Ppl keep sayin that its a waste to fill the divider if you don't also block the heat crossover, but I live where its cold and rainy 8 months of the year so the carb heat is stayin where it is.

But if it allows those cylinders to scavenge properly, and it positively effects the operation of my long tubes and x pipe, how's it a waste?

I'll also be rubbing down the bumps and casting flaws in the ports, and cutting the head .055 anyway so I don't really care if its just not worth it for the effort and shop time, the head is getting cut in any case so tats not an issue.

 

Sounds like you've got your mind made up. But how are the two center exhaust ports going to "scavenge correctly" when they're connected to each other through the crossover? In other words, the little slit of daylight between the center divider and your headers is nothing compared to the gaping maw connecting the two ports on the other side of the head.

 

Oh SNAP. Mind changed.

 

For what its worth I don't belive that the open center affects scavenging as much as its led to belive . My reason for this is if its open in the middle ( cylinder head ) then the collector would affect it even more because its a big open spot . I don't belive exhaust pushes back into the other port in the center., they way headers merge they will pull exhaust out when other pulses from the other cylinders pump out so although cylinders 3 and 5 or 4 and 6 might have an open center ., cylinders 1 , 7 ,2 and 8 are still pumping exhauts out and pulling from the other cylinders due to the common openingin the collector . I'm not saying its pointless but I don't think it affects how headers scavenge the exhaust as much as people think . If it truly was that bad then I don't know how I saw a .16 gain when I added an x pipe to a set of heads that did not have the divider welded up. Again I'm not saying its pointless but I also hate when people say it ruins how headers operate . It might affect scavenging but there is still gains in performance to be had from going to headers vs. Manifolds. Just take a look at tri Y headers they join 2 ports together before they go into the collector. I know comparing tri y headers to a small opening in the exhaust center port is apples to oranges but if the center opening in the 2 ports affected scavenging I think tri y's would be obsolete based on the same theory since essnetially two ports are crossing before the collector much like our olds heads.

 

You are basing all of this on what you "think" and not actual physics, correct? The fact is hard to ague; if the exhaust ports are connected, be it the center divider or the crossover, it is going to limit the effectiveness of the header. I do not see how that can be reasonably argued.

 

It is based on personal thoughts but in a tri Y header you are connecting exhaust ports aswell. is it limiting the header ? accodring to doug thorley headers the tri Y makes More low and midrange torque while still making power in the higher rpm's . I can see the headers effectiveness being affected in the lower rpms but in the higher rpms the echaust is pulling so fast that i doubt the center being open will affect operations. Much like an x pipe cross pulses pull exhaust out. In the header collectors the primaries pumping exhaust out pull exhaust out from non pumping exhaust ports.

 

Well, those are your "personal thoughts" and I will disagree. Not going to get into it with you, but you have very limited practical experience in this matter and for you to suggest that it does not matter is, IMO, incorrect.

 

I did not say it did not matter. I just said i dont think the headers are affected as much as its led on to believe . Have you personally tested it ? Do you have experience with non welded and welded ? Like i said i run headers and have never had the divider welded up until these ported heads i got done. But I still think wether or not the divider is welded up the engine will benifit from headers. If you can do it ., do it but if not its not like you are leaving a ton of hp on the table.

 

I never said headers would not improve performance even if the cylinders were not separated. You said this,
"For what its worth I don't belive that the open center affects scavenging as much as its led to belive "
and I disagree with that statement. You have assembled and raced how many engines? Science is what it is, the physics are really not in dispute. Not going to beat a dead horse, go on if you like.

 

"as much" key phrase there. Meaning headers will still be a great improvement. You seem to think im arguing that its pointless to weld the divider which im not even arguing at all. I think i mentioned that plenty of times that i did not think it was pointless to weld the divider . I dont know what your point is becasue i never once said its a waste of money i simply stated that i dont think it will affect performance in a way that you must weld the divider to run headers . Just how people always said grind the egr bumps and after various people tested it was found that they dont hamper flow as much as they though. After all the egr bumps is what would appear to be an obvious obstrustion to exhaust flow. I was simply stating how i think the center divider does not affect header performance (as much ) and stating why i think so based on the information that is out there.

 

Jim i atleast gave my theory on why i think header performance is not affect as much as some lead to belive based on information thats out there and i could be wrong , right or in between but i never said i was right . It might not be tested but has anyone tested the benifits of the welded center divder on an olds. If there has been i have not seen it . Better yet jim how about you stop trying to argue and enlighten us ? You only mention how in your opinion im wrong or incorrect but fail to state why ., even though i never said i was right or wrong and mentioned many times that welding the divider was NOT pointless. I atleast am thinking outside the box but using facts that are already out to support why i think what i think im not making stuff up about exhaust characteristics.

