ford highboy 390 engine rebuild
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Junior User
Joined: Nov 2005
Posts: 95
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From: Northern UT
ford highboy 390 engine rebuild
I have a 76 ford truck with a worn out 390 I am going to be rebuilding. Any sugestions as to how to maximize the power for pulling a 32 foot fifth wheel without compramising performance or fuel milage I dont want to spend alot either I currently have an edelbrock intake manifold and carb.
Elder User
Joined: Oct 2005
Posts: 907
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From: Citrus Heights, CA
The only thing that distinguishes a 360 from a 390 is the crank, rods, and pistons. The heads are the same.
In either case, headers and an RV cam (assuming it is running a stock cam now) should significantly increase the grunt.
In either case, headers and an RV cam (assuming it is running a stock cam now) should significantly increase the grunt.
Cargo Master
Joined: Aug 2000
Posts: 2,931
Likes: 12
From: SW Michigan
390 trailer puller
76, you might want to check out some other shops. If the shop said 360s and 390s have differant heads, they don't know FE fords. The 360 and 390 use the same blocks, heads, intake and exhaust manifolds. There is no way to know for certain unless you measure the stroke. Even if you have a 360, that is not that terrible, you can change the crank and rods. 390 cranks are available and not exspensive, and 410/428 cranks and strokers are available if you want to spend the money. The 390 can do what you are asking, but make certain you really have a 390, and make certain you choose the right pistons for it. 999 out of 1,000 390s are built with the wrong pistons, and many owners don't know why their engine has so little power and gets bad fuel economy. Careful choice of parts and an RV cam and headers and you'll do fine. DF, @ his Dad's house
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Postmaster
Joined: Jul 2003
Posts: 3,934
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From: iowa
df, is right on with the piston selections, many pistons have a poor compression ratio. The advertised numbers optimistic, the worst deal is using 410 pistons in a 390. I can't think of the part number off the top of my head though.
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Post Fiend
Joined: Jan 2003
Posts: 8,600
Likes: 4
From: Iowa
The worst would be using 410 pistons in a 360! ACK!
Anyway, here's the parts I would use to build a towing 390:
Silvolite 1130 pistons
Mr. Gasket .020" thick steel shim head gaskets
Crane 343901 camshaft
4 barrel intake and carburetor (your current Edelbrock setup should work fine)
Headers and dual exhaust
There's a very good explanation for each of the above components. Ask if you want me to explain it.
Anyway, here's the parts I would use to build a towing 390:
Silvolite 1130 pistons
Mr. Gasket .020" thick steel shim head gaskets
Crane 343901 camshaft
4 barrel intake and carburetor (your current Edelbrock setup should work fine)
Headers and dual exhaust
There's a very good explanation for each of the above components. Ask if you want me to explain it.
Post Fiend
Joined: Jan 2003
Posts: 8,600
Likes: 4
From: Iowa
The 1130 pistons are regular cast with a small dish. For his application, the stock heads will be more than adequate. For stock heads, the steel shim head gasket is the one to use.
If you're going to be using aluminum heads, the steel shim head gaskets will not work. You'd have to use a composition head gasket, like the Fel-Pro.
Fel-Pro = .041"
Mr. Gasket steel shim = .018" - .020"
Also, you'd probably want to change the piston selection for the different gasket. If you're using aluminum heads and the Fel-Pro gasket, you'd want to use pistons with a higher compression height and no dish, like the TRW L2291. This will give slightly more compression than the iron heads, steel shim gasket and 1130 pistons, but this is OK because the aluminum heads can take more compression without worrying about pinging.
TRW L2291 = 1.776" compression height
Silvolite 1130 = 1.760" compression height
Now you COULD run the steel shim head gasket and the iron heads with the L2291 forged piston, but then the compression would be way up there, and he might have a problem trying to tow anything. But that is the way to go for street performance and a bigger cam like the 343941.
If you're going to be using aluminum heads, the steel shim head gaskets will not work. You'd have to use a composition head gasket, like the Fel-Pro.
Fel-Pro = .041"
Mr. Gasket steel shim = .018" - .020"
Also, you'd probably want to change the piston selection for the different gasket. If you're using aluminum heads and the Fel-Pro gasket, you'd want to use pistons with a higher compression height and no dish, like the TRW L2291. This will give slightly more compression than the iron heads, steel shim gasket and 1130 pistons, but this is OK because the aluminum heads can take more compression without worrying about pinging.
TRW L2291 = 1.776" compression height
Silvolite 1130 = 1.760" compression height
Now you COULD run the steel shim head gasket and the iron heads with the L2291 forged piston, but then the compression would be way up there, and he might have a problem trying to tow anything. But that is the way to go for street performance and a bigger cam like the 343941.
FTE Leadership Emeritus
Joined: Jul 2002
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From: Long Island USA
I ran a big cam like the 941 (somewhat different), 11:1 with the L2291F's, and my '74 highboy with 4.10 gears and 33" tires picked up and hauled butt when it had 4000lbs of scrap cast-iron boiler in the bed.
I was afraid to get on it too much in 2nd gear (435NP) ... and yes, I got it rolling in 2nd gear, not using the granny gear ...
Although I would imagine it would be a little rougher to get 8000+ moving.
I'd suggest a lower compression ratio than what I used, so the L2291F's are probably out of the question.
I was afraid to get on it too much in 2nd gear (435NP) ... and yes, I got it rolling in 2nd gear, not using the granny gear ...
Although I would imagine it would be a little rougher to get 8000+ moving.
I'd suggest a lower compression ratio than what I used, so the L2291F's are probably out of the question.
Senior User
Joined: May 2005
Posts: 111
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From: Houston, TX
I am going to repowering my M715 with a '76 390 (with NP435) and I am wanting to meet the same requirements as 76FordFan (low end torque and decent fuel economy). What compression ratio will the Silvolite pistons and Mr. Gasket steel head gaskets yeild? For my engine, I was planning on using an Edelbrock Performer with either a 600/650 cfm Holley/Edelbrock carb or a 670 cfm Holly Truck Avenger (a bit pricey, though....). Rusty, is that Crane Cam an RV-type grind or a little hotter than that? I was planning on using a DuraSpark distributer and I have the "blue" module. The guy that I got the engine from told me that I might need the "brown" module. Any suggestions for the ignition system?