GN1-R's, Ported & Unported stock heads.

[Turbo1dr]

I found two pictures digging around on my computer. Again, this is to show people what these heads look like when installed on a 109 engine.

This 109 block has a .030 overbore. The red lines are where the top of the bore needs tapering. The valves do not hit the bore of the engine when opened.

[turbolou]

Originally Posted by Turbo1dr

I found two pictures digging around on my computer. Again, this is to show people what these heads look like when installed on a 109 engine.

This 109 block has a .030 overbore. The red lines are where the top of the bore needs tapering. The valves do not hit the bore of the engine when opened.

I'm trying to visualize that, I assume your using a gasket as a pattern. Is there enough material to work with & have you been able to measure how much improvement if it's worth the effort

[Turbo1dr]

I'm no expert with highly sensitive electronics or flow machines to confirm that tapering the cylinder helps but I can judge by my common sense that it should flow better when there's no "wall" for incoming air to hit. Small bore Big Block Chevrolets also have this taper from the factory. Yes there is enough material to taper the top of the bore. I don't taper the entire top of the bore just where it's needed where the chambers overhang.

Here's a crude drawing to show what I'm talking about.

[turbo nasty]

Man just want to say thanx for the pics and this thread is good. Good info swapping here.

[Boost231]

that make alot more since then the other picture. i agree it would only make sine that i would flow better due to it not hitting that lip and being a nice even curve

[turbolou]

Hmmm!You probably have a good point there, I'm going to have to look into that,Thanks for shareing,It's what we used to do years ago when I was campaigning BB Chevy's as you say it was done because it made sense. It would make more sense to run a bigger bore & shorter stroke if that were possible. You could spin the motor faster because of a lighter rotating assm. as well as unshroud the valves.

[Jerryl]

Originally Posted by Turbo1dr

Since you don't see this kind of stuff posted too much I figured I'd show what a full race ported GN1-R head (out the box) looks like when compared to stock iron heads. This gives people an idea of how much larger aftermarket heads are. I ported the stock iron head you see myself and has been a best of 6.53 at 107 in the 8th mile. Also to note, my "R" heads are not the tall port offered by Champion. There's at least 3/16" or more to make the port taller. I'm sure all the really fast guys have MUCH larger re-worked heads than these.

Ported heads question
Here is a dumb question. (Hope I did not miss it in the thread)
It appears that the plug is more towards the center in the GNR’s vs the stock heads.

Is this an illusion or does do the GNR’s use a difference casting?
Welded stock heads possibly?

Also, it appears that the squish is noticeably improved.
Is this a TTA head casting?

GREAT THREAD!!!

[Turbo1dr]

Originally Posted by Jerryl

Ported heads question
Here is a dumb question. (Hope I did not miss it in the thread)
It appears that the plug is more towards the center in the GNR’s vs the stock heads.

Is this an illusion or does do the GNR’s use a difference casting?
Welded stock heads possibly?

Also, it appears that the squish is noticeably improved.
Is this a TTA head casting?

GREAT THREAD!!!

Champion aluminum heads are a totally different casting than stock. Spark plug is also moved closer to the center.

Also, they redesigned the "squish" or combustion chamber for better flow. If you look at the new Chevy LSX style heads the chambers are almost identical to the Champions.

[Jerryl]

Originally Posted by Turbo1dr

Champion aluminum heads are a totally different casting than stock. Spark plug is also moved closer to the center.

Also, they redesigned the "squish" or combustion chamber for better flow. If you look at the new Chevy LSX style heads the chambers are almost identical to the Champions.

Nevermind. I "thought" they were ported iron heads.

[Turbo1dr]

Found some old pictures of the regular GN1's I ordered. Here is the chamber differences in the "R" and the non "R" Champion heads.

http://www.turbomalibu.com/drivetrai...rsGN1&GN1R.jpg

[Turbo1dr]

Originally Posted by turbolou

I'm trying to visualize that, I assume your using a gasket as a pattern. Is there enough material to work with & have you been able to measure how much improvement if it's worth the effort

GN1-R heads on a 3.8L engine.

[Jerryl]

Originally Posted by Turbo1dr

GN1-R heads on a 3.8L engine.

Three things:

1-Thanks for sharing! Very nice!
2-Nice shots and camera work. Took some time to get the shots I bet.
3-That must have taken some "khahuna's" to start grinding the bore!

[fastdon3]

nice work done need more info maybe reference on a good machine shop to get some port work done

[waddell87]

Very, Very Informative!!

[icepicker62]

Cool post. I replaced my head gaskets 5 years ago when I bought my car. I was told they were bad. (they were not, only a bad turbo seal) I knew nothing about these cars then. Anyhow, I had the heads cleaned up and had a basic valve job done @ a local speed shop. Never ported or anything. I guess you live & learn. After all I've heard, I may pull them again & have them ported along with my intake. I just hate doing that knowing these head gaskets have seen 28lbs & are still fine!

[Jeff Strube]

Originally Posted by Turbo1dr

I'm no expert with highly sensitive electronics or flow machines to confirm that tapering the cylinder helps but I can judge by my common sense that it should flow better when there's no "wall" for incoming air to hit. Small bore Big Block Chevrolets also have this taper from the factory. Yes there is enough material to taper the top of the bore. I don't taper the entire top of the bore just where it's needed where the chambers overhang.

Here's a crude drawing to show what I'm talking about.

This is some good info.I was wanting to go with a GN1-R Head I thought they where only Tall ports. I see you talking about a .030 over bore. Can this be done
on a .010 or .020 over bore block? I have a Stage 1 block and did not want to have the block bored over .020 because it has never been bored. I do want to
go to a bigger Vavle heads and 14 head heads. Looks like from the pictures I would have to do alot of Tapering work at top of the block on a .020 over block.
Can this be done on a .020 over block has any done this on a .020 block with these GN1-R heads?. I wanted to use my stock ported intake with a set of GN1-R?

How much better do the GN1-R heads flow race ported than the GN1 race ported any flow numbers to compare these two heads?

[1chance]

Very good info. I just got port irons, and intake. was hoping for improve perf.