High end power loss, need some input

[Mikey]

ok, i havent posted on here in a long time, so thanks for looking.

 

with my Z, the motor just doesnt have as much power as it should. its got a f54 with flat tops and a mn47. one of the local guys figured its about 11.2:1 compression. so i will say it drives just fine under part throttle. 1/4 throttle driving it runs just fine. and at half throttle it moves real well. but anything past half throttle doesnt go any faster, just a quick as half throttle. Is this a carb turning issue? or a timing advance issue?

 

im lost and im not sure what im doing wrong here.

 

 

thanks in advance

[Leon]

That's really high compression for an L engine. I would suspect detonation issues unless you are using high octane gasoline.

[MONGO510]

Is this a new problem?

Lack of fuel or plugged exhaust will cause these symptoms.

 

Mongo

[Mikey]

That's really high compression for an L engine. I would suspect detonation issues unless you are using high octane gasoline.

 

i have a knock sensor hooked up and its not reading anything. it knocked at 12 degrees initial, back it down to 8 and its fine.

 

 

Is this a new problem?

Lack of fuel or plugged exhaust will cause these symptoms.

 

Mongo

 

ive got 3psi at the carbs at WOT and the exhuast isnt plugged. ive got a full msa header, straight pipe to a magnaflow chambered muffler.

[Xnke]

Lack of timing advance.

 

You're not running full timing advance, to avoid pinging. You probably CAN'T run full timing advance and not ping without running something better than pump gas. Some claim to be able to do it, others can't.

 

Check your dizzy and see if you can find a shop that will tune your advance curve, on a steady state engine dyno. Or go to a fully electronically controlled ignition system and tune it with a computer.

[Mikey]

damn, that was what i was thinking... that there isnt enough timing to make any kind of power. ill throw a can of 110 in it and pull the timing up..

 

thanks

[Xnke]

A can of 110? You mean octane booster?

 

Fat chance. Not going to do a damn thing for you, might bring you up .2 points of octane.

 

Now, if you mean a tank of 110 octane gas, yeah, that'll probably let you run full timing advance. But you'll not be buying that at the local gas-and-go, either.

[ozconnection]

damn, that was what i was thinking... that there isnt enough timing to make any kind of power. ill throw a can of 110 in it and pull the timing up..

 

thanks

 

What's your long term solution though?

 

Water injection?

[z-ya]

i have a knock sensor hooked up and its not reading anything. it knocked at 12 degrees initial, back it down to 8 and its fine.

 

 

 

 

ive got 3psi at the carbs at WOT and the exhuast isnt plugged. ive got a full msa header, straight pipe to a magnaflow chambered muffler.

 

Are you sure it isn't leaning out? Do you have a wideband O2? Just because you have 3psi at idle, doesn't mean you have the same at full load. Temporarily run the pressure gauge so you can see it through the gap in the hood when it's popped. See what the pressure does under load.

 

Pete