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MG Midget and Sprite Technical - Cam timing (piper 270)
|Hi hope someone can help me as I think I have read too much on the internet this subject and it's done my head in. I have a 1500 midget and am rebuilding the engine to stage 2. Have had head done and have all other bits. I have a piper 270 cam and am now at the installation stage. I understand how to get TTDC with dial gauge and have Moss duplex venier my questions are|
1 Do I now put head on and continue and if so how do I time the cam in. There are no dots on the new cam gear!!
2. Do I time in the cam with the head off and again if so how
3. Do's anyone know if there is a book or vid on this subject or a page with the actual info on the internet for a 1500
Thanks for any help
|I always time the cam using a dial gauge on the valve collet, with all the rocker gear in place and adjusted, to manufacturers open/close spec.|
Others time on the follower or pushrod for max lift.
check this site out for a full explanation
Just get the crank at TTDC set up your timing wheel move the crank to the Cam's requirement and use a dial gauge to find max lift on the lobe.
Any problems, come back with..
This is not 1500 specific but for any push rod engine.
Leave the head off.
Determine TDC on nr 1
Fit degree disk to crank and fit bent wire indicator to any bolt so it can not move indicating 0 on de disk.
Rotate the crank to the disired full lift nr (only rotate in the direction the engine will turn)
Remove degree disk.
Fit cam with inlet lobe nr 1 pointing to the top of the block.
Fit cam folowers gears and chain.
Refit degree disk and recheck TDC and make sure wire is indicating this.
Fit a pushrod
You have now established your base point where full lift should be near the desired moment.
Now the fine tuning.
Go to 15 degrees before planned full lift
Zero the dial gauge on the push rod.
Then proceed to 15 degrees after planned full lift.
If this reading is also zero then full lift is right when you want it.
But most likely it is not.
Now the fine tuning starts with sliding the venier.
If 0 has not jet been achieved you need to losen the venier and slide the cam fwd to half of the value to go the tighten.
If 0 has already passed you losen the venier and slide the cam back to half of the value past.
Now recheck and continue the proces until it is perfect.
Then if you are realy fussy you can check all inlets for this compared to that cylinders TDC.
If you find a big variation you can spread the difference over all cylinders to equal things out.
Always rotate the assembly in the normal turning direction (exept for the cam when fine tuning the venier) rotating backwards will cause faulty measurmenst due to play
|Thank you all for the help will have a go tomorrow night once my heads clear Ta.|
This thread was discussed on 20/11/2011
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