[font size="1" color="#FF0000"]LAST EDITED ON 27-Aug-01 AT 09:57 AM (EST)[/font][p]Bare with me please

Ok,I for the life of me cannt get this 352 i got running worth a damn.It is in a '66 F250.
Soon as i bought it,it stumbled bad right off idle.OK,no big thing seen this a hundred times.So i rebuild the 2v MC carb.Everything is tight,i soak it in Chem-Klean,In other words super clean,New acce.pump,power valve,ect.
Bolt it back on expecting the dead spot to be gone,and it runs exactly the same!This carb was dried out and super dirty!
Ok,so take it apart again to check flaot level,make sure i got the check ball in,ect.Everything good.
So i go to the timing area.Moved the dist. al across the board,no change,put in new points/condenser,gapped @.017-.020,no change.Thought i hit paydirt when i found a long hairline crack in Dist. cap!It had a nasty carbon trail.Go out,buy a new Standard cap,rotor,plugs,wires.Never made one iota of a difference.I can't see it being the advance becuase it acts like it getting full advance right off idle or fuel starvation?
It pops through the carb also if you really open it up.
So next i check mech.timing.It is right on no.1 tower with no.1 piston on TDC comp stroke.Balancer is even dead with the pointer.
Well,I decide on a compression check(Is this bad?),I pull all the plugs,I plugg my comp tester in no.1 and get a 85 psi reading?I thought 125-160 is good?Am i right?
Then i go for number two on other back,it reads 70psi.
In other words the highest psi was 90.Also the plugs seemed oil and or gas fouled,even though this truck has never let out a drop of oil smoke!No lie!,And it idles dead smooth.But right off idel it gets bad,if you get it moving and drive it,it wants to set you in the seat,then will stumble.
Also,I checked the Fuel:Air with vac.gauge,getting about 17 inches of vacuam@ 650rpm with idel screws turned out 2.75 turns.Exhaust smells good(?).Not rich.
Also,the fuel bowl in carb is stayin' full.And the squirters squirt but not all that hard.
I know this is long.But i wonder if the answer is staring me directly in the face and i wont admit it?I am afraid the cylinder pressures are to low and therefore bad ratio of volumetric effiency?
Thanks for taking any time to read me long drawn out post.
So what is it?Am i a idiot





1970 F250 Sport Custom 4x4.351W,DuraSpark,N.P.435,Dana24,Dana diffs,4.10:1's,36x9.00 CordovonPower Kings,Blue/white.---oleblue---
1966 F-250 4x2,352,4spd,Custom Cab,Blue/white---bessie---
1979 F-150 Ranger 4x2,302,C4,cold A/C,thumpin' stereo,brown/tan---tany---

 

Have you checked for a bad timing chain?
Eric

 

Thanks for replying Eric.

As to your quesion,yeah i would say i did.What i did was when i got it on TDC on no1 comp stoke,i turned the engine backwards.That should have gave me a damn good idea of how much slack was in the chain.I turned it by hand to 0,then backwards,the rotor turned right a away.So i think it's tight.
Also,the vacuam uage needle held steady.

Thanks~

 

OLDBLUE70... >>>Well,I decide on a compression check(Is this bad?),I pull all the plugs,I plugg my comp tester in no.1 and get a 85 psi reading?I thought 125-160 is good?Am i right?<<
Some how I get a feeling that you may be suffering from the fact that the valves are going away... Like its time to put in `hardened` seats at least on the exhaust side.....
If you lay a straight edge on top of the valve stems (rockers removed) they should be `even`... My exhaust valves were `UP` about ..090

Just a guess...


