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Discussion Starter #1
Hi, I'm new here, I think I may have registered in the past but could not find my login. Anyhow, my good friend and neighbor has a 1969 Pontiac GTO. He wanted one his entire life and finally bought one. He got a little screwed. The "dealer" told him the car was restored with an original GTO engine, not numbers matching and not the original motor. Well it wasn't, it was a smog era 400 from 1975 (IIRC) that made like 185 hp. Well he loves the car so a few years ago he bought a pro built 462 with Kaufmann aluminum heads from a guy named Jeff in Michigan (I think). The dyno info he got with the 462 says it makes 605 HP. I helped him put it in. We got it running, but it was never quite right, hard starting and stalling issues, it never idled very well. This past weekend I went to help him get her woke up for spring and she was really running rough. He put a 750 Holley on it last year with a Earls fuel line kit with a filter and pressure gauge. Well, as we were trying to get it to idle I noticed he only had about 3 lbs. of fuel pressure. It was like spitting raw fuel out of the tailpipes. He told me he had replaced the pump with a reproduction Ram Air pump from one of the restoration companies that specialize in GTO's. He had a Holley he had bought new (12-398-11?) and still had it new in the box. We went down to the parts store and bought the barb fittings and hooked it up. I immediately saw the FP jump up to 6 1/2 lbs. and it began running much better, really good actually. Holley recommends 6 to 7 lbs. of pressure for this particular carb. Well that was all fine until it started leaking like a sieve from the new barb fitting where it hooked into the Earls AN type hose. I ordered a better fitting from MSC that fit the ID of the Earls hose better, leak was fixed. Fired it up and now it is back to running at 3 lbs! I was dumbfounded. I did some searches and found this place. I have read a bunch of posts to try to figure this out. The only thing I can come up with is we need a 1/2 inch supply line to the fuel pump (Thanks BearGFR). My question now is, if I have a 1/2 inch supply line from the tank will I need a 1/2 inch fuel pickup tube on the sending unit? I doesn't seem like just making the line bigger would do anything if the fuel pickup tube is still only 3/8 of an inch. Any thoughts are appreciated. Thanks in advance.
 

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What are the details of the whole fuel system - line sizes all the way from the tank to the carb, what filter(s) if any are present, does it have a pressure regulator, etc.

I'm not sure I understood everything in your post, is that Holley pump an electric pump? If so, then be aware that running an electric pump is a whole different animal than running a mechanical pump. It'll require a fuel pressure regulator near the carb and also a fuel pressure return line from that regulator back to the tank that's the same size as the fuel line to the carburetor.

If it's a mechanical pump or if he wants to run mechanical, there aren't a lot of pumps out there that will be able to keep up with that much demand. Personally, I'm running a mechanical pump from RobbMc that's more than capable.

I'm not a big fan of barb fittings on fuel lines, or of rubber lines anywhere in the system. A little 'engine fire' from a leak can really ruin your day. 100% of my fuel system is either hard line or stainless belted hose with AN fittings - even the vapor return.

Also, 750 is going to be a little small for that engine.

Bear
 

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Discussion Starter #3
Thanks for the response Bear, His car has a mechanical Holley fuel pump, His entire system is Holley. (Holley recommended the system and the carb to him) 3/8's hard line from the rear, 6 AN to the carb, Earls inline fuel filter and Holley fuel pressure gauge. I like hard lines too. At least he is running Fuel injection rated rubber at the nipple connections on the fuel pump. If he gets a new line made that will take care of the rubber and barbs. Thanks again for the response. Is it possible to get a half inch sending unit made? Thanks again.
 

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Yes, I know RobbMc has them available for certain and InLine Tube might. I have no experience with the Holley pumps so I can't offer advice there.

Bear
 

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I think it's possible that the 3/8 line will cause problems under high load, wide open throttle conditions but I wouldn't think that it would account for low fuel pressure at idle. His web site is at Welcome to RobbMc Performance Products. I'm using his starter, big fuel pump, regulator, and two of his filters. I've been very happy with all of it.

If the pressure is low at idle, I'd suspect an obstruction in the path somewhere, the pump itself, perhaps even an incorrect gauge.

I chased a fuel problem on my 69 for a long time. Under WOT it would sometimes just shut off and die, usually about 2/3 of the way through second gear, but would always restart. I sent the pump back to Robb for checking, even rebuilt it - but it was fine and showed no evidence of problems. All the filters were clear. Eventually, I found it. A piece of welding slag was in the tank from when I welded on the rear sump. Every so often, it would get lodged "just right" into the fuel pickup fitting and block it off.

Bear
 

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Discussion Starter #7
Me and Frank will be dropping the tank on his car to check the sock and sending unit. His "restored" car seems to be an interior kit and a paint job. I can't wait to see what the inside of the tank looks like.
 

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Discussion Starter #8
Well, Frank texted me this morning, The sending unit and 1/2 line are on the way. I need to figure out how to post pic's of his car, it is gorgeous. Frank is really in love with her too, and he even gave her a girl's name! I need to get him registered on here so he can do his own posting! We are dropping the fuel tank tomorrow morning, I'll let you know if we find anything interesting. Thanks.
 
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