Buy pistons first, or get block and head machined first?

[MattC]

Sorry if this is a really dumb question but I'm going around in circles over it in my head

I've been saving for a few months and now I'm ready to start on my engine rebuild, but I don't know which bits to spend money on first. Do I buy the pistons first and take them with the block and head to the machinist so they can deck bore and hone everything to the correct clearances, or do I get the block and the head done first so I know what size pistons to buy and make sure I get the correct compression height etc?

Thanks
Matt (engine building noob )

[ctrain]

get the engine builder to buy them, they can source pistons to suit your application, it may cost a little more though

[oldcorollas]

depends on engine, but..

i'd do combustion chambers first, then work out their volume.
then choose both pistons and amount of head to be removed, based on compression i wanted to run (assume some minimum amount of block decking, only to straighten it up)
then take pistons and block to machinist, and get bores .. bored.. and honed to suit the piston and clearance i wanna run, and get head machined.

so it depends if you are using an engine builder, or doing it yourself (including measeurements and CR calculations), and just farming out the machining work.
also depends what pistons you have available to help choose compression ratio.

[MattC]

Thanks for the responses guys, really appreciate your input.

I'm going to have to get the pistons custom-made because there are no off-the-shelf forgies available to keep the factory compression ratio (10.3:1) for the N/A Gen-3 3S-GE. You can get 8.5-9.0:1 turbo slugs, and you can get >12.0:1 race jobs, but nothing to keep the factory c/r (I made another thread about that a couple of months ago and was referred to a couple of places to make enquiries about custom-building them).

The engine will be put together by a mate (a mechanical engineer who has rebuilt dozens of motors, he's a pedantic fussy bastard and I know he'll do a great job), and I'm going to have a chat with Thornleigh Cylinder Heads about the machine work (again this came from a referral, but if anyone has any input on that front I'd appreciate it too)

Cheers guys

[andrew_mx83]

Yep as above the machinist needs the slugs there while he bores it. Once you've got these and any aftermarket rods/crank etc machining can begin and is the first "big step"

First Buy pistons/rings/brgs
Give these plus crank, rods, block (with main caps and timing case!) etc to machinist, get it bored/honed, decked (and balanced) Plus the head for any work you need done.
Next buy gaskets, belts, welch plugs, spark plugs, running in oil and all the other crap you forgot to budget for

Try and make sure the shop that hoes the machining has a torque plate for your block too...

[MattC]

Thanks for that Andrew, just one query though;

First Buy pistons/rings/brgs

I thought I'd wait to buy the bearings until after the machining was finished in case they need to be under/over-sized?

[oldcorollas]

get them to measure everything first, as the crank etc may need to be machined to suit the bearings.
fitting berings to parts, and parts to bearings is all part of the machining process

[andrew_mx83]

I usually check and meaure the crank journals before it goes for machining, uless it spun one previously it should get away with a micropolish/linish for about $50
If in doubt take thecrank down first and ask them if it needs to beground and what size bearings YOU should buy and supply -this avoids their markup.

They definitely need them if they are grinding the crank, sorta need them if they are balancing it all and dont need them if its just hore/hone/deck.

[Celica RA45]

if getting forged pistons i get some 86.45 1s and get it bored to suit, file back your rings
and later if you go for a refresh just hone it out to 86.50 with new rings etc
sps can make any piston you wont or give them the std item and he will make it for you plus rings and pins as well

[MattC]

Yeah that's about what I thought, send one of the stockies to SPS and say "copy this please". Any idea what they charge?

Andrew - crank is fine so yeah hopefully just a linish is in order.

[Celica RA45]

about 1200 a set with rings and pins but you would have to ring colin and ask
also why not go up in comp like say 11.5 to 1 you could run it on 100 octane fuel from united

[MattC]

Ouch, the car only cost half that, lol....

Yeah I've thought about the high comp slugs but for the moment its going to retain the factory ecu and I don't know how it will like that much compression? And finding 100 octane is a pain, at least you can get 98 anywhere..

[MattC]

OK, updates.

I've placed the first order - I'm buying a set of Manley H-beam rods and a Fidanza flywheel from Twos R Us in the states ($330 for the rod set and the same price for the flywheel, best prices I could find even with shipping added). Once I've got the rods I'll take the engine block and cylinder head to the machinist and get them to take the minimum amount off each to deck and square them plus any combustion chamber work, then I'll get them to accurately measure the length of the rods, the deck height on the block and the combustion chamber volumes. Once I know those values (as well as the head gasket thickness I assume) I can calculate the required piston compression height and order my pistons (Real Street Performance have advised me they can get CP or JE pistons made in any bore and compression height I want for $650 a set. After extensive googling it appears CP's are the better of the two so that's what I'm going to go with). Once they arrive I'll take the block back to the machinist to be bored and honed to the correct clearances and have the crank work done and then the whole rotating assembly balanced. Then I'll probably look at my bank balance and cry for a while.

Sound like a reasonable plan?

[andrew_mx83]

Sounds about right. Take the crank with you the first time if you want so they can check and measure it...

[Celica RA45]

just make sure they crack test the crank ,3s cranks crack along the bigends