What needs to be Machined

[RuffusMD]

I am planing to re build my engine . I have found re build kits that have forged everything ie crank rods pistons , and new cams and cam re build kits new valves springs pushrods ect ect.at some very good prices . In effect I am planning to replace just about everything but the block and heads. I am sure buying a short block or crate engine would be easier , but I want the expierence of re building the engine . I do know that parts can be re used . But I want forged parts .I am sure that in most cases re-using old parts does re quire a lot of machining and measuring ect.

So the question is , what parts of the engine nees to be machined , if you are using old parts ? new parts ? If the hasnt been blown would anything need to be machined ? Or would just replacing all the bearings ect be enough ? I do not know the answer so if this is a stupid question sorry . I do know how to check the bearing clearance , making measurments ect .

So if you use all new parts , can your engine just be plug and play ?

Hale

[will1258]

That's a HUGE question!!!

Many factors come into play initally.

- Age / miles on the engine.
- Usage and maintenance during above.
- Degree of wear.

If you're gonna replace everything, why not replace the block. If you use the old block, you should really first check it for cracks with magna flux. Then the rework can start (on the block that is).

and so on and so on......

[tomhorn1913]

Ruffus,

If you are only reusing the block & heads, you will want to have them inspected/measured by a competent machinist. The cylinders may need to be bored oversize. The decks may need to be trued. If the main saddles require machine work, it might be easier/cheaper to look for another block. The heads may need a clean-up on the sealing surface. A valve job is probably a good idea, & guides may be needed. If you are buying all new internals, I recommend taking them to the machine shop as well. There should be little to no additional cost for the machinist to confirm that everything is to spec.

If you are reusing the reciprocating assembly, the crank journals may need to be turned undersize to correct for uneven wear. The connecting rods should be reconditioned (new bolts, resized, matched/balanced if necessary. If your machinist says you can keep the stock bore, you may be able to reuse your pistons, & save a couple hundred bucks. If you need to go oversize, you "may" want to have the innards balanced to assure minimal engine vibrations.

This is the short list - I am certain others will add more details.

Best,
Matt

[tomhorn1913]

[hind sight]

Hale, sounds like you already have the measureing tools and knowledge of how to use them. Start by either having the block hot tanked or do a really good cleaning yourself. Once you have all the stock specs on what the internal diamensions should be you will know if crank needs turning or block needs boreing to next size. Do recommend having machine shop check for things like deck being square to bore, bore aligned to crank. Fixtures are used to check these and worth the minor cost. Most imes cylinders will need to be bored to make true, espeacally since going forged pistons as they require a different piston to cylinder clearnce compared to a cast piston. Remember, cylinder seal is the most inportant thing for making power.No out of round or tapered cylinder bores here.All ring gaps need to be fit to each cylinder. At least have the valve seats stoned,new guides installed making them straight with the seats for perfect valve seal. Probally end up having heads resurfaced so they are flat and straight. Nothing wrong with useing a seasoned block once brought into spec. Make sure machine shop has the pistons before any bore work is done, same for rods before any crank grinding if needed is done. Blue printing the block with carefull assembly and perfect clearnces are what seperate an average engine from a "good" engine.
Highly recomend you measure all you can in the motor but also have the machine shop of your choice go over other areas that are not easily check without the needed fixtures.

[RuffusMD]

Thanks for all the answers.. I think I found a good machine shop near where I live So I am going to take everything in and let them clean and measure then they can tell me what need to be machined . I was not happy with the ones I had Found , hence the question . This one looks good

A Machine Shop in South Atlanta

[hind sight]

Checking the link you posted, this looks like a nice shop to do your work. It really does matter that when having an engine machined the shop speacalizes in auto machineing. Let us know how it goes. Don't be afraid to ask them questions on the recommended tolerences of engine and their preferences on why. Be sure to tell them it is a street/play motor as opposed to a full out race motor as that makes a difference in the machining specs.