn’t a pretty ending .

I can imagine.

[GrahamFountain]

I had a similar experience once. I bought a TR7 with a Sprint engine cheap (couple of hundred as I remember), cos it was making a "horrible banging noise" from the front of the engine when I bought it. I wasn't bothered, as I had a good engine to transplant into it. Anyway, S&S transported it via their workshops and, as part of their being interested, tried to do a compression test, during which it stopped banging and they found no compression at all.

When I got it, I took the rocker cover off to find that the sprocket was spinning on the cam. One of the two bolts was just missing and the stub of the other was still in the cam end. I think the banging had been the sprocket slapping the end of the cam after the first bolt had fallen out or failed. That had fatigue failed the other after a bit, which is when it lost compression.

For the cost of two bolts and some gaskets (they were probably from SprintSpares) and a bit of work, I thought it was worth trying to fix it. I was able to get the stub of the sheared bolt out through the back just with mole-grips. And believe it or not, it was fine. No bent valves or damage to the pistons. It may not have been the best Sprint engine I ever had. But it was a perfectly good engine for a daily driver. I never found the bits of the bolts or the keeper and I wasn't gonna take the sump off to look. I just drained the oil and re-filled.

I ran it for something like 6 months and probably eight or nine thousand miles before I lost the car on a pile of wet horse apples and went backwards into a ditch.

Graham

[red&black]

It's been on my mind (and my to do list) for a while now to change these bolts for something more substantial.
I bought an engine which had 5/16 UNF setscrews fitted to the sprocket/cam,so was thinking of doing similar to my current engine. Possibly even fit another two screws,so that there are four that are ninety degrees apart.
Anyone done similar or have any recommendations please?
James

[trackerjack]

When I rebuild a Sprint engine I add two more bolts to the cam (if requested) for this I have a drill jig because due to the existing notch on the cam there is no room for error. I once dismantled an engine that someone had used stainless bolts and were lucky that they had not sheared as stainless is weaker than original. To avoid incorrect cam timing these extra bolts are 6 mm and a 1/4 UNF won't fit.
The other thing is the correct torque to tighten these bolts is vital and I reckon some people do them up too tight because there are only two and it seems not enough for such an important part.

[red&black]

Thanks for the reply Jon.
I should have known it wouldn't be easy.
I may have a go at it later this year,and possibly fit a vernier sprocket at the same time.

James

[MIG Wielder]

On the same subject, section 12.13.02 of the Workshop manual has a note that the tab-washer should not be hammered over as there is a danger of it losing it's torque.
Tony.