Porting HP 440 exhaust manifolds?

Ive thought about this and heard the same. What about just port matching to smooth out flow?

Did you get a custom ground cam specifically for the manifolds. If not, that could be where you will see some better and more worthwhile gains verses the porting

I already drilled and tapped 2 plugs into the heat riser valve holes so that should help a little...... I think I will open the exit flange up to the 2 1/2 size and do little port match on the exhaustside and call it good! TBF

Cam is crane HR #689521 and a lift of .509int/.528ex with duration at .050 of 222/230..... Nice bump over a stock cam but still mild enough for power brakes..... Andy used the .528 mopar solid and it was the best cam of any he tested for use with the HP exhaust manifolds.....

I should also mention that I will be using 1.6 rockers so that puts my lift up around .540/.560. the Mopar solid has a lot of lash at .028/.032 but Andy also used 1.6 rockers so I should be around the same effective lift and my cam shows a little less duration at .050 vs, the .241 of the solid cam but the same adv duration of .284 on the intake and a little more on the exhaust at .290 vs. .284 The power range of the cam is 1,800 - 6,000 so I am sure I am giving up some power as opposed to headers but I am trying to max out this combo for use with manifolds and I think I have done my homework and have about the best combo for a dual plane sixpack intake using manifolds.... I want to look and sound stock and make people wonder how they got beat by a "stock" 440 sixpack!

I ported mine and my it runs good, not sure if it actually helped though.

Depending on how much the ports mismatch,there is power to be gained with a port match. It made a HUGE difference on a '75 Toyota I had. They were off by 1/16". Never dynoed it but it never lost speed on a hill in 5th gear again. Best part - it only costs time unless you don't already have a die grinder. If you plan to use a 2 1/2" exhaust open up the manifolds if there's room.
Ron

On a 600hp engine it might be worth 3 hp so if I were you I would look elsewhere

I'd prefer to have the castings as thick as possible rather than ported for very minute gain. I would clean up any casting flash though.

Sheldon

I will post a few before and after pics when I get finished!! I think I need to do some cleanup work and port matching on the exhaust ports on the edelbrock heads.....

What is the ID of your exhaust tubing?

I actually found a correct date coded set for my 71 Challenger R/T Clone project...... 2951865 RT and 2989879 LT side... My goals for my project are to pretty much build a brand new 71 challenger with common sense upgrades so the car actually handles, stops, and goes much better than any stock car could. WIth a 3.54 gear Dana 60 and 500HP on tap it should be able to knock down easy 12's in the quarter while looking the part of a high dollar show car.... I am thinking about adding AC as well but need to figure out the compressor mounting with a shaker setup....

Sounds like a cool project. How about keeping the manifolds close to stock and porting the flanges to gasket size. That way there would be a step to help with reversion. I had a set we opened up to full 2.5 on a mill. It did not show up on the time slip on a 451 inch engine.

Thanks Dan! I already opened up the flanges! easy work and still plenty of meat for a good seal and strength. I went in a few inches to make a nice gradual transition to the flange so hopefully that smooths out the flow a bit....I will look into the reversion theory... I think that is more of a factor with cams that have higher overlap? I might email Andy and get his take on that! If it sounds like I have too much time on my hands I do! Lost my job as a Pilot so using this free time to finish my project.... TBF

I did a set of stock manifolds , the heads used had the exhuast port opened to the size of the gasket that comes in the felpro set , actually they were a little bigger , I opened up the gasket and then set it on the manifold the 2 end ports were the worst , over an 3/16" narrower and at least a 1/16" top to bottom ... Time well spent

On port matching - IMHO you make the sides maybe a little bigger than the head's port, the bottom smooth as you can, and open up the top of the manifold runner to create that reversion step. Go through and clean out all the boogers the best you can. Open up the exhaust opening to match your headpipe.

If you have another $600 - $900 to burn, the extrude hone process will make you feel like you've done something, but I bet there's not more than 5hp in it.

R.

Good question... I did not consider that but I think you are right! Thinking about using the TTI down pipes in the 3" size and then 2 1/2 after the x-pipe to the tailpipes... If I have to grind out the head pipes to 2 1/2 than I guess I will have too..... I will get with TTI tomorrow and ask them the inside diameter of there headpipes.... I already opened up the exhaust flanges to the 2 1/2" size so I may have to fire up the ole makita die grinder and let it rip on the headpipes when I get them! TBF

I am going to measure the exact distance from the exhaust bolt holes to the edge of the exhaust port on the edelbrock heads and trace an exact outline on the manifold face to see where I stand. Iam going to do some exhaust port cleanup on the heads first so I need to get that done. Just some light work with sanding rolls..... My goal is to eliminate every restriction that I can and get these manifolds to work as efficiently as possible..... Hey BSB, I did not really pay attention to your car until now and that thing is awesome!! 11's with exhaust manifolds and mild gears is quite a feet of engineering!!! What cam are you using? PM me if cant divulge the info, I can keep a secret!! TBF

After a bit of research it looks like the max gain to expect from porting the HP exhaust is a few peak horsepower gain...... However, there was a gain of 10ft/lbs of torque in the mid rpm range so every little bit helps! TBF

I dont think it will hurt to de burr and smooth them out some but as has been stated it wont do much for horsepower. I would gasket match the exhaust ports as well as the manifolds to ensure there are no blockages or blind ledges. Thats about all that can be done. The big exhaust pipe will help clear out the back pressure. Really people scream about headers all the time but once you bolt them to mufflers HP is down. Headers are for equal pressure per cylender and are at their best un corked!!!

Here is my opinion. You are doing yourself a disservice HP-wise by sticking with manifolds. I understand the argument for manifolds on the street. They're cheap, reliable, and you already own them. That, and headers are known for being a PITA. Then there's the installation, the scraping, the leaking... blah

What is the argument FOR headers? properly sized, better HP and toque all across the range. In your scope, for something around 500HP, you're almost assuredly giving up 40-60hp (this is dyno proven) by not using a good header and appropriately sized exhaust.

So the question becomes: do you care? if not, stick with what you got, and you'll never have to worry about exhaust until rust eats a hole in it somewhere. If you want the reliability, don't hog out the outlets for reasons stated. You won't feel the gain, but the cast iron will feel the loss. By all means gasket match if you feel there is enough meat there, and take off the sharp edges. beyond that, I'd live with them as-is.

or find some of those nice max-wedge cast iron headers

You will lose power. I did comparison on a dyno in August. 502hp with headers at 5800 rpm and climbing to 468 hp at 5400 rpm. About a 7% loss is that enough to deal with headers that you can only decide. This motor is stroker 400 w/ aluminum heads and intake exhaust not matched.

If you select a camshaft to maximize hp with headers, you will see a larger drop in hp when switching to manifolds than if you selected a camshaft to maximize power with manifolds.