another muscle car oil question?

[tickles]

Hi, I've been spying on you guys for awhile now & thought I'd ask a question.....some of you guys are very smart.
I'm looking for oil recommendations for my car.....specs are as follows:

1969 Plymouth Barracuda Fastback 340 4-spd.
Engine is .040 over, balanced, flat tapped hydraulic cam, adjustabe roller rockers, steel crank, forged pistons & rods, windage tray, air gap intake, 750 Holley, stainless steel valves, ported heads...blah, blah...all the good stuff....dynoed at 425hp & 480 lb-ft of torque.

I've been using Shell Rotella T 15w-40 since I built the engine (6 years ago). Great oil, but I cringe when I start it cold....(75psi oil pressure at idle.....40psi warmed up) I only drive it in the summer. I'd like to go to a 10w-40, possibly Valvoline Maxlife because the rear main is starting to seep oil from sitting all winter. I'd like something to keep the seals & gaskets soft & pliable. I have read all of the concerns with the lower zinc & phosphorus levels in these oils when used with flat tappet cams with high vlave spring pressure. Can i run an additive to bring these levels up (Maxlife makes a seperate additive right....can I combine them?). Or do you guys have another idea? I'd like to stick with a dino oil because of the low mileage. Would an ester based synthetic soften the seals without causing leaks?
The car is always stored properly in winter & never started. In the summer it is always warmed up fully & driven properly (ie. WOT sometimes : )

Thanks in advance...

 

[tickles]

sorry, I forgot...i drive it about 1,500 miles per year, thanks!

 

[derek244]

I HIGHLY recommend Amsoil's 10w40 AMO, I use it in my 1971 GS455. It has been a great oil. My driving matches yours I am sure. No additives needed as it has plenty of zinc.

Just my humble opinion though...

 

[westwind999]

How about a synthetic diesel oil like rotella 5W40? I'm running Valvoline Premium Blue Extreme 5W40 in my old Supra. Maybe Auto-rx would help out the seal?

 

[Merkava_4]

Quote:

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1969 Plymouth Barracuda Fastback 340 4-spd.

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10W-40 MaxLife or 10W-40 Castrol GTX HM is what I'd run in there.

There's nothing wrong with the 10W-40 Amsoil either.

 

[aquariuscsm]

I study up on several muscle car forums and alot of those guys run 15W40 diesel/gasoline oils.

 

[aquariuscsm]

Sweeeeeeet car by the way! I had a friend in high school who had one. That thing was FAST!!!!!!!

 

[Steve S]

It is ok that the oil pressure is 75 when cold and drops to 40 when warm at idle what is wrong with that? The oil will give you all the protection that is needed. Probably you won't get any better results than with any other oil.

 

[Camu Mahubah]

Wouldn't hurt to give the Maxlife 10w40 a try. A lot of engine builders recommend what you are already using. Rotella is recommended because of higher ZDDP supposedly protecting flat-tappets. It appears you are in the know already. Do you happen to have any seal material lying around from the rebuild? Wouldn't hurt to do an impromptu test. Emerge said seal in Maxlife or other high mileage oil claiming to condition seals and watch to see if the actual swelling and/or conditioning occurs.

 

[daman]

Quote:

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How about a synthetic diesel oil like rotella 5W40? I'm running Valvoline Premium Blue Extreme 5W40 in my old Supra.

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I agree eather RTS 5w40(it's a synthetic too) or PBE 5w40, both great oil's..

 

[tickles]

that's a great idea Camu, I do have some seals lying around.

Everyone is giving me alot of great options, but I pretty much know what grade of oil I need, I'm just looking for something to keep the seals fresh because it sits for 6 months straight. I should really prime the engine oil system in the spring. That would probably be best, thanks!