Manifolds or headers?

[WileE]

For the record, I am not asking if manifolds or headers are better. Everyone should know the advantages of headers, and the power they can add (if the mating components can benefit from improved flow). My question was if HP manifolds would be sufficient if I am just building a cruiser and just want a little extra torque over stock. I am using stock 906 heads, which everyone says don't have a lot of flow, so do I really need headers to build a nice cruiser motor.

We all have a budget, and body work is eating up a substantial part of that budget. I have 2 sets of 906 heads, 1 set of 915 heads (currently held for a possible 400 rebuild in the cuda), and 2 sets of HP manifolds. If I could save some money by using the components I have and still build a decent torque motor for the street, that would be helpful.

Hence my questions of:

"Can I get away with using the HP manifolds and still get good low end torque performance for the street?" (Yes/No) and "Can someone recommend a good cam to go with this type of setup."

Car has AC, and vacuum accessories for headlights and heater/ac controls, so I want a good torquey motor with good vacuum. I looked at some of the cams suggested by some, and it looks like duration on those is running from 208 - 224 on intake and 213-241 on exhaust. Lifts of those three cams suggested are .486/.473, ,454/,454, and ,466/,488

Sounds like if I want to build low-end torque, I would want a decent lift, with less duration and overlap. Am I understanding that correctly?

Specs I know of at the moment:
Forged pistons, shooting for 9.25 SCR
Stock 906 heads
Likely stock intake, possible Edelbrock RPM intake (to avoid need for adapter to fit aftermarket carb)
Stock '69 HP exhaust manifolds through 2 1/2 dual pipes out the back. Likely Super Turbo or Magnaflow mufflers (quiet but rumbly)
A833 4 spd
8 3/4 Sure-grip with 3:23 gears
Car has AC, power steering, and manual brakes
Likely 255/60R15 rear tires. Maybe 275/60R15

Psst.... it was a joke. Manifolds/headers... blondes/ brunettes... stock/custom... me on top/she on top....

 

[oldbee]

Also for the ‘street’ it’s always better too err on the “low side” on every guess of what parts to employ.

 

[FrnkNsteen]

No worries Wiley. Its cool. Sorry if I misunderstood. Just got a lot of responses saying that headers were better, when I was just wondering how to make manifolds work.

Dropping the motor off tomorrow armed with good information from everyone on here and it's appreciated

 

[JimKueneman]

No one will likely agree but I have gone through the same inter struggle. I ended up with EFI, Edelbrock Performer stock manifolds and dual 2.25" exhaust. Real question is what is your definition of "low end" torque. The link to the manifolds vs headers interestingly only goes down to 3000 RPM. You will find this is almost universal from anything I can find. Reason? I modeled my 318 with high end simulation software and really looked at the exhaust. Headers will drop torque under 2500 RPM and the longer the tubes the worse it gets but it CAN increase torque and HP in the moderate RPM range (2500RPM up to the magic 5600RPM Torque/HP crossover point) at the expense of the very low RPM. The longer the tube will resonate at a higher RPM and drive the peak torque up higher. With the software and 3-4 inch tubes (stock manifolds) the normal way I drive I preserved a lot of normal driving torque by not going to headers (1000-2000 RPM). I was happy with my decision after experimenting with the software and focusing only in the 1000-3000 RPM range were I drive 99.8% of the time.

 

[Dennis H]

No worries Wiley. Its cool. Sorry if I misunderstood. Just got a lot of responses saying that headers were better, when I was just wondering how to make manifolds work.

Dropping the motor off tomorrow armed with good information from everyone on here and it's appreciated

Good luck tomorrow. I think you asked headers or not in the OP. Headers are lighter, cooler. Your choice. Edit. Meets and greets I carried my digital laser temp gun for months. Ceramic coating on mine kept underhood temps 100 degrees cooler than any other Mopar there with stock exhaust without exception.

 

[JimKueneman]

Good luck tomorrow. I think you asked headers or not in the OP. Headers are lighter, cooler. Your choice.

No personal experience but there are a lot of conflicting opinions out there about if headers make under hood temperatures cooler or hotter. I have not seen any that have thermocouple data with and without.

 

[Glenwood]

No personal experience but there are a lot of conflicting opinions out there about if headers make under hood temperatures cooler or hotter. I have not seen any that have thermocouple data with and without.

My manifolds heat up to nearly 600F using an infrared thermometer. I'm not sure if headers would run cooler but I plan on changing them.

 

[JimKueneman]

My manifolds heat up to nearly 600F using an infrared thermometer. I'm not sure if headers would run cooler but I plan on changing them.

I am not sure if the temperature of the pipes themselves tells the story. My gut says how much surface area of the system matters too. Sort of like the old home radiators. A single 3/4 pipe running through a radiator won't heat the room much. Zigzag that pipe through the radiator and it will heat a room.

