Engine loses power around 5000RPM

[nivvy]

Do you have a fuel pressure regualtor / guage? getting enough fuel???

[Chryco Psycho]

I totally disagree , a 600 carb is the problem , I use 2 times the CI as a baseline especialy with better then stock heads , 750 CFM minimum , try the new Hp street 750 from Holley , awesome carb ifyou can live with no choke

[Jacksboys]

No fuel pressure guage, I have a mechanical fuel pump.

I am a little confused 

How could it be air/fuel when it pulls real strong and then instantly feels like it hits a wall, but then I shift and it instantly pulls real strong again until it hits the same RPM?     It does not feel at all like it is tapering off in power, just a instant halt.  

How would this affect the tach?  

[matt63]

I totally disagree , a 600 carb is the problem , I use 2 times the CI as a baseline especialy with better then stock heads , 750 CFM minimum , try the new Hp street 750 from Holley , awesome carb ifyou can live with no choke

I have this carb on my 408 stroker.  It works well.

[matt63]

What valve springs do you have?

[nivvy]

Im sure a bigger fuel line would help....my dominator was breaking up a little at 6200 rpm ish and I had it set to 6lbs on the fuel regualtor... holley reccomended 7lbs for the dominator and i boosted it to 7lbs+ and it runs alot better...also i have -6an fuel line...
I would definately put a adjustable fuel regulator on it with a guage to see what your getting plus it is cheap...also more gph's on the fuel pump will help... all cheap upgrades.... 

[moparclown]

HP2
I didn't mean anything by asking?I was just curious thats all.

[Stacked440]

Does it choke? or just loose power?  If it actually chokes, its probably timing....

[HP2]

moparclown, I didn't think you did. I was just sharing my experiences is all.

[Jacksboys]

Im sure a bigger fuel line would help....my dominator was breaking up a little at 6200 rpm ish and I had it set to 6lbs on the fuel regualtor... holley reccomended 7lbs for the dominator and i boosted it to 7lbs+ and it runs alot better...also i have -6an fuel line...
I would definately put a adjustable fuel regulator on it with a guage to see what your getting plus it is cheap...also more gph's on the fuel pump will help... all cheap upgrades.... 

I have new 3/8" fuel lines, so that should not to small for a 360 at 5500RPM.

I may consider a guage, if this persists. 

[Jacksboys]

Does it choke? or just loose power?  If it actually chokes, its probably timing....

What is your definition of "choke"?

[Aussie Challenger]

    A question was asked further back about springs? did you check how much preload is on the lifters?? Are they adjustable rockers??
    I had a head delivered to me with the valves tooo long, when I tried to adjust there wasn't enough, suspect that springs were not at correct seat pressure also, so I didn't even bother going any further.  Manufacturer told me he had had a couple heads returned which had long valves fitted ( not an American head ).   

[moper]

I'd bet it's either dist drive and bushing, or the preload on the lifters. Who assembled the engine? Was the oil pump dirve and bushing new when it was fired? I would pull the distribuotr out, and take a screwdriver to the slot on the drive. Wiggle it. If it moves in any direction except straight up and out, you need to replace them both. If the bushing isnt sized properly when it's pressed in, the drive and bushing can wear out in a verys short amount of time. Seen it twice on rebuilt engines assembled by guys who didnt know about the dist drive broaching tool, or who figured the tight fit would loosen up when it ran. He was right. But at 3K miles, the drive and bushing were worn bad/shot. The fac that another dsitribuor did the same at a different rpm is the hint.

[Moparal]

A 268 cam and a 600 cfm is bottom end stuff. And right at max at 5500.  Tuning is critical to get it to spin with power all the way to the top end. And you are sure your tach is accurate? It just sounds like you are running out of top end on a low flow system to me.  Valve springs can hamper you if not correct and can only open and close so much and so fast per settings. Timing and jetting is critical and things change after breakin and engine use. Bad wires, week coil, and some electronic boxes hamper upper engine rpms.

Welcome to the world of hp tuning. Milking every possible fraction out of an engine is an ongoing skill. Your 360 has lots of potential. If I was gonna use 5500 as a max rpm guide, my setup would be built for 6500.

Bring it over, I'll help you tune it to your wallet. But there are a bunch of checking stages you need to do.

[Chryco Psycho]

a 3/8" fuel line will not starve a 360 at 5000 rpm this is not your problem unless the feul pump is weak