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March 18th, 2012, 01:59 PM
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Join Date: Sep 2011
Location: Sapulpa, OK
Posts: 5,892
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351M/400 Tips and Tricks
So you've got a 351M/400 in your truck, these were found in 1977-1982 Ford Bronco's and the F-Series. These were pre-emissions smog engines, so basically they were Generation 1 of your smog. The first thing that can be done for the budget minded person is a timing gear and chain swap, what it entails is buying a 351c timing set(less than $25 for LLT Cloyes) and installing this set either(your choice) 2* degrees advanced, or straight up, now keep in mind this is for a stock engine with NO aftermaket cam. You will notice a power improvement, next I see guys replacing their stock 2bbl intake and carburetor with a 4bbl and NOT doing anything to the heads, just because it runs doesn't mean it's at it's peak, I've stalled one more with a 4bbl on it than a 2bbl, engine's are like air compressor's, make it breathe in it's gotta breathe out, so atleast port the heads, have the emissions hump in the head ground down, clean up your pushrods and rockers and check the valve springs and valve's while it's off. After you've done these(budget mindedly) then you can slap on a 4bbl and some headers, I believe Heddman are the best for Bronco's BUT you must remember, longtube headers will put the collector's right at the front of the crossmember, I DO NOT recommend running the pipes under the crossmember, that's asking for a world of problems. You probably have to make an angled turn-up to get over the crossmember then run it back.
If anyone has anymore feel free to add.
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March 18th, 2012, 02:20 PM
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Join Date: Mar 2012
Location: Back to NC one day
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Excellent write up.
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March 18th, 2012, 02:38 PM
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Join Date: Jun 2009
Location: Northwest Georgia
Posts: 15,019
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good going Blue
on a side note
if you can keep your foot out of it a 4bbl will give you better MPG than a 2bbl
point being most 2bbls are about 550 CFM as compared to the primarys on a 4bbl at 350-400 CFM
but that all goes out the window when the secondaries kick in; need a little more speed suck a little more gas
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October 13th, 2014, 11:13 PM
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Join Date: Oct 2014
Location: Westminster MD
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BigBlue....I don't really understand what a timing gear and chain swap will change in my 351M...I guess I mean what is the difference between what is in the motor now, compared to a new set up. I've owned my 1979 F150 for about 4 months now, and I really don't know too much about what was done, but I feel I should make it right.
Also, you mention stalling with a 4 bbl carb, my truck came with a 4bbl Holley, and when I punch it, it usually stalls, or at least hesitates, as I learned to let off the gas when it begins to stall, is that what you were talking about ?
Joe
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October 14th, 2014, 07:16 AM
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Join Date: Jun 2009
Location: Northwest Georgia
Posts: 15,019
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your right a new chain & gear with not improve performance
but some gears allow a 2* advance to; something not felt on the butt dyno
on your stalling
first I would make absolutely sure you don't have a vacuum leak
next check your timing, it may need a little advance
other issues could be a improper float level
clogged air filter
sticking choke
out of adjustment
lastly if unknown mods have been done to the engine, say a cam change then stock jets need changing
then there are other possibilities with the valve train/cam/push rods/lifters
does it ever pop through the carb when you get on it ?
also are you positive it's a 351M?
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For Those Who Fought For It...
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Last edited by JSoko; October 14th, 2014 at 07:24 AM.
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October 15th, 2014, 08:33 PM
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Join Date: Oct 2014
Location: Westminster MD
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Quote:
Originally Posted by JSoko
lastly if unknown mods have been done to the engine, say a cam change then stock jets need changing
then there are other possibilities with the valve train/cam/push rods/lifters
does it ever pop through the carb when you get on it ?
also are you positive it's a 351M?
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First off, thanks for your reply
yes it does appear to be a 351 according to all the indentiyfing info I've read and the VIN
and yes it has popped when I was playing with the carb with the air filter off, a brand new filter that I bought, 14" mustang 4" open element
well I have lots of receipts from the previous owner, here's what the engine work reads
cylinder head surface
install cam bearings
fit pins
valve job
(the following is hard to read, I'll do my best, some may not make sense)
rebore block?
hone cylinders
recondition rods?
clean motor and parts
install f plug
pc heads?
Knwl valve guides?
and as I said, its a 4bbl Holley carb, also has a Holley Electric Fuel Pump
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October 16th, 2014, 06:57 AM
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Join Date: Jun 2009
Location: Northwest Georgia
Posts: 15,019
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the 351M uses cleveland heads, has 8 valve cover bolts as opposed to 6
it also came with a 2 bbl carb
that popping could be timing or pushrods not adjusted proper (to tight, bent or a bad spring)
or it could be the carb
the electric fuel pump may be putting to much pressure on the carb ( they do make an in line regulator that take the pressure down to around 7 PSI) also check the fuel filters ( i would have one befre the fuel pump and one at the carb )
what size carb is it ? a 750CFM is pushing it and an 850CFM is out of the question on your stock engine
I think a 650CFM or the Holly Avenger in 670 CFM would be more than enough
but carb choice has a lot to do with the type cam installed; I would think he used the same stock cam
to answer some of your questions:
hone cylinders= all he did was take the glaze off the wall and installed the old pistons and the old rings (if the ring gap was within specs) hopefully he installed new rings
rebore block? = they line bored for new cam bearings & crank bearings (hopefully it was line bored)
recondition rods? = check for cracks, bend & twist, check bore fro proper size insert
pc heads? = pressure tested / surface checked
Knwl valve guides? = knurling valve guides, is a quick fix as apposed to replacing or reaming for oversized stems
the inside of the guide is raised, then reamed to fit your reworked old valves
sounds like he did just enough to get it to stop using oil and to stop smoking
on a side note if you keep this engine for some time and decide to do more work to it, it's easy to make it a 400; many of the engine parts are interchangable
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For Those Who Fought For It...
Freedom Has A Taste The Protected Will Never Know.
 
Last edited by JSoko; October 16th, 2014 at 07:11 AM.
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