Engine freshen up

Mick · 5th May 2012, 11:32 PM

Need a bit of advice, freshening up my 302 as a result of a blown head gasket. When I pulled the motor down I notice there are 4 pistons with there valve reliefs installed on the wrong side, I don't mean upside down but with the exhaust relief on the intake side of the piston suggesting that the pistons had been installed on opposing rods by mistake. Forunately valve clearance was not a problem.

This appears to be the way the rotating assembly had been returned after balancing, because the pistons had been originally machined for additional valve clearance the pocket on the pistons are all uniform expect for a small relief the remains indicating which side the original position for valve clearance must have been.

My concern is which direction the piston should be facing and whether If I take the pistons off the rods and relocate them correctly do I need to rebalance the assembly again considering it has already been done and I am not changing any thing accept the rings and deglazing the bores. Any advice would be welcome.
Mick

Dimi Terleckyj · 6th May 2012, 01:18 AM

Hi Mick

With regard to the pistons they should have a notch on the top edge to indicate the front of the piston which should be facing the front of the motor.
If you take them out and turn them around make sure you replace the big end bearings as they will have bedded themselves in to the crank and by turning them around all the bedded surfaces on the bearing will not match and they will fail very quickly.

The rings also have a dedicated way they should be installed with respect to the endgaps of the rings facing towards different sides of the bore.

Do not reuse any rings when you pull the pistons.
It is a small price to pay for the new parts and you wont have to worry about reliability.

Dimi

Mick · 6th May 2012, 02:52 AM

Thanks Dimi, should have provided more detail. All bearings are new all ring are new just trying to understand why the so called f#*king experts reassembled the pistons on the wrong rods originally and I missed it when the engine was first assembled. Just wasnt sure if moving the pistons altered the balancing, my understanding is it doesn't change along as they are all the original components?

Mick

Mike Huddart · 6th May 2012, 05:05 AM

Ford pistons are not handed, you can swap them from bank to bank and they will be the same. Think about it, you can swap the heads from bank to bank so it follows the pistons will be the same. UNLESS you have stock replacement type pistons that all have to face the front and in that case you would have four valve reliefs, top and bottom.
Sounds like someone has just machined them wrong for the extra valve clearance.
Do you have a photo or part number.

Mike

Woody · 6th May 2012, 05:07 AM

Hi Mick
All the pistons Should be balanced to the same weight and all the rods balanced individualy too. So swapping them shouldn't hurt the balance. Check the rods they should be numbered and keep them in order. If they are after market rods they may not be numbered so check the big end, one side will have a bigger champher than the other side. This champher goes to the radii on the crank. when the bearing is installed you will also notice it is offset away from the champher too.
If everthing has been balanced correctly swapping them around wont hurt.
You know what they say " If you want a job done right do it yourself"
Good luck
Woody

Mike Huddart · 6th May 2012, 05:09 AM

Just had a thought, are we talking about a regular American type 302 (Windsor ) here or one of your Ausy Cleveland type 302 thingys.
Mike

Woody · 6th May 2012, 05:55 AM

Hi Mike
The 302 Cleveland uses 351 pistons so they don't have an exhaust relief or pocket.
but weater its a winsor or a cleveland the intake valve notch will be at the front on the bank numbered 1-4 and on the back on the bank numbered 5-8.
Woody

Mick · 6th May 2012, 07:39 AM

Thanks for the replies guys, Mike / Peter its a Windsor the pistons I used are KB hyper flat tops. The valve relief work was done to suit the cam, rockers & heads with 2.02 intake valves so they aren't wrong I' not looking to relocate the rods just pistons that appear to be in the wrong positions. I appreciate the advise guys question was answered balance is not affected if you move the pistons around.

Mick

flatchat(Chris) · 7th May 2012, 06:09 AM

Should look like this, Intake valve reliefs to the top front on the right bank and exhaust reliefs to the top front on the left bank --then be sure the rods are on the right way around