Thread: first 390 build

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Originally Posted by riley1996

Hi I'm riley I'm new and I'm just needing some expert advice on my 390 build so thanks for your time and here's what I got

390 bored .30
650cfm carb
4 hole spacer
Probe pistons 1.765 4cc
D2teaa heads milled 65cc 2.09/1.66
275deh cam @.50 213/232. 275/285 514/541 110lsa
.020 gasket
Stroke 3.78
Rod length 6.486
Deck clearence .029
11:19.1 compression
Full length big tube headers
2.5 duel exhaust flowmaster 40s
C6 stock stall
3.25 gears

Cylinder pressure will be high (short cam with 11.19:1 SCR), so make provision for a strong ignition system. Begin budgeting for a higher stall converter. You want to light 'em up at will and I think you'll need a looser converter to do it. I predict that you'll grow weary of paying for 110 pretty quickly. The motor will want more carburetor and a good high-rise, dual-plane intake manifold for max power. Use an Edelbrock Performer RPM part number 7105, 71053 or 71054 and 750 vacuum secondaries carb. Use a 14" x 4" air filter system so the motor can breathe.

Please read through this tutorial to learn about making a flat tappet cam work in today's world....
http://www.crankshaftcoalition.com/w...ips_and_tricks

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Originally Posted by techinspector1

Cylinder pressure will be high (short cam with 11.19:1 SCR), so make provision for a strong ignition system. Begin budgeting for a higher stall converter. You want to light 'em up at will and I think you'll need a looser converter to do it. I predict that you'll grow weary of paying for 110 pretty quickly. The motor will want more carburetor and a good high-rise, dual-plane intake manifold for max power. Use an Edelbrock Performer RPM part number 7105, 71053 or 71054 and 750 vacuum secondaries carb. Use a 14" x 4" air filter system so the motor can breathe.

Please read through this tutorial to learn about making a flat tappet cam work in today's world....
http://www.crankshaftcoalition.com/w...ips_and_tricks

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i plan on buying a Fe engine book, to learn more, and the truck will only be a weekend worrier so the gas wont be a problem, so my checklist is
750 car
High amp Msd ignition,
Perforermer rpm intake
And a 4 inch air cleaner
And a higher stall converter

What kina stall should I get?
And i got a k&n 3 inch air cleaner already on hand would that work ok?

Originally Posted by riley1996

What kina stall should I get?

Converter manufacturers will generally recommend 500 rpm's over the low operating range of the cam. Comp says that your 275DEH cam will make power beginning at 2000, so a 2500 rpm stall converter would be the ticket. I recommend a 10" diameter unit rather than one of those fosdick 12" units with the fins bent over. Not only will a looser converter get the motor "up on the cam" quicker, but it will also prevent you having to lean on the brakes to prevent the truck trying to pull through intersections at red lights due to a higher idle over a stock cam.

Originally Posted by riley1996

And i got a k&n 3 inch air cleaner already on hand would that work ok?

That's gonna be a little slack according to K&N, depending on RPM's. They say you have to deduct 3/4" from the height of the filter to account for the glue that bonds the element to the rubber seals at the top and bottom of the filter, (3/8" at the bottom of the element and 3/8" at the top of the element), so you EFFECTIVELY have a 2 1/4" tall filter element. Assuming a 14" diameter, multiply 14 times 3.14159 and find a circumference of 43.98 square inches. Multiply that by the effective 2.25" height of the element and find 98.95 square inches of effective filter area.

Your motor will be 396 cubic inches (395.36 rounded up due to cylinder wear ). To figure the effective filter area needed, multiply cubic inches times RPM and divide by the constant 20839.... 396 X 5205 / 20839 = 98.91, so your filter will cover the formula up through 5,205 RPM's. At RPM's above that, you would theoretically need more effective filter area. I know this is nit-picking, but I'm trying to teach you something here.

Install an X or H pipe immediately after the collectors and run the exhaust to the rear bumper through mufflers of your choice. Nothing sounds more amateurish and "ricky-racer" than pipes terminated under the truck and reverberating the sheet metal.

As far as selecting the correct pushrod length, Scott Foxwell presents the best tutorial I have ever seen....
https://www.youtube.com/watch?v=o5is9BsH5OU

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