Pontiac Owners Club UK

I have a 1978 Trans Am with a 400ci engine which has been standing for quite a few years. It is now on the road again. Can you advise whether I should flush the engine through before dropping the oil out. Would engine flush affect the hydraulic lifters? Also what make and viscosity of oil would you recommend I use?

I would not use engine flushing oil on it. Standing a car doesn't necessarily mean things will have gone bad and congealed, but flushing may loosen any deposits. Due to the design of the lifter gallery and the exposed camshaft and mains below that it's easy to contaminate with metal debris or other stuff. The lifter gallery does tend to become a settling ground for any deposits that accumulate over the years but usually stay put and never cause an issue until such times as a head gasket is changed etc.

I'd give it a good hard run, drain the oil and replace with a good 20w50 oil and new filter and it should be fine.

Make sure it's something like valvoline or equivalent. 20w50 mineral oil.

Many thanks for the quick response and good advice.

yes i agree with bhm1712 unless a car has been flushed from new it is probably the worst thing you could to it i have seen it in customers cars more than once what normally happends is it runs fine for a few miles than the sludge starts to move to the sump then it blocks the oil pump pick oil pressure drops through the floor then it tend s to blow the big ends on these 400 engines i have seen it seize engines as well

i know it sounds a bit over the top but if it was mine i would remove the oil pan and clean it out the amount of crap in the bottom is normally huge you can also clean the oil pump pick up or i normally just replace the oil pump as they are pretty cheap just my opinion after rebuilding many engines good luck