SR20DET Porting Info. (Jeff read)

[Jim96SC2]

Jeff, I see what you mean about not getting much power from porting the heads on my SR vs the Chevy's much more now. I knew there wouldn't be as much need for porting, but damn, they were in excellent condition (so to speak). The chevy heads required about an hour of work per port using grinding stones. We removed a hell of a lot of stuff (guesstimated at about 1 cubic inch). Today we ripped off the intake manifold and heres what we found.

The ports are in fairly good shape, almost perfectly matched to the gasket. We found three main areas of focus:

The first was the top of the port where most of the flow would be coming from (outside of the radius). They were usually off by up to 2mm from the gasket. We simply blended them larger to remove the obstuction without drilling out the whole port and adding unwanted volume unnesscerily.

The second trouble spot we found was on the left wall and left runner on each but #4 (closest to the firewall) was found to be the worst. Here the gasket was improperly matched slightly but more importantly it walled off the flow into the left runner by 2-4mm. We cut the wall of aluminum back and blended in both before and after.

Thirdly, and lastely, on all intake ports we found a noticable bump on the floor of the port. While it wasn't raised that much, it probably would decrees flow slightly so we simply grinded it down so that the floors were smooth and flat.

Inspection of the runners showed them to be equal in width down to the valve area and fairly smooth execpt for the casting lines <?> which we left to rough up the air slightly and increase fuel mixing and decrease depostion onto the walls.

Total time taken: ~1 hour
Total HP gained: ~5-10
Fun with friends: Priceless

We also labeled and took off the wiring harness as best we could. We are going to work on the exhaust side next, porting out the manifold, extension, and possibly the head. Any feedback or suggestions OK. Pictures to come once film is developed.

[Jeff240sx]

I really don't remember this conversation (if I'm the correct Jeff), but anyway, as you know, every little bit helps. I wouldn't really expect huge gains for what you did (basically port-matching and gasket trimming), but 5 hp seems like a good guesstimation.
Also, the sr20det has a "3-angle valve job" from Nissan, so you won't get exceptional gains from that (aside from mabey a Serdi swirl job).
Anyway... put up pics!
-Jeff

[sL103]

i do this kind of work, i can clean, do 3 angle valve jobs, 30 degree angled back cuts, bead blast, mill,port, port match work. if anyone intrested e mail me.

[Jim96SC2]

It was about a month ago when somone suggested a company to do porting work for a KA (I think). Anyways, yeah. We think 5-10HP is about right for what we did. Just smothed out a lot of initial flow obstructions.

Anyone who wants to do this kind of stuff, just pick up a dremel from Sear ($50) and use the rough sanding bits to grind down the Al that it in the way. Don't start working till you get an idea of where the flow obstuctions are coming from though. Don't gouge out things. Just smoth it out so the obstriction slowly dissappears. Any question just ask.

Originally posted by Jeff240sx
I really don't remember this conversation (if I'm the correct Jeff), but anyway, as you know, every little bit helps. I wouldn't really expect huge gains for what you did (basically port-matching and gasket trimming), but 5 hp seems like a good guesstimation.
Also, the sr20det has a "3-angle valve job" from Nissan, so you won't get exceptional gains from that (aside from mabey a Serdi swirl job).
Anyway... put up pics!
-Jeff

[sL103]

300ZX TT heads that i did and scan them
hopefully they turned out well,

yes getting a dremel tool is the first step but its a very good idea to have the head cleaned , a wand will help tremendously, also dont get too smoothor HOG IT OUT!! NO NO or take alot of the port floor,, you want to create turbulence in the intake side to get a better a/f mixture.... that should help if you dont feel confident in doing it your self send your stuff to me

Sincerly, Shawn

[xsboost]

There are actually a lot of things wrong with the SR20 Head. I have a highport head on the flowbench at the shop right now. The short side radius of the exhaust is one of the worst I have ever seen. For one there is a ledge right after the valve seat that needs to be addressed. The Short side is almost a 90* angle.

I have a whole write up I will dig up on the flaws of the SR20 head. I am getting a low port head soon to cut on as well as a KA24DE head. We have already seen promising gains on the High port even before we did the valve job. We now have oversized SS valves in the head and we are going to start some more porting and get some more numbers from the flowbench. This head is going on a customers car, but we are doing mine next.

I am waiting on the flow numbers from the low port head to see if we can get a little better cfm out of it without loosing too much velocity. I like the port angle on the High port head (S13) except that the lifter galley dips so far down into he port it spreads the valves apart too much. We are working on converting a Sunny GTiR Solid lifter head to fit on the S13 Block. As long as we can get the oil drain backs to work we will be fine. The solid lifter head does not have as deep of lifter galleys so it does not dip as far into the port as on the hydro motor.

I will have some more numbers later

Danny

Polk Performance

501-847-7223

[Jim96SC2]

Originally posted by xsboost
There are actually a lot of things wrong with the SR20 Head. I have a highport head on the flowbench at the shop right now. The short side radius of the exhaust is one of the worst I have ever seen. For one there is a ledge right after the valve seat that needs to be addressed. The Short side is almost a 90* angle.

So your saying when I rip off the opposite side I'll find more problems huh? Is there a water jacket that runs below the short side radius? I'm gonna pull off my exhaust side stuff and get to work on it Sunday. Can you send me that writeup or the port section at least to my email? [email protected]

[xsboost]

I need to find it. It is at work somewhere. I was snowed in today so I could not look for it there when I could. It might be on SR20DEFORUM.COM somewhere. I will see what I can find..

Are you porting with the head on the car? ? If so be carefull not to do much more than a port match. I personally wont do anything more than a port match without a flowbench. I am lucky enough to have one at work though..

Danny