small-block intake questions

[roadracerjeff]

I have a '67 273 Hi-Po with factory intake 2536771. This is the CA emissions intake. My first question is what makes it so? What is different about it from the 2536536 non-CA emissions intake?

My next questions are in regard to the tin cover on the bottom. It's held in place with 2 press-fit pins and has 2 small holes in it. I know there's crud up in there, so I am inclined to shear off the pinheads and toss it. What purpose does it serve and am I okay with tossing it? It's beneath the carb so my guess is to help keep that area cooler, but I can't see how it would do much in that regard.

[Slingshot383]

It would help with hot oil splash. You can by a galley pan that does a better job for small blocks, you just have to put it on before the heads as they are what traps it in place.

[340_GTS]

The tin plate is to keep the oil from vaporizing/cooking when it hits the hot exhaust crossover passageway under the carburetor. If you are keeping the crossover, it is a good thing to have on there. I have never seen a valley cover for a small block LA motor. I can't see what good it would do, really.

[aarracer]

Originally Posted by roadracerjeff

I have a '67 273 Hi-Po with factory intake 2536771. This is the CA emissions intake. My first question is what makes it so? What is different about it from the 2536536 non-CA emissions intake?

My next questions are in regard to the tin cover on the bottom. It's held in place with 2 press-fit pins and has 2 small holes in it. I know there's crud up in there, so I am inclined to shear off the pinheads and toss it. What purpose does it serve and am I okay with tossing it? It's beneath the carb so my guess is to help keep that area cooler, but I can't see how it would do much in that regard.

The rivets are twist lock type that are pressed in an undersized hole.

You can probably turn them out with some vise grips. Once the plate is removed you may find the underside of the intake manifold completely saturated with carbon buildup.

The holes can be threaded to 1/4" nct and bolts put in to replace the rivets. I wire lock the ones I have done.

340-gts - I have seen a tin valley cover produced many years ago, but I never saw a use for the one produced. The manufacturer called it a lifter valley windage tray.

The best lifter valley oil control device I have seen (Diamond Racing (the piston people produced it)). is a single stip of 1/8" x 2" aluminum flat bar running the length of the lifter valley covering the three oval holes in the block you can see the cam through. It blocks the camshaft area windage from throwing oil upward and it helps direct drainage back to the rear of the lifter valley down through the distributor drive area.

[roadracerjeff]

Many thanks guys. Also, I've found the answer to what distinguishes the CA emissions manifold from the non... There is an extra section on the back of the manifold between the rear intake ports. It does not connect the ports in any way. Rather, the bottom simply dips down to seemingly catch some hot oil splash. That's ironic if not plain stupid given the tin tray in the middle.

Regarding the exhaust cross-over, I'm doing a resto, which is the only reason I'm using this intake, and will have the factory carb with choke rheostat in place (yep, I have a new one, two in fact, pricey little part on e-bay...). Do I need to use the ex-x-over in order for the rheostat to function properly? I would think not, only that it will take a little longer to warm up the car and kick in the rheostat -am I correct?

One more ? Does anything go in the valley for the rheostat? Oil maybe? I was thinking it's just open air since there's not much of a seal to it.

[340_GTS]

I do not think your stock choke will work at all without the exhaust crossover. The area below the choke spring (a bi-metallic spring... not a "rheostat") will never get hot enough to expand the spring enough to correctly open the choke. You also need to make sure that the flapper valve on the RH exhaust manifold is working correctly also, because that is what directs the correct amount of exhaust flow thru the crossover. (The "valley" you speak of does not get filled with anything.) May I suggest buying a factory service manual? Reprints are easily found and well worth the price.

[roadracerjeff]

Thanks and I've got the manual. I was just trying the chat first, call me lazy. Also, there's plenty of times when the manual presumes that the user knows certain things. It's a factory service manual for a dealer tech, not a Hayne's manual for the DIY'r (that's me). Thanks again,

[Dart 360]

Fitting the shield as described above over the cam is good, removing the tin splatter shield from the base of the manifold is a personal choice.
Blocking off the exhaust cross over is a good idea but if you are going for a resto look then you will need to leave the exhaust valve in place but you can pin it open so it won't work. You will then need to adjust your choke so that it doesn't stay on or make sure that when the engine is at operating temp. it is fully open.
If you are running an auto in a cold climate you might have to let the motor warm up before driving as the engine might stall.
When I disconnected the choke on my 360 a few years back I was fortunate to have a driveway on a slight inclining down and then didn't have to stop for several miles giving the motor time to warm up so it wouldn't stall.

[roadracerjeff]

Okay, progess has been made. I tried getting the rivets out per aarracer's info ("The rivets are twist lock type that are pressed in an undersized hole. You can probably turn them out with some vise grips."). However, that didn't work. I gave in and broke out my grinder, a real one, not a Dremel type of tool. That made short work of grinding the heads off, and I was even careful enough to preserve the tin baffle if I decided to re-install it. What I found was that rivet shafts are star shaped -meaning there's no way to twist those babies out. Those are pressed-in and what remains won't be coming out. So, I simply ground both down to near flush and then tidied it up with my Craftsman knock-off of a Dremel tool.

Dart 360, thanks for the new info. That too is helpful. My exhaust flapper and knob are long-gone, and I don't know if I'll mess with trying to restore it or find another one that is intact. So, again, thanks as your input about addressing the choke operation is helpful. I would have figured that out through testing, but you've saved me the time.

One last piece, I've scoured my factory service manual, and as I suspected, there's nothing in there that makes any distinction between the CA-emissions intake and the non; and very little about what I referred to as a rheostat, apparently a bi-metallic spring, nor the valley above which it mounts. So, again, thanks to all for extra info for this DIY'r.

[John Kunkel]

The attachment device is called a drive screw (see pic), the star pattern is spiral and they can sometimes be removed by turning them in the opposite direction of installation but they're not really intended to ever be removed.

[Krooser]

That "flapper valve" is called a "heat riser" valve...

[340_GTS]

Originally Posted by John Kunkel

The attachment device is called a drive screw (see pic), the star pattern is spiral and they can sometimes be removed by turning them in the opposite direction of installation but they're not really intended to ever be removed.

Yeah, but what a mess one of those left-over pins will make inside the motor if it ever falls out. I say get them out of there. Or maybe you could stake them, or weld them so they can't fall out?

[aarracer]

Originally Posted by 340_GTS

Yeah, but what a mess one of those left-over pins will make inside the motor if it ever falls out. I say get them out of there. Or maybe you could stake them, or weld them so they can't fall out?

Or, drill and tap the holes and wirelock the/some bolts in?

[roadracerjeff]

I know, don't temp fate, but I really can't see what's left of the pins/screws ever coming out. Maybe I should post a pic. Those babies are IN THERE and for good. No different than when they were intact. The factory never intended for those to come out. Taking the heads off of them doesn't change that so it'll be our little secret that I left 'em there ;-)

[Rich Kinsley]

Originally Posted by aarracer

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The best lifter valley oil control device I have seen (Diamond Racing (the piston people produced it)). is a single stip of 1/8" x 2" aluminum flat bar running the length of the lifter valley covering the three oval holes in the block you can see the cam through. It blocks the camshaft area windage from throwing oil upward and it helps direct drainage back to the rear of the lifter valley down through the distributor drive area.

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An engine builder helping me with some machine work also uses the blocking plate idea. We did it to my 318 poly.