The V8 Owners Forum -

Hello,

If somebody has an idea, it will be very helpfull.

I have already in the past changed valve guide on RV8 heads with success, but this time I have an problem.

Removing genuine valves guides was already difficult but insert new valve guides is almost impossible.

I heat the head to around 120°C, and use drift and hammer.

It almost impossible to insert the new valve guide more than 50% of their lenght before the valve guide top cracks. I use later valve guide with provision for Neoprene valve seal.

I don't try with press of fear to damage the head. Someone knows how much pression to insert valve guide.

Any idea to help to insert valve guide. Do I need to oil with WD40 before to insert.

Heat the head and put valve guide in freezer ?

Thank for your help.

You real need to find out the size of the hole and the size of the new valve guides, it could be theyve been manufactured oversize to allow for machining, i n which case your going to have to find a suitable reamer and possibly drill to suit, do u have the old ones? do a check on them with the new ones

Hello,

the most strange I have worked out well with 3 inlet valve guides in one head.

As I know OD of valve guides is standard size. I have measured and no difference. Valve guides come from V8Tuner and Paul adviced me just to heat heads up 150 degres Celcius.

I dont think heating the heads up are going to do you much good drifting them in with a hammer. Its too slow and by the time you get half way down the guide will have heated up and expanded. Beg / borrow / steel a press and they will go in easy.

Wotland wrote:Hello,

If somebody has an idea, it will be very helpfull.

I have already in the past changed valve guide on RV8 heads with success, but this time I have an problem.

Removing genuine valves guides was already difficult but insert new valve guides is almost impossible.

I heat the head to around 120°C, and use drift and hammer.

It almost impossible to insert the new valve guide more than 50% of their lenght before the valve guide top cracks. I use later valve guide with provision for Neoprene valve seal.

I don't try with press of fear to damage the head. Someone knows how much pression to insert valve guide.

Any idea to help to insert valve guide. Do I need to oil with WD40 before to insert.

Heat the head and put valve guide in freezer ?

Thank for your help.

Use a press, as hitting them with a hammer sounds remarkably brutal to me. You shouldn't need massive pressure to get them in, but check the interference first.

I wouldn't want to see more than 0.05mm interference, but that is just an educated guess.

And yes, try freezing the guides first, and a dab of lubrication before you put them in.

Hi
Have changed these using a press myself the best way by far as Paul says. Dont know if you guys agree but we always use to recut the valve seats (lightly) just to ensure everything 100% in line. Was working at a Rover dealership at the time so had all the correct tools which helped a lot.
Cheers John.

Hello.

Many thank for your advice. Not have yet time to try again with press.

I have in my garage an 10 Ton bench press.

john 215 wrote:Hi
Have changed these using a press myself the best way by far as Paul says. Dont know if you guys agree but we always use to recut the valve seats (lightly) just to ensure everything 100% in line. Was working at a Rover dealership at the time so had all the correct tools which helped a lot.
Cheers John.

Definitly, a light skim of the valve seat after installation must be good, as there is very little chance it'll all be lined up exactly after you have removed and re-fitted the new guides.

The local machine shop that does my heads drills out the old guides, reams the hole back to size, then presses in new guides with special tools.
The head has been heated up in the cleaning bath first, and he uses a press tool that fits the top of the guide.

Even after all of that, they sometimes break!

Chris.