What work should be done to a head in a rebuild?

[Howieau]

Ive burnt a hole in an intake valve in my 3SGTE, though while the engine is out and in pieces, I want to rebuild it to an extent and get it cleaned up, starting with the head. Ill be replacing the standard head gasket with a metal head gasket, and might replace the standard pistons with forged. So along with replacing the busted intake valve, what other things should I best get done to the head? Ive no idea.

Do I need to machine a slight amount off the bottom of the head to sit flat on a new head gasket? Should I get a slight rebore on the inside of the intake port that had the blown valve if there is any scarring.

I am completely illiterate when it comes to working with engine internals so bare with me, but Ive also been told something about reshimming the valves? Is that only if you remove the cams?

And once you remove the cams, how exactly do you reinstall them so they run with the proper timing again?

I want to save as much money as I can with this rebuild, even if it means me learning from absolute scratch, so any and all help is much appreciated!

Thanks in advance

[oldeskewltoy]

what other things should I best get done to the head? Ive no idea.

Books have been written on this subject, to cover it here in a forum is not realistic. Before you do anything I recommend you do some basic head rebuilding searches.

To cover things simply....(ill do my best.....) first... check all parts for damage. Any part that is damaged... check ALL the corresponding parts that went with it for damage... using your example of a burnt valve... check the valve seat and be prepared for a machine shop to install new ones.

I don't know 3SGTEs... but I have extensive expereince with 4AG... are you sure your pistons are not already forged?? Since you don't plan on extensive modifications, I'd use the OEM gasket for it seals better than any metal gasket will

Reshimming valves is done once you have the entire head rebuilt with new valves. You then adjust the valve clearence by check the gap between the cam lobe's bottom and the shim in the bucket. If your clearences are too much(too tight, or too loose) you'll reshim them till they are just right

I STRONGLY recommend a factory service manual for your 3SGTE... READ the overhaul sections... your understanding will grow with your increased knowledge.

[fixeruperer]

head should be crack/pressure tested checked for straighness, valve stem seals should be replaced and valve guides checked, when you assemble it together lap your valves in and check valve clearance.

[BeRad]

Books have been written on this subject, to cover it here in a forum is not realistic. Before you do anything I recommend you do some basic head rebuilding searches.

To cover things simply....(ill do my best.....) first... check all parts for damage. Any part that is damaged... check ALL the corresponding parts that went with it for damage... using your example of a burnt valve... check the valve seat and be prepared for a machine shop to install new ones.

I don't know 3SGTEs... but I have extensive expereince with 4AG... are you sure your pistons are not already forged?? Since you don't plan on extensive modifications, I'd use the OEM gasket for it seals better than any metal gasket will

Reshimming valves is done once you have the entire head rebuilt with new valves. You then adjust the valve clearence by check the gap between the cam lobe's bottom and the shim in the bucket. If your clearences are too much(too tight, or too loose) you'll reshim them till they are just right

I STRONGLY recommend a factory service manual for your 3SGTE... READ the overhaul sections... your understanding will grow with your increased knowledge.

the 3sgte gasket is a bit like the 7m gasket it needs a metal one..
the 3sgte doesnt have forged pistons but they are fine unless you go making "hectik" amounts of power. i was running 16psi through a gt30r and it was fine for over a year and would still be running if the car wasnt sold for bits.
as was said above, valve stem seals seem to die with a bit of punishment, so replace them.
if your going all out with forged pistons may as well rebuild the whole motor.
a bit of head work/cleaning up will help the 3sgte flow a bit better. reground cams/aftermarket jobbies if you want to go that far and have an aftermarket ecu to tune the engine to make use of them.

you can remove the cams without having to shim etc. they are installed in the opposite order that you pulled them out , dont just go removing bolts etc there is a set order so that you dont stress, bend and break shit. the same goes for the head dont just go removing 1 stud at a time, a few turns each in the correct order. Richard or Lance whichever you prefer has a big green book of the 3sgte on his webspace that will help greatly to understand how to remove, reinstall and diagnose faults heres the url http://ugbox.net/~lance/GT4/Technical/

the cams , cam gears and the head have markings on them to retime the cams before reinstalling the timing belt.


while you have the head off source a gen 1 3sge intake manifold comes in through the side, the plenums a tad bigger stops a bit of heat soak and looks neater.



engines bays a bit messy but you get the picture.


The list can go on and on budget, performance needs/wants are the governing factors. if you want to do it as cheap as you can dont bother with the bottom end of the engine unless its showings signs of failure, then its probly cheaper to buy another block rather then rebuild yours depending on what your after.

