five7kid

iTrader: (14)

I'm finally getting around to my winter project of doing the SA-porting of the 396 heads. I keep hearing that bowl work and general flow path smoothing does wonders to factory BBC heads.

Specifics: 3872702 castings, oval port, closed chamber, 2.06"/1.72", 98cc, 260cc intake. Previous work included hardened seats and bronze guides. According to a source more comprehensive than mortec.com, these are some of the better oval port/closed chamber factory heads. Looking down the ports compared to SBC heads, looks like caverns - "Do I really need to port these things?" But, I figured gasket match, polishing, bowl work (doesn't look like much is needed), and guide smoothing anyway. Sound reasonable? For the time being, I do have a fairly mild cam (270 advertised, 214 @ .050, .501" single pattern).

2nd question: Should I gasket match the intake? Again, fairly mild setup; would the anti-reversion effect of not matching the intake be more beneficial than the smoother flow of gasket matched flow path? Any benefits from modifying the plenum divider?

Some day, a bigger cam, Stealth intake, and higher stall converter are in the plans (not to mention the block, casting 3855961, was also used for 427's...). But, probably not this year.

Vader

5-7,

Same philosophy, larger ports (and displacements). What is the intended RPM range? If it isn't going to venture into the 6's very often, the port matching may not be a necessity. Rumor has it that it may not be worth a lot of gain, as long as the upstream ports aren't larger than what they're feeding. Then again, every little bit helps, but I've seen a lot of aftermarket intakes that have smaller ports.

F-BIRD'88

Upgrade to larger 2.19 x 1.88 valves.

You'll want to deshroud the combustion chamber quite a bit
for the bigger valves. take a look at the open chamber heads to see what and where. You don't have to open the chambers quite a much as the open chamber heads but it will give you an idea.

The oval port heads really come alive with a thourough porting and larger valves. They want valve lift after porting.

The more valve lift the better.
Big blocks also favour mechanical lifter cams because of their
heavier valvetrain.

The factory 396/375 hp L-78 454/450 hp L-S6 cam is a
easy yet powerful cam to live with on the street.

The Comp Cams Magnum 294S works great too.
Replaceing the stock valve springs is a must.

five7kid

iTrader: (14)

I really wonder about larger valves. At most, I'll feed 427 cubes sometime down the line. On a 396, cylinder shrouding is substantial. I will consider them when the block is in the machine shop for the 4.250" bore (not this year, I'm afraid).

I should have mentioned springs. I currently have 502 crate take-off springs & retainers from Competition Products. My plan was to reassemble this time with Comp Cams springs they recommend for the 282 duration, .561" lift solid cam I've got my eye on (I think the 294 would be a little too much). That would put me in the 6000 RPM range (perhaps slightly higher with the smaller displacement).

Most BBC aftermarket parts and information assume 454 or larger. Well, that's just not in my wanna-be budget. But, I'm sure I can improve my current smaller displacement performance, but I don't want to assume "big-Rat" approaches will work on my "baby-Rat".

SSC

I used 2.19 1.88 race flow valves in my 402 build also did alot of porting on the heads, closed chamber also. I got a plate from Weiand to adapt the car BB stealth manifold to the tall deck block that had larger opening so it made a good pattern to follow. I took alot of meat from the intake side and only opend the exhaust up a little bit to match the headder gaskets/headders but alot of meat was taken out of the port itself. The combuston chambers were opend up quite a bit too. I just got the engine in, sounds nasty and even though I havent romped on her its got alot of go. The question is it worth it, Id say yes. Just watch out for a fire mist blue 76 short box this season, If I can make it to Bandimer.

F-BIRD'88

57 if your 396 was bored .030 over for the TRW pistons it is already unshrouded.
The closed chamber head is the thing that shrouded the larger valves. But once the chamber is tweeked, look out!!!
Big blocks really need the bigger valves ( to match the bigger ports) trust me. 396 or 454 doesn't matter.

the 294s is not too big. you will be shifting the car at 5800/6000. Shouldn't need any more.

the 282s is a nice cam but the 294s is way better.

