Piston to valve clearance?

[85_Ranger4x4]

What is the minimum safe distance between the valves and pistons in a 5.0?

I have searched and searched the web, one guy said .1 for an automatic (which mine is) but I didn't know if somebody had it in a book or something rather than some random guy on the internet pulling a number out of an aft orfice.

 

[shane96ranger]

I've always heard it's .080" on the intake, and .100" on the exhaust with the stock connecting rods. However, if you are using an alternative connecting rod, such as aluminum, you need to make that a bit more because aluminum expands under heat. I don't recall what that difference is though.

Also, I'm really not too sure what being an automatic has to do with it. I've never heard of a difference between the two.




EDIT: Racing Head Service says the same thing. They say add .030" for aluminum connecting rods.

http://www.racingheadservice.com/Information/Technical/PistonToValveClearance.asp

 

[Mac]

Heard the same as Shane and gone by that.
Dave

 

[85_Ranger4x4]

I have stock rods, trying to mix a lo-po '87 shortblock with factory flattop/dished pistons with an HO cam and E7 heads. Nothing too fancy.

The exhaust has miles of room, the intake was close to .125 off... my play doh kept shiting and I was getting tired of setting the head on and pulling the head off after multiple. I was going to do it today but we have had some interesting weather so I didn't get a chance too.

 

[projectnitemare]

I've heard the same as listed above. Unless you are changing away from stock pieces 99.99% of the time you'll be safe. It's good that you are thinking to check it though.

Matt

 

[85_Ranger4x4]

I've heard the same as listed above. Unless you are changing away from stock pieces 99.99% of the time you'll be safe. It's good that you are thinking to check it though.

Matt

The snag with these is that because the E6's had the valves a tiny bit farther up in the head Ford cheaped out and didn't put valve reliefs in the pistons.

Basically I think it comes down to if the engine or heads have ever been decked and if so how much as to if it will work or not. Some people say it works great and others say it won't.

 

[baddad457]

I have stock rods, trying to mix a lo-po '87 shortblock with factory flattop/dished pistons with an HO cam and E7 heads. Nothing too fancy.

The exhaust has miles of room, the intake was close to .125 off... my play doh kept shiting and I was getting tired of setting the head on and pulling the head off after multiple. I was going to do it today but we have had some interesting weather so I didn't get a chance too.

You're fine with .125" that's a full 1/8" inch of clearance. Run with it. The difference for an auto vs manual is the chance of missed shifts and over revving with the manual, for some, that equates to tightened clearance values with the higher revs with the chance of valve float letting the valves hand open longer.

 

[PetesPonies]

You say factory flattops, do you mean '86 GT or other year non-GT style pistons with no valve reliefs? I have put other heads on a shortblock like this, with the GT cam with no problems. But that is only one time for me. I have heard of others doing the same. So chances are , no problems, but no promises.

 

[baddad457]

You say factory flattops, do you mean '86 GT or other year non-GT style pistons with no valve reliefs?.

Other than the material they're made from (forged vs cast) there's only a few thousandths difference between these two pistons.

 

[PetesPonies]

but no reliefs for extra valve clearance.

 

[baddad457]

but no reliefs for extra valve clearance.

As is the case with the 86 HO pistons.

 

[PetesPonies]

I mentioned that already But that's not the point. The '86 HO did not use the E7 or other "normal" type of head. Even the GT used the E6 heads in '86. So using E7 heads, it gets real close. But as I stated, it probably will be fine.

 

[85_Ranger4x4]

You say factory flattops, do you mean '86 GT or other year non-GT style pistons with no valve reliefs? I have put other heads on a shortblock like this, with the GT cam with no problems. But that is only one time for me. I have heard of others doing the same. So chances are , no problems, but no promises.

Yup, like an '86HO (but not forged) or all the ho-hum engines they slapped E6's on in to the early 90's.

 

[PetesPonies]

So you saw my response, chances are you are fine. It worked for me and many others. I did read probably, 15 years ago, about a guy who said he had clearance problems?????? So you never know for sure I guess.