Basics

[ride4lame]

Ok, i am a newb to all motor...I just got another 240 with a blown motor, its a 90 hatch with a blown motor. So i was thinking since my other 240 is midway in an SR swap, maybe when i am done i would build this newer one all motor. But i am not even sure where to start...I was thinking like, upgraded fuel system, higher compression pistons? thinner head gasket?thanks for any advicesorry if this has been discussed but i couldn't really find anything real basic.

Steve

[bazan]

If you can, start with a complete rebuild while the motor is out of the car. I know the SR swap is not cheap so your disposable income is probably in the red, but even so. After that, do the usual intake, headers, and exhaust. Then worry about cams, fuel, ignition, etc.

[ride4lame]

yeah, right now i am broke, but i am thinking ahead. I was thinking instead of rebuilding with stock internals...what would i throw in there instead to get something real quick, and all motor?

[RedShred]

If your gonna do it...go for the flat tops from courtesy... 9 something to 1step up on the camport match, do it yourself... the E head on the exhuast side has alot of material...HotshotK&Ncall it good.

would make it fun.

[Scott McLellan]

Port matching on the exhaust side seems to be a little overrated. Even professional engine builders sometimes leave a "step" into the exhaust manifold/header with the smaller side being of course the cylinder head. It makes sure the gasses keep going the right direction along with other advantages. The purpose of porting, which I suppose port matching is kind of a sort of, isn't to make the cylinder head "look" like it would perform better because a mod might look like it would increase performance when in reality it could add little, no, or maybe even a loss in performance. If there is a lot of "material" there, Nissan probly put it there for some reason. Don't get me wrong though, a good porting job can do wonders, but removing lots of "material" is kind of a risky move.

[RedShred]

The material I removed ensured the diameter and shape stayed consistant through all 4 ports. I'm certainly no engineer and wouldnt begin to speculate flow patterns or rates... but I can tell when there is casting flash or when material should definately not be there... as the other ports dont share its shape. 80 percent of the material I removed on the exhaust side was do to the gasket matching. And then I only went in about 3/4 " to remove aluminum. There was no step in this process... it was more like a cliff . The head size was up to 3/16th's smaller in alot of spots than the head pipes are. I also spent a lot of time flapping the shiz out of it as well to polish it.The intake side is also gasket matched and flapped with 80 grit to remove flash and give it a much smoother approach to the valves. Yes, I was very careful on the intake side to avoid making it too smooth so it wouldn't make fuel seperation issues... This whole process was closesly watched by my machinist who has built race engines for more than 30 years.

As for a step, I remember reading years ago where in motorcycles or other engines that have the exhaust header make a quick turn down that you must flatten out the port on the bottom side to quicken the flow so the exhuast velocity doesnt slow down on the bottom.

Besides, It's only the head. If the PnP didnt do right by the other mods... I'll replace it. I wont know until next week when the new cam is installed if the PnP provided any benefit. However, I have enormous confidence in my Machinist and his methods.

-Ric

[Scott McLellan]

Sounds like a sweet setup RedShred!

[RedShred]

here are a few pics of just the exhaust side... Nothing really to show on the intake side. I made straighter ports and smoothed them out.

looking down...It's hard to see how much I had removed to match the gaskets... there was as much as 3/16ths in some spots. All the ports are now fairly uniform and smooth.

[Scott McLellan]

Thanks RedShred! I hope to do a little porting someday when I have the time and money to do a complete engine rebuild. What is that blackish line on the bottom picture on the left port? Is that just a picture flaw or shadow? How long did that job take you? What tools did you use? Thanks again for those pics. Do you have any before shots just for a visual?

[RedShred]

No previous shots... didnt think of that.The black line is a grease smudge.Took me about 5 hours total to do the whole job and that was with instruction thrown in.As for tools:Big assed Makita dremel like toollong extensionmachinist dyenew gasketsvariety of extremely sharp Aluminum cutting burr bitsrolled and pointed sanders40 grit short flap sanderemory flapper 80, 120 and 240 grit

[TrunkMonkey]

Port matching on the exhaust side seems to be a little overrated. Even professional engine builders sometimes leave a "step" into the exhaust manifold/header with the smaller side being of course the cylinder head. It makes sure the gasses keep going the right direction along with other advantages.

just to add a bit more...

the same procedure is applied to the intake side. only the intake manifold ports are smaller than the intake ports on the cylinder head.

-demetrius

[RedShred]

...I did leave the intake a hair smaller than head port.

I got the car today... Very fast, very strong over 4000 rpm. Not a damn thing off idle to 2500. It is not indexed yet... the gear is ordered but isnt here yet... I'll get to it in a few weeks. idle is kinda ruff, but the cam is a bit much.

all in all... I'm happy. Not a bad way to spend 4 large.