# Port matching and boring



## dominojd (Aug 1, 2002)

My ques to the SR20 guru's is:
According to ITS rules you can Port match the manifold and head and bore the cylinders .040. Will this make a big difference and is it worth the cost? I'm trying to do ever legal thing to see if the SE-R can actually be competitive in ITS.


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## bahearn (Jul 15, 2002)

> I'm trying to do every legal thing to see if the SE-R can actually be competitive in ITS.


By your own mission statement, yes, it's worth the cost. Competitive cars don't come cheaply and they are the sum of ALL their mods.

Is 0.040" over the 2nd standard overbore size for SR20? I keep forgetting to bring my copy of the road-racing GCR to work, but SoloII GCR states maximum of 2nd standard overbore, and for SR20 I thought that was only 0.020" overbore.


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## dominojd (Aug 1, 2002)

All it says is "Engines may be bored to a maximum of .040 inch over standard bore size"


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## Geo (Apr 30, 2002)

dominojd said:


> *My ques to the SR20 guru's is:
> According to ITS rules you can Port match the manifold and head and bore the cylinders .040. Will this make a big difference and is it worth the cost? I'm trying to do ever legal thing to see if the SE-R can actually be competitive in ITS. *


Joe, if you are going to pull the engine out of the car (you aren't going to replace the pistons with the engine _in_ the car), then definitely take the time and effort to port match. It's not hard to do. It just requires some patience and some good grinding wheels. Regular stones just gunk up when grinding aluminum. I did gasket matchin on my DET myself. First time I have done something like that. Just have patience.

Bruce is right. Just do _everything_ legal you can think of if you are building an engine. I would spend the money to have someone balance it to a much tighter spec than you normally might. Why? Because you can do so little to these engines that I think this could make just enough difference.

I think a really really good 5 angle valve job would be key to getting max power out of these engines. Valve jobs have to be within FSM spec, but the FSM specs out 5 angles and has some slop in the specs IIRC. I also believe you can blend the seat into the head. Have this done as well.


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## slowSER (Jun 14, 2002)

bahearn said:


> *Is 0.040" over the 2nd standard overbore size for SR20? I keep forgetting to bring my copy of the road-racing GCR to work, but SoloII GCR states maximum of 2nd standard overbore, and for SR20 I thought that was only 0.020" overbore. *


The shop that did the engine in my car only did a .020 overbore because they thought that's the max overbore the block could handle.


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## eric96ser (Apr 30, 2002)

.020 is the service limit in the FSM. George, I did my engine rebuild with the block in the car. I didn't have a way to remove it.


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## dominojd (Aug 1, 2002)

actually Geo I have a spare engine that i'm thinking of doing. Me and Kawski bought a parts car last year I grabbed the engine he took the tranny. 

I should have clarified myself in the beginning. Is it worth it in HP to dollars value? 

I will probably do it anyway because I am a sick person who likes to spend money that I don't have.


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## Geo (Apr 30, 2002)

slowSER said:


> *
> 
> The shop that did the engine in my car only did a .020 overbore because they thought that's the max overbore the block could handle. *


Nah. They're wrong. The 300ZX pistsons are just a hair under 0.040" over. There are several high compression engines running around now with the 300ZX pistons and no problems what so ever with that.


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## Geo (Apr 30, 2002)

dominojd said:


> *actually Geo I have a spare engine that i'm thinking of doing. Me and Kawski bought a parts car last year I grabbed the engine he took the tranny.
> 
> I should have clarified myself in the beginning. Is it worth it in HP to dollars value?
> 
> I will probably do it anyway because I am a sick person who likes to spend money that I don't have. *


What dollars? Do it yourself. It's not hard. I did it with my DET (even though it's not mentioned in the article). Basically, get a gasket and put it on the studs. Use a fine Sharpie marker to outline the port limit in the gasket. You'll probably want to mark the port 1" in somehow (I'd use a pencil for this - don't leave any permanent marks for someone to easily see in tech). Then, using a die grinder, burrs, and sanding rolls, smooth out the port. It's not even all that time consuming.

There might be a bit of power to be found in the way the ports are smoothed, but I doubt it's enough to make it worth paying someone else to do it.

Now, blending in the seats is entirely another story. I wouldn't mess wth that myself.


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