71 198 slant new head

-
Johnny71dusty

Johnny71dusty

Well-Known Member
Joined
Jul 6, 2021
Messages
829
Reaction score
110
Location
Maryland
My new head is a late 70s or 80s head .

it has no spark plug tubes and has lots of water jacket holes across the top .

main question is , the farthest back ( closest to firewall ) bolt that holds down the valve train . The hole is different than all the others and takes a smaller diameter bolt . Also it's not threaded until very bottom of the hole itself . That bolt is spraying oil out of the top of where bolt head is . It's torqued down Same as the others but still sprays oil all the way out of the engine bay over the fender even . These are casting numbers off this new head I got . Can any tell me why that one bolt is different than the others ? And why I may be spraying ? Oil seems to flow across all valves well still .

9B136D09-DC95-4D5D-91BF-A32C9B97E34C.jpeg


16D65B85-56EC-47B3-B180-98D64F8F8667.jpeg


E1FC6AF5-E8D2-41EE-B38B-C3693B874299.jpeg
 
That rear rocker arm bolt is different than the rest. It is longer and as you noted, has a smaller thread. The upper part of the bolt has a larger shoulder that matches the rocker arm shaft.
 
halfafish said:
That rear rocker arm bolt is different than the rest. It is longer and as you noted, has a smaller thread. The upper part of the bolt has a larger shoulder that matches the rocker arm shaft.
Click to expand...
How and where did I get that bolt ? Because my 71 head didn't have it . ?
 
Johnny71dusty said:
How and where did I get that bolt ? Because my 71 head didn't have it . ?
Click to expand...

That will require an answer from a better slant smart-guy than me. Mine always came on the engine, but I don't know if there is a difference between drool tube or peanut heads. You didn't have one when you disassembled your old head?
 
halfafish said:
That will require an answer from a better slant smart-guy than me. Mine always came on the engine, but I don't know if there is a difference between drool tube or peanut heads. You didn't have one when you disassembled your old head?
Click to expand...
Old head is 71 , new one is newer head so it has lot of other things different too . But bolt wise it's only that back bolt all other bolts dropped in no isssue
 
Johnny71dusty said:
How and where did I get that bolt ? Because my 71 head didn't have it . ?
Click to expand...
Older heads simply had a longer cap screw in the rear position the same thread as the rest. Newer heads set up for hydraulic lifters, which supply oil to them top-down, are machined for the smaller thread to allow more oil volume & have an enlarged shoulder cap screw. The rocker shafts are also different, which shaft are You using?
 
Search back a few pages, maybe more, this has been covered recently, & I've posted pics of the diagrams.
 
Killer6 said:
Older heads simply had a longer cap screw in the rear position the same thread as the rest. Newer heads set up for hydraulic lifters, which supply oil to them top-down, are machined for the smaller thread to allow more oil volume & have an enlarged shoulder cap screw. The rocker shafts are also different, which shaft are You using?
Click to expand...

So all my bolts are correct other than the back one . But the back one is longer and smaller thread size buttes it should be shouldered at top as wide as the originals .

i only have Rocker and rocket shaft from my 71 . Ian having major timing issues now as well . The distributor was never moved and wires not even removed . Unplugged them all and pulled head and replaced it . We set the lash cold then hot but it's runs like **** now no matter where I set the timing. Do I need a proper year rocker shaft ? Did my casting numbers tell anyone what year it's from so I can attempt to get ?
 
You need to get over to slant six dot org and get some information.
Here is the head matrix, you can ID your head and years used.
The redesigned head and rocker shaft were done to reduce the chance of installing the shaft wrong. But if anything it has confused the subject. With the correct bolt and shaft, you can't install it wrong. That was the reason for the step.
matrix-pg1.jpg


Rocker Shaft Bolt.jpg


This information from Doug Dutra's Chrysler Slant Six Engines book talks about the different rocker shafts.
Peanut Head Rocker.JPG


Hope this helps you.
 
Doug Dutra's book seems to be saying that the rocker arm shaft was changed at the same time the special shoulder bolt was introduced. According to the parts catalogs and service manuals the special bolt first appeared on the 1975 engines. What's confusing is the rocker shaft 1947614 was used from 1960 thru 1980. Maybe some of the slant six experts can explain this.
 
So how do I get one of those bolts . I'm googling head bolt kits and rocket bolts from 75-86 heads and not seeing any sets with one different bolt in it like I need.

and can I use my rocker set I already have ? Or is it so different it's not usable and may explain my timing issues and it running like a turd . Mid June when I blew the head gasket it still ran great and sooth ( no water in oil ) I was getting exhaust pressure out of radiator . It never lost water . But it ran great on and off the trialer . And I did nothing but swap the head . I reused all old parts , lifters stayed in , push rods reused in same order , and valve train all stayed together and it all went back good obviously not that one back bolt . Any one can tell me how to buy that one bolt that be amazing .
 
Also mine is a last year 70 198 slant . I was assured before that there was no head difference in that and 170 or 225 heads. Or blocks for that matter . From all I can read no 198s came cast with 198 they all identify as 225 because they are . Just a shorter connecting rod. But used all same parts as 225 other than that
 
Johnny71dusty said:
So how do I get one of those bolts . I'm googling head bolt kits and rocket bolts from 75-86 heads and not seeing any sets with one different bolt in it like I need.

and can I use my rocker set I already have ? Or is it so different it's not usable and may explain my timing issues and it running like a turd . Mid June when I blew the head gasket it still ran great and sooth ( no water in oil ) I was getting exhaust pressure out of radiator . It never lost water . But it ran great on and off the trialer . And I did nothing but swap the head . I reused all old parts , lifters stayed in , push rods reused in same order , and valve train all stayed together and it all went back good obviously not that one back bolt . Any one can tell me how to buy that one bolt that be amazing .
Click to expand...
There is no problem using your old valve train. Did you readjust the valves? Should be .010 on the intake, and .020 on the exhaust. Don't forget the valve sequence changes between cyl 3 and 4. As far as I know that bolt is not available, except as used from someone's private stock.
 
Johnny71dusty said:
Also mine is a last year 70 198 slant . I was assured before that there was no head difference in that and 170 or 225 heads. Or blocks for that matter . From all I can read no 198s came cast with 198 they all identify as 225 because they are . Just a shorter connecting rod. But used all same parts as 225 other than that
Click to expand...
Actually the 198 has a longer con rod, and a shorter stroke crank.
 
Charrlie_S said:
There is no problem using your old valve train. Did you readjust the valves? Should be .010 on the intake, and .020 on the exhaust. Don't forget the valve sequence changes between cyl 3 and 4. As far as I know that bolt is not available, except as used from someone's private stock.
Click to expand...
Yes I did cold adjustment & hot at 10 /20 hot .
 
No, 70 was the 1st year of the 198 not the last.
 
You must log in or register to reply here.
-

Back
Top