 

From here,
http://www.epi-eng.com/piston_engine...technology.htm

"There are two separate components to the exhaust event. The first is the removal of exhaust gasses from the cylinder, which occurs as a pulse of hot gas exiting the cylinder and flowing down the header primary tube. The second is the (much faster) travel of the pressure wave in the port caused by the pressure spike which occurs when the exhaust valve opens, and the various reflections of that wave. Taking proper advantage of these pressure waves (component two) can produce dramatic improvements in clearing the cylinder (component one) and can strongly assist the inflow of fresh charge."

There is no way this can work if the pressure is lost through either the crossover or the divider into another cylinder. IMHO.

 

But if velocity is maintained one cylinder at a time in the collector through the firing order then the crossover is not a affecting agent per say . The way i see it is unless multiple ports pushed pressure to maintain exhaust velocity then yes the divider would create an effect on it but since the cylinders fire one at a time that means exhaust velocity is maintained by one cylinder at a time . I understand exhaust pressure will be lost in those two ports but it still has two ports on each side that will pull exhaust through their pulses and atleast aid the center ports in pulling trapped exhaust gasses or gasses that may crossover. This i like jim the exchange of thoughts. im not arguing and im not saying the facts are wrong im saying how it may not be some thing to loose sleep over if you dont weld your divider. if engine speed was really slow i can see the dynamics of pressure being lost but engine speed also has a play on to how the exhaust pulls or how frequently cylinders are pumping exhaust the faster the engine speed the faster the exhaust cylce is and the faster the non siamese ports are pushing exhaust out and pulling from the other ports . I know how an x pipe works but how does an x pipe pull exhaust out when its wayyyyyy further back from the are that would have the most exhaust velocity ? The cross pulses keep pulling exhaust out. If there is enough velocity to effectively pull exhaust out with an x pipe away from the collector then there is enough pressure at the collector to keep pulling exhaust out from the ports regardless of the cross over or divider. That is my thinking atleast its an opinion and it could be wrong but im not basing it on made up stuff here. Just to add to this if header function was hampered by the center diver and cross over and exhaust velocity was lost I don't think an x pipe would have given me gains. Went 14.00 on open headers went 13.86 with an x pipe and mufflers. It all has to work together.

 

So question, does blocking only the intake side improve scavenging? Obviously the impedance to flow of the crossover not being filled would still exist but the pressure would remain separate.

The dividers were already welded come to find out, the crossovers left stock. Great information though in the debate, I'm glad to hear the x-pipe was more than just a fad item, I put good money into the exhaust.

 

Wait looking at it now (the head) I see how that's a silly question.

New question though, is it worth the time to rub out the egr casting area in the exhaust port? Mine aren't even tapped.

 

Just to keep the debate up!! I am not so sure that x pipes are that great!! If i had a job which i don't right now i would debunk it and see. Now i have run my car down the track capped with exhaust dropping off just in front of rear axle. Then went within ten minutes uncapped was worth five hundredths. Now i run a 3 inch exhaust system and two inch tubes. What i done over the winter was in stall ARH and deleted the 2 inch hooker headers that wrap around the frame.

 

For me the x pipe worked and it put me where I wanted to be for a very mild sbo set up. I will not lie that results will vary but our oldsmobiles are choked up on the exhaust side anything we can do to aid the flow of exhaust out will improve performance. My x pipe netted me gains and its way further back than where its supoused to be for opimum gains.

 

Well i don't think the x pipe will gain me a tenth so that is why i thinking not worth the effort. My exhaust has one of the better flowing mufflers magnaflow so i think this breaths good coppercutlass.Mine is a 1970 442 with a 468 ci, turbo 400,390 posi,3750 me in it.Pump gas looking for mid 11's in a couple weeks.

 

Perhaps you do have a good flowing exhaust. But I was runing 14.00 with open headers , I ran 13.86 with the x pipe and mufflers. The white 65 cutlass from rocket racing runs an x pipe . Probably for a reason. The x pipe further scavenges exhaust its more than just sound but i will agree it's not right for all combinations. My current combo should be good for 12's with my 355 so thats the goal.

 

Yahhh they sound freaking AWESOME : P

 

I know for a fact the flow bench don't care if the crossover is filled. Hell, to be honest, on the flow bench it didn't care what you did porting-wise to the exhaust port......my 3-angle valve job with no porting and open crossover flowed the same as Dave's filled crossover 3-angle valve job and bowl porting with the AIR bump removed up until around .500 lift.......and by that time, the exhaust should be flowing pretty well by then.

However, I'd like to do some velocity probe tests on that. Kinda working on that as we speak. As they say, good work takes time.....and money......ok, basically it takes money. Coincidentally, playing with cast iron stuff with Dave (Cutlass Freak) has led to talking with a lot of bright minds in the Olds world, and I must say, I know a hell of a lot more about an Olds head then I did a year ago.

