Differences between side draft manifolds?

[Whizbang]

I have been wondering if there has been a side by side comparison between the two styles of side draft intake manifolds. I have an Aktins short runner side draft manifold (same as the now long gone lake city) and there is a longer wrap over style on the motor ill be receiving from Driver216.

Now what i would love to see is a side by side run of what the difference in power delivery are. I figure the short runner will raise the point at which peak power is achieved whereas the long runner will give more low end. I also assume there may be a difference in the max power development as well.

So has anyone seen the differences in action? Or should i take it upon myself once the car is running and do some comparisons?

Pictures below are for reference of what im talking about:

[PercentSevenC]

I'd also love to see a side-by-side comparison. If you'll have both, might as well try them both.

[RotaryProphet]

The angle between the manifold runners and the ports was always too big for me to seriously consider the short manifold. I could see the wrap-around manifold flowing better just because of the gentler angle.

However, if you want concrete numbers, I have the dyno in the corner, and we could do this scientificamally.

[TheDriver216]

you rent the dyno we can compare lol ... but then again i have 40mm chokes in my carb. which on a shorty side draft might be too much and lose alot more low end than if i were to have in 38's or even 36's.(which i left that set of 38's at your old shop hoepfully they didnt get tossed) Plus my carb is tuned via smell and plugs which i can be completely wrong about, but it doesnt smell as bad as when i first got it installed. but right now after 4k rpm it rips pretty good.

[Whizbang]

pretty sure those are floating around still. I think maybe even in the MS box of crap. But for sure not tossed.

[Whizbang]

im going to go uncover my short runner manifold and give it a look over. From previous examination, i think it could use some work with a Dremel to optimize it. But i think ill attempt to do a comparison between manifolds.

Now what im not sure about is HOW to do it properly. When the manifolds get swapped, i feel as though i might have issues with having the carb tuned properly. At the same time, i want conditions to be similar. so i might have to do the runs on different days due to the tuning and wait for similar temp and humidly days.

[Whizbang]

okay i dug out my Atkins manifold and gave it an overview.

As you can see in the pictures below, the runners do need to be finished. The machining of the ports is direct cut inward but does not transition to the cast runners well. This is probably because its cheaper. Which, honestly, is fine by me. I would rather have to do a little touch up and spend less money. Plus you can still port match as needed. My engine is a stock port engine, so for now, there is really nothing to exotic to be worrying about.





You can also see that air entering the manfold has a very low restriction before it moves on into the runners. The inside is a smooth casting so there is nothing nearly as rough as anything oem. There is no fancy dynamic intake effect happening, but the air is also not forced on a elaborate path or into the walls of chambers. This will probably allow for a very good flow at high rpms. We shall see once i can strap the car to a dyno.



Also the concern that the air will have too great an angle to turn into the port on the iron really doesn't seem justified either. As you can see below, the top view shows the angle of the runners. For starters there is only one plane that isn't level, unlike the longer wrap around style. So the path the air is taking is only altered on a single dimension. Secondly, look at the picture and you can see how the center runners have approximately a 30 degree angle with the secondary ports having about a 45 degree angle. That is not to shabby in comparison to the wrap around which forces the air to make a sharper turn as it comes down, in order to center the port.