AN fitting size vs. HP output?...

[cjshaker]

What is the general consensus on how much horsepower a certain size AN fitting can feed?

Example: Can an -8AN fitting feed 600 horsepower? 700 horsepower? How about a -10AN?

[jayb]

From personal experience I know that a #8 line with a big mechanical pump (Clay Smith) will feed a 700 HP engine with no problem, because that's what I ran on my Mach 1 in 2005, before during and after Drag Week that year.  I think I would move to a #10 line at the 800 HP level.  May or may not be required, just guessing on this...

[scott foxwell]

Way too many variables to answer that question. How much pressure are you dealing with? Just the fitting alone or are we talking about lines attached? Some manufacturers have small holes, some have larger for the same AN size fitting.If you take into consideration the lines it's attached to (or that is attached to it) how long is the line? Are we talking from the regulator to the carb? From the fuel pump to the carb? It's an easy answer if you have fuel flow numbers. I've seen -6 lines off a regulator feed more than 1K hp easy. A -6 line @ the carb can flow a LOT of fuel compared to a pair of 90 jets... but most of the time the fitting will be the restriction in the system. There are also "high flow" fittings vs. standard fittings, and then there are drilled out fittings like I do with most of them.

[cjshaker]

I'm talking about from the tank to the pump, then to the regulator. It'll be feeding 2 carbs, so I know I can go smaller from the regulator to the carbs. I'm also aware that the fitting is always the restriction, so no need to overthink it. I'll be looking into the fitting hole size before I make a final call.

Jay, I was looking at the Clay Smith mechanical pumps. Have you ever had a problem with yours? The 1/2" fitting size will match my tank pick-up, so it should work fine for my needs given their flow capability.

[scott foxwell]

My philosophy on main feed lines is you can't get too big, especially with a mechanical pump. I would run a -10 line from the tank to the pump but most guys run 1/2" line or a -8. In that case, just make sure the fitting isn't a restriction. Remember...the pump is sucking through that line and any resistance will work against the pump. Volume in the line, in that case, is your friend. If you have an electric @ the tank, then you're pushing and you can crank up the pressure so a smaller line won't necessarily hurt.
We deal direct with Clay smith and I've been to their shop in CA. If you're hard set on a mechanical, there isn't a better one on the market. I've seen their pumps feed 1200hp BB Chev blown off-shore marine engines.

[thatdarncat]

Not a "problem" exactly, but a heads up - Due to the physical size of the pump body there will be a small point of interference between the pump and the corner of the block near where the oil filter adapter bolts on. It will need a small bit of clearance grinding done on the block. This is for the factory cast iron block, I don't know if it also applies to any of the aftermarket blocks. Also, if I remember, the inlet and outlet ports are 180 degrees opposite each other, that part of the pump can be clocked, but the relationship between the two doesn't change. It's a small possibility, but that could be an issue with interference with the fittings and lines depending on if there is anything else on your car in that same area. Jay has given the heads up about the block interference issue before, I just recently bought a Clay Smith pump for my project, so I've been looking at some of the mock-up issues, but I haven't actually installed and run it yet.

[cjshaker]

Thanks for the heads up on the fitting orientation, Kevin. I'll look at that a bit closer. I'm not sure if that will cause an issue with the CVR pump and Jays' adapters or not. I saw the clearance issue warning on Clay Smiths' website, but that shouldn't be difficult to deal with.

Scott, this is the intake. And it will be going on a stock stroke/bore 360 in my daily driver truck, so fuel flow numbers shouldn't be that high.

[cjshaker]

Also, if I remember, the inlet and outlet ports are 180 degrees opposite each other, that part of the pump can be clocked, but the relationship between the two doesn't change. It's a small possibility, but that could be an issue with interference with the fittings and lines depending on if there is anything else on your car in that same area.

After thinking about this, I don't see how they could be 180* from each other. If that was the case, it seems that no matter how you clocked it, one fitting would be aimed pretty much directly at the block or water pump. Could you verify this with your pump, Kevin or Jay?

