10 replies to this topic

[TopCatCustom]

Hi, schoolboy error of breaking into the pushrod holes whilst porting my inlets the other day, I'm planning on sleeving them with 13mm steel tube, the holes are 13mm at the biggest points (both ends as they seem to get smaller diameter towards the middle) and just wanted to see what wall thickness I should use if people have done it before, I plan to locktite them in place once everything is done.

[Cooperman]

Hi, schoolboy error of breaking into the pushrod holes whilst porting my inlets the other day, I'm planning on sleeving them with 13mm steel tube, the holes are 13mm at the biggest points (both ends as they seem to get smaller diameter towards the middle) and just wanted to see what wall thickness I should use if people have done it before, I plan to locktite them in place once everything is done.

A lot of head porting experts used tyo grind away until they broke through, then bore and sleeve with a piece of steel tube. About 1.5 mm wall thickness is fine, so you would bore and ream the holes out to 16 mm for a snug fit. The 'Loctite' to use is the bearing locking stuff, can't remember the number and I've run out so can't check the bottle.

[TopCatCustom]

I thought you would know Peter! I didn't want to go too big as it means more protruding into the runner, I was thinking a much thinner wall like 0.5mm-1mm max on the assumption that it is only blocking a hole with next to no pressure on either side of it. I have been thinking about the aluminium pushrods from minispares as a future modification, which I reckon are a fair bit thicker than the standard steel ones, and not sure if they require the pushrod holes to be opened up in a standard head or not.

[mini13]

I have used this before, and silver soldered it in place.

http://cgi.ebay.co.u...em=120708771752

[MRA]

bearing fit to hold it in place and with a ball bearing about 5/8" diameter... CV one will do tap it in the end of the tube to bell it out, do this both ends and it will lock in place, you may need to chamfer one or both holes first though....

[TopCatCustom]

I have used this before, and silver soldered it in place.

http://cgi.ebay.co.u...em=120708771752

bearing fit to hold it in place and with a ball bearing about 5/8" diameter... CV one will do tap it in the end of the tube to bell it out, do this both ends and it will lock in place, you may need to chamfer one or both holes first though....

Great thanks guys, that brass tube looks like it may do the trick along with locktite, 17/32 is about 13.5mm which should be fine, the 1/2" may even just fit so will test it out by drilling one through with a 12.5mm bit to see how it looks first.

Martin thanks for that- I was thinking of swaging the tops out slightly as a secondary restraint but forgot since I've been thinking about it again!

[pogie]

My MED head has sleeved pushrod holes on the inlets and it looks like they used steel for the sleeves. One thing that caught me out is that the diameter of pads on the bottom of the push rods had to be reduced by a few thou to allow them to pass through the sleeves.

[MRA]

Hold on... you cant really use a drill for this operation, a reamer is minimum otherwise the iregularity, out of roundness etc will bite

[TopCatCustom]

I meant drill first Martin then reamer, there's probably in the region of a mm to come out the the holes...

[MRA]

leave about 0.020" on the diameter turn it slow and push it quickish...

With a good sharp reamer you could take it out in one hit .... on a machine anyway

[TopCatCustom]

We've got a radial drill that will push a 3" drill bit through solid steel without making any fuss, but it doesn't stop for anything and think it's asking for trouble putting a reamer in there incase it rings it off! It's the only machine that will go slow enough, I think about 80rpm or something.