 

[Glenwood]

I am not sure if the temperature of the pipes themselves tells the story. My gut says how much surface area of the system matters too. Sort of like the old home radiators. A single 3/4 pipe running through a radiator won't heat the room much. Zigzag that pipe through the radiator and it will heat a room.

Sort of like any heat exchanger i guess. The difference is that each tube spreads the heat along its length compared with thinner metal that should cool faster than a mass of cast iron. Also i would think that headers are less resistive at the head and should flow better with less heat build up, especially the two middle ports.

 

[JimKueneman]

Sort of like any heat exchanger i guess. The difference is that each tube spreads the heat along its length compared with thinner metal that should cool faster than a mass of cast iron. Also i would think that headers are less resistive at the head and should flow better with less heat build up, especially the two middle ports.

Maybe talking about 2 different things. I think that the overall under hood temperature will INCREASE because there is more surface area under the hood to radiate. The overall spot heat on the manifold/header itself may be cooler but I am more concerned about under hood temperature here in the desert. The stock manifolds have minimal surface area under the hood.

 

[Glenwood]

Maybe talking about 2 different things. I think that the overall under hood temperature will INCREASE because there is more surface area under the hood to radiate. The overall spot heat on the manifold/header itself may be cooler but I am more concerned about under hood temperature here in the desert. The stock manifolds have minimal surface area under the hood.

It would be an interesting study! I guess it depends on how the heat is removed from the surface of long tubes that move away from the engine bay compared to a large heat sink inside the bay.

 

[FrnkNsteen]

No one will likely agree but I have gone through the same inter struggle. I ended up with EFI, Edelbrock Performer stock manifolds and dual 2.25" exhaust. Real question is what is your definition of "low end" torque.

Thanks Jim. When I say "Low end torque" I am talking about normal driving conditions when you want to get on it a bit, but not open it up. I'm talking RPM ranges from just over idle (say 1000 - 1200 rpm) up through say 3000 - 4000 rpm (like you mentioned we do most of our driving). You know,... when you want to get on it a bit without drawing attention from any cops that are within hearing range .

I'm just looking for that low end grunt that gets me up to speed quickly when I want. I've heard that too big of pipes can hurt torque in the lower ranges too. I was looking at the TTI exhaust that someone recommended. I think they offer a 2 1/2 or 3" for connecting to stock manifolds, but for the same price (or maybe a bit cheaper) I can have a local shop here do a full custom 2 1/4" or 2 1/2" out the back. They did my Cuda exhaust with 2 1/4" (because of fit around rear axle, shocks and gas tank) through Magnaflows and out the back to stainless tips for just over $500. Downfall is they aren't mandrel bent if I do it local.

Bottom line is I don't want something that won't even break the tires loose, (unlikely with a 4spd) or just bogs when you get on it. Sounds like I should be able to get what I am looking for. The combo you mentioned seems to line up nicely to the conclusions I am getting. Edelbrock performer, lower duration cam, 906 heads, HP manifolds, and 2 1/2" exhaust.

I am not sure if the temperature of the pipes themselves tells the story. My gut says how much surface area of the system matters too. Sort of like the old home radiators. A single 3/4 pipe running through a radiator won't heat the room much. Zigzag that pipe through the radiator and it will heat a room

I think it would also be interesting to see where people have their vacuum advance connected to (if they have it hooked up). I know there are varying opinions if it should be connected to manifold vacuum or ported vacuum, but I have read a lot of information saying manifold vacuum gives more timing advance at idle, and cruising, allowing gas to burn earlier and cooler (not in the exhaust). Just a thought.

Anyways,... Thanks again. Looking forward to getting them started on the motor today.

 

[JimKueneman]

I think it would also be interesting to see where people have their vacuum advance connected to (if they have it hooked up). I know there are varying opinions if it should be connected to manifold vacuum or ported vacuum, but I have read a lot of information saying manifold vacuum gives more timing advance at idle, and cruising, allowing gas to burn earlier and cooler (not in the exhaust). Just a thought.

Anyways,... Thanks again. Looking forward to getting them started on the motor today.

I just moved mine from ported to non ported. It start better, idles better and comes off the line better.

 

[FrnkNsteen]

I just moved mine from ported to non ported. It start better, idles better and comes off the line better.

I did the same thing on my '67 Barracuda (400 4spd, Demon carb). It starts better, idles and drives better, and seems to run cooler. Kind of why I said what I said

 

[451Mopar]

I guess it has been awhile since I looked at the cost of the TTI exhaust (and headers.) Prices sure have gone up in the last 5 or so years.
I have the 3" H-pipe TTI system on the '71 Charger, and it is way better than the exhaust shop system it replaced.
On the '69 Coronet, I wanted a quieter exhaust, and the 2-1/2" allows a larger selection of mufflers, and it had more clearance around the gas tank.
I used the Hughes Engines SEH1620AL cam with 1.6:1 rocker arms in my 9.5:1 compression 360 in a 1984 Ram Charger and was really impressed with the power it made. Really nice for a daily driver. When I first posted, I forgot about the higher ratio rocker arms I was using.
With the 440 and lower altitude, a low 220 @ 0.050" cam should be OK too. From what I have had, when getting into the high 226+ duration range the low end starts dropping off (talking 9:1 compression engines) and the car really wants a higher stall converter.