__JOHN__Õ¿ö
FTE Club #7
Member-
http://www.cruisin-north.com/
Santa Rosa, Calif.
72 F-250
ICQ#6030753
http://www.ford-trucks.net/users/jbhf250/
https://www.ford-trucks.com/pictorial/big/1972_f250_2.html

 

Seems to me that bad exhaust seals would create pressure in the crank case, so if this were the case you'd see more mist than usual coming out of your breather cap. If there's a bunch of stuff coming through the breather, then it's likely a problem somewhere in the cylinder heads. Usually if your rings are making your engine burn oil, you have to get on the gas, get the rpm up there a ways, then let off the gas and check for blue smoke as the engine is slowing down. I'd say it's combination of well-worn rings and something going on with the valves. 90 psi is below specs for these motors, and a spread of 20 psi or more over all eight definitely is not acceptible. There's no way you'd get clean acceleration with this much difference between cylinders.

 

Low compression, hmmm ..., did you prop the carb open and check compression with all of the plugs out when you did the compreewsion check, or did you check with only one plug out at a time? Low compression readings can also be a caused by a non-stock cam with more over lap and/or longer duration although your manifold vacuum readings lead me to believe that the cam is not that hot.

Timing issues: have you checked the vacuum advance to see if it leaking. Where is the vacuum line (source) for the distributor connected? It should be to the carb and not to the manifold. Is the mechanical advance OK, ie, how much slop when you try to turn the rotor?

Bob
'66 7 Litre, top loader, 3.25 Traction-lock, Sidewinder Intake, SCJ Exhaust
'88 F150 LWB 4x2, XLT Lariat, 302, 5 speed, 3.08
'99 Ranger, 4x2, 3.0, 5 speed, 3.73 posi

 

Thanks guys.

No slop Bob.I turned via crank both ways and rotor follows right behind.
I also know about pressurizing crankcase.Had a 390 that blew a cmp ring and was a mess.This one does not do that at all and pcv is clean.
Thanks for the idea JB.I will check stem hieght.

What i dont get is the accel. pump squirt is shot on the side of the nozzles and not right into the flappers.It seems to dribble once you hit the nozzles.If the butterflys open before you get a good squirt would (to me)create a lean ,off idle condition?
I am not a expert on MC 2v's so i dont know.
I really appreciate the help.
The test were with all plugs out.But damn!It want's to go!It will just fall on it's face,but wants to run.
The vac. advance has the orig metal line and i havn'messed with it other than block it off,which changed nothing.

The symtoms lie in squirter circuit to me?But i have given it a super clean and have moved rod to each different location.
Even with a real slow movement of throttle wants to screw it up.
And yeah,no vac leaks.I can kill it quick cupping my hands over carb.
Thanks again~

 

Bob,

Yeah,the advance is at the part time port on carb.The only other vac port on this truck other than the full time for brakes.I love these ol things though

Yeah,stock cam.

 

I think where it's squirting is fine, but it should be without delay. I'd check for carb linkage wear between the throttle plates and the squirter. Also, you can disconnect the sqirter part and just tap it about 1/4" quickly and I think you should get a little squirt. I'm not sure of the specs, but it should be near exactly the same time as you tap the linkage. I've seen this happen before and it might be a bad check ball or the pump might not seal properly.

I've even seen a warped top plate cause this problem.

Poping back out the carb is usually from being too lean, so I think your on the right track. Don't those pumps have a spring in them, I'd check for play in the area of the pump and make sure it's actually contacting the plunger.

As for compression, it should be much higher. I'd do a full check (wet check w/teaspoon of oil) and see if it goes up much. If it doesn't go up much, I'd say your looking at a new valve job with hardened exhaust seats.

the flat edge check method is the proper way to check and it's not that hard to do.

 

Karl,
I believe the carb is orig.It has the tag for '66.I will check the squirt without the linkage.Thanks for that idea!

Also,when i checked compression the engine was dry.I hadn't started it before hand for two weeks.

John,are you refering to seat pressure on the springs or the rate they snap shut?
I have built some fairly radical engines and floated the valves in one and bet pushrods.That was from mismatched springs for the rpm i need.This prob is right off idle but yet goes up through the rpms.Would sring weakness come into play at such a low rpm?I have it idlings at 650/manual trans.

Thanks again guys.You have given me some more ideas.I have to paint a car tommorow but will get back on the truck hopefully wensday.

So when i measure the stem heighth,that is showing me that the exhaust valve has sunken in the seat?