[011]

Sorry not to be more helpful, but take it to a shop and get it done properly. If you accidentally do something wrong, it will probably just lead to more problems, more time and more money.

Learning can come at a price if you're teaching yourself.

[Vios-GT_07]

since noone has said it, i was going to mention that yea u should get the head machined or skimmed so the surface is smooth.. and make sure u don't get it dirty with your fingers when u put on the head gasket...

and erm.. yea do a pressure / vacuum test before anything, to make sure there's no leaks in the head... should be easily patched up unless it's a very big crack..

[Howieau]

Well it turns out that I have aftermarket cams in mine, and theyre much bigger than stock. I was looking just to get the head reconditioned, get the water galleries in the block cleaned out with an acidic liquid injected into them (Im told thats how they do it), have the cylinders bored out a fraction to clean up some scarring, change all the bearings over and such. Also go with metal head gasket, forged pistons and main studs. Thats the plan so far.

But first things first is to get a hold of a 3sgte intake valve to send off with the head to a machinist. Have him pressure test it for cracks, check/replace the valve stem seals, have the valve seats cleaned up, check/replace (if needed) the valve stem guides, machine the bottom of the head to make it flat for the metal head gasket, and clean up any intake/exhaust ports that might be scarred.

Does that on par for a head reconditioning? Have I missed anything?
Thanks for the replies thus far, rep coming your way.

By the way before I blew the engine I was running aftermarket 3" exhaust, pod filter, EMS, front mount intercooler, cams, 13psi.

[J0RD0]

Get some adjustable cam gears, cheap and noticeable increase in power! especially if you have aftermarket cams

[oldeskewltoy]

Does your machinist have 3SG expereince? As I didn't know much(about forged slugs and "creeping" head...again I have 4AG exp...) If your machinist isn't 3SG savy you may pay the price...

For instance - http://www.hachiroku.net/forums/showthread.php?t=5722 in essence the guy overbored the engine to a spec that 4AG slugs aren't made too......

Just check your machinist..... thats all I'm saying

[allencr]

First is why it failed, so we learn something besides how to remove & replace parts, and it doesn't do it again in a short time!
How do you know it is an intake valve problem? Symptoms & tests?
Intakes don't burn very often, and if I recall correctly there have been Very Few exhaust valve problems ever written about on these boards & Zero about intakes. Sticking in the guide is about the only possibility, or a bad job when the cams were replaced.
Yes, the valves will need to be adjusted/re-shimmed, unless you do only the most basic & crudest of repair jobs, then only one intake will need it!

[Vios-GT_07]

just out of curiosity when u say bigger cams, how much bigger are they? are your valve springs binding? does the rest of your valve train support the bigger cams?

[3sgte]

Carefully check the head above where the exhaust manifold bolts to.
I have seen a couple of Gen1 crack heads in this area, from the valve cover surface downward, presumably due to stress from the mounting of the intercooler.

[Howieau]

Jordan76 - I forgot to mention, the car does have adjustable cam gears

oldeskewltoy - Good point about 3SGTE experience, Ill have to chase that up

allencr - Ill get the guides and all checked to see if theyre still in working order. Pretty stupid but the car wasnt tune very well with a new EMS and it was pinging a little bit but I still pushed it. Id say that could be where my problem was, Im surprise nothing else broke (that I know of yet).

Vios-GT7 - I dont know how to descrive cams too well haha, but theyve welded extra cam on top and then machined it back to the shape they wanted. Anyway you can see where the old cam is and where the new cam is on top of it, the new cam is like an extra 2mm if I remember correctly (havent looked at head in a few days). Much bigger than stock, and a bit more rounder too at the sides. Im not sure what you mean by valve springs binding - is like when they compress are they getting stuck and not spring open again? Im also not sure about the valve train supporting the cams. How can I tell?



Heres a shot of the valves

[Vios-GT_07]

erm... OC mentioned this a while back and i remember bits of it.. and yea also from bits i picked up here and there.. basically the stock valvetrain can support bigger cams to a certain extent.. i don't think there's a problem (though u could just double check it's okay..) with your bigger cams but that's a very interesting way they've done it

edit: found the link, which i thought was really helpful in understanding the subject

http://www.toymods.net/forums/showth...ight=progkamol

(time to rep OC again )

[BeRad]

8mm lift rings a bell? on the std valvetrain, shim under bucket is the way if you want to go bigger..