Do I need to machine my chevy 350 block?

[nugent]

Hi All,

I could do with some advise on whether I should machine my block or not. After inspecting my chevy 350 block, the bores are smooth with no visibly score marks, but you can see the extent of the piston travel as there are raised areas at the top & bottom of the bores. Are these just build ups of carbon & can they cleaned off or do they need machining out?. I have checked the machined faces of the block & they are all flat. The main bearing journals are smooth apart from dirt on either side of the bearing shells, I assume these can just be cleaned off. There were a couple of bearing shells that had picked up but there are no deep score marks on the crank, I think it might get away with a polish.
What do you think? Will it need machining? or should I just get it machined to make sure everything is true & aligned.

Thanks.

[TINKA]

If there is a lip at the top of each bore then this might indicate some wear in the bores, but what you really need to do is check if they have started to oval at all, this is one of the main reasons for requiring a rebore. Can you see the honing in the bores at all or are they totally smooth, if they are totally smooth then I would say you need a rebore. The crank bearings again it is more down to wear, this you will really need to get checked. Sorry you can’t tell most of this by it being smooth or not it is down to how much wear has happened.

Personally I would just get it machined to make sure everything is true & aligned.

[Vidge]

Use a piston ring and a set of feeler gauges in the ring gap to measure at frequent intervals down each of the bores, your looking for variations within a bore and variations between bores.

If there are no variations at all, establish the current bore size by first measuring the diameter of a piston, putting it less it's rings into the bore and using the feeler gauges to measure the gap between the piston and the bore wall. Do this at a few points on each cylinder using the same piston each time.

Then you should have a fair indication that you need a rebore or perhaps just a cleanup and hone job. The block will need to be honed anyway if your going to be fitting new rings.

The machine shop you take it to will (should) perform their own assessment which you can compare to your findings to see if your plonker is being pulled.

Just rebuilding my second small block, this one came out of a boat. It smells of oil, stagnant salt water and strangely of fish.

[Clarkson]

If you have some sort of lip at the top of the bore, then at least it needs measuring and a rebore, same for your crank too.