302 engine id

Simon · 01-23-07, 04:11 PM

I have a 302 engine that was supposedly taken from a mustang GT.
I bought the engine knowing that I have to strip it down and inspect it.
I have one of the heads off and have already found a large dark mark on the bore which seems to have been caused by water making the inside of the bore rusty (the engine has been sitting in a leaky garage for a while) which will probably mean a rebore.
I just wanted to ask if the piston in the picture is standard for that type of application. As far as i'm aware, it's a mid 80's engine, originally fitted with an efi system. It has a roller camshaft and a serpentine pulley on the water pump (which will need changing)
Simon

StuartB · 01-23-07, 08:28 PM

Hi Simon,
It's a 1986 EFI spec Ford piston, original C/R is 9.2:1 for this motor, the good news is it's forged so that can be sorted.

Jac Mac · 01-23-07, 09:55 PM

The bad news is it specific to the cyl head that has the valves set deep in the chamber ( note no valve notches ), and they will need to be cut if you plan on using most other or aftermarket cyl heads. Having said that the heads that go with those pistons respond quite well to a bit of a rework in the combustion chamber.

Jac Mac

Simon · 01-24-07, 04:40 PM

I think like I said, the engine may need a rebore to sort out the rust damage in one of the cylinders. I guess this'll mean I can pick and choose another set of pistons.
Da*n....thought I was going to get away with just a hone

Simon

Keith Hardy · 01-24-07, 04:44 PM

Quote:

Originally Posted by simonjrwinter

Da*n....thought I was going to get away with just a hone

Simon

Uh oh, here we go.....

Simon · 01-24-07, 04:48 PM

yep...it's gonna get 'spensive!

Simon · 01-24-07, 06:24 PM

Mind you, i've just had a better look at the bore. after a miniscule amount of surface corrosion was scraped away, the bore feels so smooth now, with no ridges at all, I MAY just get away with just a hone. I guess it all depends on the advice of the machine shop (and the state of the other side when the second head comes off)

Simon

Simon · 01-24-07, 07:20 PM

Jac mac, you're right, there's no pocket in the pistons and the valves seem to be set a long way into the head. Would doing something as simple as changing the rocker arms to 1.6 roller rockers mean contact in the valve piston department? Can these heads be skimmed at all?
What sort of work can improve them?
Thanks

Simon

Jac Mac · 01-24-07, 08:08 PM

1.6 is std rocker ratio so should not cause any problems, any head skimming or cam change it would be prudent to check valve to piston clearance.

If its the head I am thinking of it needs unshrouded around the valves and radiused on sharp edges particularly on the cusp that extends between valves.

Skimming of any Ford prod heads should be kept to a minimum for deck strength reasons.

Jac Mac

Howard Jones · 01-25-07, 12:10 AM

Why not cut the valve reliefs when you have it apart. I would think it would be cheaper than new pistons and you can change heads later if you want to. While you have the pistons off the rods , have it balanced. Money well spent.

Simon · 01-25-07, 12:03 PM

I've now taken the head off the other side......oh boy!
No corrosion or wear, but somethings been down one of the cylinders at one time. loads of tiny pin marks in the piston top and head surface. Worse than that some hefty scratches down the cylinder. I've yet to take the block to an engineering shop (this WON'T hone out) but I'm not even sure a +30 rebore will take out these scratches (damn!!!) just in case they tell me that, is re-sleeving an option on the 302 block?
I'm not after massive power so I don't suppose the block will be under massive strain.
Oh yes, as I'm in the UK, and it is possible, will I have to source a liner from the US?
Thanks. Any advice appreciated.

Simon

Big-Foot · 01-25-07, 02:13 PM

Quote:

Originally Posted by simonjrwinter

I've now taken the head off the other side......oh boy!
No corrosion or wear, but somethings been down one of the cylinders at one time. loads of tiny pin marks in the piston top and head surface. Worse than that some hefty scratches down the cylinder. I've yet to take the block to an engineering shop (this WON'T hone out) but I'm not even sure a +30 rebore will take out these scratches (damn!!!) just in case they tell me that, is re-sleeving an option on the 302 block?
I'm not after massive power so I don't suppose the block will be under massive strain.
Oh yes, as I'm in the UK, and it is possible, will I have to source a liner from the US?
Thanks. Any advice appreciated.

Simon

First off - the engine is not a Mustang HO engine but is probably from a full-size passenger car. The pistons in the non-HO cars were typically cast Hypereutectic design pistons. This can actually work to your advantage - read further..

"tiny pin marks" - this is usually a result of detonation / Pre-ignition. From the sound of it, this could have come from potential oil consumption problem in one or more cylinders.

Getting by with a re-hone (here's where the info from above comes into play).
Cast / Hypereutectic pistons are typically fit with a tolerance of .0015-.0035". If you measure the bores and they are still round within tolerance - you can have the block honed to fit a set of replacement "forged" pistons which are usually fit from .0045-.0065".
By replacing the pistons with forged - you can get pistons that are already notched appropriately for the higher lift camshafts.

Re-balancing
Not typically necessary with a set of replacement pistons as there is a published spec for piston weights for the original pistons that all piston manufacturers reference.
The replacements (cast or forged) typically fall within a couple of grams of that spec.
Unless your engine is going to be seeing sustained high RPM useage on the track, balancing to a tighter spec is just spending money for the sake of spending..

Sleeving blocks.
The 302 block is known for having strength issues to begin with - particularly in the support area of the main bearing webs.
I would sleeve no more than 2 cylinders in a 302 block and at that they should not be adjacent nor directly across from each other.

I hope this is of some help..

Jac Mac · 01-25-07, 03:48 PM

First, the extra clearance is usually built into the piston- Bore size remains same @ 4.000" ( Cast-Hyper pistons will measure up @ 3.997"/3.998 approx while Forged will be in the 3.994'/3.995" zone ) Ford did make replacement Forged pistons to suit 0.005" O/S to allow for correction of warranty problems etc . These may no longer available though.

ACL ( Australia ) Make a Hi- Silicone Cast piston of performance design with narrow rings, coated skirts and drilled oil drainback ( no slots ) which is available in 0.020"/0.030"/0.040" OS. It also has a single large valve clearance pocket. These are also available for the 3.4" stroker version ( a 0.005" OS was also available for these. Taper wall pins & enough material in pin boss for circlips if you desire are a couple of other features.

The reason Howard & others urge you to rebalance is in the 40 situation you will require a non Ford flywheel, several forum members have had exspensive problems with mirror balanced flywheels and since the piston weight is likely to change in this instance it would be prudent to do so. ( Randy obviously has a lot more faith than in the ability of replacement part manufacturers to adhere to production weights than I do.)
I agree with Randy on the sleeve issue- not side by side- and as an added thought, I make all my own sleeves, just go to the local tractor/truck workshop and scrounge some of the old wet sleeves and spin them up in the lathe to the size I require, turn a step about 0.500" up from the bottom & bore the block to suit, That sucker aint going nowhere!

Jac Mac