How about this one CB-280S-10 #11-551-5
280-285 244/250 .571/.603" 110LSA

proven winner and right down the middle of our two choices.
Good street /strip choice. Wish it was available back when I was messing with big blocks...

five7kid

iTrader: (14)

Hmmm, a cam for "Jet boat with A or B impeller. Sking, pleasure, performance."

You really think moving the cylinder wall out .015" would unshroud larger valves? The factory notched the cylinders as it is. The larger valves would move their edge out .065", the 4.250" bore would move the cylinder .063" from where it is now. Sounds like large valves would be more shrouded with the larger bore than I am now. Granted, the portion shrouded by the cylinder wall is only a part of the total flow area.

I think I'll wait on the larger valves. Right now, budget doesn't support buying new ones. Or cam & lifters for that matter (because doing that will drive other expensive changes). I think I can handle springs now, so I'll get something that will work with the current cam and support future dreams.

I plan on being able to drive this car to my high school reunions (since I drove it to my high school graduation), so I don't want to go hog wild here. I also don't want to do too much now that will hurt me before I get the cam/intake/converter/bore. But, I believe some improvement is available without them.

Any thoughts on modifying the intake plenum divider?

SSC, if you make it up to Bandimere and I don't find you, look for me. I plan on Friday and Saturday ET series, Club Clash, Super Chevy, at least.

five7kid

iTrader: (14)

Took pic of intake ports:

five7kid

iTrader: (14)

And manifold ports:

five7kid

iTrader: (14)

I pulled the rockers off tonight. I didn't like the way the retainers/keepers looked on the intake valves of one bank - less stem above the keepers than the other side, looked a little cocked. Wondering what's waiting there for me (keeper problem? valve stem problem?). Might explain its lack of desire to rev above 5500 RPMs last season.

The intake valves are the original '66 325 horse parts. If bad, I might end up doing that larger-valve-thing now, after all...

Riley's35089rs+

Uh Oh ! Here goes the..I'm just swapping out the springs...whats that? Uh oh! Looks like I need a new valve...shoot might as well replace all of them..shoot, sure could use that new cam to work these new valves...oh no! Now I need a higher stall...on and on and on $$$$$$$....

five7kid

iTrader: (14)

You been talking to my wife?

F-BIRD'88

If the keepers are pulling thru, it is not likely the valves.

Replace the retainers and keepers.

Your motor will be all done by 5500 with that 'lil RV cam.
Could even be valve float ( springs).

If you want to buzz it that high then get the above mentioned cam and appropriate valve train. Then you'll see the difference.
Hang on!!!! He hee hehee.

The 'lil 282s will be all done by 5500 too.

Nice pics,,, ok rip those heads off and port them up.

With pics of course.....

five7kid

iTrader: (14)

Sometime after I actually woke up this morning, I remembered when I had the heads done (bronze guides, hardened exhaust seats & valves), they also replaced four intake valves. Duh, guess which ones?

The retainers were installed about 1/2 way through last season.

I'll get the heads off and apart, see what I find. If it is those 4 valves only, I'll probably just put in some replacements for now. I will look over the retainers and keepers very thoroughly, you can be sure.

The cam is supposed to be good to 5800, according to the manufacturer. Weiand says the intake will support 6000. I'd sure love to find some 1-7/8" primary headers that fit the engine/chassis (Summit says the Patriot headers won't fit with 1" forward side mounts, which is what I have).

five7kid

iTrader: (14)

Funny, the retainers/keepers/stems didn't look bad after the heads were off the car. Must have been the lighting. The springs are still getting replaced, though.

This is the first time I've had the heads apart myself. The bowls look fine, actually more than 85% of the valve diameter (what SA says they should be), need the 2.19/1.88's so they will be 85%. But, the intake guides really stick down into the ports (as you can see in the pic above). Should be some improvement by reducing them. Otherwise, remove a little casting nubs here & there, polish as appropriate, there really isn't much to do to them (unless gasket matching is worth anything - can't be w/o the intake being opened, too).

The exhaust ports have a little nub on one wall, in the same place on all of them. Any idea why that would be? Think I'll go ahead and grind them away, but my headers are already smaller than the ports (got to find some 1-7/8" primaries!).

