cam tower questions - 47mm, four bearing?

jpnovak · 10-25-2007, 08:12 AM

During a routine Fall valve adjustment two weeks ago I found the dreaded broken head stud on the outer exhaust side of #1. (Yes, it was dilivar) This means I will be finally finding a use for all those parts collected over the last few years.

A few years ago when I was less knowledgeable I bought a set of cams and matching rockers that have a similar grind to a Mod_S. They were 4 bearing cams and I thought they would fit perfectly in the planned warmed over 3.0. Of course, I didn't think to ask the question of what size the journals are.

I pulled them out of the box last week to start doing my measurements. HMM These are 47mm cams and will not fit a 49mm 3.0SC cam tower.

To get new cams reground from billets might be out of my build budget. However, It occurred to me that some 2.7 motors might have had 4 bearing, 47mm journals. They must exist since that is how my cams were installed.

Does a 47mm, four bearing cam tower exist that is 1) not a racing application and 2) has the oil galley drilled for the 4th journal? Could I run them in an early 3 bearing cam tower with the extra journal spinning free?

I think it might be cheaper for me to get some new cam towers than to have new cams built.

Thanks

BURN-BROS · 10-25-2007, 09:34 AM

Jamie, Yes there is a cam housing set up for 4 journal small dia. But it needs a mod done to get oil to the omitted journal. The housing was a 4 journal but the late 2.7 used 3 journal cams.

jpnovak · 10-25-2007, 09:37 AM

Thanks Aaron, I was just looking for info. Henry posted in this thread about a concern using early cam towers on late headss. I don't know where his cutoff distinction is. Will 2.7 towers on 3.0 heads pose a problem? I think the valve angle is the same. I know that the 2.0 "early" heads had much different valve angles.

DC60 Cams made for 74 will they fit 3.2

Is the mod as simple as drilling a hole to bring oil to the journal? I would think so. Maybe my best bet is to just use a 3 journal casting.

BURN-BROS · 10-25-2007, 09:45 AM

Quote:

Originally Posted by jpnovak

DC60 Cams made for 74 will they fit 3.2

Is the mod as simple as drilling a hole to bring oil to the journal? I would think so. Maybe my best bet is to just use a 3 journal casting.

Yes, drill through the spray bar then tap for a pipe plug or ream for a plug.

The valve angle IIRC don't pose a problem. The angles spread the valve head out more but compensate to keep the valve tip in the original position. I am not sure if there is any problem associated with 2.7 cam towers on 3.0 heads. I'd try it if it were me.

BURN-BROS · 10-25-2007, 10:07 AM

You would be looking for like a 77 2.7 camtower. Don't assume that all 77's came with this type of tower. You may have to search around

MBEngineering · 10-25-2007, 10:17 AM

HI jpnovak
the prob you will have is that the valves in your heads are shorter than the earlier engine's and the smaller cam bearings and cam base circle will put the rocker and the adjuster out of line with the valve, a chance of buggering up the adjuster swivel, if you must use this combination then I would suggest a set of race shims to bring the valve stem up to the correct length.

race shim's

the valve on the right is in your SC head and the one on the left is a long early valve

now with a shim to make up the difference on the right

hope this makes sense and helps

regards mike

jpnovak · 10-25-2007, 11:12 AM

OK, now we have a visual on the problem. that is what I had envisioned reading the post I referenced above.

Where does one find such race shims? I assume these are better than extending the rocker adjuster bolt to its maximum. I also suspect the rocker adjustment bolts are not even long enough to make up the difference between the valve stem lengths.

BURN-BROS · 10-25-2007, 11:36 AM

Look for alfa lash caps.

jpnovak · 10-25-2007, 12:11 PM

Excellent recommendation.

I don't have a spec (Wayne's rebuild) book in front of me. Can anyone tell me the nominal diameters and the overall length of a 2.7 and 3.0 valves? I seem to recall a 3.0 valve is 8mm OD.

I found some caps but need to know the difference in length to determine the thickness.

So should I run the 3 bearing tower or a modified 4 bearing. I also just spoke with John Dougherty. I might just be solving the problem with new cams and rockers.

jpnovak · 10-26-2007, 04:46 AM

I was off. Valves are nominally 9mm in diameter. There should be a 4 and 5 mm difference in length for the intake and exhaust valves, respectively. Time to look for some caps that match these dimensions.

jpnovak · 04:56 PM

Mike, I am having trouble locating the right size lash caps. Do you supply them or know a source? I checked our host first.

edit... I just found a source for them. more details to come.

rs-vic · 02-04-2022, 07:32 PM

How about the other way around, 4 journal 49mm cams and cam housings on a 2.7. Looks like the valve tips will be too long.

And how about the different valve angles 2.7 vs 3.0. How does that play out?