With that being said, and I might sound like a broken record, but the 355 small block I did years ago went 12.74 in a 3800lb 84 Delta. #4 heads with no porting and small valves. The crossover had iron plugs in the intake and the divider was......well, stock.....so it was open.

I really think this whole debate gets a bit silly because at the end of the day we are not really talking about setting land-speed records, we are talking about simply hitting 12s with a pump gas small block Olds (actually, the OP stated in a different thread he wants 14s, to which I say I'm sure there are plenty around that can help him detune to 14s if he so wishes).

With that being said.......to the OP......put plugs in the crossover, and don't worry about welding up the divider. Your carb will get more then enough heat in the cold, and you will not notice anything by having a stock open center divider. When you decide you want to go 11s on pump gas with 350 cubes, then let's have a chat.

I keep telling myself I am going to post simple small block engine recipes, including converter and rear gear specs to hit 13s and 12s with a small block Olds.......I've been lax on that. In my defense I was building a 9 second small block Chevy lately (not mine, please don't shoot me ).

 

Those bumps in the ports are for the A.I.R. system, not EGR, and yes, removing them helps. The Olds exhaust ports want to be raised, as the stock 90 degree turn isn't the best for flow.

 

What bothers me about the divider and crossover are that they are only affecting the center cylinders. Doesn't this make the tune inconsistent from cylinder to cylinder??

Maybe this isn't a big deal for a mild setup.. 13's would be fantasy realm because then at least I can play with some modern v8 stuff... Not a lot of Hondas try to run against a v8 w visible headers, even if they got *****

 

All this conversation does for me is reinforce my position that it is crazy to put any kind of money into old iron heads.

 

Jim on that aspect you are definitely beating a dead horse.

 

Money? I was qtd $10/per to weld divider and grinding air bump is like 8$ of bits so no money here.

If those mods would make my head feel strong for a stock head, that's 30 bucks well used in my book, even if the HP gain is truly minimal.

 

Thats a deal but realisticaly i think it cost more to do that stuff. minimum 1 hr to weld each one the 1 hr to grind each one then probably another 2 hrs for the egr bumps . at a minimum of 60 per hour thats 240 at minimum.

 

The divider is already filled but it looks ratty and isn't what you'd call perfectly flush, they are just laying a new bead across the top for me to file down, and I'm grinding the bumps myself.

Once the divider is close, I'm just gonna have the shop that mills the head for compression take enough off the exhaust side to make it true.

 

I'm suprised that I'm hearing a mildly modded smog 350 w gears is within spittin distance of 13's.

Car probably was not sub 15 in previous iteration

 

My set up was just set up corectly. It started out at 14.23 and once I had it dialed in it would turn 13.8's all day. This was also with me running a th400 they eat about 25 hp up. I had a 2200 stall and 3.73 gears . Stock 72 7a heads 73 350 short block , 260h cam performer intake . Nothing crazy . My car was all steel at that time when I went with fiberglass fenders and hood I went 13.71 . I later built a 10 to 1 compression 350 and went 13.3 I left a lot on the table running a tight converter and small carb.

 

As a spectator I found the ping ponging extremely entertaining! I live for entertainment! Just my 2 cents.

 

Wow that cam is smaller than the one I'm going to use, 212@.050 single pattern .460 lift I hope it works OK with my tamer 3.42 setup. If the maths are correct I should be at 8.9:1

 

We had a $2500 budget for the Delta. We went with irons because obviously the budget would have been eat up by the aluminum heads if we went that route (there was really no point for aluminum heads). Then we went 12s on pump gas in a heavy car.

Tell me again how we are crazy.

 

Whatever, Don. Keep preaching like everyone else to do things as cheaply as possible, it always works out the best that way.

 

I sense a lot of butthurt . Im sorry jim but you constantly say I dont agree with this or that and thats about it. You should build something and let us know how it goes if you even have something to build. Last i remembered you sold off all your stuff. Isn't that like going to the gun range with out a gun ., or going fishing with out bait. I think you have spent more time telling people you disagree rather than actually contributing.

 

I could be wrong but that's the way of the world now. Cheap as possible. It's the only way to keep busy and stay competitive.

 

This isn't a religion, and one person's anecdote is not data. It's just fluid mechanics, read up on it and learn. That open divider will make an impact as it wrecks the flow later on.

 

Where did I do that? Or you just decide from time to time to throw out unwarranted jabs?

 

I don't think anyone would say that it doesn't make a difference.......just that it doesn't make a difference for the intended usage in this situation. You'd almost think it is impossible for an Oldsmobile engine to run reading some of these threads around here.

 

The thing is no one ever said it did not impact it at all. I simply stated why i feel its not something to get hung up on specially for a mild build. I also stated multiple times how it was an opinion. If it was take as data then someone failed to read that. The only way to debunk it is to take 2 cylinder heads and test them on the track to see what the diffrence in performance is .