help with HEAD REBUILD

laserfrog · 02-18-2007, 08:45 PM

Hi, just for kicks, I decided to pick up a head at the junkyard for my 92 Plymouth laser 1.8. Got it completely torn apart and was looking at it and realized that there is no bearings on that guide the crank shaft. Am I seeing this right? and if i wanted to rebuild it, do I need to have the camshaft guides ground, or is there something i AM MISSING. any help would be great.

Thanks,
Kris

Defiant · 02-19-2007, 12:22 AM

You're sure missing something. The crank goes nowhere near the head, and cams ride on the aluminum of the head. I think the last motor to use cam bearing inserts was some eighties Toyota.

1gcrazy · 02-19-2007, 12:54 AM

http://auto.howstuffworks.com/engine1.htm

absolute_DSM · 02-19-2007, 01:12 AM

Head rebuilds and head upgrades arent for the amateur. It takes skill and knowledge. Theres so much to rebuilding a head and so many things to measure. Id google it and maybe youll see what I mean.

1gcrazy · 02-19-2007, 01:15 AM

Hell rebuilding a head is easy....MACHINING a head is the difficult part...

DJYoshaBYD · 02-19-2007, 07:57 AM

yeah... if you have the right tools and a shop manual, its easy.... again, you have to have the RIGHT tools.... machining gets done my pros anyway... assembling the head is easy.... just make sure EVERYTHING goes back in its original location.....

JayRolla · 02-19-2007, 08:36 AM

Quote:

Originally Posted by absolute_DSM

Head rebuilds and head upgrades arent for the amateur. It takes skill and knowledge. Theres so much to rebuilding a head and so many things to measure. Id google it and maybe youll see what I mean.

This is why people dont do anything on there own. People make them think its so hard.

95blackGsTurbo · 02-19-2007, 08:57 AM

There is more to rebuilding a head than just buying parts and putting it together. Some people aren't confident enough and that's fine. There are a lot of measurements that need to be taken when rebuilding a head and if you aren't comfortable doing it then don't do it. But on the topic there are no bearings in the head and the crank goes nowhere near the head. I would either readup on what's all done in rebuilding a head of take it to a proffesional.

absolute_DSM · 02-19-2007, 10:49 AM

Quote:

Originally Posted by 95blackGsTurbo

There is more to rebuilding a head than just buying parts and putting it together. Some people aren't confident enough and that's fine. There are a lot of measurements that need to be taken when rebuilding a head and if you aren't comfortable doing it then don't do it.

Thats what I meant earlier.

I know throwing a head together isnt hard, but some people dont play it safe and measure anything.

Then they wonder why it makes noise or breaks.

laserfrog · 02-19-2007, 04:28 PM

Okay sorry about the mistake, I know it is a camshaft, and not a crank shaft. I make that mistake quite often, and Don't know why. Okay than if there is no bearings that the cam rides on, than what happens if that needs to be machined and ground down a little bit, or when it wears out.

Well I have to go, and don't let that mistake miss lead you, The reason I am doing this is mainly to learn. It is a form of recreation for me, so if you have any good advice than I would appreciate it, and if you want to say, don't try it and let the professionals do, than I would rather you not rain on my parade.

Thanks
Kris

stuckwithgsx · 02-19-2007, 05:48 PM

so there's lots of talk on needing to take measurements. so what needs measured? sure your valve guides need to me set to .00 and so what i'm getting at is inform us of this oh so much stuff that needs measured. please.

dieseltech · 02-19-2007, 07:19 PM

Don't forget when going back together with the head to be generous with the lube on the camshaft journals and lobes. Steel and aluminum don't get along without lube for very long and will displace aluminum in the cap.

absolute_DSM · 02-19-2007, 10:39 PM

Quote:

Originally Posted by stuckwithgsx

so there's lots of talk on needing to take measurements. so what needs measured? sure your valve guides need to me set to .00 and so what i'm getting at is inform us of this oh so much stuff that needs measured. please.

.00 wouldnt move. The minimum is .001"

Lets think of some measurements.
valve stem height
valve spring retainer to valve guide clearance
spring installed height
spring coil bind clearance
valve guide wear
squareness of the spring
rocker to cam clearance
lifter preload
flatness of the head
flow CFM of each port
CC of each combustion chamber
valve seat width
seat margin width of the valve
quench area .....

You wanna "build" a head then do it right the first time. Im not saying you need to measure EVERYTHING just to rebuild a street daily driven head as its obviously not going to wear like that. But hey, you asked.

Ill get back to the original question again since he made an honest mistake. Like someone stated before, the cams ride on oil on the aluminum head. If you dont see galling or marks that can be touched with your fingernail, you will more than likely be ok. The only time you would need to put in bearings is if the head was galled up and you align honed it, putting bearings in the place of the metal removed. Usually people just get a new head if that happens.
Mostly "rebuilding" a head involves refacing the valves and doing a valve job. Thats when the meaurements come in handy. Im just strict on this stuff. I dont want anything to go wrong just cause I skipped something easy to measure as a precaution.