: N* cylinder heads question, Bbob



dloch
04-14-04, 02:51 PM
Bbob

Yes.. I'm still playing with this engine...... not much time right now, trying to get the boat ready for the race next weekend.

My question, what it the difference in the heads between 93 - 95 and 96 and later? I think I have most of it figured out I have some questions about what looks like EGR gas slots going into the intake ports

STS
04-14-04, 02:55 PM
EGR slots are in the spacer plate between the heads and intake on early N*

dloch
04-14-04, 02:57 PM
EGR slots are in the spacer plate between the heads and intake on early N*
That is not the case in the engine I have on my stand.

BeelzeBob
04-14-04, 08:35 PM
EGR slots are in the spacer plate between the heads and intake on early N*

Ignore the info above as it is not exactly correct.....sorry STS....



The 93/94 cylinder heads are readily identifyable as they have only two tapped holes per head on the intake face for mounting the intake manifold. The 95 and later heads had 5 tapped holes per head on the intake face.

The 93/94 cylinder heads had the EGR troughs or slots cast into them. They are designed for use with the phenolic spacer plates that mate up to the cylinder head troughs and form the EGR passage to distribute EGR to each port. There are two holes in each head on the intake face that are NOT tapped to align the plates. The EGR delivery ports are MACHINED INTO THE CYLINDER HEAD parent metal. You will see a square slow milled into the head aluminum at each intake port ...... those are the "mouse holes' that have been mentioned time and time again in posts about cleaning the phenolic spacer plates. There is no question that there are slots machined in the cylinder head....not in the phenolic plates. The plates form the passage to deliver the EGR to each port but the actual delivery slot is in the head material....not the spacer plate.


There are some other differences but you should be able to tell from this.

The 95 and later heads that were used with the one piece injection molded plastic intake manifold did not use the phenolic spacer plate as the manifold seats directly onto the cylinder head, it uses the 5 bolts per side to hold it down instead of the 2 bolts per side with the 93/94 setup and the EGR is introduced directly into the plenum of the intake manifold...directly behind the throttle body....not delivered to each port like the 93/94 setup. BTW....the 95 and later heads had the vestiges of the EGR troughs in them I think....they just didn't do anything.


The intake was is tuned so strongly that the small amount of crosstalk and loss of tuning due to the small EGR ports (those little square mouse holes) caused a loss of 5 lbft of torque at 4400 RPM. With the 95 one piece plastic intake and no EGR ports the 5 additional lbft came from eliminating the EGR ports believe it or not. The 5 HP with the plastic 95 intake came from the reduced plenum volume of the plastic manifold compared to the large plenum in the 93/94 FIS style intake.

dloch
04-15-04, 11:06 AM
Ignore the info above as it is not exactly correct.....sorry STS....



The 93/94 cylinder heads are readily identifyable as they have only two tapped holes per head on the intake face for mounting the intake manifold. The 95 and later heads had 5 tapped holes per head on the intake face.

The 93/94 cylinder heads had the EGR troughs or slots cast into them. They are designed for use with the phenolic spacer plates that mate up to the cylinder head troughs and form the EGR passage to distribute EGR to each port. There are two holes in each head on the intake face that are NOT tapped to align the plates. The EGR delivery ports are MACHINED INTO THE CYLINDER HEAD parent metal. You will see a square slow milled into the head aluminum at each intake port ...... those are the "mouse holes' that have been mentioned time and time again in posts about cleaning the phenolic spacer plates. There is no question that there are slots machined in the cylinder head....not in the phenolic plates. The plates form the passage to deliver the EGR to each port but the actual delivery slot is in the head material....not the spacer plate.


There are some other differences but you should be able to tell from this.

The 95 and later heads that were used with the one piece injection molded plastic intake manifold did not use the phenolic spacer plate as the manifold seats directly onto the cylinder head, it uses the 5 bolts per side to hold it down instead of the 2 bolts per side with the 93/94 setup and the EGR is introduced directly into the plenum of the intake manifold...directly behind the throttle body....not delivered to each port like the 93/94 setup. BTW....the 95 and later heads had the vestiges of the EGR troughs in them I think....they just didn't do anything.


The intake was is tuned so strongly that the small amount of crosstalk and loss of tuning due to the small EGR ports (those little square mouse holes) caused a loss of 5 lbft of torque at 4400 RPM. With the 95 one piece plastic intake and no EGR ports the 5 additional lbft came from eliminating the EGR ports believe it or not. The 5 HP with the plastic 95 intake came from the reduced plenum volume of the plastic manifold compared to the large plenum in the 93/94 FIS style intake.
Ok... These were obviously 93/94 heads as they only had the two tapped holes on each intake face of the head. I already drilled and tapped the additional 3 holes per intake face of the head to accept the newer injection molded intake used on the 96/97. That was no big deal other than the fact that the holes directly above coolant passage.... There is no extended boss below that location and the thickness between the bottom of that hole and the the coolant passage was only about .300, that being said I drilled and tapped directly into the coolant passage. My remedy will be to use studs or threaded rod in those two locations that I will apply a sealant to so I don't have any coolant running up the threads.

The intake I have is a 96/97 version and I did see where the EGR gases are introduced just behind the TB.

Since I am going to use the 96/97 intake and the gasket for that intake won't seal the mouse holes I was going to put JB weld in the mouse holes to seal them up so the 96/97 intake gasket will seal flush with the intake surface of the head.

Modify.... adapt and overcome..... new moto.... :rolleyes: once I understand why it's there I'll figure out how to make it work.

If the EGR passages in the intake face weren't used on 96/97 was the hole in the head at the coolant port not drilled at the point? I will need to do something about that since the vestages of the EGR trough in the head will not be sealed by the intake gasket or manifold, correct? That being the case I can either seal it with JB weld or tap it for a pipe plug and plug it. The water crossover manifold has the holes that match up with the EGR ports of the head at the coolant passages.

Are we having fun yet??

Thanks for all your indepth explinations, I love detail......

BTW the Yank converter is on it's way, should be here today... tomorrow for sure.

BeelzeBob
04-15-04, 01:07 PM
I would tap the EGR hole for a plug...it needs to be plugged somehow, yes.


Make sure the intake gasket for the plastic intake covers and seals all spots on the early heads....it may need a touch up with RTV in some spots...

Tapping into the coolant is no big deal if you use some sort of loctite sealer and let it set up before the coolant system is filled.

JB weld for the mouse holes is perfect.

STS
04-15-04, 01:08 PM
well if ya'll wanna get specific. i didn't even read ya'lls posts. :)

dloch
04-21-04, 09:28 AM
Bbob,

I looked at the old intake gasket/seal for the newer plastic intake and there is what I would call a cutout that makes it not completely sqaure in it that matches the intake where the injector shoots down into the intake port. Does the head need to have this cutout ground into it as well for the correct spray pattern of the injector?

Is there any benefit in port matching the intake to the head?

Dennis