Milling a slant six head
#3219739
03/11/24 01:32 PM
03/11/24 01:32 PM
|
Joined: Jan 2003
Posts: 28,067 Irving, TX
feets
OP
Senior Management
|
OP
Senior Management
Joined: Jan 2003
Posts: 28,067
Irving, TX
|
A friend has the head off his 225 to fix an oil leak. The only reason he has the truck is to abandon it at the airport terminal when he is flying. As such, he doesn't want to spend any unnecessary money on it. It's a lean burn hydraulic motor. Compression was a nice even 135-139 psi on all 6.
Other than accounting for the difference in head gasket thickness how far can he cut the head without having problems with the hydraulic lifters?
It would be nice to get a bit more compression.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon
|
|
|
Re: Milling a slant six head
[Re: feets]
#3219767
03/11/24 03:44 PM
03/11/24 03:44 PM
|
Joined: Jan 2003
Posts: 9,875 Weddington, N.C.
Streetwize
master
|
master
Joined: Jan 2003
Posts: 9,875
Weddington, N.C.
|
I never did a Hydraulic cam but I had a solid cam 71 That I think I milled about .080 but gave about .020 back going from a .017 steel shim to an .037 Fel-pro blue. Stock cam I just put in i think they were 1.88" (360 size ) intake valves, a Factory aluminum 2BBL a 6 into 1 JR Header and a single 2 1/2" exhaust with a walker super turbo muffler, this was back in 1988! Used a 2 barrel 318 carb but I wanted to try a progressive 2bbl Weber on it and try to get 30MPG.
It ran really good....for what it was but the compression (and my mid 20 yr old lead foot!) eventually wore out the tired old rings.
I always wanted to find an old 170 with the short stroke and the old aluminum case 833 O/D 4 speed and build an old 64 valiant coupe and turn it into some kind of MPG champ.
Last edited by Streetwize; 03/11/24 03:48 PM.
|
|
|
Re: Milling a slant six head
[Re: Streetwize]
#3219771
03/11/24 04:05 PM
03/11/24 04:05 PM
|
Joined: Jan 2003
Posts: 28,067 Irving, TX
feets
OP
Senior Management
|
OP
Senior Management
Joined: Jan 2003
Posts: 28,067
Irving, TX
|
170 has much lighter internals, too.
In this case, I'm worried about bottoming hydraulic lifters with a milled head using stock pushrods and non-adjustable rockers.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon
|
|
|
Re: Milling a slant six head
[Re: feets]
#3219815
03/11/24 08:07 PM
03/11/24 08:07 PM
|
Joined: Jan 2003
Posts: 20,177 Park Forest, IL
slantzilla
Too Many Posts
|
Too Many Posts
Joined: Jan 2003
Posts: 20,177
Park Forest, IL
|
That's the big question is how much room in the lifters?
The head can stand -.100" easy. If he has a valve job done it will sink the valves a little too.
Realistically, you need to take .060" at least to do much good. I'd bet the lifters will be bottomed out or very near.
What did it have in it for a head gasket, steel shim? If so a Fel Pro will add about .025" back.
"Everybody funny, now you funny too."
|
|
|
Re: Milling a slant six head
[Re: Twostick]
#3219830
03/11/24 08:58 PM
03/11/24 08:58 PM
|
Joined: Jan 2003
Posts: 20,177 Park Forest, IL
slantzilla
Too Many Posts
|
Too Many Posts
Joined: Jan 2003
Posts: 20,177
Park Forest, IL
|
I'm assuming a hydraulic slant doesn't have adjustable rockers?
Can earlier adjustables be swapped in?
Kevin No. The hydraulic Slant oil the lifters from the top down through the pushrods.
"Everybody funny, now you funny too."
|
|
|
Re: Milling a slant six head
[Re: slantzilla]
#3219853
03/11/24 10:44 PM
03/11/24 10:44 PM
|
Joined: Jan 2003
Posts: 28,067 Irving, TX
feets
OP
Senior Management
|
OP
Senior Management
Joined: Jan 2003
Posts: 28,067
Irving, TX
|
The stock gasket on the layer /6 was composite, not a shim. Measuring the fire ring shows it to be close to thickness of the replacement. Van he get away with .020 or .030 without crashing the lifters?
Again, the only reason he bough this old low mileage farm truck was to avoid leaving his Redeye at the airport terminal for days on end.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon
|
|
|
Re: Milling a slant six head
[Re: calrobb2000]
#3219873
03/12/24 01:22 AM
03/12/24 01:22 AM
|
Joined: Jan 2003
Posts: 20,177 Park Forest, IL
slantzilla
Too Many Posts
|
Too Many Posts
Joined: Jan 2003
Posts: 20,177
Park Forest, IL
|
Without knowing how much travel is left in the lifters the only correct answer is "maybe". In all honesty a .020 or .030 cut isn't going to gain anything. It's .0066" cut per CC of chamber, so .030 won't get 5 CC. You might get the compression up to 8:1.
IF my old brain remembers correctly, there SHOULD be about .090" of travel left in the lifters.
"Everybody funny, now you funny too."
|
|
|
Re: Milling a slant six head
[Re: volaredon]
#3219971
03/12/24 01:34 PM
03/12/24 01:34 PM
|
Joined: Jan 2003
Posts: 28,067 Irving, TX
feets
OP
Senior Management
|
OP
Senior Management
Joined: Jan 2003
Posts: 28,067
Irving, TX
|
If you pulled a composite gasket out it has most likely been apart before. 1981-1984 truck /6 used composite head gaskets.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind. - Stu Harmon
|
|
|
|
|