Broken Rod
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Elder User
Joined: Sep 2012
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From: Smokey Mountains TN
Broken Rod
Hello Guys,
i have a old 300 straight six in our 1979 F150 Supercab 2wd , 4 speed ,we are starting to restore. ( for Granddaughter :-) )
Wee discovered a broken rod on #4 cylinder. The block looks to be Ok , however i have not torn into it any further, besides pulled the Pan.
My Questions :
- is a broken rod a common problem on those engines?
- we want to have a good decent power 300 in this truck that provides somewhat decent fuel millage, but is also capable of pulling a 2-horse trailer.
-Besides a set of headers what else would you guys recommend in regards to carb, intake , cam, valves ? the truck will be taken to shows but also will be a daily driver.
-where would i even find a set of rods ? i assume i should replace all six ?
-due to the need of a crank and rods, would it be better to find another engine ?
i know those are a lot of questions, but i appreciate any advice.
i have a old 300 straight six in our 1979 F150 Supercab 2wd , 4 speed ,we are starting to restore. ( for Granddaughter :-) )
Wee discovered a broken rod on #4 cylinder. The block looks to be Ok , however i have not torn into it any further, besides pulled the Pan.
My Questions :
- is a broken rod a common problem on those engines?
- we want to have a good decent power 300 in this truck that provides somewhat decent fuel millage, but is also capable of pulling a 2-horse trailer.
-Besides a set of headers what else would you guys recommend in regards to carb, intake , cam, valves ? the truck will be taken to shows but also will be a daily driver.
-where would i even find a set of rods ? i assume i should replace all six ?
-due to the need of a crank and rods, would it be better to find another engine ?
i know those are a lot of questions, but i appreciate any advice.
Fleet Mechanic
Joined: Nov 2002
Posts: 1,643
Likes: 69
Broken rods are rare. But so is getting struck by lightning. But if you get hit it matters little what the odds were.
I would inspect the other rods and recondition them with new bolts. Maybe they were over-torqued leading to rod failure.
There are two different pin sizes for 300 rods, either .912' or .975" dia. The big ends are all the same size. Yours is likely the 975" size.
I would inspect the other rods and recondition them with new bolts. Maybe they were over-torqued leading to rod failure.
There are two different pin sizes for 300 rods, either .912' or .975" dia. The big ends are all the same size. Yours is likely the 975" size.
Thread Starter
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Elder User
Joined: Sep 2012
Posts: 611
Likes: 0
From: Smokey Mountains TN
Broken rods are rare. But so is getting struck by lightning. But if you get hit it matters little what the odds were.
I would inspect the other rods and recondition them with new bolts. Maybe they were over-torqued leading to rod failure.
There are two different pin sizes for 300 rods, either .912' or .975" dia. The big ends are all the same size. Yours is likely the 975" size.
I would inspect the other rods and recondition them with new bolts. Maybe they were over-torqued leading to rod failure.
There are two different pin sizes for 300 rods, either .912' or .975" dia. The big ends are all the same size. Yours is likely the 975" size.
actually the bolts were still tight, the rod broke just above the crank and the two bearing halfs were folded open and laying in the oil pan.. i never seen this before though..
Thread Starter
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Elder User
Joined: Sep 2012
Posts: 611
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From: Smokey Mountains TN
i definitely need rods and a crank. machine shop will have to tell me about the block. not sure if it can be saved.
how about the other mods ? what would you guys recommend in regards to came, intake, exhaust and anything else to make it a good pulling reliable engine ?
Fleet Mechanic
Joined: Nov 2002
Posts: 1,643
Likes: 69
If you are looking for improved pulling power and decent fuel economy Id go with an aftermarket aluminum intake, like Clifford, Offy C, or Aussispeed, an Autolite 2V carb, EFI exhausts (not headers), and an RV or towing cam. Also use a clutched fan.
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More Turbo
Joined: Nov 2015
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If your block is good you can get a crankshaft and connecting rod.
Here is a crank that has been remanufactured and comes with rod and main bearings.
CRANKSHAFT W/ BEARINGS Fits: 1965-1996 FORD 300 4.9L OHV STRAIGHT-6 | eBay
Have the other 5 connecting rods magnafluxed for cracks
If you only need to replace the one broken rod.
FORD 69-96 300ci/4.9L Connecting Rod (cleggengine.com)
Here is a crank that has been remanufactured and comes with rod and main bearings.
CRANKSHAFT W/ BEARINGS Fits: 1965-1996 FORD 300 4.9L OHV STRAIGHT-6 | eBay
Have the other 5 connecting rods magnafluxed for cracks
If you only need to replace the one broken rod.
FORD 69-96 300ci/4.9L Connecting Rod (cleggengine.com)
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More Turbo
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A hypereutectic piston is highly recommended over the regular cast piston.
The least expensive is the sealed Power H519P at $80 for a set of 6.
FORD Sealed Power H519P 30 Speed-Pro Hypereutectic Pistons | Summit Racing
The compression ratio will be low so you can have at least .025" milled of the block deck to get the piston closer to the top of the cylinder at TDC.
There are several cams to choose from but I'm going to recommend the Melling MTF-6 RV/Elgin E1178P cam and lifter kit.
Ford 240 300 L6 RV Torque Camshaft Cam F150 Kit Lifters E-1178-P MTF6 STAGE 1 | eBay
An Autolite 2100 two barrel carb will work well on any of the aftermarket aluminum intake manifolds.
The intake manifolds designed for a 4 barrel carb will need an adapter plate.
Aussie speed has a dedicated two barrel intake.
You can also use a vacuum secondary 4 barrel carb on one of the aluminum intakes.
What's great about the 4 barrel is you operate with the small primaries as a two barrel carb and the other two barrels are there for the extra power.
The vacuum operated secondary won't open more than the engine needs.
A headers will give you good power but you have to remove it to get to the starter.
The two stock exhaust manifolds from a 1987 and later EFI engine does a good job power wise and doesn't shroud or heat the starter.
The least expensive is the sealed Power H519P at $80 for a set of 6.
FORD Sealed Power H519P 30 Speed-Pro Hypereutectic Pistons | Summit Racing
The compression ratio will be low so you can have at least .025" milled of the block deck to get the piston closer to the top of the cylinder at TDC.
There are several cams to choose from but I'm going to recommend the Melling MTF-6 RV/Elgin E1178P cam and lifter kit.
Ford 240 300 L6 RV Torque Camshaft Cam F150 Kit Lifters E-1178-P MTF6 STAGE 1 | eBay
An Autolite 2100 two barrel carb will work well on any of the aftermarket aluminum intake manifolds.
The intake manifolds designed for a 4 barrel carb will need an adapter plate.
Aussie speed has a dedicated two barrel intake.
You can also use a vacuum secondary 4 barrel carb on one of the aluminum intakes.
What's great about the 4 barrel is you operate with the small primaries as a two barrel carb and the other two barrels are there for the extra power.
The vacuum operated secondary won't open more than the engine needs.
A headers will give you good power but you have to remove it to get to the starter.
The two stock exhaust manifolds from a 1987 and later EFI engine does a good job power wise and doesn't shroud or heat the starter.
Fleet Mechanic
Joined: Sep 2012
Posts: 1,608
Likes: 53
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