Fuel Starvation on my 69 Z?

[sixt9rsx33]

My Z is losing power at 5K rpms. Acts like a fuel starvation problem. Previously this same situation was present at 4500 rpms. I installed a new fuel pump and now it runs hard up to 5K rpms. The stock rubber fuel lines were installed in 2009. I am thinking that the ethanol laced fuel may have done them in? The other thing I was thinking is the fuel screen in the tank is clogged. Anyone every shot air in the fuel line towards the tank to try an blow debris out of the screen?
I have rebuilt the carb, and changed the filter in the carb.
Thanks

Lawrence

[earntaz]

Lawrence -- I had an old 69 Buick Estate Wagon with a big, big, big engine and I went thru the same drill ... fuel pump, fuel filter, etc. etc. Finally blew out the line back to the tank and that would cure the problem for about 1K miles. She was a battle wagon and sold it later to a dude who dropped the tank and found rust and more rust. So yes -- blow out the line back to the tank ... suggest pretty low pressure as to not shred the sock. I would assume you've already pulled a pump pressure test and checked the inline filter. Also, some Holley carbs came with a sinthered metal filter at the inlet(s) -- make sure they are not plugged. TAZ

[sixt9rsx33]

I installed a new tank, no inline filter, just the filter(s) in the carb. I need to check the rear sinthered filter now that you mention that. I don't think I changed that one [img]<<GRAEMLIN_URL>>/shocked.gif[/img]

[PeteLeathersac]

'
Couple more thoughts...
- Float adjustment
- Fuel Pump cam lobe
[img]<<GRAEMLIN_URL>>/beers.gif[/img]
~ Pete

[sixt9rsx33]

Checked the float adjustment. Man I hope it's not the fuel pump cam lobe..... [img]<<GRAEMLIN_URL>>/cry.gif[/img]

[Salvatore]

spark plugs look real lean? any vacuum leaks do you think? valve spring issues?

[PeteLeathersac]

'

Good thoughts too Sam!
I hope it's not cam lobe wear too...try a gravity feed supply from above the carb or road test w/ temporary elec' pump installed?
When/how did the problem first begin...slowly worsened or all good one day/not the next?
Any chance the T'chain is off a tooth, loose and jumped or installed new and lined up w/ keyway slot not timing mark?
How's the dizzy itself, advance weights not seized and vacuum advance pot working plus points also plug gaps checked and Ok?
Unlikely w/ your year/model but exhaust obstructions can hold back revs too, sometimes clogged Cat' Converters etc on newer vehicles.
Best of luck!
[img]<<GRAEMLIN_URL>>/beers.gif[/img]
~ Pete

[Mr.Nickey Nova]

Do you have Hi perf points installed?? Points should have a heavy spring so they don't bounce at high R's.

[earntaz]

AND while you're in there -- check the dist shaft for excessive side to side movement ...

[sixt9rsx33]

High Perf points installed, distributor weights nice and free not sticky. I need to map this distributor and see if I get any spark scatter at high rpms. Have not looked at the plugs yet. Will start with the filter and go from there. Easy first then go more difficult. Thanks for the suggestions.

Lawrence