any1 check 2nd video? i think that's key to my problem what is happening there

 

That is not right for sure. I have a Holley Black pump with AN-10 hose going to a Barry Grant pressure regulator. My fuel pressure never varies more than .5psi. All though the carb fuel bowls will help with a very short temporary fuel pressure loss, it is not good to have pressure drops to the point of fuel starvation. What pump do you have? What size line?

 

95gph summit racing (but it's actualy a holley/different branded) with 5/16" and 6AN hoses and hardline in use.

http://store.summitracing.com/partde...rt=SUM-G3136-1

Happens only hot though

edited a few times as i didn't get numbers rigtj. sorry. that should be it now.

 

I am not sure. Maybe the pump is getting hot, loosing prime, cavitating, etc.? I am not sure vapor lock from boiling fuel in the line would cause a fuel pressure drop. It will for sure cause problems with the fuel flowing correctly from the bowls into the engine. Do you have the ability to show fuel pressure at the pump? I know some pumps have a port for a pressure gauge on the pump itself. Does the pump make a different noise when the pressure drops? That might indicate a cavitation or pump prime issue. Do you have a return line? I had terrible problems with fuel pressure drops when the pump got hot. The return bypass would basically stick open thus dropping the fuel pressure at the carb. When I went to a deadhead setup, that problem went away.

You mention that you are running -6AN line and hardline. I have seen supply issues with too small of line (hardline) on performance motors, but this is happening to you at idle, so the line should be a not issue.

 

i had the saem problems when I had the pump at the front of car near engine. so i thought it just wouldn't suck right. i tried a different one (one that is supposed to suck properly) and that didn't work. so i mounted the summit one to the back which resolved the issue but only until the engine gets hot.
As with the noise of the pump: that thing is awful loud. sometimes less, sometimes more. but the pump is mounted directly to the tank, so there is always fuel flowing into it. that shouldn't be any problem. it seems directly related to temperature of engine (or exhaust for that matter).
So i'll recheck again tonight if I have any other ways of running the fuel line unless there are any other ideas ..

 

Is your feed port on your tank mounted low like in a sump? I am not calling you out at all, but are you sure there is always fuel flowing into the pump from the tank? If you are, then we can eliminate the tank feed port and fuel line from the tank to the pump as possible problems.

 

yes. the feed is low at tank. and i can vouch for lots of petrol coming there with no hose attached *g* i know from when I mounted the pump
going over to buddy tonight. will take a few pics

Kalli

 

i went over to a friends pklace we didn't really have time to check on it.
What I found was that this fuel pressure issue only appears when hot. and my Buddy measured the pulleys for me as I forgot.

old:
crank: 7.5"
waterpump 6"

which (if my maths are right) should have the fan run at 1250 rpm at 1000 engine rpm

the new setup is
crank: 6"
waterpump: 7"
which results in only 850 waterpump and fan speed at 1000 engine rpm.
I couldn't measure new correctly as it was in car, but i'll doublecheck with a string tomorrow.
that might already be a good part of my problem. slow pump and fan ...

 

Yep. Underdrive pulleys. Lots of people buy them, but my thinking is that the factory put the size pulleys on that they did for a reason. The underdrive are good for freeing up horsepower, but for a daily driver you gotta have enough cooling more than that extra few horsepower. If I were you, I would either put the stock ones back on or at least a smaller water pump pulley.

 

thanks for confirming.
I had a 289 with 3bolt crank pulley and someone on the forums already warned me before i put it together that that pulley will not fit (the 72 302 needs 4bolt). So I asked the seller of the engine to drop a set of them with the shipping. that's how I ended up with them
i'm more interested in sitting in front of a traffic light without stalling than racing ... so ya I'll get a different WP pulley if the original one doesn't fit as well as a proper fan. I hope that will sort me out.

I'm very sure that my fuel problem is directly linked to temperature. It happens only when the engine decides to get hot. I have a feeling it's hot fumes in carb feding back into the line as I checked on all fuel lines and they are not getting too hot. I can put my hands between them and exhaust when issue happens. So I'd say it's rather the carb sitting on a very hot intake, which is very hot to the touch

Kalli