Small block 400 just isn't enough....?

[Hazieview]

Okay fellas I have a small block 400 with a 350th trani and I think .308 gears. My sb400 has a mild cam, performer edelbrock intake, 600cfm edelbrock carb, and dual flowmasters. I dont have performance heads, headers, nothing like that. Only what I listed.

Guys it just aint enough power for me. I thought about getting some edelbrock heads but, for $1,000 or more, how much will that even help me?

My 3 speed 350th trani as we all know shifts really quick so by the time you hit 70mph your running some pretty high rpms as it is.

My .308 gears dont let me leave near as hard as my old .373 posi rearend did which really sucks.

So what should I do? Throw some more money into the engine? Swap my trani for a 700r4? I'm trying to be realistic so where would my dollar be spent in the wisest way?

[xtreme80]

If you're gonna spend a grand on heads, I would try going with a 700r4 transmission first. I think that truck is geared pretty high right now. At that point, you could even switch to a 3.73 rear, and I think you'd be very happy with the power at that point.

I've got a truck probably worthy of a decent quarter mile time if I had a better geared transmission. You could be the same.

[crawdadfox]

I think you could use more carb. 600 c.f.m seems a little small for a 400 w/ a little cam! I would go with a 650-750..

[N2TRUX]

GEARS! No matter what you do those 3.08's aren't going to generate the stump pulling torque you are after. I would go with 3.73's and a built 700r4. After that decide where you need to spend your money, but gears an an OD tranny are going to be a HUGE plus.

[LMDGUY]

my truck has a 400 stock rebuild with a 650 edelbrock carb and intake, mild cam, shorty headers and will smoke the tires. it does have a good tune on the carb. i would spend the money on gears.

[Pyrotechnic]

All that 3.08's are good for is keeping the rev's on the highway back in the days of 1:1 transmissions.

A 700R4 or 2004R will be your best bet. You will also want a high stall converter if you want to go fast.

[shrtbx]

I would go with the gears too. I have a 400 sb in my elcamino bored out .030 over with pretty much the same set up you have and its a burner. I just picked up a grand national rear end and im sure that will make one hell of a difference. You just cant beat a 400 motor they are great.

[82ZZZR]

I really like my 700r4 with my 4.56 gears. I only drive mine in the summer here in Illinois, otherwise I probably would have went with 3.73s or 4.10s

[Pyrotechnic]

I don't think any small block can do very well pushing 3.08 gears. It's almost worse for a modified motor, because the powerband usually ends up higher than stock.

[Hazieview]

the truck will spin that one tire like crazy no doubt. If you stomp the gas your gunna leave some smoke no doubt.

I too think that a 700r4 and a .373 posi will give me what I'm looking for.

I have a .373 posi rearend but it is 6 lug. Sooooo... would it be cheaper to convert it or just buy a new one?

[crawdadfox]

Pull one of the 6 lug axle's if it measure's 31 5/16 from the flange to the end, just use your 5 lug axle's and drum's on the 3.73 rearend!! Presto....3.73's!!!!

[spudz]

This is what I would do... I had a similur setup in my 76 elcamino... loved it....!! I picked up a set of 373s and a factory posi unit and installed in place of the 273ss...that alone was a big difference... But depending how tall of a tire, I would almost go with a 4:10 gear with you truck.... Also if you going to do any driving I would get a 700r4 built for it.. With a few upgrades its a nice trans and has a better first gear then the 350th.. SO now your drive train is awesome you may decide you dont even want to mess with the engine....if you do this is what I would do... Get a set of dart iron eagals... I bought a new fully assembled set for 750 a year ago.. great iron heads... The heads is where the power is it... then step up to a air gap style intake.. some rollor rockers, good pushrods, call comp cams and tell them what you have and what you want to do and they will recomend you a new cam. your going to want like an 800+ cfm carb... good headers, and you will be pushin some serious power!! also you probably going to end up needing a 2800+ stall in your trans...so you are going to need some traction bars or something to help with traction as with all the upgraded drivetrain and increased power...she is going to be a beast!!!

[shrtbx]

i hear that the 3:73 gears are perfect for the 700 r4. I just dont understand why GM didnt make them like that from the get go.

[SRH916]

I am going to second the gears, I went from my 75 with a 350 with 3.08s to my new toy a Gen1 ford lightning with 4.10s and an OD trans. Made a huge difference (since i dont think 1 extra cube will do it).

[1986Silverado]

nobody use camel hump heads anymore? Had a 400sb once in a 84 camaro, had a lunati 492 cam and old camel hump heads......could keep tires on it!

[slugish]

Had a 3.08 in my truck with a similiar set up as yours with a 3peed 350 trans.
trans rebuilt with a good shift kit . 7before that I HAD A 3.73 WITH THE SAME TRANS. (DRIVE THE TRUCK TOO MUCH for taht combination ) Wantd a 7004r also but had spent right much money on the trans & it worked great . So I compromised 7 SPLIT THE DIFFERENCE & put 3.42 gears in . If you have a good 350 already , you may want to consider doing what I DID & USE THE MONEY YOU SAVE FOR OTHER GOODIES.

By the way I TALKED TO A VERY REPUTABLE PERFORMANCE SHOP IN rICHMOND. been in business for 28 yrs & their specialty is fuel systems. they will tell you that a 600 cfm is not enough for a 400. www.aedperformance.com. they know what they are doing. ask for John

[Pyrotechnic]

3.42's are a really good all purpose gear. I had them in my truck for awhile with 28" tires and they were excellent. So much torque, great gas mileage too. The only draw back is that 65-70 is like 3000 RPM. That's perfectly fine if your daily commute requires a few miles of highway driving a day and won't have much ill effect on your motor.

If you have to take on a 4 hour each way highway trip every month like I do, then 3000 RPM for a measly 65-70 MPH on the highway isn't good. That was the primary reason for the switch to 3.08 gears, because 65 with the 3.08's is 2500 RPM.

However one solution if you are in the doing the occasional long highway trip with the 3.42's, is to get a spare set of rear rims and mount some 31x10.5x15 truck tires on them. The 31" tall tire brings that 3.42 back down to what 28" tall tires and 3.08 gears would give you.

I'm actually considering the tall tire setup just because it's the cheapest way out. Another side benefit is that the LT type tires are rated for a heavy load, which is often in the bed when I take these trips. Might look a little billy bob, but they wouldn't be on there other than for trips.

[Albatrossian]

A 700R4 with the first gear that it has puts alot more torque to the back tires than a TH350 or 400.. so if you have 100hp, a TH350 puts about 680 or so ft/lbs to the tires, a 400 puts like 660. A 700R4 puts about 950 ft/lbs to the back tires and has a .70 OD for mileage. It costs a little more, but you get more bang for your buck too.