[ERIC17621]

OK, here is the deal. I had the engine out of my GTO to fix an oil leak, but when I pulled off the oil pan, I found part of a piston skirt on the bottom of the pan! So, looks like I will end up rebuilding the engine. While I am at it, I plan on making at few upgrades as well.

So, my plans are basically to replace the pistons with some forged and dished pistons. Keep the Crank and Rods assuming magnaflux checks out, hopefully only a minimal amount of machine work, and I’ll get the valves done. While I am in there though, I want to replace the cam with something a little bit peppier, which is where I am hoping to get a few opinions.

My combo. Original 1965 389, stock crank and rods, Tri-power converted to progressive linkage, orig. ST-300 2 speed Transmission, 3.55 safe-t-track rear end, and 77 heads w/ 1.92/1.60 valves, and pressed in studs.

Now I know that there are better heads out there, but I do want to keep the original setup at least at this point. I plan on getting a valve job, and probably convert the pressed in studs to screw in style. Not sure about the valves though. Will a bigger valve fit, and if so, how much bigger?

Now, for the cam questions. I am thinking about a few different setups, and was wondering about a ram air IV cam (230/240 .469"/.469"), with Rhoads lifters. Obviously with the 1.76 first gear ratio of the ST-300, and 3.55 rear, stock torque converter, I need to develop some low-end power to get moving. And yeah, a ram air IV in a 389 is not the cam to develop low-end power. But I do not know how much difference the Rhoads lifters would make in the combination, or if it would be enough.

So, what do you think? If it's the wrong cam, and wrong setup, what do you think may be more suitable? Any other recommendations you can give me while I’m rebuilding??

[ERIC17621]

OK, here is the deal. I had the engine out of my GTO to fix an oil leak, but when I pulled off the oil pan, I found part of a piston skirt on the bottom of the pan! So, looks like I will end up rebuilding the engine. While I am at it, I plan on making at few upgrades as well.

So, my plans are basically to replace the pistons with some forged and dished pistons. Keep the Crank and Rods assuming magnaflux checks out, hopefully only a minimal amount of machine work, and I’ll get the valves done. While I am in there though, I want to replace the cam with something a little bit peppier, which is where I am hoping to get a few opinions.

My combo. Original 1965 389, stock crank and rods, Tri-power converted to progressive linkage, orig. ST-300 2 speed Transmission, 3.55 safe-t-track rear end, and 77 heads w/ 1.92/1.60 valves, and pressed in studs.

Now I know that there are better heads out there, but I do want to keep the original setup at least at this point. I plan on getting a valve job, and probably convert the pressed in studs to screw in style. Not sure about the valves though. Will a bigger valve fit, and if so, how much bigger?

Now, for the cam questions. I am thinking about a few different setups, and was wondering about a ram air IV cam (230/240 .469"/.469"), with Rhoads lifters. Obviously with the 1.76 first gear ratio of the ST-300, and 3.55 rear, stock torque converter, I need to develop some low-end power to get moving. And yeah, a ram air IV in a 389 is not the cam to develop low-end power. But I do not know how much difference the Rhoads lifters would make in the combination, or if it would be enough.

So, what do you think? If it's the wrong cam, and wrong setup, what do you think may be more suitable? Any other recommendations you can give me while I’m rebuilding??

[joegio]

I think you can do better with a little less cam than the RA4. I liked the CC 268 for a weekend driver. Good idle with power brakes.

[Goatracer1]

If you are going to all that work lose the trans and put in something with more gears, either 3 or 4.

[ERIC17621]

Bob, I do plan on that, however rebuilding the engine is already an expence that I hadn't planned on. So that won't happen right now. For now I want to find something that will work with the present combination, and think about replaceing the tranny later.

[Mr. P-Body]

Eric,
You have now experienced first-hand, "inaudible detonation" (some say it doesn't exist...). While you may not have heard the pistons getting beat up by too much compression/not enough octane, that ;s why there was piston pieces in the pan. We went through the same issue, going in to clean up oil leaks, in our '69 428 from the Catalina wagon. Found pieces of skirt in the pan. Never heard a lick of pinging.
In answer to your question, we always use Comp XE262H as a replacement cam for "stockish" Pontiacs. GREAT cam in a 389 with TriPower. Avoid the old 268H. That's a Magnum grind, with symetric lobes and "single pattern". XE262H is parametrically smilar, with all the modern features of the XE series. It works fine with stock valve train components. You can even use it as "non-adjustable" (base circle is same as stock cams).

[ERIC17621]

What static compression ratio would you recommend shooting for with using the XE262H? I need to figure what dish to order in my pistons. I will also do the basics like zero deck, polished combustion chambers, ect. Looks that that cam will give me a fairly high Dynamic compression, so I don't know what is acceptable.

[Rholmes]

Eric I'm not sure of the cc volume of your 77 heads,but assuming they're 72's.With a 0.03 overbore 389(4.063),3.75 stroke,and a .041 gasket crush volume you will need 16cc dish pistons to obtain approx 9.35:1 c/r.