Engine runs but no power

[Mukilteo911]

THE DETAILS are,
2.5L with 10:1 compression
104/102 webcams
4PSI of fuel pressure
New plugs, new coil, new wires
New fuel filter
Distributor is timed correct and I've tried it advanced and retarded (because I was frustrated)
I've timed the cams at 4.6 and also at 5.2 lift (just incase the cams were not what I was told I bought.
I've used my Zenith carbs built for this motor and also set of nice 2.4 S spec webbers

Nothing I am doing is helping the car have power. It revs great in the garage and will climb to the redline under load, but slowly. Its about like driving a 80HP diesel rabbit instead of a 210 HP 911 which is what it should have. I've clamped off the vacume line to make sure it was not leaking, no change in performance.

So what have I missed, anyone have ideas on what to check next?

[911pcars]

Hmmmm. Plugged exhaust?

I'm outa ideas.

Sherwood

[Steve@Rennsport]

Hi:

Frustrating for sure,............

A few things come to mind assuming that the engine doesn't have an internal problem.

Those cams must be timed to 4.2-4.6mm; 5.2 is too much.

Even though you have 4.0 psi of fuel pressure, you need to ensure that your float levels are PERFECT that assures sufficient volume to the engine. Personally, I think 4.0 psi too much and usually floods a Weber or Zenith. I set the fuel pressure to 3.5 psi and set the floats at that operating pressure.

You need 80-90 gallons/hr to feed these engines so make sure your fuel pump delivers at least a qt in 30 seconds (into a jar).

Make sure your jetting is appropriate for the motor's configuration.

Make sure the advance mechanism is in perfect operating order,..........

Make sure your valves are correctly adjusted.


As they say, "The Devil is in the Details" so never assume ANYTHING.

Sherwood's suggestion is simply excellent and often overlooked. Try a different muffler.

[Mukilteo911]

I've checked all the above, except dialing the fuel pressure back to 3.5 psi.

ONe thing I was thinking was what if my pistons were not milled to the right compression ratio and they are higher than 10:1, what would that do? It's not pinging.

Thanks for all the help.

[DonE]

What timing are you using?

[Mukilteo911]

MOre like what timing have I not used, I've tryed several positions, see above.

[Steve@Rennsport]

Hi:

Did you check & measure the compression ratio to confirm the CR on those pistons? Thats something that every DIY engine builder must do regardless of what brand pistons one uses. Never, ever assume anything in this regard. (I don't think that your problem here, tho)

Don asks a legitimate question: Precisely what ignition timing settings have you used? Did you ensure that the advance mechanism is working?

[john walker's workshop]

are all the venturis in correctly so the dump tube draws off the emulsion tube well?

[PPilot]

I know it sounds dumb, but check for a totally dead cylinder...It will run OK but be very doggy, will not miss or give you other clues- its the cold one!!

[hcoles]

just about the same thing happened to me....you might check your cam timing...
turned out I put one cam in 180 out
check that both banks get hot when running for a short time
it would run not that bad but no power..surprised it ran so good on 3 cylinders

[Eagledriver]

Sorry to be picky but 1 quart every 30 seconds is 30 GPH of fuel flow not 80-90. And 30 GPH is fine for engines of less that 250 HP.

I'd suspect ignition timing, check for about 30 degrees of advance at 6000 RPM.

-Andy

[911pcars]

Here you go. Check engine compression.

10:1 CR doesn't do any good if the squeeze doesn't happen when it should. A misfiring cylinder will cause the engine to run rough which doesn't seem to be one of the symptoms.

We'll assume the rings weren't installed upside down, all rings were indeed installed, 90mm pistons fit into 90mm cylinders and all that.

Perform a compression test - easy to do in lieu of the other choices. If it's okay, then all you need is air, fuel and spark in the correct quantities and at the right time. Good compression validates the valve timing is close enough to produce some power if not ultimate power.

Sherwood

[2.7RACER]

I'm with hcoles on this one. After running for a brief time check the temps of the right and left heat exchangers.
If one side is warm and the other is cold, likely one cam is 180* out.
At TDC #1, compression, keyway, dots or numbers on both cams should be up. One up and one down is a problem.
Another way to check without pulling timing chain covers is to verify that #1 cylinder comes up on compression at 360* crankshaft from #4.
Put a compression gauge into #1 and rotate the crank until the pressure begins to rise. Stop at Z1. The distributor rotor should be pointing at #1.
Put the compression gauge in #4 and rotate the crank clockwise, the pressure should begin to rise after the crank has been turned about 300 degrees and continue to the next Z1.
The distributor rotor shold be pointing at #4.
In other words, the compression for #1 is 360 crankshaft degrees from #4.
If they both compress at the same Z1 the right or left cam is in 180* out.

[Mukilteo911]

As for timeing for DonE, I set it about every way one can, not only me but another mechanic as well (just in case I was crazy)

As for Walkers question. I've puled the carbs apart 3 times to make sure I did not mess something up and then after that used a good working set of webbers for a 2.4S.

I will check all the other items my fine pelican team has mentioned. Thanks and I'll give a report when I get to check this stuff. I know it will end up being something simple.

[Eagledriver]

You keep saying you've set the timing every way you can but you don't say what the numbers are. What is your idle timing? What is your timing at 6000 RPM? What is your total advance?

-Andy

[Wayne 962]

Double-check your spark plug wires to make sure they aren't switched...

-Wayne

[ischmitz]

Subscribing out of curiosity - any new findings yet?

[914/6]

right cam 180 out, runs good now.

[kenikh]

NICE CATCH!

[ischmitz]

Amazing how sturdy those engines are that they even run with a cam 180 degrees out....