what lenght pushrods? wiped out cam? 78 ford 302 - Hot Rod Forum : Hotrodders Bulletin Board
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Old 03-19-2007, 12:09 AM
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what lenght pushrods? wiped out cam? 78 ford 302

I have a friend with a rebuilt 302 out of 78 mustang ii. The motor is a stock rebuild (aftermarket flat tops, cam, intake, carb, everything else stock) with about 9:1 CR. The cam is a hydraulic 218* .488" lift, stock heads (no milling) and pro form alum full roller rockers(to work with stock push rods length).

They had a real hard time starting the motor, cranking it over many times for probably more than 30 min., and after it finally fired and ran, I was surprised to see they reved it up past 4,000 many times and did not break it in at the as recommended holding at 2000 rpm. They then shut it off after about a minute of running. They did this about 2 times after it cooled. start reved up high for bout 1 min. and shut off. THEN he said they "broke" it in.

They pulled the valve covers off bout a day later cause they heard some valve train noise. They found that the push rods are too short??? - they were loose and wiggling. But before they started they adjust the preload(weird ford type pedestal mount so you have to shim them) and he said that they weren't to short then. He also said that the ones towards the front of the motor weren't as loose or not at all. While the ones near back were looser.

Now to me this sounds like a possible wiped out cam??? he said he was using 6.8** length and now he needs 6.9**. If he indeed does need longer length could their be any damage done?

What do you guys think?

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Old 03-19-2007, 10:00 AM
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SBF cylinder heads up to about mid year 68' had fully adjustable rockers and shorter (6.8") push rods
the non adjustable 76' heads have "bolt down" non adjustable rockers and do use the longer rods with shims if necessary (6.9"approx)
tell him his valves are longer also than the adjustable rocker heads
I call it: "the L-4 change bear trap"

cause of what he did for the break in......he really should do a lift measure at the rockers on all 8 cylinders because: "some were loose and some were tight"
no calipers on hand, a crude way is to make a lift "reference stick" to compare all 16 valves at TDC...cut it/shape it so you can measure each at the same location on the head....wooden paint stick works...easy to cut and trim
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Old 03-19-2007, 12:26 PM
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Quote:
They had a real hard time starting the motor, cranking it over many times for probably more than 30 min., and after it finally fired and ran, I was surprised to see they reved it up past 4,000 many times and did not break it in at the as recommended holding at 2000 rpm. They then shut it off after about a minute of running. They did this about 2 times after it cooled. start reved up high for bout 1 min. and shut off. THEN he said they "broke" it in.
Well, the extended cranking cleaned off the assembly lube and the 4000 RPM bursts with too soon shutdown took care of what was left...
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