Originally Posted by topside
Used their 10W-30 with both a SFT Hughes & a HFT Engle BB, zero issues, both engines' valve springs over 400# on the nose.
I use their Hot Rod 10W-30 on a few cars. Ran it in the SB roller-cam racecar too.
20W-50 is kinda thick IMO on a fresh engine or normal bearing clearances.

Thanks for the reply.
My last build was normal,10w40 with Lucas Additive, the one before that was 30W straight weight high Zink racing.
I just looked at Lucas site and Summit Racing looks like I must have bought the 20w50 Lucas Brake In since it only comes in
20w, 30w straight and 5w20 and 20w50 flavors.
My guess is I did not want a straight weight as thin as 20 or 5w20 and passed on straight 30 as well to get a muli weight.
Seems like they would make / sell a 10w30, 10w40, 15w50

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VP of the MPM in New Orleans
73 Dart Sport 340/ 70 challenger vert. That may still get built, If I live long enough