Full engine rebuild ??'s

[Diff Whack Daddy]

I am starting a full 4.0lL rebuild out of a 91. I plan to use the comp street grind cam, replace all the normal stuff with a rebuild and then add some headers and a high flow cat. My question is, would boring it out add more HP or torque? If it doesn't I don't need to spend the money. If it does, will the stock injectors be enough and do I need a custom chip?

 

[SteveVB]

answers + suggestions

If the cylinders need to be bored to correct for wear than do it. Boring to get more power wont get you much. You dont want to bore more than .040 over anyway. If you did the max you may get a % or 2.

Stock injectors will be fine, the chip may have to be reprogrammed to work with the cam. The stock chip will work fine.

You will need push rods for the cam. Smith Brothers custom CM are the way to go. New springs - stock work with the street grind cam - check height though. Get new rocker shafts and rockers.

Have the combustion chambers polished, the heads port matched, and if you have the money- bowl work done. The combustion chamber work is almost a must though- lots of sharp edges.

have fun

 

[Diff Whack Daddy]

The heads are being sent to a place in AZ as a core and I am getting a rebuilt set that has a 3 angle grind on the valves, new springs, and rockers. As far as the combustion chamber, is it something I can do myself witha die grinder and what does it consist of?

 

[SteveVB]

sure..

I did my combustion chambers and some prot matching myself. I used a small pnuematic die grinder. I didnt do any bowl work, but you could if you have the time. I have done some other heads myself also. Used a Dremel, or a die grinder and some emery paper.

Basically I ground down any sharp edges- combustion chamber corners, around the spark plug, and I think one of the valves has an eyebrow near it with a sharp edge. One of my heads also had some flash near the spark plug boss. I just ground out the casting texture, to smooth it out. Remember youre just trying to smooth the existing, not reshape the chamber. I used a few stones and then some various grades of paper. I know Summit, and Eastwood have "porting " kits that you could use also.
If you have the tools to disassemble the heads that would be best- then you can clean it up really well when you are done. If you dont take it apart then bag everything to keep the grit to from getting everywhere. Cover the valve seats, or valves themselves with a couple of layers of duct tape, to keep the grit out and to protect them incase the grinder gets off course. If you think about doing bowl work it should be done before the valves are ground and set.

Have Fun.