5 replies to this topic

[babsbrown]

Morning guys,

I'm doing my first engine rebuild and gaining knowledge and advice from a number of sources.

I'm undecided as to reuse the current pistons and get new rings and deglaze the bores

Or rebore 0.040+ with new pistons and rings.

Also the crank has visible marks but they don't feel like any ridges or wear, more like discolouration. Regrind needed?

The pistons seem in good condition apart from number 4 piston, which has scoring up the right hand side.

Thanks in advance Babs

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[gaspen]

What engine is this ? 

 

I think that piston is scrap as well as its bore

 

You should measure all the bores with a dial gauge at top/centre/bottom across and lengthwise to determine the condition (taper and ovality). Likely it will need re-boring, honing only does not make any sense.

 

On the new piston's technical data they will give you the bore-to-piston clearance. This value will determine the re-bore diameter.

 

Personally I'd go for the next oversize not the biggest. It will leave a reserve for the future.

 

 

Same with the crank : measure all journals with a micrometer 1st. It's worth to check if it's bent or not.

[KTS]

you really need to start by measuring everything (bores, pistons, crank journals etc) .  those measurements will tell you what work needs to be done

 

as above; i'd assume that piston is scrap and the bore it's been running in is likely to need a rebore

[DeadSquare]

How often do you want to work on your engine ?

 

Some people against whom I used to race, love stripping, examining and rebuilding their engine after every race meeting.  I did mine once a year.

 

As your engine is dismantled, It would be sensible to bore the block and grind the crank as this will bring two essential, wearing areas, back to spec, and it would be prudent to replace the oil pump.  Doing this, the heart of the engine is sound.

 

If money needs to be spread over time, other parts can be worked on with the engine in the car, such as clutch, timing chain and cylinder head.

 

If your block doesn't have "Tappet Chest Covers" which enable you to get at the cam followers, now rather than later, is the time to replace (as it is usually cheaper than regrinding) the camshaft, perhaps fitting an alternative that gives you a little more power.

[Cooperman]

I'm with 'Dead Square' on this.

It's false economy to only part do the job. You will end up doing it again sooner rather than later if you go the 'cheap' route. 

Do it once and do it right is the best advice.

Measure everything accurately and do any calculations needed, get the block re-bored and 'decked' to bring the new pistons virtually flush with the block deck at TDC. Buy good quality pistons.

Decide what compression ratio you want and then measure the head chamber volumes to see how much needs to be skimmed off of the head surface.

Check the valve guides for wear an d the valves for signs of burning on the seats. Renew as necessary.

Fit a new top-quality oil pump.

Make sure the crankshaft end float is 0.002" to 0.004" after final fitting. If not, use different thickness thrust bearings.

 

That's just the basics of what would be ideal for you.

[babsbrown]

Thanks guys,a bit late back to the party here.

The engine is a 1098 stock build. I'm looking to rebuild the engine to replace my 998 as I want something more torquey and fun. I did plan on fitting a new cam.
After reading your advice I think I will go ahead and get the machine work done
Albeit in stages to keep the monthly expenditure down to a reasonable amount haha


Cheers again