[cammerfe]

Another consideration is the affect of inertia on the fuel, on a drag-based 'launch' with a much larger than necessary tank-in-the-back to an engine-mounted fuel pump. You may find it advantageous to use a 'pusher' pump in the back to overcome such problems.

KS

[thatdarncat]

Also, if I remember, the inlet and outlet ports are 180 degrees opposite each other, that part of the pump can be clocked, but the relationship between the two doesn't change. It's a small possibility, but that could be an issue with interference with the fittings and lines depending on if there is anything else on your car in that same area.

After thinking about this, I don't see how they could be 180* from each other. If that was the case, it seems that no matter how you clocked it, one fitting would be aimed pretty much directly at the block or water pump. Could you verify this with your pump, Kevin or Jay?

That's why I bring the subject up, it can be an issue. I dropped my pump off recently to my machinist so he has it for his mock-up purposes, so I don't have it handy. Maybe Jay can dig out his. In the meantime here's a screen shot from the Clay Smith website, this is the small block pump just because of how the picture is oriented, but I think the mid section of the body is the same on all. You'll notice on this picture how one port is on the right and you can't really see the other port. It may not be exactly 180 degrees, but they are generally opposite of each other.

[scott foxwell]

Thanks for the heads up on the fitting orientation, Kevin. I'll look at that a bit closer. I'm not sure if that will cause an issue with the CVR pump and Jays' adapters or not. I saw the clearance issue warning on Clay Smiths' website, but that shouldn't be difficult to deal with.

Scott, this is the intake. And it will be going on a stock stroke/bore 360 in my daily driver truck, so fuel flow numbers shouldn't be that high.

Nice!
I still say get as much fuel to the regulator as you can, take care of the needs after that.

[jayb]

Kevin is right, the inlets and outlet are 180 degrees apart and you can't change them with respect to each other.  Mine was installed on a Shelby block and there was a significant amount of grinding involved on the block, plus a little on the pump, to get it to fit.  I had it clocked as shown in the photo below; the line pointing down is the inlet:



Have I ever had any problems with it?  Well, yeah I have.  When I first got it, it didn't work!  I was in a hurry so I took it apart to try to figure out what was wrong.  The one way check valves in the pump are pressed into the main body, and a couple of them had just fallen out!  I pushed them back in and staked them in place, and have had no problems since.  But, I only ran the pump for about 4000 miles in 2005.  I switched to electric pumps after that.  Part of the reason for that was the headaches in dealing with this pump, but the electrics haven't exactly been trouble-free either...

[Russ67Scode]

Try this link.    http://aeromotiveinc.com/wp-content/uploads/2014/06/power_planner_carburetedsystems.pdf

[cjshaker]

Thanks for that information. I can see where space would be an issue, especially with my factory oil cooler lines adding to the mix. I still think I'll give it a go, for reliability reasons.

Ken, I don't think I'll be pushing enough G's to have that issue, but I'll deal with it if it becomes one. I know it'd be wise to keep a half tank full to help keep that from happening, and I can modify the pick-up to extend further rearward, if need be. I'd like to stay away from a fuel cell or welded on sump for several reasons.

Russ, thanks for that link, but I'd prefer to stay mechanical. Electrics just add more complexity and chances of failure. During Drag Week, Freiburger said something that rings true every year: Closely paraphrasing..."The three main issues causing breakdowns during Drag Week are roller lifters, electric fuel pumps and automatic transmissions". I can't even count how many guys had issues with their automatics. I know of at least two guys who had to rebuild their transmissions 3-4 times during the week! I may not be able to avoid the roller lifters, but I can the other two.
Edit to add that it does give some interesting info on the AN sizes required though. Thanks again for that link.

[Russ67Scode]

Thanks Doug
 I used that link when I was building my fuel system and I had to use the electric pump for EFI
See you next year at Drag Week