Inliners International Forums General Discussion Engines Intake Manifold Profile (Height) - 4 Barrel

Does anyone know which Chevy 194/250/292 four barrel intake manifold has the lowest profile (carb mounting height)? I am trying to maximize hood clearance in hopes of getting a 292 under the hood with an EFI throttle body and turbo hat setup. I am considering the Aussie Speed, Offenhauser, and Clifford, however I think the Clifford might be out as it is listed as only working with headers.

Alternatively, if any of you have an Offy or Clifford (or other 4 barrel) setup on a Chevy 194/250/292 could you measure the vertical height from the top of the intake port to the carb mounting surface and send along your number? The guy from Aussie Speed was kind enough to do this for me already and he said that is 30 mm (just over one inch) for their intake (but they can machine it down some).

Actually, it would be really helpful if anyone can report on the height of their EFI throttle body and turbo hat if you have them? Thanks!

Perhaps the Clifford will work as well. I have seen a photo of a Clifford manifold bolted on with the SPA cast iron exhaust manifold I plan to use but I could not tell if it was the same Clifford I am considering.

PM sent.

I am using a Clifford with the stock 250 exhaust iron. Mine is an early Clifford and you can tell it was made to work that way - there's a big flat pad on the bottom where it bolts to the exhaust iron. I milled mine a little more so a steel plate would fit in between. I don't like exhaust crap eating away at my alum intakes.

But it does work, nothing else hit. Havent tried the Clifford with headers yet.

IIRC the Clifford and Offy are about the same height though I don't think I measured. I am running a 292 Clifford in a 63 Nova, still room for a flat 14x2" air cleaner, though a 14x3" will hit the hood.

Yes the Clifford will clear the spa exhaust manifold. It is close but does clear. http://t6racing.org/sitebuildercontent/sitebuilderpictures/DividedCliffordSPA2.jpg Here is a photo.

DeuceCoupe,
Did early Cliffords have bolt holes to connect manifolds?
Just wondering about the big opening for manifold heat on the stock exhaust and how you sealed that up.

BaroneDog,
Don't forget baseplate on Clifford and Offy is fairly thick, you can probably make some room with thinner mounting plate as long as linkage can still clear.

Pete

Yes my early Clifford has bolt bosses for the long bolts to the exhaust manifold. I think I had to drill the short hole up from the bottom. There was a flat pad on the bottom of the Clifford meant to mate up to the iron exhaust opening. As I said I milled it more, 1st cuz it didn't line up / not flat, but also to leave a gap for a steel plate to keep the exhaust gas and heat off the aluminum.

I also had to drill out the vacuum holes although the bosses were there. No provision for heat. If I needed heat my plan was to use a Ford carb spacer that runs water thru it, though that would be tight with the tall 292. Cant complain though, I got the Clifford for $40 circa 1994. Even with 2% inflation that's only $200 or so today, LOL.

Cant wait to try headers on the setup but life intervenes.

DeuceCoupe, could you give me a little more info on your 292 stack in the 63 by filling in the heights listed below?

Clifford Intake Carb Mounting Height = X inches above intake port
Baseplate = Y Inches
Carb Height = Z Inches
Air Cleaner = 2 Inches

Adding (X+Y+Z+2) results in less than one inch of hood clearance (since a 3 inch air cleaner will hit). Do you know about how much the 3" air cleaner misses by?

So far, I know the following about my setup:

Intake Manifold Carb Mount Height = X inches above intake port (Depends on Intake chosen)
Carb Baseplate = 0 Inches (not sure if I need this for my setup - maybe for linkage clearance?)
EFI Height = 3 Inches (This is the height of the Holly Terminator EFI according to the Holly Rep)
Turbo Hat = 3.5 Inches (random one listed on Summit but maybe there is a lower profile one out there)

(X+0+3+3.5) must be less than 7.75 Inches (which is the estimate of how much hood clearance I would have with the 292 measured from the top of the intake port), which means the intake manifold cannot add more than 1.25" more than a stock intake (which is about level with the top of the intake port on the engine block). The Aussie Speed is 30mm so it is darn close, but they said they can machine it down some, just waiting to hear how much. Also, I need to figure out if a base plate will be needed for my application.

Thanks to all for your replies!

