396 bbc build

[bradleyent]

My neighbor is looking to have some work done to his 396 bb chevelle, actually 402. I am not a big block guy and have very limited experience with them. He is wanting to go to an aftermarket head. What are your suggestions for this build. Street use, wants it drivable, likes doing burn outs and going fast. It does have some mild work done to it already, cam, roller rockers, minor stuff. Thanks

[wyrmrider]

which heads (and intake) now
oval ports- square ports post up the current head number
what pistons? the dome shape/ valve clearance notches will determine which other heads can work
one option is to port his current heads and use the money saved for a big stroker crank
is he going to leave the short block alone?
need all the details- like trans, what cam? headers?

[vortecpro]

I wouldn't use any aftermarket head on a 4.125 bore engine. I would find a competent machine shop to do a set of 290 215 or 063s that would work the best.

[novadude]

I wouldn't use any aftermarket head on a 4.125 bore engine. I would find a competent machine shop to do a set of 290 215 or 063s that would work the best.

Just a curiosity question... are the castings listed above still readily available, or are good closed chamber iron heads getting scarce? My Dad has a '69 265 hp 396 with the '148' larger chamber heads, and a set of rebuilder cast pistons in an undecked block. Very low CR. I am trying to talk him into some upgrades, and I am thinking going to a 100cc head might be the best bang-for-the-buck. I haven't started looking for used heads yet, so I am wondering just how hard it is to find the 66-69 closed chamber ovals.

[machinedave]

Has he considered changing to a 454 block? I know its a much bigger undertaking but it could easily be worth 60 HP over the 402. It is hard to build compression from a 402 without going to a big dome piston. The current pistons in the 402 may not work with some aftermarket head chamber shapes.

[RevTheory]

How about these AFR 265s? http://www.airflowresearch.com/index.php?cPath=68_111

What color is the car?
If it was painted, what color was it before? Primer?
Bench seat or buckets?
Denim jeans?
Mail box in front of the house or gang box?
Gas tank filler on the left or right?

[D.S.R.E.]

I was brought a 402/408cid bbc last year to fix some valvetrain issues and see if I could make it faster than it was
I am partially biased as I don't like 396's at all, you are much better off getting a 454 imho
Anyway this setup is how it was brought to me
70 402-408cid big dome pistons from the 70's actual compression was 10.8:1 with 121cc chambers
Huge solid roller cam 278-288 @ .050 .690 lift 110 lsa backed up 4* for p-v clearance
aluminum pro comp heads 320cc intake runner
big single plane and 1050 dominator with 2.25 primary headers 4" collectors
its one of the worst combinations of parts I've ever seen
it was in a 3000lb 67 Chevelle race car and ran a best of 11.17 @ 117mph
the best I could get it to do was 10.83@121mph
total dog but if you do research you will not find many faster Natural aspirated 396's
Imho its the most over rated engine chevy ever built
and if I were going to spec one for street duty here is my parts combo
4.185 bore block zero decked, scat 4.25 stroke crankshaft for 467cid
9.75:1 compression with iron heads 10.6:1 with aluminum
custom hydraulic roller cam 236-244 .636i .638e 112lsa 108ilc
roller rockers, factory closed chamber heads fully ported but not hogged out
ported factory aluminum hi rise or RPM air gap with a holley 850 ultra hp
1-7/8 primary headers, tight 3500 continental stall and 3.55 gears
that should be an 11 second street car under 3500lbs and will make 475-500hp 525-540tq jmho

[rfoll]

As mentioned before, getting compression is a problem with these motors. Think in terms of a 400 sbc with a combustion chamber volume of no less than 100 CCs. I used a TRW 2240 in mine, and with a 0 deck, .028" head gasket, and 106 cc head, compression came out to 8.9:1. The bath tub shapes are not the best shaped chambers. The up side is the flow available in BBC head selections. I have heard the 96 and later 454 vortec head, (it has a small combustion chamber), works well on a 396, but piston domes might need a massage. The 454 crank and the KB piston to go with it will help solve the compression problem, and you gain 30 plus inches.

