Hardin cyclones
 

Salt water or fresh water? Engine application? PM me all the questions you have as I am very familiar with the Cyclone shorty headers.

I too am wondering about these. Do they help or hurt hp and torque?

I have a set I got used. i havent ran them yet but they look very nicely built. One had a pinhole leak and I repaired it. Pressure tested both with 150psi and it held over night so I called them good. I am really looking forward to running them though.

Where was the pin hole, at a weld? If it wasn't at a weld I would think the rest has to be pretty thin.

I think a lot of the issues must be we not flushing with a LOT of volume of water and using salt away/ dawn, granted my E-Tops and not full length runners but they are still in good shape with 7 years of salt running at 20 years total.
Not pushing my luck will replace them after the new years run.

Ran these on my 565's. Good alternative to the gils with no tailpipe modifications. I was very pleased with the quality.

Any power loss?

I had the Gil cast aluminum manifolds that leaked and became impossible to wield went with the cyclones and could not be happier https://cimg8.ibsrv.net/gimg/www.off...b19d4c245b.jpg

Never ran them In comparison with the gils. They were an upgrade when I built my 565's. I knew i wasn't keeping my 35, so I didn't want to spend a ton on complete new exhaust. We made good power with them over 750. I would use them again if I didn't want to do completely new.

I have been eyeing these also. What do you think will be the most reliable in the long run cyclone, cmi fusion or eddie marine manifolds?

I bought them in 2009 for use in the 2010 boating season

I just removed the stock manifolds and did away with the quick and quite.

my question is where do you get green serp. belts?

Gates HD belts have green backing

Mine are 2012. The leak was at the internal brazed joint under where the gil tail bolts. It was absolutely due to them not being flushed well. Came off a salt water boat. I got them for a fair price and once I spoke with hardin about how they could possibly have welded that they told me that part is not welded. It is brazed. Easy enough. I sand blasted it and cleaned it well. Then brazed with a ssf-6 rod. Put 2 plugs in he lower outlets and a valve stem on a plug in the top. Shot it up to 150 psi of shop air. Sat it in a tub of soapy water and watched for about 5 mins. No bubbles. Next day before I removed the plugs, I read the pressure and it was still right at 149-150.

Has anyone run these in a bigger(540 650 hp ish) NA setup? I have gils and was considering buying a pair of E tops but if these will do just as well(or really close) I can save quite a bit of money.

Looking at them it doesn't look like the runner on E-Tops are all that much longer. If you want I can measure mine E-Top runners. I just happen to have one off.

The green belts are gates and there heavy duty version they seam to hold up better than the regular ones

https://cimg4.ibsrv.net/gimg/www.off...2a98d133ea.jpg
565 cu in, 750 hp.

thank you

E Tops have a 15 1/2 inch primary into a 4 1/2 inch elbow.

They look good but do they help or hurt power?

That would depend on what you are comparing them to

I would think these would hold up well against e tops, and pretty much any manifold except the old Kieth Eichert's. Against a Sport Tube or some other long runner header I think they would start restricting power???

Are those 02 sensor plate something you had machined or is that available from a vendor? How do they affect the fitment at the transom?

I don't think they will restrict power , But in a naturally aspirated application they won't be able to scavenge exhaust and gain you some extra power like a long tube header will.

we made them up at Island racing. Put a small wedge in when running them in the boat to compensate for added height.

https://cimg7.ibsrv.net/gimg/www.off...51026e6d01.jpg
don't have a honest answer to that as we didn't run any comparisons. I'm sure we left some on the table with them but we were happy with the results.