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Author
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Topic: rail vs non-rail
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shoe
Gearhead Posts: 163
From: midwest
Registered: Feb 2001
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posted 11-19-2002 08:36 PM
   
Having a terrible backfire through the carb including fire on a Mustang I bought that was suppose to be rebuilt. Timing is on. Compression is good. Noticed they are rail rockers on non-rail heads(slot instead of round hole in push rod guide) Could this be the problem?
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kcode
Gearhead Posts: 2623
From: alvaton,ky,usa Suburb of Bowling Green, M&M #79, MCA #29208
Registered: Jun 99
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posted 11-19-2002 11:10 PM
I would make sure the alignment is correct, pushrod rubbing. Also some rail rockers had lash caps on the tips of the valve stems. Just make sure that the tip of the rocker is actuating the valve and not the rails pushing on the keepers. If everything is ok, it should not be the problem. This is kinda elementary, but are the plug wires in the correct firing order? Mike
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Moneymaker
Administrator Posts: 19751
From: Lyons, IL, USA
Registered: May 99
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posted 11-19-2002 11:58 PM
The push rod slot does not dictate the rocker style shoe. It's the length of the valve stem tip. Rail rocker valves are .125 longer above the keeper groove than the non rail valves.
I would double check the firing order. Possibly the rebuilder installed a 351 FO cam and you are using the traditional 15426378.
Or the wires have been routed in the 351 FO and you have a standard cam. Both scenarios will cause a back fire.  ------------------
Alex Denysenko
Co-Administrator and Moderator NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Professional Manwhore
The Barry of BarrysGrrl Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
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mustangboy
Gearhead Posts: 670
From: Ont, Canada
Registered: Mar 2002
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posted 11-20-2002 12:01 AM
I doubt that is whats causing your problems unless something is binding,but I would either drill out the pushrod holes or get the proper type non rail rocker arm.Personally I hate the rail rockers it has been my experience that they chew up the ends of the valve stems.
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69stanger
Journeyman Posts: 59
From: Northridge, CA
Registered: Aug 2002
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posted 11-20-2002 02:08 AM
maybe you tightened the rocker arms too tight?when I did this on my car I had back-fires till I adjusted my rocker arms properly
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shoe
Gearhead Posts: 163
From: midwest
Registered: Feb 2001
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posted 11-20-2002 10:08 AM
I might mention that I have had the motor actually running( not driven) in the garage but& it seamed to respond well to a poke on the gas pedal but once in awhile it would spit,smoke & actually start the carb on fire. I thought it was valve adjustment & went the Chilton's way with #1 at top dead center & divide the balancer into 1/4's & adjust in the firing order turning it 1/4 turn & spinning pushrod until you can't & then turn 3/4 turns tighter.... Then I couldn't get it started at all. So last nite I backed off each valve 3/4 turns. Still won;t start & shoots into fire with several backfires when I try to start it. The spark plugs are in the correct firing order, compression is 132 to 142 range on all cylinders. Would it even run at all (which it did) if he put in a 351W cam & I used a 289-302 firing order??Any help. I've been around Ford for 35 years & this one has got me...Shoe
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bifs66
Gearhead Posts: 169
From: Maryland
Registered: Apr 2000
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posted 11-20-2002 11:59 AM
While it may not be the root cause of your problem, I would ditch the rail rocker arms. With your heads, the pushrods (and associated rockers, etc) are being alligned by the "slots". The rail rockers perform the same task (allign the push rods, rockers, and valve stems) on heads with round pushrod holes. So, by combining both at the same time, you are most likely causing some interferance/misallignment issues that will show up sooner or later. This is particularly true since both methods are non-adjustible. Way back in the "Muscle Parts" era (1970s), Ford recommended getting rid of the rail rockers as they create problems in performance applications. Most often, when rail rockers are replaced, guide plates are used to allign the valve train; but since you have the slotted heads this wouldn't apply. ------------------
Bernie Frank
66 Fastback restomod project
85 GT (preserved)
82 GT (original)
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Moneymaker
Administrator Posts: 19751
From: Lyons, IL, USA
Registered: May 99
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posted 11-20-2002 01:26 PM
Yes Shoe, it would run with the 302 FO. It would idle somewhat acceptable but, and it would pop, fart, and back fire just as your simptoms describe when you try to give it gas. ------------------
Alex Denysenko
Co-Administrator and Moderator NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Professional Manwhore
The Barry of BarrysGrrl Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
IP: Logged |
shoe
Gearhead Posts: 163
From: midwest
Registered: Feb 2001
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posted 11-20-2002 02:06 PM
I'm going to try the 351 firing order tonight. I don't know what else it could be. Thought it might be a bad carb(power valve) but I tried a brand new carb ,another Holley I had ,& also a 3rd Carter carb. It backfired into me blowing out the fire( & cinged my beard trying)..All the simple things I checked out real well.The valves are all opening & closing according to a visual look & must be shuting completely because of the great compression each cylinder has.I'll let everyone know tonight on the 351 firing order try. And THANKS for all the ideas... Please let me know any other options...Shoe
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shoe
Gearhead Posts: 163
From: midwest
Registered: Feb 2001
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posted 11-20-2002 10:53 PM
Well That was the problem The previous owner must of put in a 350 cam. I switched the plug wire around to te 350 firing order & wammo it started & didn't backfire. But it wouldn't run well at 6 degrees before TDC So I had to pull the distributor & move it a hex or 2. The 289 came to life. Now I can get down to finishing putting the car together. Thanks to all & Moneymaker you hit it on the head with the suggestion of the wrong cam .. Pat, pat on the back....Shoe
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Moneymaker
Administrator Posts: 19751
From: Lyons, IL, USA
Registered: May 99
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posted 11-20-2002 11:11 PM
 ------------------
Alex Denysenko
Co-Administrator and Moderator NHRA/IHRA/SRA member and licensed Superstock driver
MCA member# 53321
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Professional Manwhore
The Barry of BarrysGrrl Quote #1: "I never met a magazine mechanic I liked."
Quote #2: "Make sure brain is in gear before engaging mouth!"
Quote #3: "If you can't run with the big dogs, stay on the porch!"
IP: Logged |
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