Hello all, Here is a good one and although I think I know what it is I need to know which rocker arms to get. So here we go. I have a 68 Firebird originally a 6 cylinder and I found a 68 GTO 400 265 HP with the smaller valve heads casting number 14.When rebuilding, I had the machine shop put the larger valves in from 1.92/1.66 to 2.11/1.77 which fit with no problem and it has the stock stud. Here is the issue. After adjusting the valve lash, priming the oil pump and starting the motor the rocker arms began moving sideways and two of them on separate occasions actually walk off and the push rod popped off the lifter(luckily no damage). At first I thought it was just a loose adjustment or lifter that didn't pump up. Then I took a closer look and it looks like the rocker arms are literally touching the top of the spring. It appears obvious that i have to wrong rockers my question is what rockers do I order. When looking online I can't find any rockers for a 68 400 with the smaller valve heads, Should rockers from another year head with the same size valves work? Any input would be appreciated and yes I know someone will say put the right heads on and it is on the table. Ty all
I thought all Pontiac 400 heads had pushrod guideplates. I see none on your heads. I'd say this might be your problem.
In your lower pic, you can see a small portion of the hole where one of the guideplate hold down bolts is supposed to go.
And, the rockers shouldn't contact the spring retainers. As far as I know, all stock 1.5 ratio Pontiac 400 rockers are the same. I've swapped rockers from 350's, 400's, & 455's. Never noticed any difference, & never had any hit the retainers. I have seen the valve tips worn down to the point where the rockers were almost touching the retainers.
Don't have any pics of #14 heads. But below is a pic of some #11 heads. It clearly shows the guideplates bolted into place. The 2nd pic, of some 7J2 heads, shows exactly where the hold down bolts are located.
Oldskool is right You might be able to add the pushrod guides Take a picture looking down at the head so we can see between the rocker arms Do you have the stock cam or did you put a bigger cam
Oldskool is right You might be able to add the pushrod guides Take a picture looking down at the head so we can see between the rocker arms Do you have the stock cam or did you put a bigger cam
I tried to put in new guide plates but no go. No holes to fasten them to.
[/quote] I tried to put in new guide plates but no go. No holes to fasten them to.[/quote]
Isn't that the edge of a hole I see in the bottom pic you posted ? If not, what is it ?
It's right beside the stud, showing just under the rocker arm.
1st pic below is a close up pic of a guideplate bolted down on a small valve #16 head. Are you saying that your heads do not have any bolt holes in the 2 bolt locations shown ? The 2nd pic shows the holes, without any guideplates. As you can see, the bolt holes are between each pair of studs.
Sounds like your valve adjustment may be off. How did you adjust your " lash"? Since you have stock rockers, pushrods and valves, all you need do it run the rocker nut down and torque to 20lbs. Hot, cold, running or not, doesn't matter You're done! No gap, no lash. If the nuts are old they may not have the locking power they once did and might have a tendency to back off. Think about replacing them.
If someone changed the valves there could be a few different problems. 1- what length valves did they use. 2- what springs and retainers. 3- were the correct length push rods used 4- what camshaft and lifters were used 5 - were the heads and or block milled Torquing down nuts on factory bottle neck studs only works when the factory valves are set up to factory valve heights using the factory camshaft, lifters,push rods.
Hello and thanks for all the input but now I'm confused.I thought only Oldsmobile's had guide plates, Everything I've been reading says bring cylinder one to TDC, then adjust valves xxxxxxxx til push rods have no slack then another 1/2 turn then repeat for other 8 rockers, I put a mild cam in Cam - 214/224 duration at 050" // 444/466 valve lift Push rods - Comp Cams 7851-16 Rocker arms - Sealed power R-1032 New balls and lock nuts Melling valves 2.11/1.77 length 4.998" I'm adding pictures of 2 rocker arms, 1 from a 68 400 4bbl Firebird and 1 from a 67 326 I did order a set of the 67's and from the pictures you can see the height difference from the 2 where it's closest to the spring perch. The first from a 68 and second from a 67. One last note is that the valve's I installed according to Melling will not fit a 1968 GTO 400 2 barrel
"...guide plates..... Guess ill be ordering them..."
You can probably buy some good used ones from a Pontiac guy on most any of the Pontiac forums. There may be some who will actually give you some, just for the price of shipping them. Since they can be shipped in a big envelope, shipping charges would be very low.
Or, if you know any long time Pontiac guys in your area, they probably have plenty of 'em they'll never need. It'll just save you the price of new ones. There are a lot of Pontiac heads that nobody wants. So, there are lots of Pontiac guys who would be glad to sell or give away the guideplates off of these worthless heads. One example would be some of the 455 heads which had huge combustion chambers. I had a set of '71 455 2-barrel heads, which had press-in studs. Can't imagine that anybody would want these on their engine. There are some of the '72 heads which had press-in studs & no end exhaust manifold bolt holes. There are others. Some Pontiac guys never throw away any Pontiac heads. So, there are lots of these heads out there. Plenty of unneeded guideplates.
If you buy new guideplates, be aware that many of these are made for use with screw-in studs. Make sure that those you buy can be bolted down using the factory hold down bolt locations.
Ok so here is where I'm at. I ordered the guide plates and they should be here by Tuesday. The new rockers came in just a short time ago and they don't touch the spring perches like the other ones so i believe Im good to go and will update all when its running
What olschool says is true but it sounds like you are running stock length valves and as long as you are running 9.17 pushrods you should be ok with stock valve adjustment guidelines. Your cam may have a bit more lift than stock but there is a pretty large length of travel with a stock style lifter. Shouldn't be much chance of bottoming out based on the information we have.
Hello all, All fixed and figured out. I installed the push rod guides and went with the the original rockers I installed the first time. Runs well and no issues. thanks again all