I'm planning on taking the heads to a fellow racer Friday, who's an engine builder in real life. Ask him what I should do to them, probably have him apply a 3-angle valve job, etc.

five7kid

iTrader: (14)

Here's a pic of the chambers w/o valves. Note the lack of any material below the seats. The port is wet because the valve seals just weren't doing the job (I think Perfect Circle Teflon are on the horizon).

I tried to get a picture of the nub in the exhaust port, but it just didn't show up well.

Vader

Eeeew! Open chambers? Or am I just seeing the deposits and outline of the gasket print?

Since your lighting it THAT bad, you oughtta just throw it all on a trailer and send it my way. Over a 100' of fluorescent will fix that in short order.

I promise I'll get it back shortly. Of course, there could be extensive "testing" at 735' or elevation...

As long as the intake is off and the grinder is available, it can't hurt to match up the intake to the runners, and taper that back into the manifold a little. A little more overall runner volume shouldn't hurt a larger displacement like that at higher RPM at all.

And if your header primaries are already smaller than the exhaust ports, you have about eight other issues to resolve, but you probably already suspected that.

Vader

5-7,

Never mind. Mr. Paint Shop and I cleaned up the photo a bit, and added some lighting. Your valve bowl diameters look good with those valve face sizes. I can see that the guides could use a little trimming, but other than that, nothing in the photo looks like a big impediment. There's probably a little room to raise the bowl and port roofs a bit, but it's hard to tell from one photo. Are your valves undercut?

Instead of three angle seats, you might want to ask your machinist about back-cutting the valve after the 45° grind angle and a radius on the front face/margin area of the valve for a little more flow. You're not shrouding too badly on either of the valves, but larger faces without some chamber trimming could put you into that zone.

five7kid

iTrader: (14)

Those are closed chambers. The gaskets were generic BBC, so they would fit 4.25" bore as well.

I just talked to the engine builder, he echoed what you said about porting from what I could tell him over the phone. The valves are stock (4 literally). I briefly mentioned 3-angle to him, I'll see what he says about your back-cutting suggestion. The Perfect Circle seals are a must. He said he'd check the springs to make sure they're really a problem (says he's seen great variance in factory spring quality/sources).

I talked to Patriot (Pertronix) last night. They said they just mocked up their headers on a car with 3/4" forward mounted engine. I've got 1" forward - they are only saying they wouldn't guarantee there wouldn't be any interference. I think I can live with that. Got to be better than what I've got now. Builder suggested welding around the outside flange/primaries and grinding them open to match the ports at a minimum, but the larger primaries should be a better way to go.

Of course, last night after I came in from the garage the motor in the clothes dryer went up in smoke - you know you can get a good Holley carb for what a gas clothes dryer costs...????

five7kid

iTrader: (14)

Took the heads to the builder Friday. He tanked them, checked for cracks, checked the guides, tested the springs, checked for flatness. He says, "Get new springs." Otherwise, everything looks good.

He also said to gasket match the intakes, remove casting flash/nubs, round off sharp edges, open up exhaust ports to the header gasket. He didn't think polishing was worth much, but didn't tell me not to do it.

Also said bigger valves won't help unless a much larger cam is installed, and even then the stock valves will be fine for a 396. Nor would reducing the guides help enough to make it worth the time. So, I'm about to get the die grinder out and get started. Then, he'll grind the valves (shouldn't take much), reassemble them with PC teflon/nitrile seals.

In the past, I had hesitated to talk to him about the engine, because he races a roots-huffed 383 in a '37 Chevy pickup. As I was loading the heads back into the trunk Friday, he said, "I always ran big blocks until I built the '37. The frame was too narrow for a Rat, so I started building small blocks." He started racing before ET meant anything...

Riley's35089rs+

Some guys have all the luck.....new springs......chickenfeed!!! Guess you can get that new dryer and fix your car .

five7kid

iTrader: (14)

Actually, all the dryer needed was a new motor. $109.67 including next-day shipping, hour & a half to get it in, works like a charm again.

The springs are only a couple of bucks less than that. He convinced me to go with the 924-16 Comp double springs, which will cover me when I do get that solid cam some day. The headers will probably have to wait, though. Guess I'll find somebody to weld around the flanges on my current headers and grind on them for now.

Riley's35089rs+

Yep...headers are on my wish list right now also.....the Summit Brand wont hold up for too much longer....