oil weight opinions wanted

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i have a 68 gto factory a/c car.i decided to rebuild original 400 with a crank kit(basically a 455).engine has about 1500 miles on it.i have delo 15/40w in it now.after doing some reading i was thinking of going to 30w vr1,etc?i live in phx,az so the temps are 100 plus now til mid sept.car without a/c on runs around 190/200 depending how long i sit at a light.with the a/c on engine sees 220 at long stoplights.will 30 weight be able to handle the heat of the engine and enviroment i live in?it's my weekend cruiser and when it gets cooler it will be going to the track.i flog it every chance i get when i take it out cause it's just a torque monster and it doesn't take much to beak the tires loose.it has a flat tappet hydralic cam.no oil cooler.high volume/high pressure oil pump.should i try a good 30w or stick with good ol' 15/40? if i was going to use 30w i was going to use a straight weight.i know there are two different camps on thick oil versus thinner weight oil.right know i'm on the fence on this one.i value your input and thoughts on wether i should try 30w or not.
 
What does your engine builder recommend - he knows your bearing clearances and pump flow and bypass settings. You can try a 10w-30 fleet oil, rotella Cj4. Straight 30wt are usually just 10w-30 without winter pour point depressors. I would NOT run a diesel oil that has Mg additives in it, you might get metal loauding in the CC and valve heads and start to get ping then knock.
 
You could use a 30 HDEO but I would use a 15w40 HDEO. I am presently installing a rebuilt similar to your engine with factory clearances and trans on a 67 GTO for a freind . I suggested he run a 15w40 HDEO in his new engine. It is the best oil for the money you can get.
 
my oil pressure at idle is 25psi hot(190/200)alittle lower when
hovering around 220.i have a melling RAIV/SD high volume/pressure pump.i'd have to call my buddy about the spring pressure's on the cam.it's a flat tappet hyd,cam 507/530.i'll have to get back to you with the rod and main clearances.the best i got it run so far since the new rebuild is 13.20 @ 109 mph with a really bad sixty foot time.but then came the heat of summer so,i'll take it to the track when it gets cooler to dial it in.thanks for your replies. also another member suggested not using hdeo with mg additive,whats mg additive and how do i tell what hdeo has it or not?
 
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IMO a diesel oil is different from a HDEO oil. Any HDEO oil like Delo 400 or Rotella or Delvac 1300 and the like will work well.
 
You should also consider M1 TDT or shell RTS 5w40 synthetic to give you an edge with that extream heat,both great oil's as well.
 
Nice ET, those are hard to launch well.

The oil you're on may be a tad thick if the engine is clearanced tight, but only your builder can answer that. I can't understand the need for a HV/HP pump on a properly built motor, but each place has their own reasoning.

The 15w/40 is a great all around oil.
 
my engine is not exactly stock.i have crank kit eagle crank and rods,je pistons,edelbrock perf rpm heads,si valves,comp springs/retainers,10 degree locks,ultradyne/bullet cam,perf rpm intake,RA IV/SD exhaust manifolds,hei with msd 6al box,3.08 gears,2800 stall conv.turbo 400,proform 850 carb.

i agree about the oil pump.in hindsight i wish i would have changed out the spring and put the sixty pound bypas spring in.
old mindsets and habits are sometimes hard to break.

the tolerances are right in the middle of factory clearances because i told him i may through a small nitrous system on it in the future.
 
Yeah I was about to say the same thing. That thing must get up and go at the end of the track with 3.08's. I would definately install 3.73-4.11 gears, especially with that 2800 stall.
 
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