Smokeywolf

1954 Pontiac Starchief Streight Eight holds back

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I'm new to the world of flat heads as I have just purchased a 54 Starchief with L8 engine.

My problem is this.

The Engine holds back and does not freely rev.

Getting to 45 mph is slow but reasonable but will not accelerate much more than that.

So what could it be?

First thing I noticed was the exhuast had a small blow. Causing the air fuel mixture to be incorrect.

New gasket fitted.= No improvement in performance.

Next was  possibly weakened spark at higher RPM .

Petronoix igniter and coil fitted = very small improvement.

Ignition timing checked, looked miles out so readjusted the timing to between 3 and 5 deg before TDC.taken from the Harmonic blancer. 

A road test found this made things wrose.

I'm now  running 19 deg BTC and can get 50 at a push.

Still not working correctly.

Other Observations : While running the engine I noticed the throttle connecting rods becoming very hot to the touch!!

Spark plugs all have a small spark but all working 

Advance and retard appears to all so be working.

Any ideas will be greatly received. 

 

 

 

Edited by Smokeywolf (see edit history)

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Checked compressions today on average came out at 70psi

This can't be correct as you need 90 psi to compress the fuel enough to push the piston down then the spark ignites 

Oil pressure is 40 psi so piston rings and big ends must be ok 

Exhaust is breathing ok

Heat raiser is working moving freely and held open  when engine was reved up.

 expansion spring is not moving

Sticking values possible but on all is questionable.

Cam Timing not sure any ideas?

Edited by Smokeywolf (see edit history)

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You stated that you had just purchased the car,  did the previous owner have problems with it?  Had the engine been apart? If not the cam timing is probably correct.  Had the car sit for awhile? Old gas, dried up and  gummed up passages in the carbureator, a stuck power valve could starve the engine at higher rpm yet idle OK.

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Spoken to the original owner.

Yes the car had these problems before.

I'm checking out the power valve .

Also the distributor bob weights.

But  I could do with some information regarding the operation of the valve in the manifold.

Does the spring on the outside of the manofold expand moving the valve to direct the exhuast gas flow down the exhuast system.

Or is it a damper if so how does it work?

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The spring is bi-metal and moves with temperature, The spring holds the heat. riser "on" while the engine is cold. The preload usually seems to be half a turn (wind it up about a half turn and hook it). In this position, the exhaust should be flowing up to heat the carb.

 

As the spring gets warm from the exhaust heat, it relaxes and gets looser, allowing the heat riser to move to the open position, where the heat bypasses the area under the carb and goes right out the exhaust pipe. If the spring gets tighter with heat instead of looser, it is on upside down. Flip it over and try again.

 

There should be a weight that holds the heat riser open when hot. It should stick straight up, with the weight at the highest point when cold. The weight should fall toward the block almost 90 degrees when the engine  heats up and the spring relaxes.

 

There could be a second spring, but if so it's only purpose is to prevent rattles. On my 1936, this is just a tiny coil spring with loops at the ends.

 

 

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Two suggestions for you to try, after you implement Bloo's:

1. 19* BTDC running better than on factory setting makes me question the accuracy of the timing marks as installed.  We used to "power time" with a vacuum gauge--at idle with vac gauge hooked up, advance timing to maximum vacuum, then retard 0.5 inch of mercury (e.g., if it goes no higher than 20 in. Hg, retard to 19.5).  If you subsequently get a detonation ping, retard another 0.5 inch Hg. 

2.  You can non-invasively check for plugged muffler/exhaust (as per poci1957's excellent idea) with a vacuum gauge:  With vacuum gauge attached at stationary idle, have a helper accelerate the engine to about 1800 rpm and hold that speed for two full minutes.  After the vacuum gauge initially stabilizes (maybe 20 seconds), watch to see if the vacuum reading drops substantially over the next 90 seconds or so.  If it does, that indicates plugged exhaust.  I sent my first car to the wrecking yard when this test, and a new muffler, would have kept it alive--of course I was 17 and had a better one lined up.

 

Afterthought:  Have you checked the operation of the vacuum advance with a timing light?  Or by applying vacuum to its line (engine off, dist cap removed) to see if application of vacuum advances the points plate?

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Smokey, I see that you put a Pertronics conversion kit in also, the `54 is still 6volt system? Is your conversion a 6volt kit? My brother put one in his `69 Vette over 10yr ago and has never had a problem. Another friend put the conversion in his `56 Ford and it would run, but not very good. I suggested, put in a new set of points and new condenser, and it ran perfectly.  .025 gap on plugs, and .016 gap on points for 8cyl.,  (.022 point gap on 6cyl)..   I agree with Grimy to recheck the vac. advance.

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I'm not going to get into the Pertronix good / Pertronix bad debate, but I wouldn't want it on there while trying to troubleshoot a pre-existing problem.

 

I agree with Grimy about what to do next.

 

Good luck!

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Not sure we're my reply has gone so I will rewrite. 

The Pertronix is 6volts and also fitted a new coil as well the results are good and ignition seems to have improved.

Timing has been set from 19 deg to 3 deg it now starts on the button everytime.

Using Bloo's information the heat raiser is fitted incorrectly I will refit as per Bloo's instructions. 

Grimy, great advice I will follow up and check than you. 

It does appear that the engine is not set to workshop specifications.

This means I will need to start from the basics and check everything first up will be rechecking compression and testing leakdown.

Then moving forward once I am happy with the results.

Lastly thank you to everyone that has given advice it's much appreciated.

Keep it coming and I will update the results as I go.

 

 

 

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2 hours ago, Smokeywolf said:

This means I will need to start from the basics and check everything first up will be rechecking compression and testing leakdown.

I know from experience how much of a PIA this is on a newly acquired car, but please consider all the basics and rechecking others' work part of the Baseline Shakedown / Sorting required of any newly-acquired car.  May I suggest that you document WHAT you do and the RESULTS of each incremental effort, either in a digital file (my preference) or even stubby-pencil.  I strongly approve of your approach of making one change at a time and testing the results.  Best wishes for success!

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Here is an update on the work completed to date.

Compression 110 psi average across all cyliners. 

Heat raiser checked and working correctly 

Exhaust removed to check if the exhust system was blocked.. all ok.

Carb rebuilt no improvement. 

Non of the work done has improved the engine

Does anyone have a good distributor they would like to sell?

 

 

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Before buying a replacement distributor, are you positive that yours is bad?  With a timing light, you should be able to see the timing mark advancing as you rev the engine and as you disconnect/reconnect the vacuum advance.  If the timing moves steady and doesn't bounce around, your distributor is probably in working order.

 

Have you replaced the fuel filter and made sure that there is enough fuel getting to the carburetor?

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Hi Faso thanks for your reply

The fuel filter was checked then removed and refitted after I had proven it was not causing any problems.

The distributor advance and retard has also been checked and works.

But it's not an indication that the advance curve is correct.

 

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This will be my last post on this problem.

Why!

 Because it's now going the way Pontiac intended 

Cruisers along at a comfortable 85mph I think, it will go a bit faster but simply not got the guts.

The last thing to be replaced were  the HT leads.

They were not replaced earlier because the last owner just had a brand new set fitted.

But as a last resort a new set was fitted.

Which solved the problem.

Which just goes to show not to take things for granted, including the obvious 

I would  like to thank everyone who has taken the time to offer advice.

 

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