How much can I build a motor with HP exhaust manifolds?

How much should one build a big block if they have to use HP exhaust manifolds? Is there a known flow or HP level they are known to support or limit? Does one work back from that number when selecting heads, intake, cam, and so forth?

checkout Andys build in the archives, 470 cubes 550 horse (iirc). used std 68-70 BB HP manifolds, 3" mandrel bends.

Port match goes a long way.

As said by Robert, check out Andy F's build

I would look at it from another perspective.
If you're building it to compete in a class, then you should determine how much power you need to be competitive, and build to that target goal.
If it's just a street car, then it will likely come down to the same determining factors that go into many street builds...... Which usually revolve around the theme of what your tolerance is for how rowdy it can be. In this scenario, you build it according to what you think you can live with, and that engine combination just makes what it makes.

Some inspiration...

http://www.fastraces.org/members/fastraces/fastraces.nsf/top-menu-items/ghp00

Just takes cubic inches and cubic dollars. As does most motor racing.

Kevin

Along with extrude honing the exhaust manifolds

A lot of money for a small gain, so unless he is building to race in a in FAST type class, and needs every last HP, it's really a waste of money. I think people that have done it saw maybe 5hp, it cost over $500 last time I saw someone talk about it and that was maybe a decade ago ?


Listen to fast68plymouth , he has been involved in a number of builds for this.

My experience is the port openings on the manifold are a lot smaller than the ports on the head , especially if the head is opened up to the gasket , port matching the manifold on both the inlet and the outlet to the head pipe , along with smoothing as much as you can reach in can't hurt.

andyF didn't do much of anything to the manifolds he ran, maybe port matched , but he did use a pass side without the flapper valve setup, I'd remove that if the crossover is blocked.

That is true, I did very little work to the manifolds. I opened up a couple of ports that were smaller than the gasket and that was it. The manifolds I used did not have flapper valves. The big "trick" on my setup was the custom flanges I had built to go direct from the manifold to a 3 inch pipe. I had thick flanges machined from SST with an internal step so the 3 inch tube would slip in place.

I'm still running the same setup today although I have a different engine. I sold the 470 low deck a long time ago and replaced it with a 512 inch low deck. The 512 makes a little more power but is still very mild. I think the cam in the 512 is 240 @ 050, might even be a bit smaller than that. Has plenty of vacuum at idle and lots of torque down low. It has been a long time since I worked on the car but I think it made around 500 rwhp which puts it right up near the top of any musclecar list.

Watch this video: https://www.youtube.com/watch?v=azPKIjxmmdU&feature=youtu.be

Also, I would agree that extrude honing helps to promote smoother flow with manifolds. I have never used headers on anything - manifolds for me.

Sparky, your post contradicts itself. Extrude honing ($100 per horsepower) is the opposite of bashing in the header pipes.

Here's what I take from the video: The extra flow advantage from headers is only a small component of the total power gain. Most of the power gain comes from the pressure wave tuning.

This is the reason that shorty headers don't gain much over manifolds. Not enough length separating the pulses.

To the OP, I would say follow AndyF's examples.

Recently I have seen quite a few dyno tests with Volumetric Efficiency numbers over 100% for quite a high percentage of the operating range. It should be physically impossible for a piston to suck in more than its total swept volume. The difference is in tuning the pressure pulses, used to be called ram tuning. Isky Cams touched on it in the early '60s by talking about 5-cycle cams. The fifth cycle was overlap. I am pretty sure that at least a few of early hot rodders like Ed Winfield were playing with this back in the '40s.

R.

600 hp is doable. It is a bit of what you are willing to do or spend to get there, but it's not rocket science either.

Thanks for the replies. Is there any concern with plug wires on #6 and #8 with angled plugs on manifolds?

Using AndyF's motor as a guideline, would something like the Trick Flow 240 heads be too big for this type of motor?

Would a split pattern cam be something to avoid, or just keep the intake around the 240° to 245°@.050", and not worry too much about it?

Sparky? OKAY...............

