Originally Posted By: Finn
Hello!
As it happens I have the old flat tappet L98 on the floor and a master builder is building me a mild 383" with forged Scat crank and rods, forged Wiseco pistons and AFR 180 heads. This is built on 87-> roller cam block so no more worrying about the lobes. The engine will be mild ie. 350...375 hp but with 475...500 lb-ft.
My question is as follows:
I have noticed that when the power levels rise from the original on built motors also viscosities people use tend to rise. Is there any need for this as the clearances are the same? Several of my buddies seen to run 5...10W-40 or even 15W-50 in this type of built "modernish" late 80s to mid 90s small block Vettes. Is there any need for this or would they do just fine with a quality 5W-30 viscosity oil?
I'm a bit puzzled as the builder said he'd run this new engine with 20W-50 Pennzoil GT.
Thats a nice car. The builder liked 20W-50 because he felt it would protect those cams. And it probably will. He isnt "wrong," just old school. Nothing wrong with that. Could even put 5W-50 in there. 0W-50 is.. too much cost. Again, thats why i recommend 0W-40, its virtually the same oil and maybe even a little better!
May i recommend a RL 0W-40 for this car. Sweet ride!
40-weight Group V RL (yeah i know but RL is good oil i should point out primarily why) should/may help woith consumption, and RL seems a good choice. Moly for months, too.
My biggest question is if you need ANY additional ZDDP in the oil, and if so, how much of that additive to put in.
I seek a car like yours.
Quote:
Most engine builders know what works in the engines they build. If he recommends a 20W-50, then in my opinion, that's what you should use. I can't understand why everybody is recommending a fuel economy 5W-30 for a built up 383. You gonna try to get 40 mpg out of that? I'd be more concerned with preventing metal to metal contact if it were my expensive engine.
Very well said. +1!
Some engines do well on 5W-020 or 0W-30, but this engine has needs that disqualify it from most lighter grades, including those except for MAYBE GC, MAYBE. Merkava is right, its not a Toyota Prius. You can have "thinner oil" but it still needs to be as thick as necessary.
GC or better, 0W-40 is my pick and some say 5W-40, thats a good grade too.
RL 0W-40 gets my vote, all things considered. It is a VERY good oil. M1 0W-40 if you dont feel like going the mail order route.
M1 makes a 5W-50 too.. could use that.. instead of 20W-50. The W number isnt hurting you..