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break in of rebuilt engine
My 351 C has been torn down and rebuilt with quality parts. Break in was done on a dyno and I've only 10 miles since then, never going above 3000 rpm, had some starting issues in the begining. Now to my question, should the heads be retorqued? If yes, when? and how much. Should I first loosen them and then retorque?
Not if good head gaskets were used. That's kinda old school, I do not think anyone sells gaskets that need re-torque.

Jeff T.

Low buck, touring style, '73 Convertible "rolling restoration", 351c, 2v heads with a shave and a haircut, Performer intake, Holley 650(ish), roller rockers, screw in studs, guideplates, stainless valves, Duraspark / Motorsports MSD, T-5 conversion. 1-1/8" front, 3/4" rear swaybars KYB shocks and some home brewed subframe connectors. Future plans; JGC steering box, Cobra brakes and... paint, interior, etc.

When I die I want to die like grandpa, peacefully in my sleep... not screaming, like his passenger.

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You shouldn't have to re-torque the heads. If you just want to, don't loosen them. Just re-torque to the same specification. I do suggest checking the intake bolts again.

I would check the intake manifold bolts. One item in Ford's 'pre-delivery' to do list is to retorque the intake bolts. This is done when the car is delivered to the dealership. Another item on the list is 'wash the car'.


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Yeah, head gaskets don't need retorquing these days, particularly the MLS gaskets (Cometic). +1 on headers and intakes bolts, though.

1971 Mustang fastback: 10.3:1 C90E 408W hydroller - CDAN4 EEC-V w/EDIS8, girdled, lowered and caged
about time to rev up that engine...........break it in like you expect to drive it.......

73 ragtop, 1999 Mustang Bright Atlantic Blue Paint, Phoenix Engine 302-335HP,  Edelbrock Carb & Performer manifold; c4 with 2000 stall and shiftkit; 3:55 auburn limited slip differential, Hedman shorties; Car Chemistry Exhaust

Classic Air; Tilt Steering Wheel; 1999 Chrysler Sebring bucket Seats ; power windows;
This is definitely true these days as well. If you're running moly rings, the rings will seat within the first 15 minutes of runtime!

1971 Mustang fastback: 10.3:1 C90E 408W hydroller - CDAN4 EEC-V w/EDIS8, girdled, lowered and caged
Was it broken in with non-synthetic motor oil? Did you add some type of zinc addititve? The flat tappet cams shouldn't be broken in with synthetic motor oil and a little extra zinc doesn't hurt.

73 Convertible - 351C/4V CC heads/4bolt/forged flat tops/comp 270/rhodes/mallory unilite/tri-power/hookers/glasspacks/c6/3.50 limited slip/Gear Vendors/Global West sub frames, strut rods and shelby style traction bars/ Rear sway bar/tilt steering (not original)

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