[wyrmrider]

saw 3 454's at last months pick a part half price sale last month- told the guys about them- not hard to find
if this is not some kind of matching number deal building a 396 is a PITA

[bradleyent]

The only reason he is wanting to keep what he has is because that's the exact engine that came in the car. I am in no way shape or form big block smart. I have freshened a few of them and that's it. No more than replacing parts for parts. He loves it the way it is right now, he just wants to see if we can get a little top end out of it. This car will never see the drag strip. While the engines out we are going to put in a tremec 5 speed and do some other tunnel work etc. The main thing he will be doing with it is smoky burn outs at the end of my driveway by our gang box mail set-up. Haha

[bradleyent]

There are no trustworthy head porters in my area that I am aware of, who would you recommend when I talk him out of aftermarket ones!

[PackardV8]

My Dad has a '69 265 hp 396 with the '148' larger chamber heads, and a set of rebuilder cast pistons in an undecked block. Very low CR. I am trying to talk him into some upgrades, and I am thinking going to a 100cc head might be the best bang-for-the-buck. I haven't started looking for used heads yet, so I am wondering just how hard it is to find the 66-69 closed chamber ovals.

We just had a couple of sets of 396" heads and intakes come in last week. What casting numbers are the closed chamber or any just worth having?

[GOSFAST]

Using the 396" platform, 10.5:1, with some older original (over-the-counter) G.M. aluminum heads, and based on a flat-tappet cam, you can make 500+ HP. You will also see over 460 Ft.Lbs. Torque.

If you go retro-hyd roller you can get to 550 HP. Then you have the 454" crank option (internal-balance) and the numbers go higher! And it all still looks stock to a point.

Thanks, Gary in N.Y.

P.S. The issue we find with "shopping" for the early closed-chamber oval heads is they are much more valuable to the resto guys. Dated correctly the 215's, 290's, 390's, etc. will bring in the neighborhood of 1000.00/pair, and this is bare, no parts! Some dated square-ports bring even more.

[rfoll]

It would seem obvious that in the same displacement range a big block with canted valve heads would have a large advantage over a small block. However, for the price of a nice pair of small block heads you can buy one nice big block head. If you are going to spend big block money, it makes sense to use a large displacement big block.

[Alan Roehrich]

You can use the Edelbrock oval port that is angle milled by Edelbrock to 100c, it's part number 60489 for the bare head. A closed chamber small dome Speed Pro piston will yield plenty of compression, and the head will flow as well with a decent valve job as most of the "ported" cast iron oval port heads you see. Or use one of the other Edelbrock 110cc chamber oval port heads with a piston with a bigger closed chamber dome. I've had some really good success with those combinations in some fairly hot street cars. All of them with the stock 3.766" stroke.

The downfall of the Speed Pro pistons is the lack of piston to valve clearance on the intake valve, so if you want a really stout engine, use the head with the bigger 110cc chamber, and get a set of JE closed chamber 396 pistons.

You could spend $3,000 on a set of cast iron oval port heads and still not get the flow you would get with a set of the Edelbrock heads with the correct valve job and some minor touching up.

You do not need a stroker kit or any high dollar stuff to make pretty big power with a 396. My problem with a stroker kit is that the bore still shrouds the valves, so the head still doesn't get to flow, you just spend more time pulling on the head, it just creates pumping losses. If you want 468 cubic inches, just start with a 454, you'll be around 40-50 HP ahead of the small bore engine for less money and less work. Because of the ease with which you fill the cylinder on the bigger bore, you will not need as much cam to make more HP, and you'll be making about as much torque, too.

We race both the 396, and the 427. I can tell you that the bore size really hurts the 396, and you cannot make up the difference with stroke and cam. Given the valve size and orientation, you simply cannot make the head flow as much on a 4.175"/4.185" bore as you can on a 4.310"/4.320" bore.

The open chamber head does hold a small advantage over the closed chamber head. For the vast majority of street cars, you will never see it. And it is far easier to make enough compression with the closed chamber head. There are a lot of real fast cars with closed chamber heads, and a lot of real fast cars with 396 based engines.

One thing you can do to help a 396 based engine, especially if you use the Edelbrock head, or one like it, is to notch the top of the cylinders the way Chevy did it for the 396/375, and then use a set of Moroso 0.030" offset dowels to shift the exhaust valve toward the cylinder wall. The Edelbrock head has far superior exhaust flow, so much better that you really can't hope to make an iron GM head come close without welding. Shifting the head so that the exhaust valve will not really hurt the exhaust side, but it will really help the intake side. Just be sure you check the clearances.