The one thing I have learned over and over is that a lot can happen in 50 years. No telling what I will find.
I think that single plane manifolds do produce just marginally less vacuum but nothing on this scale.
Now I find poor rocker arm alignment
The studs are screwed in so guide plates are probably in the future
Or bent push rods maybe?
Well this doesn’t look good
Funny wear pattern inside the rocker
And then it gets worse. The fulcrum has worn a deep groove in the stud.
So new steel roller top rockers and studs wit a set of guide plates is on order
Was it the use of non rail style rockers in a rail rocker type head?
Not this time. The heads are 64 casting and modified with screw in studs. Rockers look original and no rails. I can see some wear in the guide slots.
Hopefully tomorrow I can do a compression check.
Okay it is time to update this. In Arizona it is just bloody hot in June and this one is parked in the barn. So I switched back to working on my '68 XR7 4 speed puzzle box. It is now running so back to the 289 car.
Compression looks pretty good:
- 160
- 165
- 150
- 150
- 165
- 150
- 170
- 160
3 and 4 might go a bit higher if I could get a tighter fit on the compression tester.
It makes sense now and seems that there was too much clearance on some of the rockers with the smaller diameter studs. Likely it never had full lift on those valves compared to the others. I wonder if there is another engine out there with the other studs that were ment for this engine.
Yeah, that’s not good.
I have a larger cam in a 351w (224 at .050 and 112lsa) and it pulls 15 inches.
If that were me I’d mock the studs and rockers up again and measure the pushrod length. Also double check the stud location. I had one machine shop drill some cleveland heads wrong angle and make a huge mess. Also had a 283 that was drilled something like .050 too far outboard and chewed the studs like that.
I wanted to come back on and update this. What I found was NOT a Comp Cams 252H. It turned out to be a Crane H-288
I also found several lifters that were not holding pressure. So this one is a mixed bag all the way around. The bad part is that this car has a stock C4 with the stock torque converter and 2.79 rear gears.
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What’s your goal for the car? With the stock driveline, I’d be tempted to just put in a stock cam and get it running like the day it left the factory. Not as much fun, but less expensive and more original!
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I just don’t see many choices for a stock cam. It looks like there’s not much demand. Anyway I will be using this cam. I’ve been really happy with it in another car.
I’m first amazed no one has commented on the LSA. Now that I know the real cam in your car, I’m amazed you’ve not bent pushrods or valves with this cam, With an LSA on your ‘other’ cam of 110 degrees I would have suggested that was the culprit. This one, with 108 degrees, high duration and and high lift IMHO that’s your issue. That’s quite the radical cam for a 289, especially if its not a roller (more forgiving). To the others’ questions - what is your goal? If you want decent idle, then get a grind with a higher LSA. I had a retrofit roller in my 289 that with an LSA of ONLY 110 degrees and less lift than you, I was not pleased with the idle (largely due to low vacuum with such specs). I instead went a bit more the other way with an LSA of 116 degrees but still , what a difference. It idles with authority - but decent vacuum and nice torque. You must advance timing with more radical cams like this.
Okay so I started studying the valve springs and discovered that they appear to be dual springs with a damper in between. So probably that was to work with the 6000 rpm power band of the 288 cam. It might also explain the screw in studs
Way too much spring for the cam I am using. So today I decided to get the complete kit from Comp Cams with springs keepers tetainers and lifters.