RCinXS

Running 300HP Euro cams on a supercharged 4.7 US engine.

86.5 TB, Air guide, etc.

Long story short, I ended up with a pair of P&P Euro S heads. They have been checked out, freshened up, and are ready to bolt on.

Since I'm already deep into the Spring project, I thought I would use them instead of doing a valve job on my US 4.7 heads.

The US pistons have reliefs for the US valves and would need to be flycut to accommodate the larger diameter Euro valves. Not sure about the depth.

When I brought this up to one of the vendors that I buy a lot of my parts from, he indicated that the cast pistons cannot be flycut, and if I did this, they would fail. He said that only forged pistons should be flycut.

Now I know a few guys have flycut the 5.0 pistons and I haven't heard of any failures. The flycuts they did are much more intense than just taking another 0.040" out to add to the diameter of the relief.

So, I what I need to know is:

Has anyone flycut reliefs in 4.7 US pistons?

Were there any failures?

And if you used Euro S cams and heads, did you need to make the reliefs in the 4.7 US pistons deeper as well?

Any information on this would be greatly appreciated!

Roy928tt

Shouldn't be an issue, the tops of the pistons are already machined, so it is not as if you are introducing stress raisers where there were none already. It is a relatively common mod and is not renowned for causing issues.

Go right ahead,

Cheers Roy

Iwanna928

Others that know better will chime in for sure.

I have euro cams on a 4.5L and no machine work, flycutting etc required!

I believe that everything should bolt right up!

The question is if the engine is still non interference

All the 4.7 stuff should bolt up just fine.

The only thing I have read in regards to flycutting is with the 5.0L and 16v heads!

So you have euro heads and cams on a US 4.7L shortblock...no problem!

Lizard928

Stephen, he is talking about the euro valves which are larger diameter and yes need larger reliefs in the pistons.

However adding the reliefs should be fine.

RCinXS

Thought I wold do a 2D mock up of the expected cuts. It might make it clearer as to what I'm trying to ask.

Scale may be off a bit. But gives a good ballpark.

mark kibort

Ill chime in here, because I think ive done more of the fiddling around with the 2 valve hybrids than most, and have no issues.
you are concerned with the flycuts on the 4.7, and that is an unknown. I dont think anyone has just bolted on a 4.7 euro head on a US 4.7. if so, then you dont have an issue. however, it is a real easy hand grind job to take about 1mm out of the radius of the existing flycuts. unfortunately, after my flycut mods to the stock 85 ( 5L) pistons, after claying it up, they were making contact with edges of the cuts. I had to tape it all off , and dremel the edges slightly. dont worry about the depth, you will have an interference engine anyway. the cams push the valves down over .4", but valves contact the piston at .3", so unless you have an early model 4.5, you can have contact.

my advice, just take a dremel to the edges of the flycuts.

the guy advising you that the cast pistons cant be cut is wrong. there is nothing wrong with flycutting the pistons to the depth needed (mostly needed only for installing a timing belt, not for operation )

here is a picture of me grinding off 1mm off the edge of the machined 2 valve cuts on the 5 liter pistons
also, look at the real euro 2 valve pistons. those are deep pockets on the 80 --83 . you cant physically make the pockets this deep on a 4.7 or a 5 liter piston. the 84-85 pistons are much more shallow. those newer pistons have only a .175" pocket depth. this is what we us for modiing the 5 liter pistons.
keep in mind, this keeps the compression up too, which is good.

RCinXS

Many many thanks to everyone.

Project will go forward as planned.

I will post results, pix and any insight that I can provide when finished.

Again. many, many thanks to all 1

123quattro

Actually, that's exactly what I did. I have Euro 4.7 heads/cams on top of my US 4.7 short block. I didn't touch the pistons. I am just assuming it's an interference engine now.

Sueden

Same as what John (123 quattro) said ! I just bolted the 85 euro top end to my 4.5 and thats that runs real strong!

mark kibort

so, here is the part that is most confusing. no contact with the euro heads when running or bolted all together and rotated? or no contact when rotating the cams , when the crank is locked at 45 or 0 degrees BTDC?

a lot of people think that the valve reliefs are for clearance when running, and thats not exactly true for our engines. the pistsons wont touch the valves, because they move down farther than the valves chase them down.
remember, the valves at full lift are .4" depressed. that happens somewhere between TDC and BDC. when that piston is 1/4 to 1/2 way down, (about 2") the valve is depressed less than .5, so the dont touch even if the piston is flat.
however, when rotating the cams at TDC, you get about .3" of valve depression and they contact the piston at the cut out. (with a devek b1 cam which is high lift). this is why you cant rotate the cams in the S4 engine without the crank at 45 degrees BTDC.
as a note, if you remember S4 cam timing, you remember that at 20 degrees crank movement, the vavles move down 2mm or so. the valve reliefs are 4mm deep., and near 8mm for the euro '80. so, you can see why you can be off a few teeth on the cam pulley and not hit valves, or have it be non interference with the '80 valve cuts (euro). anyway, i forgot how far the piston moves down with a 20 degree crank movmenet, but i think its pretty far down the hole vs the slower moving valves.

I guess what you have found and confirmed, is that the above is the case, and also, the valve cuts might have that 1mm already built into the cuts for the smaller valves , just as a safety margin and you are still in that window.

I dont know. the only way to check this, would be to clay things up and see how far you can depress the valves, without them touching the pistons. if you didnt do that, you will never know unless , you break a timing belt.

123quattro

I didn't spin the assembled engine with the cams locked to see if there is cam interference. I figured there was for sure. It definitely runs just fine though.

karl ruiter

I have 4.7 Euro S heads on top of a 4.5 US block. Runs great with no problems but incontravertably an interference motor. I have the bent valves to prove it.

RCinXS

Mark, Going to clay the pistons as described in my previous PM to you. TDC only.

I've gotten several PMs from guys considering this mod as opposed to the 5.0.

Looks like mostly because they already have a 4.7.

Since there is a bit of interest, I'll post pix and measurements here in this thread. Should get a chance by next weekend.

Also will be putting in new rings.

If I end up doing the reliefs, I'll probably just cut them by hand.

Any suggestions on cleaning the pistons up? Chem-Dip??

123quattro

A scotch brite pad on the end of a die grinder works really well for cleaning up pistons. Just get a fine one so that you don't get into the metal.

mark kibort

If any engine is interference, how can you possibly turn over the cams with the cranked locked at TDC?
the only way I know is to put the engine at 45 degrees and then you have some room . otherwise, you will have to remove or loosen the cam towers to rotate the cams.

claying the set up the traditional way is very hard. you have to bolt it all together and time it out. why not just clay the pistons, and push down the valves, making a note of how far you push them down. you can use a bolt in the heads, to lever down with an open end wrench . when you make contact, you release the valve and remove the heads. (maybe only using 2 nuts to hold the heads on. now, you have a signature of were the valve is going, and know the depth to contact as well. claying it up and rotating wont tell you anything, because in all likelyhood, it will never touch anything on the piston for the reasons I described above