New Engine/Low HP

Guest

Dan,
I have checked the gap of the plugs, they are .045+, and a little oily where they seat in the block. I wonder if they could possibly be getting oil fouled at high rpm? I might try another tach to see if it responds the same way as my stock one. The dyno sheet shows HP dropping off dramatically at about 5650, I'll try to attach a copy of the sheet.
Thank you,
Art

3/22/065:22 PM

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danieljonesMember

> I have checked the gap of the plugs, they are .045+, and a little oily where
> they seat in the block.

Gap a new set to 0.035". If your ignition is marginal, the narrower gap will
allow it to hang in longer.

> The dyno sheet shows HP dropping off dramatically at about 5650,
> I'll try to attach a copy of the sheet.

The slope of the curve indicates the engine is nout running out of the
basics. If the heads or intake or carb were choking it off, it would
flatten out more gradually. It looks more like something was unable to
keep up with the RPM.

1. You may have ran out of fuel. Put a gauge on it and make sure the
pressure isn't dropping off at RPM.

2. You may have ran out of spark. Tougher to daignose but a narrow gap
may allow some additional RPM before it nose dives.

3. The hydraulic roller lifter and spring combo hit its limit. Given
the weight of the 4V valves, the lifters and springs you are using this
is a real possiility. Get a look at the article "The Truth about Street
Cams" by David Vizard September 2005 Popular Hot Rodding. It has test
data on hydraulic roller cams doing what your engine appears to be doing.
The fix was Crane link bar lifters and beehive valve springs.

Dan Jones

3/23/068:14 AM

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panteradougMember

I think that you are seriously undercammed here.
You should be looking at somewhere around a 250 degree duration @ .050. The lift is less important . .578 lift should be fine. With 377 cubes you could easaly go to 256-260.
Overlap probably should be kept to around 72 degrees.
You are opening the door wide enough but you aren't leaving it open long enough.
It's good for 6000rpm on a 351, less on a 377. 5650 is about right.
300 hp is all that profile is going to give you.
Also that's a 300hp intake manifold as well.
There isn't anything wrong with the engine other then that.

3/23/069:43 AM

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Astephens (Guest)

Dan,
I have a fuel pressure gauge which the dyno operator monitored during the dyno pull, he said it never dropped below 6 psi. Will do on the rest of the stuff.
Thank you,
Art

quote:
Originally posted by Daniel_Jones:
> I have checked the gap of the plugs, they are .045+, and a little oily where
> they seat in the block.

Gap a new set to 0.035". If your ignition is marginal, the narrower gap will
allow it to hang in longer.

> The dyno sheet shows HP dropping off dramatically at about 5650,
> I'll try to attach a copy of the sheet.

The slope of the curve indicates the engine is nout running out of the
basics. If the heads or intake or carb were choking it off, it would
flatten out more gradually. It looks more like something was unable to
keep up with the RPM.

1. You may have ran out of fuel. Put a gauge on it and make sure the
pressure isn't dropping off at RPM.

2. You may have ran out of spark. Tougher to daignose but a narrow gap
may allow some additional RPM before it nose dives.

3. The hydraulic roller lifter and spring combo hit its limit. Given
the weight of the 4V valves, the lifters and springs you are using this
is a real possiility. Get a look at the article "The Truth about Street
Cams" by David Vizard September 2005 Popular Hot Rodding. It has test
data on hydraulic roller cams doing what your engine appears to be doing.
The fix was Crane link bar lifters and beehive valve springs.

Dan Jones

3/26/069:48 PM

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