Questions concerning lack of power after 4K

[GRM-REPR]

I haven't been on this site for almost 1 year due to certain peoples b.s, and decided to try to find help here once again. I would appreciate intelligent repsonses on this thread and nothing else which doesn't pertain to its relevance.

It's a Chevy 355, 10:1 compression, 10 deg of timming, Holley 650 double pumper, Moderate cam (I don't remember the specs), Vac advance dist, Perfomer RPM Q-Jet intake (will be replacing soon) and all high performance ignition with an MSD control module.

It has a TH-400 with 3.42 gears in the diff. I'm not sure what type of torque converter is in it either. No line lock or trans brake.

The car doesn't pull for crap over 4k. When I leave the line under soft acell and throttle the engine, it just feels powerless, it won't even spin the tires. This engine is by no means a beast but it should certainly get up and go, which it doesn't.

This problem has existed since I've owned the car. I feel as though maybe the torque converter is wrong for the cam. The cam is lopey but not huge by any means. Possibly not enough carb? It almost feels like it's starving for fuel?

Converter? Carb? (which was tuned well by Prince Valiant last summer), Q-Jet intake?

I'm out of ideas, any suggestions on where to start would be appreciated. If anymore info is needed, let me know and I can update the thread.

Thanks, Jon

[Reverend Cooper]

i doubt the converter is a issue,i would go threw the basics,check and make sure cam timing and dist. timing are correct, if so check for fuel issues a bad accelerator pump in the carb could cause an issue like this or maybe the jetting in the carb is too small. pretty open question,fuel filter getting plugged

[wrath]

It's probably fuel related. If you mash the throttle it should spin the tires. It should at least spin the tires 1-2 seconds after you hit the throttle then stop spinning as soon as it's rolling 10mph.

I'd check:

Accelerator pump. It should leave a puddle in the intake. Move it slowly, you need about 20cc of gas being squirted out over the full sweep of the throttle blades. Quadrajets usually have "quadrabog" because of a crappy accelerator pump. I'm a Quadrajet guy, I'm sure there is a Ford guy around here that knows Holley.

The timing. You'd find that it probably wants base timing around 13°. As long as it advances at least 10° you should still have plenty of power. Having the right distributor can make a big difference also. If you've mixed a smog distributor (ESC/electronic spark control... most had centrifugal advance between 25-30°) with a non-smog ICM and vacuum advance you can end up with a real mess. You want 30-38° total advance. The wrong combo can get you 30°+ more advance on top of your base advance. I like to check ideal base timing in gear using a vacuum gauge and a dwell/tach meter (more sensitive than a regular tach). You want peak STABLE vacuum at the lowest RPM. I then usually back it off a degree.

Air leaks. Windshield washer fluid in a squirt bottle works pretty good to spray around gasket areas. Air leaks can introduce a wicked stumble. Windshield washer fluid doesn't provide the incredibly noticeable RPM change as WD40, carburetor cleaner, brake cleaner, et cetera... but it also doesn't make a mess.

Spark plugs for lean condition. Get it hot, run it at WOT up a long hill and as soon as you get to the top let off, put it in neutral, and turn the key off. Pull a couple spark plugs (not #1 or #2). They should be chocolate colored, not white. Kind of a hillbilly method but it works.

[Prince Valiant]

Hey Jon,

Good to see you back....

A couple of questions:

I recall that we basically did two things...set the base timing for around 13-16 degrees, and set the carb for a "lean-best" idle and then slightly richened by 1/4 turn, and that was pretty much it. I can't recall if that improved at least some of your complaints...I know not all though; Did it?

Also, I seem to recall that your ignition wouldn't advance very far over the base setting...is that correct? Did you have a different distributer last year? I do recall you having some pretty quality pieces though.

IIRC, you were generating b/w 15-17" of vacuum on the gauge...do you recall if that's correct?

[GRM-REPR]

I appreciate all the responses.