 

[threewood]

I think it would also be interesting to see where people have their vacuum advance connected to (if they have it hooked up). I know there are varying opinions if it should be connected to manifold vacuum or ported vacuum, but I have read a lot of information saying manifold vacuum gives more timing advance at idle, and cruising, allowing gas to burn earlier and cooler (not in the exhaust). Just a thought.

Anyways,... Thanks again. Looking forward to getting them started on the motor today.

I think if you have a fairly stockish cam, stockish timing, manifold vacuum would be better. I have my 440 hooked up to ported because I have plenty of initial timing dialed in (24°) so it doesn't need more. And mine idles smoother with the ported because my idle vacuum is in the 12in/hg range which made idling on manifold vac choppy. And with it set to ported, when I set timing I don't have to readjust after the vacuum is plugged back in. When I had it set to manifold and I removed the vac hose to adjust timing the car would die unless I adjusted the curb idle screw in. Set to ported I don't have this issue.

 

[JimKueneman]

I think if you have a fairly stockish cam, stockish timing, manifold vacuum would be better. I have my 440 hooked up to ported because I have plenty of initial timing dialed in (24°) so it doesn't need more. And mine idles smoother with the ported because my idle vacuum is in the 12in/hg range which made idling on manifold vac choppy. And with it set to ported, when I set timing I don't have to readjust after the vacuum is plugged back in. When I had it set to manifold and I removed the vac hose to adjust timing the car would die unless I adjusted the curb idle screw in. Set to ported I don't have this issue.

Great point. If the cam is big enough and the vacuum low enough it would come off the stop and end up wallowing the timing and in turn the idle quality. If the vacuum is high enough to rail the canister to max vacuum then it is much more stable.

 

[FrnkNsteen]

I guess it has been awhile since I looked at the cost of the TTI exhaust (and headers.) Prices sure have gone up in the last 5 or so years.

Yeah,... 2 1/2" from manifolds to bumpers, with flanges, mufflers, and hangers is $658 for H-pipe and $717 for X-Pipe. Like I said before though,... that has mandrel bent pipes, which the custom shop here wouldn't offer. That being said,... 2 1/2" pipe with my stock heads and manifolds shouldn't be needed because I won't need that extra flow

I have my 440 hooked up to ported because I have plenty of initial timing dialed in (24°) so it doesn't need more. And mine idles smoother with the ported because my idle vacuum is in the 12in/hg range which made idling on manifold vac choppy.

Wow! 24 degrees of initial? Yeah, I can see how the extra advance could mess with you. On my 400, I am running 15 initial. at a steady 2500rpm I am at 33 with mechanical and 49-50 with vacuum attached. Car runs good. I could see how ported would work better for you with how you have it set up.

 

[Lazerwolf]

Headers have their advantages but in your case, like mine, don't think you will get much out of them. I wanted a street cruiser and did a lot of research. Ended up going a similar route to JimKueneman. When purchased, my 74 Charger had the original 400, stock bottom end (I think), EStreet heads, Davis United Street/Strip distributor, Comp Cams 268 high energy cam, Performer RPM manifold, Edelbrock 600 cfm carb and butchered stock exhaust. Ran like crap. Called Lunati, Edelbrock and TTI. Lunati recommended 702 cam since no headers or stall converter. Edelbrock said switch out RPM manifold for Performer. TTI said keep HP manifolds and go with 2.5" H-pipe exhaust. The reason to keep HP manifolds was quieter and headers would only gain maybe 10-12 HP, in higher RPM range, which I would never notice when driving. Also X-pipe more for higher RPM range and H-pipe for lower range. The only thing I changed from recommended was I put on a 750 cfm carb since the 600 cfm always bogged or delayed slightly when heavy accelerating. Would like to go with EFI when I have the cash. These were recommendations for my build not for every build. Runs great now, even driving to work most of summer.

Much like everything else, I think manifolds or headers depends on build. Mine originally had mismatched parts using different RPM ranges. Might be worth a few calls to tech support also.

 

[m79ded]

I put hp manifolds on my newly built rb. The lunati cam i chose (10230703) says it should be used with headers on their spec, but i used manifolds anyway. They seem to build up too much heat, although probably my imagination. They seem to have a different tone than headers usually do, but I'm half deaf these days so who knows!
One problem i found is that the passenger side is very close to the rocker cover and made it impossible to switch to aluminum rocker covers. I will likely replace them with headers soon.

Same here exactly the same issues with manifolds. It actually baked the paint. I switched to TTI headers and liked them. Car picked up substantial power.