You mentioned baseplate several times, yes they actually are an adapter to allow bolting the carb to either the Clifford or Offy and they are required or the carb can't bolt to the intake. In Landon's 292 Chevy II swap he used an Offy intake with the stock carb adapter and a 3" open element breather without hood issues.

Thanks CNC-Dude. What I really mean by "Baseplate" above is an additional spacer (on top of the intake adapter plate). I just was not sure if a little extra lift would be needed for the linkage to clear the underlying intake body or something like that. Again, I am hoping I would not need this.

Good to know that was a 3" breather in Landon's build. It was hard to know from the photo.

OK I sat the whole assembly on the floor (I'm running trips 3x1v right now on the car) - so here is the Clifford setup.
Measured from the floor:
2-1/8 Top of port, inside
2-1/2 Top of port, outside
3-1/8 Flat of intake where adapter bolt on
3-5/8 Top of adapter (carb gaskets sit on this)
4" Top of carb gasket pack (I might have needed this 3/8 pack for clearance, not sure)
7-1/8 Carb Air Cleaner Flange
9-7/8 Top of flat center (Ford non-dropdown 14x2" air cleaner)

So in your nomenclature then
X=1"
Y=1-1/2"
Z=6"
T=7-3/4" = top of air cleaner vs top of port opening

This probably gave 1/2" clearance to the hood, but it never hit.

Hope that helps!

Thanks DeuceCoupe! That is really really helpful.

Is it possible to mill the Clifford down a little further if needed for a bit more clearance? Also, do you run water through the water jacket? If so, does it help in any way?

You won't be able to run water with the SPA manifold. Luckily its not really going to need it the way it's designed. You'll want the two manifolds to be as close as possible to keep the fuel from pooling.

Mine doesn't run well until warm because of fuel pooling. Even when it's hot out but not as bad then. I'm running water through my Offy intake tapped right into the water pump so it's circulating water as soon as the motor turns over. Even then it won't run well until the temp comes up to about 120 degrees. Until then it wants to stall.

I've never had my hands on an SPA manifold but I can't imagine it allows exhaust gases to circulate around the intake manifold like the stock one does. That would take away from boost and be a detriment. From the pics that I've seen it looks like it's designed to transfer heat through the top of the exhaust manifold through the bottom of the intake through convection. It'll probably take even longer to warm up than stock but if you're doing a turbo setup I'm guessing you don't care nearly as much. Even with an intercooler the charged gas is going to be warm enough to prevent pooling shortly after start-up anyway.


Long story short: logically you won't need water heat.

Thanks gbauer. Do you think the cold start issues you speak of will be any better with EFI or would you expect the fuel to pool just the same?

To be fair I could probably tune the choke a bit better and not have nearly the same effort so EFI would probably take care of it.

If I were you I'd definitely go EFI with a turbo setup. No doubt about it. I'm on the slow path to go your route myself. EFI is on my list before turbo charging it. EFI and an MSD with more control to prevent detonation is a must in my opinion when your going FI or nitros.

Others here can probably fill you in better as they've already gone down this road.

You may also have an issue getting the SPA manifold to fit your Chevy II even before you mount the turbo. Also, unless your fuel source into the engine is directly at the head, like the intake I showed you, heating the intake may be necessary if it enters the engine like a conventional carburetor. That's a huge advantage with the intake I showed you, it doesn't require heating. But there's pros and cons to many things.

CNC-Dude, does the SPA manifold stick out too far and interfere with the shock towers? I got the specs for the manifold but have not yet measured inside my engine bay for interference. I figured that the turbo would have to be mounted in a different location (not directly on the SPA) but I guess I had taken for granted that the manifold itself would fit! Glad you mentioned it.

I think you'll have steering component interference, that's what most people seem to mention even with larger engine bays. Also keep in mind that the SPA intake is not designed to fit any American vehicle as they are made in Brazil and they only have their vehicles down there in mind for engine compartment fitment, and they are much different than we have here. They do and can fit some engine bays of USA cars and trucks, but only if they have a generous amount of room. The Chevy II is about as tight and compact as they get for USA engine bays.

You're not going to know 100% until you get your hands on one and mock it up with your engine in place. If you have some fab skills you can build you own custom turbo header and be ahead of the game.

Thanks for the advice CNC-Dude. A lot to think about. I should be able to get a 292 and start to mock things up within the next months so we'll see how it goes. Thanks again.