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Discussion Starter #1
Engine gas fouls at start up and low RPM.
Engine vacuum is low at idle 600 RPM 3-5 LBS.
Only way to get vacuum up is to advance timing 8-10 degrees.
Started with Holley dual pumper and now has Edelbrock thunder 1802 SERIES 600 CFM and changed jets and metering rod springs but no help.
roller cam .543 intake 554 exhaust 218 intake /226 exhaust [email protected] degree lobe separation.
10-1 compression.
Intake single plane low rise from Summit intake EDL - 2121 performer
timing at 15 degrees base and 35 at 3500 rpm.
champion plugs 792 gap 45"
13726548 firing order.
Blue print heads58cc champer .
intake valve 2.02" exhaust valve 1.60"
Thanks for any help or ideas
 

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Discussion Starter #3
Thanks for the reply.
We have done everything to find a vacuum leak. Several intakes and gasket sets. checked brake booster.
What carb and intake are you using?
Is your 347 from blue print engines?
This is our third engine from them.
First one a 331 was bored .040" with standard pistons.
Second one galled pistons and cylinder walls they said run hot we said no way.
Third and last one they sent us under warranty was a 347 they had redone or reworked heads showed signs of been used or run , not a new rebuilt.
I suspect wrong cam or carb or intake may be vacuum and plug fowling problem.
 

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Mine is a Blueprint 347 base dressed engine. It comes with a Holley 600 cfm carb and a no-name dual plane intake manifold. The carb is a little small for the size of the engine but the throttle response is incredible so I never bothered changing it. And if I can believe Blueprint, it dyno'd at 418 hp with that little carb. My ass-ometer seems to confirm that.

I spoke with Blueprint after I installed and drove the engine a few miles just to confirm a few things, and they told me they generally set the carbs up a little rich and are a little conservative with the ignition timing just to be on the safe side. Same with the spark plugs. The 792's are a little on the cold side. I switched to NGK plugs one heat range hotter and they color perfectly. You said you have gas fouling of the plugs. Do you mean carbon fouling?

Incidentally, all of their engines are .040 over as they state on their Web site. In the old days we never went more than .030 over on Windsor motors, but .040 seems to be the new normal with most builders.

Another thought: your Edelbrock carb has vacuum ports for both manifold and metered vacuum. Make sure you use the metered port if you are utilizing vacuum advance on you distributor.
 

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Discussion Starter #5
Mine is a Blueprint 347 base dressed engine. It comes with a Holley 600 cfm carb and a no-name dual plane intake manifold. The carb is a little small for the size of the engine but the throttle response is incredible so I never bothered changing it. And if I can believe Blueprint, it dyno'd at 418 hp with that little carb. My ass-ometer seems to confirm that.

I spoke with Blueprint after I installed and drove the engine a few miles just to confirm a few things, and they told me they generally set the carbs up a little rich and are a little conservative with the ignition timing just to be on the safe side. Same with the spark plugs. The 792's are a little on the cold side. I switched to NGK plugs one heat range hotter and they color perfectly. You said you have gas fouling of the plugs. Do you mean carbon fouling?

Incidentally, all of their engines are .040 over as they state on their Web site. In the old days we never went more than .030 over on Windsor motors, but .040 seems to be the new normal with most builders.

Another thought: your Edelbrock carb has vacuum ports for both manifold and metered vacuum. Make sure you use the metered port if you are utilizing vacuum advance on you distributor.

Thanks
The plugs foul with wet black gas at low cold and warm idle and low rpm.
Always stay black and wet.
Advancing timing 10 more degrees is only way to help it. On fouling plugs.
Have went up several heat ranges plugs.
From C59YC to C61yc to C63YC
Have leaned carb jets and metering rods and set metering rod springs for lowest manifold vacuum.
Does have single low rise plain manifold.
MSD IGN system.
When timing set to blue print specs 16 degree idle and 35 degree at 3500 RPM manifold vacuum is 3 hg.
Advance timing another 10 degrees and vacuum comes up to 17 hg.
And quits fouling plugs.
I suspect wrong cams shaft or cam timing.
 