Chris, to answer your questions, I had replaced the distributer with a vac advance model, with an MSD control module. The carb is still the same Holley 650 DP, with the the same adjustments we made to it last summer.

Since I had replaced the distributer, I had to turn down the base timming, roughly to 10 degrees. Your adjustments last year by the way, had solved all the odd misses and idiling issues. However, since I rarely ever "beat on the engine" the times I have, I've noticed it just doesn't pull at all over 4K.

I agree with Wrath 100% on the basis of wheel spin on soft acell, and mashing the gas pedal, it does no such thing, feels like it's in second gear when I try it (which it isn't).

Yes, the vacuum was roughly about 16'', a good mild/moderate cam too.

I dread to think I may have put the new distributer (installed after you were here) a bit off but it runs too smooth in my opinion for such a chance like this.

Thanks again for the replies.

[GRM-REPR]

Spark plugs for lean condition. Get it hot, run it at WOT up a long hill and as soon as you get to the top let off, put it in neutral, and turn the key off. Pull a couple spark plugs (not #1 or #2). They should be chocolate colored, not white. Kind of a hillbilly method but it works.[/QUOTE]

Thanks for the reply, I had just replaced the plugs before the Automotion Dells car show this year. If I were to say what color they were, for the most part, white but certainly not black.

[jon_we4]

I'm only mentioning this because it was not mentioned before.

If you've checked everything. Fuel, Spark - everything is right. I would consider doing valve springs. They are a wearable item and if they have had a hard life, or the cam is large for the spring selection - they might not last forever.

But I would put it on a chassis dyno. It will really help with trouble shooting and add the ability to show the real gains/losses involved with the things you try. That along with a wideband reading can be useful with fueling as well.

I'm sure it could be anything, I'm just trying to add another perspective.

[GRM-REPR]

I'm only mentioning this because it was not mentioned before.

If you've checked everything. Fuel, Spark - everything is right. I would consider doing valve springs. They are a wearable item and if they have had a hard life, or the cam is large for the spring selection - they might not last forever.

But I would put it on a chassis dyno. It will really help with trouble shooting and add the ability to show the real gains/losses involved with the things you try. That along with a wideband reading can be useful with fueling as well.

I'm sure it could be anything, I'm just trying to add another perspective.

Valve springs would be a good idea, however, I failed to mention the engine was rebuilt in 04' and has only roughly 3,500 miles on it.

Thanks for the suggestion.

[WickedSix]

do you have hydraulic lifters in the engine? when improperly adjusted they can float the valves prematurely.

do you have the right length pushrods? are they screw in rocker studs? or press in?

have you degreed in the camshaft?

to me it sound like your cam in substantially off which will cause the timing to have anomalies as well

[forest]

But I would put it on a chassis dyno. It will really help with trouble shooting and add the ability to show the real gains/losses involved with the things you try.

it does make things go a LOT faster, and with more accurate information, you can make the right changes, once, and be done with it. 80.00 for 1 hour with A/F if you need it.

[GRM-REPR]

do you have hydraulic lifters in the engine? when improperly adjusted they can float the valves prematurely.

do you have the right length pushrods? are they screw in rocker studs? or press in?

have you degreed in the camshaft?

to me it sound like your cam in substantially off which will cause the timing to have anomalies as well

Good points, the entire engine was rebuilt and set up at Engine Rebuilders in 04'. I'd like to think they know what they were doing there (I would never go back for personal reasons).

I know the lifters are hydraulic with roller rockers.

In all honesty, another angle to address the concern is this: It feels like it's totally revved out at about 4,200 rpm's, a "falling on its face feeling." When I had it at the track last year, I thought my tach was off (which it's not). It does this throughout all gears.

[juicedimpss]

falling off after 4 is going to be a fule pump/filter or valve springs,maybe a coil.

if the plugs are WHITE it is starving for fuel.

