Engine/Transmission (1994 - 1998) porting the head?

[Cooker]

Originally posted by HoleshotHolset

Chris' head failed due to voodoo and I think Gene had something to do with it.

LMAO

 

[Strick-9]

Todd T,



Have you actually measured the wall thickness before and after a true gasket matching?



Wall thickness is cut approximately in half. It's not just a few thousandths.



But as I said earlier several factors contribute to it breaking. It's not just HIGH egt because everyone's doesn't break. You can't honestly say it's 100% due to the stock manifold because I know trucks with 300,000+ miles with the stock manifold with no problem.



It's a combination of factors.



I'm not saying that ported heads are going to cause heads to break, but if you take a part at risk of failure and cut the wall thickness in half, you're running at a much higher risk than before.



I'm with Matt. I think Gene and his voodoo truck dolls had something to do with it.



I was looking through my pile of spare parts today and stumbled across another head that's already been o-ringed. Problem solved.



-Chris

 

[C Schomer]

This has been interesting! My manifold is leaking a little from shrinking and rolling up the ends. I loosened all the bolts so I could get a look at the port matching. The manifold ports are only 1/8" shorter overall, than the head ports and the bolts aren't in a bind yet. I plan on waiting til it leaks more - I need a clutch worse. I put never-seez on all the bolts and just hope it pulled down better. I think I'll make sure the ports are matched and forget about hogging them out to the gasket size, when I finally get the ATS. Craig

 

[83 crew cab]

like strick-9 said to gasket match is not just a couple of thousandths#ad

 

[C Schomer]

Looking at the shape of that break on page one, I think it had more to do with the lack of support against the tab on the head combined with the weakened casting, more than the pull from the shinking manifold. Just my take! Craig

 

[HoleshotHolset]

George: I didn't know that Mag-Lite made a Cummins cylinder head tool... . :-laf



Matt

 

[Todd T]

First of all Strick, we all know the wall thickness should not be taken down into the danger zone for the sake of exact port matching it. A prime example is the picture 83CC posted. if you look at how that port has been distorted and is now out of shape to "gasket Match" it. I would love to see how this port flows now, compared the its five brothers. More importantly, its companion. That head is probably scrap IMO. the whole point here, is porting really doesn’t gain you much. unless you are pushing 500+HP and 80-100 PSI then the tables turn a bit. more dependant on the PSI. you then have to deal with the higher volumes and higher velocities. keep in mind you can only do so much at that point anyway. I have flown these heads and used clay modeling to simulate all sorts of crazy things that pass through my noggin and turbo inlet tubes as well. the heads aren’t that poor to start off with. you have to remember we are dealing with supercharged engines. the old gas engine "port matching" is not as critical. in fact you can create a scavenging effect with the technique of leaving the port smaller than the manifold and putting a scoop on the edge of it to create swirl in the right direction. To gasket match at the port and then stifle it an inch or two down the runner is not doing anything but creating turbulence anyway. the key is to BALANCE the flow of the entire head. some need to scavenge more than others. a flow bench can tell you where you have been and where to go.



On the intake side. The plenum volume needs to carry the volume for two cylinders plus a bit in its reserve. A few pounds of boost handles this pretty well. If you are pumping out the backside too damn fast the intake starts to get choppy though. this was the hardest thing to simulate on a bench. you have to dump two cylinders at the same time. my 900CFM bench really couldn't handle this accurately. keep in mind the firing order and that these engines fire in a companion configuration. When flowing a head you have to remember which cylinders are paired and "port match" accordingly. this will keep the plenum pressures more equal and not so spiky. Overall it helps balance the flow out the other side. same amounts in, same amounts out. Right? The next task is to deliver these like amounts at the same time to the turbine. and for those not to enterfere with the next pair of charged air coming down the pipes(balanced). This should create a constant flow of like volume and velocity air charges to the turbine. 2, 2, 2, into 1.



You’ll probably find out some day, that this is the blarney stone a certain king of HP we know, has then again, maybe not



Clear as mud? BTW I live by a don’t ask don’t tell Philosophy, so don’t ask!

 

[Todd T]

Originally posted by C Schomer

Looking at the shape of that break on page one, I think it had more to do with the lack of support against the tab on the head combined with the weakened casting, more than the pull from the shinking manifold. Just my take! Craig

are you saying a shot peening job was in order? maybe a bead of cast O loy along the outside



ATS Babe!

 

[SlyBones]

So Todd, You say porting a head doesnt gain you much. Gain you much what? Power, EGT reduction what? How about answering my question, its only a few posts up.

 

[HVAC]

Porting

Sly, you won't gain any horsepower and little cooling. Both depend on you level of performance. Of course some will hear other opinions. I think Joe was one of the first to discover this on the dyno. While at approx 400 hp there was no performance gain resulting from the port work. I would also mention that in conversation with Brett of Edge Products similiar results were noticed. There is possibly some cooling effect depending on who you talk to.

 

[Todd T]

sorry sly your question (i thought) was pointed at HVAC. you can gain a saving of between 200 and 300 degrees with a moderately dressed head. to pay $450 for just a port job and flow bench work is a bit excessive.



spend your money on the valve job and setup. pull the head, clean it up (port) pay close attention to the following; #1 bump, plenum letters, fuel filter boss and intake guides(narrow them, you can take about twice as much material off the seat area as you can the guide area). gasket match the exhaust. that's about it. nothing any of you can't do at home in OH SAY!! 8 hours or work



put a good 3 angle, 10 degree back cut valve job, matching the depth to within . 055" of the deck.



that is where to spend your money. CC'ing the head and cleaning up a few poor spots. not on porting work alone. a good valve job is more important than gasket matching the exhaust manifold. you are looking for balance. equal in, equal out, its that simple! once that valve closes all cats are black in the dark.



you want to blow some money? buy yourself one of those high $ head gaskets and try to pump 80 PSI through it i think Nowell can help you spend the 80PSI part (twins)



I'm not saying twins are a waste, I'm saving every dime i can to buy mylself a set. Oo.

 

[HoleshotHolset]

Todd said: "10 degree back cut valve job"



Finally! Someone see's the light! I have been preaching back cutting of the valves for a long time - and nobody even commented about it until now.



Matt

 

[83 crew cab]

Matt the mag light is a tool for everything



Todd here is the numbers for the head this is exh numbers only





ported stock

lift cc cc

. 400 181. 3 134

. 350 175 128. 6

. 300 159 123

. 250 137 111. 6

200 114. 7 96

. 150 93



for what I am doing I dont thank the head is any were close to scrap it falls right between a piers #2 and #3 port job

 

[SlyBones]

Thanks,



Sorry Todd, didnt mean that the way I guess it came across. I originally was asking HVAC, but I really didnt care. I was not trying to pick on him, I just wanted to know why doing the head was not worth it, and you spoke up too.



I figured that it did not add much power if any, like I mentioned above I was after the EGT reduction factor.



I also guess that I assumed a bit. When I read "ported head" my brain read what I see on Piers site, on both the Ported Head page and the Technical page pics, all nicely bundled together. I sorta assumed cleanup, the guide area, as it shows over there in that one pic, the valve job, etc. -- I guess I was not thinking of stricky exhaust gasket matching or a like port job. I suppose I read too much into the comment.