First Bigsix rebuild

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homeboi77
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Joined: Thu Jul 05, 2018 12:18 am

First Bigsix rebuild

Post #1 by homeboi77 » Fri Jul 06, 2018 7:25 pm

Hey I'm new here but im looking for some information. I just got my hands on an 85 f150 4.9L Inline 6 and it's kickass. only thing is engine has 480k on it, runs rough at times and it most likely needs a rebuild. I also have another 86 f150 inline 6 that's in the bush at a coworkers place. I plan on rebuilding the 86 and dropping it into my 85. im looking for just a basic information on rebuild kits, your guys preferences and how I would get some more hp Thanks :D

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wsa111
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Re: First Bigsix rebuild

Post #2 by wsa111 » Fri Jul 06, 2018 9:54 pm

First, welcome aboard. The 4.9 is a workhorse.
Some of out big six experts will guide you.
67 mustang,C-4, with mod. 80 hd, custom 500 cfm carb with annular boosters, hooker headers, dual exh.-X pipe, flowmaster mufflers, duraspark II dist. with MSD-6AL. Engine 205" .030" over with offset ground crank & 1.65 roller rockers. 9.5 comp., Isky 262 cam.
2003 Ford Lightning daily driver. Recurving Distributors. billythedistributorman@live.com
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Harte3
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Re: First Bigsix rebuild

Post #3 by Harte3 » Sat Jul 07, 2018 3:06 pm

You are in the right place! Start reading and taking notes...everything you want to know is already here.
'83 F150 300, 0.030 over, Offy DP, Holley 4160/1848-1 465 cfm, Comp Cam 260H. P/P head, EFI exhaust manifolds, Walker Y Pipe, Super Cat, Turbo muffler, Recurved DSII, Mallory HyFire 6a, ACCEL Super Stock Coil, Taylor 8mm Wires, EFI plugs.

homeboi77
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Joined: Thu Jul 05, 2018 12:18 am

Re: First Bigsix rebuild

Post #4 by homeboi77 » Sat Jul 07, 2018 8:53 pm

Thanks guys. I've got a question about the feedback carb system. couldn't seem to find a definite answer on here. To change out the carb for something a little bigger or aftermarket ive read that I might have to get rid of the computer and change the distributor or it would run like crap, is this correct? because I read somewhere here someone with an 85 changed theirs along with the intake manifold and didn't have to. I've never worked on a carbed engine. I'm thinking of getting a Holley or ederbrok 2 barrel carb. nothing huge

pmuller9
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Re: First Bigsix rebuild

Post #5 by pmuller9 » Sun Jul 08, 2018 11:08 pm

https://www.ford-trucks.com/forums/1018 ... ost9672397
If you change the carburetor you will need to change the ignition system also.

Stock regular cast pistons have a tendancy to break the bottom part of the piston skirt off into the oil pan.
Here is one I pulled from a 1983 300.
https://www.dropbox.com/s/899lcfvwyf004 ... n.jpg?dl=0

A hypereutectic piston will hold up much better.
The 4 highest compression Hyper pistons are:

5/64 x 5/64 x 3/16 piston ring set:
Speed Pro/Sealed power H519P
KB/Silvolite 1186H

2mm x 2mm x 4mm piston ring set:
Speed Pro/Sealed power H674P
KB/Silvolite 3171H

All have a 22cc "D" dish.
The metric ring set has less cylinder drag.

If you deck the block for zero piston to deck clearance, the compression ratio will be 8.8 which is good for 87 octane pump gas with most "Off the shelf" aftermarket cams.

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