Bushing rocker spindles

marshg246 · 2026-02-08T06:47:42-0700

Also, Loctite 680 can be used for heat installed interference fit.

From: https://next.henkel-adhesives.com/u...ite-680/BP000000153464/variation/1835205.html

"Apply the adhesive onto the male component; heat the female component to cause expansion for free assembly.

Assemble components and allow temperatures to equilibrate. Wipe of excess adhesive."

Andy Higham · 2026-02-08T06:56:20-0700

If you counterbore the outer end of the outer bores, 1mm deep and 2mm bigger than the diameter of the bush. Then make up stepped bushes to suit with the step very slightly proud, say 0.01mm - 0.02 mm the spindle end plates will clamp the bushes in place

Peteyoung75 · 2026-02-08T08:18:04-0700

mdt-son said:
I suggest you try a proper interference fit before you reach for peening, which deforms the bush. Heat the head to 100 'C (212 'F) and cool the bushes to -193 'C (-315'F).
Make the bushes a sliding fit at these temperatures. Cool the drift as well. Bushes should new withstand the torque created by the reamer. You may try out using your test block.

- Knut

Thanks for the info. I’m currently heating the head to 200c and cooling the bush and mandrel to approx -50.
Suggestions how to get the bush cooler would be good although going to liquid nitrogen isn’t really doable.
As the bush will be reamed to final diameter after peening is deformation of the bush an issue?
The fit I currently have is a cold press fit but shrunk in rather than pressing. It’s basically between +0.015 and 0.020mm for the bush relative to the hole. I think this works out as equivalent to H7 p6 ISO press fit tolerance but inoten get confused when I look at fit tables

Peteyoung75 · 2026-02-08T08:24:12-0700

Andy Higham said:
If you counterbore the outer end of the outer bores, 1mm deep and 2mm bigger than the diameter of the bush. Then make up stepped bushes to suit with the step very slightly proud, say 0.01mm - 0.02 mm the spindle end plates will clamp the bushes in place

Thanks although the primary concern with the outer bush is stopping it from rotating and shutting off the oil supply. Having a step might take up room needed to pin it. I’ll have a look and see. It would make drilling a pin hole a bit nicer if I drilled through the rim of the stepped bush.

mdt-son · 2026-02-08T10:50:11-0700

Peteyoung75 said:
Thanks for the info. I’m currently heating the head to 200c and cooling the bush and mandrel to approx -50.
Suggestions how to get the bush cooler would be good although going to liquid nitrogen isn’t really doable.

Heating the cylinder head to 200 'C is not advisable, as temper state of the alloy will change. Also, you risk valve seats and valve guides dropping out, depending on head position in oven. Maximum heating temperature for today's alloys is 180 'C, but I'd be careful with any temp above 150 'C for this alloy.

- Knut

mdt-son · 2026-02-08T10:53:07-0700

Peteyoung75 said:
As the bush will be reamed to final diameter after peening is deformation of the bush an issue?

Yes. You are essentially reaming an oval hole. The reamer will not centralize.

- Knut

mdt-son · 2026-02-08T11:11:02-0700

Peteyoung75 said:
Suggestions how to get the bush cooler would be good although going to liquid nitrogen isn’t really doable.

Perhaps not in your garage, but a lot of machine shops and plumbers keep liquid nitrogen for their needs. Other users are medical labs, colleges and research institutes.

By heating the head to 150 'C, you may use dry ice also (-79 'C). Dry ice (frozen CO2) is much easier obtainable.

- Knut

Peteyoung75 · 2026-02-08T11:14:04-0700

mdt-son said:
Perhaps not in your garage, but a lot of machine shops and plumbers keep liquid nitrogen for their needs. Other users are medical labs, colleges and research institutes.

By heating the head to 150 'C, you may use dry ice also (-79 'C). Dry ice (frozen CO2) is much easier obtainable.

- Knut

Thanks I am currently using dry ice.

Peteyoung75 · 2026-02-08T11:18:56-0700

mdt-son said:
Yes. You are essentially reaming an oval hole. The reamer will not centralize.

- Knut

I’m reaming from 12.3 to 12.66mm, I’d be surprised if peening the aluminium onto the bush would cause enough deformation to be a concern. I can always run a drill through first or start with a smaller pilot hole in the bush before drilling and reaming in situ.
Edit - not sure why I thought drill as i can always get the bore realigned and sized with the boring head

Peteyoung75 · 2026-02-08T11:55:47-0700

mdt-son said:
Heating the cylinder head to 200 'C is not advisable, as temper state of the alloy will change. Also, you risk valve seats and valve guides dropping out, depending on head position in oven. Maximum heating temperature for today's alloys is 180 'C, but I'd be careful with any temp above 150 'C for this alloy.

- Knut

Thanks - I’m heating the head locally with a torch rather than in the oven. This is so I can keep the machine set up. I’ll go a bit cooler on the head. I’m currently practicing on a scrap one. Only trouble with going cooler is that’ll limit the interference available

marshg246 · 2026-02-08T12:10:08-0700

Peteyoung75 said:
Thanks - I’m heating the head locally with a torch rather than in the oven. This is so I can keep the machine set up. I’ll go a bit cooler on the head. I’m currently practicing on a scrap one. Only trouble with going cooler is that’ll limit the interference available

100C is plenty hot for the main bearings and camshaft bushings without cooling the bearings or bushings - I don't see a need for higher for your purpose.

Peteyoung75 · 2026-02-08T13:30:01-0700

marshg246 said:
100C is plenty hot for the main bearings and camshaft bushings without cooling the bearings or bushings - I don't see a need for higher for your purpose.

Thanks. I’m basing the technique on recommendations in Phil Irving’s Tuning for Speed book which gives the same method for fitting bronze sleeves to main bearing housings in aluminium crankcases and also for fitting valves seats into aluminium heads. I can go cooler but this will reduce the amount of interference available unless I go to a press fit with the head hot and the bush cold. I think this would be pretty risky as they’re small bushes that are fiddly to fit as a sliding fit. Food for thought though

Bushing rocker spindles

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