Just so you know;
a 318 is just the equivalent of a big-bore 318.
So, anything off a 318 , except the piston assemblies, will swap over.
Except the 65 and older heads, sorta need the matching bolt-angle intake. So then;
if you intend to put a 4bbl on it, at some time in the future, IMO, I would start with 67>69 closed chamber heads. If you go with the open chambers and a bigger cam, then the cylinder pressure will fall way too low to be fun.
as for cams;
> on a low compression engine, with an automatic, if you install a lopey cam, you will be sorry, see Post 13, above.
> if you change the cam, I highly recommend to tighten up the LSA(Lobe Separation Angle) in an effort to keep the cylinder pressure up.
> IIRC, the factory gasket was 020 thick, with an appropriately-sized borehole. Those are no longer available, off-the-shelf.. the closest available is 028, and the bore-hole is huge. the new gasket is thus 6.3 compared to about 3.5cc/atock.
This one single change will drop a true 8/1Scr 273 to 7.76 and the pressure is expected to drop to 130, from 136psi. It may not sound like much, but that is the same as installing a cam of 8* more intake duration, which is more than two cam sizes bigger. Bad trade-off.
Closing up the LSA from the factory 112* to 108, with no other changes, on the 7.76SCR engine, is predicted to jump the pressure back up, to 133 Good Deal. and the bonus is better fuel-economy. Now, if you advance this cam to in at 102, this will reduce your Powerstroke back to what you now have, but increase your pressure to 134, over the factory, 129(with the 028 gasket). This is another good deal.
The point I am trying to make is this;
the factory 2bbl cylinder pressure is already extremely low. and it's only gonna get lower after the gasket swap. That's bad. Adding a bigger cam with a later-closing intake event, is gonna drop the pressure even lower.
If your engine needs pistons anyway, and you need a cam
now is the time to pump the compression ratio up, and neatly get around the problems.
As an example, building to a true 9.5 Scr, will allow you to slide a cam in there of about 10 degree later Ica(intake Closing Angle) and the pressure might jump to 161psi. Excellent deal.
Ten degrees is about equal to 4 sizes, going from a 112Lsa to a 108. That's a lot.
and, on a 108LSA, the compression /power degrees end up about the same as you have now, But the overlap jumps to 46 from 28. If you put headers on that, those extra 18* will make a nice little power bulge starting in the midrange. and the pressure increase will make the bottom-end feel about 22% stronger.
Again, the point is this, careful selection of parts at this stage, can make or break the combo.
Putting that same bigger cam into a 7.75 Scr engine is predicted to lower the pressure to 117psi, and the engine will feel about 15% LESS powerful, on the bottom, as it does when stock.
That's a bad trade! This will require a much higher stall convertor, and likely, a deeper rear gear, just to get moving as it once did.
and/but
46* of overlap is about what the 340s had, so, not much of a lope to it, but maybe enough to satisfy your hunger, lol.
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Oh and to answer your question about the cam lobes falling into the pan,
"My first thoughts wouldn’t this just continue to break down quickly and send shrapnel through the system into the block and bearings and so on?"
yes, that is a possibility. In my case, I was willing to take that chance.
The post you are referencing, was about what I did.
As stated, "your results may vary".
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Several decades later, I did lose a cam that way.
However, I run very little preload on my hydraulic lifters, and the ticking began almost right after an oilchange. This was back in about 2004 when the oil companies took the zinc out of the oil, and failed to send me a memo.
Anyway , I figured it out pretty quick, slammed a new cam into it, changed the oil and filter again, added a bunch of supplement, and hoped for the best.
The following winter, I took the engine down, cleaned it out, made some compression/spring changes, and slammed it all back together.
Back then, my car was a DD, so every fall, I took the 360 out for freshening, and swapped in a 318 for the winter; sometimes with an automatic, and sometimes with a manual, sometimes with an overdrive, whatever I was planning to run the following summer. and I changed the rear end ratios around pretty regularly as well. By 2005 or 2006, my kids had all grown up and moved away, so I bought another DD, and the 360 has been under the hood ever since........ with no more cam-trouble.