[jmichaelre]

I have a 69' 396 I would like to rebuild for my 4x4 truck.

Block casting 3935440
Head casting 3919840


This will be a street driven and in front of a 700r4. Obviously I would like a happy medium between horse power and drivability. I would prefer to keep the existing 3.42 rear gears, but if need be at that to the list.

My question is what kind of cam profile, intake, piston, and carb selection would you guys suggest?

[mud.man.rj]

Not to sure on your compression ratio without going into my books in garage, but to build it with some good useable power but not to overboard I would use a Comp cam 4x4 Extreme hydraulic x4270h ( part#11-239-3) has a lift of .544int/.564 exh. with a lobe sep angle of 111 degrees. It would work real good with an Edelbrock performer #2161 or Performer Rpm #7161. The performer works from idle to 5500 and the Rpm works from 1500 to 6500. With an aoto and no stall converter (stock) and that gear ratio I would prefer the Performer with a manual trans the Rpm intake will work great. As for a carb, most car people who like the edge of performance use a Holley but building an all around truck that will still perform I would use the trouble free 750 electric choke Edelbrock carb #1411 or Thunder series better for a bouncy 4x4 #1825(650- good up to 400hp) Nothing wrong with that gear ratio as the components listed will work great with the Big block torque so you won't have to run to high of Rpm's. I run a 530hp Ford 460 and have 3.50 ratio with a 38.5" tire and a 2700 stall converter. Without the converter I would have to drop tire size a bit unles it was a manual trans. An auto has a bit more drag. The 396 cyl heads are not as good for flow as the 454 for instance but with a little bit of porting really come to life, but if not running a lot of rpm you will probably not notice.

[Ron Golden]

The major problem I see is the 3.42 gear with a 700R4 tranny. The 700R4 has a 30% overdrive and in 4th gear your final overall drive ratio will be 2.39:1. At 70 MPH, with a 28" tire you'll be turning 2007 RPM. Generally, an engine with a cam and performance carb doesn't like to run at that low of an RPM. Taller tires will make the problem worse.

Something to think about.

Ron

[mud.man.rj]

Remember a 700r4 has a lower gear than a t350/t400 so leaving the line will be easy and 4th gear isn't that tall, besides it is big block torque not a small block so it will pull itself easily, but all depends on actual tire size as a stock tire of 29" going up to a 35" tire is actually only 3" taller(center of axle out) so not a lot of tire and the cam is not a big cam but perfectly set up for torque and some Rpm with intake and carb recomended. All depends on tire size. Over 35" the regear diffs, 35" and under will work fine w the 700r4.

[Ron Golden]

With a 35" tire the rpm at 70 mph will be 1606 rpm and I'll guarantee you the driveability will be terrible. I've discussed this with Holley Tech and its a common problem. However, you can run the tranny in 3rd gear and it should work OK.

Granted the 396 will have plenty of power for acceleration but the 4th gear driveability will suffer. Been there, done that.

Ron

[mud.man.rj]

The only problem is that we don't really know if he is running a 35" tire, we ara assuming, not cool on our part, but have just had the same truck with same setup and just sold it to pay for a Mudracer and it worked just fine every single day and still is and also depends where the truck is used. It is hilly here and works great. But lets get some more info, hopefully the owner will look at the site soon.

[jmichaelre]

Thanks for the info........I looked up these heads and they actually don't look bad they are closed chamber oval port heads used on 396 and 427 engines at the time. will 100.9 cc combustion chamber.

I tore it down today and it has domed pistons without valve relieves and has been bored 30 over. I read somewhere earlier that some of these early 396 blocks could be bored out to a 427.....but I'll have to do more reading on that.

As far as tire size I'm running 30s right now with a 355 and I have no problem spinning the tires.....

Another question I forgot to ask is what is the max lift you can safely go on the stock rocker setup?

[mud.man.rj]

Nice so you have more compression than stock, and are good heads listed. So easily a 33" tire but will work with 35" at the most. The cam listed is about the max lift with stock valve springs, the arms unless a different ratio don't make a difference, but stock arms are not great quality so the safe lift is still what I listed without overstressing them. Sounds like it will work out to a nice build.

[mud.man.rj]

At least with the .030 overboar your are closer to a 427 bore, the stroke is the same for both at 3.76 and the bore for the 396 stock is 3.094 and the 427 is 4.250 but now you are at 4.024 so still less but basic bore size on a dyno from stock to .030 over doesn't yeild much for a horsepower difference on any V8, but stroke deffinitly makes a big difference. Thats why a lot of engines today use a 350 with 400 crank to build a 383. Major power difference but not much with a 350 at .030 to a 355 ci.

[jmichaelre]

Thanks for your help.......I have one other question......when it comes to compression ratios on big blocks can you run a little higher compression than small blocks and run on 93 octane? The reason I ask is because I was told on my small block build to not go over 9.5 to 1.

[mud.man.rj]

It's not great to go much more than a 10.5 comp ratio today due to lousy fuel, I checked the block # which is a 1969 block rated at 350-375 hp depending on cyl heads but the head # you gave is for a 1965-1969 rectangular port closed chamber head which is a real good head, so would be at least 375hp but not a great street head because lacks good flow at low Rpm's. Good on a car not so good on a heavy truck. Better to have an oval port head for all around use and there are 2 different ones of those a large port(very desirable) and a small or peanut port. Hav ported peanut port heads with good success but the larger port responds even better. If you build it like it is, it will go like hell but lack abit of bottom end so in an auto truck or anything heavy you would need at least a 2500 stall converter.

[jmichaelre]

Sorry I posted the wrong head number it should be 3904390

[jmichaelre]

Sorry I'll get this right one of these days.........I was looking at the wrong heads.......they are actually

3872702

[mud.man.rj]

Whew, that is a 1966..427 closed chamber oval port head, exactly what you want, will work good with that cam and good enough flow to step up to Rpm intake if wanting a bit more higher Rpm useage. Would use a 750 carb. One more thing is do yourself a favor and at least run a roller tip rocker, they make such a difference on botom end and gas mileage when use and at least are more stable for abuse. Not expensive either.

[jmichaelre]

Roller tip as in the type I've seen on vortec style heads?