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I'm thinking that you may not have your timing marks indexed correctly. I say this because when you advance the timing, your manifold vacuum goes right up to where it should be. Does the engine ping under load when you advance the timing?

Ford used at least three different combinations of vibration dampers, timing pointers and front covers on the small block Windsors. If you mix them up, it's possible to be off on your tdc mark.

I would try bumping your initial timing 2 degrees at a time until you get a slight pinging under load, then back it off 2 degrees. This may solve your problem.
 

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Discussion Starter #7
Thanks
Good idea.
You may be right.
Will double check with no 1 piston TDC compression.
Also check cam timing with 1 TDC and opposite firing cylinder on valve rocker arm rocking intake to exhaust.
I can not hear good enough to hear pin/spark knock but will get owner to drive it with timing advance up to good vacuum..
 

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How can it idle at 600 rpm? My last 347 and current 408 idle at 850 . The 347 had a B cam and the 408 has an X both are in the 224-226 range @.050. "I" found I had to run a hotter plug with an aluminum head. "I" use an Autolite 3924 with 34* total timing. Idles in gear with a "stock" 11"C4 convertor , not a stall convertor. No black plugs
 

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Discussion Starter #9
How can it idle at 600 rpm? My last 347 and current 408 idle at 850 . The 347 had a B cam and the 408 has an X both are in the 224-226 range @.050. "I" found I had to run a hotter plug with an aluminum head. "I" use an Autolite 3924 with 34* total timing. Idles in gear with a "stock" 11"C4 convertor , not a stall convertor. No black plugs


Thanks for the info.
No problem on idle it down even 500 RPM.
Just loses manifold vacuum an dumps to muck fuel in and gas foul plugs at low idle at base timed.
Our 347 at 415 HP from Blue print engine was one they redone with used stuff from there warranty stock.
They may have put a mismatched caw or wrong cam.
We have tried hotter plugs and all kinds of Edelbrock carbs from 500 cmf to 6500 cmf Edelbrock jets and metering rods and metering rod springs.
Even a Holley dual pumper.
Only thing that helps is to advance timing another 10 degrees over base.
 

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Does it drive OK......no pinging??:wink2:

If so sounds like your timing marks are way off.......I think you said you are going to double check TDC on #1 and report back....this could be your answer to very late timing and fouled plugs !!:grin2:
 

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Discussion Starter #13
No ping or spark knock. with time advanced 10 more degrees.
TDC timing mark right on with no.1 piston TDC. compression.


I turned a order into summit racing for the ATOMIC EFI MASTER KIT.
Will see what that does for it.
 

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Discussion Starter #15
Base timing.
15 a idle and 35 at 3500 RPM.
MSD ign. and dist. with vacuum advance.
Sorry for not replying faster but I can not get forum to notify me of answers to my post.
 

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So Base Timing becomes 25* and Max Timing becomes 45* with no pinging??:surprise:

Your timing marks have to be inaccurate somehow??:frown2:
 

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TDC timing mark right on with no.1 piston TDC. compression
are you sure you used piston stop correctly...
heres how to....

 

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Discussion Starter #20
Thanks for the reply and video to it.
Would be a nice tool.
But Never used on for 50 years mechanical work.
Just use brass rod in spark plug hole.
My next step is to check the timing chain for off 1-2 link or worn out and true cam shaft timing.
Taught to me by a old machinist 40 years ago.
Just rotate engine to TDC compression no 1 cylinder.
Find opposite firing cylinder and pull valve covers on opposite firing cylinder.
Rotate engine from just before TDC compression no 1 cylinder to TDC compression
Look for intake and exhaust valve rocker arm rocking from intake to exhaust.
If not the timing chain to camshaft timing is off.
 
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