If you can us the TF, I would suggest that. Others have been able to make other aftermarket aluminum angle plug heads work with manifolds, but don't know anyone doing it specifically with the TF. I would assume they would be the same.

If you don't want to leave any power on the table, You should get serious about piston configuration, compression ratio, cam event timing, and cylinder pressure to maximize power at your elevation. A guy like Dwayne Porter can step you through all of this.

If I was building a new motor today for my car I'd use the Trick Flow heads. I don't see any reason not to other than the angled spark plugs which are not super friendly with the HP manifolds.

If you read my cam testing article in the tech archives you'll see that cam selection is a little tricky. If you go too big you lose bottom end power and the manifolds prevent making top end power. If you go too small you make a lot of torque but you give up top end power. I had to test a bunch of cams before I figured out what my engine wanted. Dwayne is a good guy to ask for a cam recommendation. He has a fair amount of experience with manifold engines.

Part of building power with exhaust manifolds is trying to keep the intake port velocity up without the benefit of exhaust scavanging.
The bigger the intake port, and valve, along with more low lift flow(which almost always means more flow in both directions), relative to the size of the motor, the harder it is to build velocity at moderate engine speeds.

To me that means that you'll want to make the motor as big as is practical to use the TF head with it's fantastic low lift flow and 2.19 valve in this type of application.

I think it's also worth noting that headers definately work.
You'll spend a lot of $$$ on other areas of the build to make up for what you're losing by not running headers.

That is a good thing to go ahead and point out. When I switched from my 470 shortblock to a 512 shortblock I also changed from RPM heads to CNC ported Mopar 452 heads. I think that a 512 would be big enough to work with the TF 240cc heads but you might want to be even bigger than that to keep the velocity up.

You can spend a ton of money figuring it all out that is for sure!

At lower engine speeds, keeping the velocity of the air high as it discharges around the intake valve while at the lower lifts(during the overlap period when the piston is moving in the "wrong direction" as far as the intake port is concerned) is easier to accomplish when the valves are smaller rather than bigger.
Like with most things horsepower related, there is going to be a crossover or tipping point for each combination.
With regards to intake valve discharge coefficient(i think especially in a restricted exhaust application), too big of a valve allows for more reversion, and too small of a valve limits peak power output.

This car is a 1964 Dodge 880. I can't figure out what to call this body. It's not a C-Body, and it's not a Forward Look body, but it shares much with that earlier style engineering. I have not found anybody that has gotten a set of headers that will fit this type of car. The steering box is right against the firewall. The driver's side manifold is a center exit, like a truck. I think I can get B-Body HP manifolds to fit, but if anyone knows if long tube headers will fit, let me know. I've even seen people have problems with shorty headers in this style of chassis, but I'm open to suggestions.

Have you looked into big block A body headers?

What about hugger headers or is that what you refer to as shorty headers?

http://www.protuninglab.com/hds-moparbb-v8.html

That is kind of an oddball chassis.
Don't take that wrong.
I love the 880's.
The predecessor to the C-body.
Kinda heavy aint it?
I would be looking at building torque instead of H.P
Logs would not be a concern of mine.

If I knew longtubes would fit, I'd get them, but I don't think any for the popular bodies will work. The drag link, pitman, idler, and steering box are forward, and the torsion bars are further outboard on my Charger. The drag link and steering box are further back on the 880, and the torsions are further in. Shorties aren't for me. The HP manifolds have 1-3/4" area, and people are getting 500HP out of them. That's fine with me. Build for torque, but if anyone knows of headers that would fit, let me know.

These are TTI C-Body headers, followed by the 880. They look great, but my torsions would run right through where the tubes are, along with the pitman and idler, I think.

The 880 is the same as the 300 in 64, chassis wise anyway.

Hedman claims these fit the 880. part number 78030

http://www.hedman.com/site/?d=119&dt=108

Could you use Max Wedge exhaust manifolds? Seems like they would work in that chassis, and flow decent, too.

ceramic coating the inside and outside of the manifold seems to be better bang for the buck than say extrude honing, keeps a big source of heat out of the engine compartment.