[GRM-REPR]

Juiced, good point, SUPPOSEDLY Engine Rebuilders "rebuilt" the fuel pump in 04' during the rebuild. When I brought it out this year, there was a lot of wetness around it as well. I've looked since and there is none. Fuel filter is replaced every year so I know it's not an issue. Coil is brand new as well.

What tool do I need to assess the weakness/strength of the valve springs? I can't be sure they've been replaced.

[jon_we4]

Do you know what brand/part # the springs are?

You can test springs with a tester - I would think a quality engine builder would have one. Compare them to the spring's specs. The springs could still be "good" - they may just be a little on the weak side for your cam.

Again - just throwing out ideas here.

[GRM-REPR]

Do you know what brand/part # the springs are?

You can test springs with a tester - I would think a quality engine builder would have one. Compare them to the spring's specs. The springs could still be "good" - they may just be a little on the weak side for your cam.

Again - just throwing out ideas here.

Sadly they never gave me a cam card or anything of the like. I have no clue what type of cam/springs or specs available. The person who owned it before I did had too large of a cam in the previous build. I'm unsure of whether or not the springs were ever changed to match the new cam I have in it now. If they were changed out, I doubt it would be the springs due to lack of any mileage or punishment to the engine. I treat it nice.

[jon_we4]

Sadly they never gave me a cam card or anything of the like. I have no clue what type of cam/springs or specs available. The person who owned it before I did had too large of a cam in the previous build. I'm unsure of whether or not the springs were ever changed to match the new cam I have in it now. If they were changed out, I doubt it would be the springs due to lack of any mileage or punishment to the engine. I treat it nice.

Sending the cam out to be cam doctored (or if there are etched #'s on the end of the cam I can see if we can pull the spec's off that) and having one of the springs tested will show right away if your problem is valve train related. Plus it gives you more knowledge on what is in your engine.

[wrath]

Will it even make it to 6k? If it was valvetrain related you'd definitely hear it by then. You can't miss the sound of valves floating.

It's kind of a dumb question, but is the timing fubared? Like, a couple plug wires being reversed or the harmonic damper being spun on the hub?

[GRM-REPR]

Will it even make it to 6k? If it was valvetrain related you'd definitely hear it by then. You can't miss the sound of valves floating.

It's kind of a dumb question, but is the timing fubared? Like, a couple plug wires being reversed or the harmonic damper being spun on the hub?

Nah, no such thing as a dumb question, I appreciate them all.

I don't even bother taking the engine to 5k, it doesn't do anything, it just seems like I'm already at 6k but I'm only at about 4,200!

I put the dist in last summer after Prince Valiant came and tuned my carb. I set the balancer to 0, lined up the rotor with the number 1 cylinder. It was new, so it was kind of tough, I bumped the engine a couple of times to mesh the gears and it dropped in.

Then engine idles great, cruises great and sounds well. I know I have the f.o right because it's always the first thing we check.

[wrath]

I'd still probably focus on seeing if it's running lean.

Do the secondaries ever get a chance to open? They should open briefly when you hold it at WOT. There is no load on the motor so they'll quickly close. I wonder if the reason why it's so wimpy is that it's not getting enough air and fuel. All sorts of crazy crap can keep the secondaries from opening.

I'd probably start with ensuring the harmonic damper hasn't spun on its hub. You can do this by cranking the engine until the distributor rotor is pointed at where #1 plug wire is plugged in and that the #1 cylinder doesn't let air out the intake or exhaust when you put compressed air to it. The timing mark on the harmonic damper should be somewhere close to where you expect it to be.

I'd then check to see that it is advancing. You might have to buy some timing tape if you have a cheap damper like what I run. If it's getting to 30° total advance by 3,000 RPM that's not the problem.


I made this 6 or 7 years ago, I don't know if anyone else might find it helpful:

[torque.hit]

Do you happen to have a fuel pressure guage before the carb?