[99v6stang]

OKey so i dropped a 4.2 in my mustang and apparently the engine was bad as the rings are stuck, and one of the valves were bent. The seller of course didnt tell me this so i spent tuns of time putting it in only to find it didnt work. So now im in a situation where i need to get that engine rebuilt. I already ported and polished the heads and intakes and have an aftermarket cam and and springs. I figure since im rebuilding it anyways i midaswell (not sure if that was a word) bore it out .030 and maybe get a little higher compression pistons. WHat are your thoughts on this? I am getting a very good deal on the labor as it is only costing 600 for everything since im not doing it myself this time, but i dont have much money so i cant spend crazy amounts on the best products. So im wondering how much should i bore it out and what should i raise the compression ratio to to be cheap and reliable yet get more power as well?

[stephen]

If you want to just rebuild it, I would bore it out the minimum to clean up the cylinders.

As to bottom end components. Super six has a lot of information on that

http://www.supersixmotorsports.com/

My understanding is that the 4.2 is the same as the 3.8 except for a longer stroke.

From the super six website I understand that the stock pistons and rods are fairly weak links, so you might want to go with something better.

[Onemanzu]

$600 for a rebuilt engine... using all stock parts isn't a bad deal i think... hopefully things get working for you and you can get back on the road

[99v6stang]

no thats just for the labor, i still have to buy the parts, but get a discount on those as well.

[ESG-642T]

Originally Posted by 99v6stang no thats just for the labor, i still have to buy the parts, but get a discount on those as well.

The pistons for higher cr are gonna cost ya

[itschristorres8]

you wana bore it .030 over...when the its been bored over .040 already?

high compression pistons will be costly. and the pins will have to either be pressed in the piston or connecting rod

also are you replacing all the rings?

might as well replace the main bearings as well
wat kinda cam is it?

rebuilding an engine requires alot of time and PRECISION! im rebuilding my second one now in school.
if you dont know what your doing...dont try it...something as small as putting the main bearings on the back side of the bearing with oil or grease can cause a problem
or a thrust bearing thats off by .010

and rule #1 never trust anyones work, always recheck....we sent heads to a shop to get the valve seats surfaced and 2 seats were bad after we sent it out...

[99v6stang]

OK i dont know where people ceep getting these ideas
"
--------------------------------------------------------------------------------
you wana bore it .030 over...when the its been bored over .040 already?
" its not bored out at all so i dont know where you got that from.

-yes i am replacing rings, rods, pistons, valves, and lifters
-my cam is a spec b from morana racing
- Im hiring a mechanic to do the work so ? if you dont know what your doing...dont try it? This wont matter.
-How much more would high compression pistons cost, how much power would they gain, and what ratio would i want?

[itschristorres8]

k if your gunna be like that then a big to you.

a mechanic?! lol is he ASE certified with engine rebuilding or engine overhaul

watch who you take it too.
go to ssms as someone already suggested for the high CR.
if not tom morana or delk


and spec b cam?
that doesnt help with description at all...lift? rotation?

and why would you replace rods if there is nothing wrong with them...and dont you only have 1 bent valve?
why replace them all? same with the lifter...i doubt they're bad


how is it not bored out? if you got it from precision, they stroke and bore the block from a core that is sent in and cleaned...which would be a 3.8

you bore that .040 over you get your 4.2....then you ask a machine shop to bored that .030 over they'll just tell you hell no. unless the ORIGINAL block is 4.2. which i highly doubt if you gotta it from precision. them like most engine shops take the cores. have them dipped into an acid tank. and then checked for leaks then prepped for engine rebuilding
which for that company the stroke LOTS of motors. mainly V8s. they bore it there to save money and thats it
THEY DO NOT! buy a new block. if that cast iron block has no leaks and is clean they aint throwing that away.

and if it is a 4.2L and you bore it to a 4.7 then you gotta find pistons that can fit that diameter

and i DOUBT you have the tools for that and i garuntee most these mechanic shops dont have the tool. they might have a micrometer..but that wont help measure the bore. unless they have an inside mic which is as accurate and a bore gauge.

[Stang6899]

Just curious but how u kno he got it from precision? I'm tired did i miss something?

[Avaric3]

i believe he mentioned it in another thread maybe a week or so ago

[99v6stang]

i was trying to be mean, i appreciate you help i was just wondering where you wer getting some of these ideas. And my 4.2 is from an f150 not precision so it hasnt been bored out at all.

[99v6stang]

also the cam has 224 on intake duration and exhaust it is a regrind, and the mechanic is not a ceritified ase but he is a good friend and works for a shop plus i have seen many cars that he has rebuilt and they have all turned out fine.

[stephen]

Not trying to add to the confusion, but what I have always done is the following.

Remove the engine and disassemble it.

Do preliminary cleaning to get the block exterior reasonably clean using rags and solvent followed by a power washer.

Take the block, crankshaft, piston and rod assemblies, and heads to the machine shop and have them clean them up further and do any machine work that is necessary.

Reassemble the engine and install it again.

The machine shop will be able to quickly determine what the bore size is etc.