Inliners International Forums General Discussion Hi Performance Height of Offy carb mount?

Trying to figure out how much underwood space I have for the spacer, carb, and air cleaner. I know the Holley 0-8007 is 3.5" tall, needs at least a 0.75" spacer underneath (more is better?), and at least 0.75" of air cleaner space above the primary bowl vent.

But I don't know how tall the plate the car bolts to on top of the Offy intake is? 0.5" to 0.75" maybe?

A little extra info, on my 1978 Camaro has 8.5" between the top of the integrated manifold carb mount to the hood. Depending on how thick the carb mount plate on the Offy is, I likely have 2 or more inches to play with for additional air filter height and/or carb spacer height. This is assuming that the carb pad level for the integrated head is the same level as for the non-integrated stock manifold.

I'll measure later. What, exactly, are you wanting for a height reference? Runner to top of carb? It'd be far easier for me to just tell you a 2" filter and 1/2" spacer will work....

The carb mounting plate that screws onto the runners. I'm assuming that the bottom piece of the Offy manifold is the same height as the stock manifold, and the same height as carb mount on my integrated intake.

I thought someone measure 3/4" spacer to get the Holley 390cfm linkage to clear underneath? Filter height is dependent on the air cleaner base, flat or recessed. So the 2" is dependent, but I've got room to fit a lot more air filter.

Just rifled through old threads and found where mshaw230 determined 0.5" spacer is all that's needed to clear, not 3/4" like I thought. Extra 0.25" available for either filter or more spacer. Not sure which will give more bang, adding more spacer or filter height?

I noticed no difference between a 1/2" spacer and a 1" spacer for performance.

So the 1/2" spacer got better results than the 1"? So what was the height on that carb mount plate on top? I'm guessing 1/2", am I right?

Not better. Just not any difference that I could tell.

Is there any difference above 1"? I got 8.5" from the manifold mount to the hood, and the Holley with 0.5" spacer, 0.75" minimum air cleaner height that is 3.75" I can add to it. Plenty of room for a 2" spacer if that is beneficial, otherwise I'll just add more air filter.

I'm trying to figure out which of the stock air cleaner lids will fit under my hood. The stock '78-'81 LM1 single snorkel Qjet air cleaner will fit the carb. But I could use the Z28/L82 lid that comes with it, if it fits, and have a 12" x 3.48" air filter. Or swap the '76-'79 LG3 lid and use a 12" x 2.5" air filter. Both options retaining the Thermac snorkel for cold day start reliability, and the ducting to my ram air vent.

Mine came out about 8.25" above the manifold to the top of the 2" air filter ribs. I kept in the 1" spacer at the base of the carburetor because I didn't want the choke to get so close to the manifold. Larry at Twisted6 drilled new holes in my base plate to allow me to rotate the carb 90 degrees to simplify the throttle and ATV installation. I used the original throttle rod, bent it, cut new threads to shorten it from the original.

Thanks. Hmmmmm.......looks the baseplate plus 1" spacer is not quite 1.5", so I'm assuming the baseplate is less than a half inch?

The specs on the Holley 0-8007 might not be right then. It's listed as being 3.5" tall, which I assumed was to the top of the vent for the primary bowl. But if I take 8.25" and subtract less than an inch and half for the base plate and spacer, then subtract what looks like 2.5" for the air cleaner........that's still some what more than 4.25" for the carb height?

I got 8.5" of clearance under my hood, so your combo above would just fit underneath if the wingnut and stud didn't rub. The stock Monojet and Thermac air cleaner are 7.25" tall.

I should also mention that I don't have auto, so I only need to hook the throttle cable up, fuel line, and vacuum hoses.

Hmmmmmm......been crunching numbers with LM1-base/LG3-lid and don't see how it will clear the valve cover with the measurements I got. The old trick on Holley 4150/4160 carbs is to use the Moroso drop base air cleaner for hood clearance or adding extra filter height. But the 14" base won't clear the valve cover either. I can see why so many people have a stock size 10"x2" in a raised open element, or use an oval to get a little more filter. It's a tough fit. Or maybe why the Clifford manifold is a little wider than stock.

I'm starting to think a more low buck approach might be to keep my air cleaner and 10"x2" K&N filter, and cut the bottom of it to mate an old 5 1/8" open element base to it to turn it into a 4bbl air cleaner. It keeps the Thermac for cold weather, and the snorkel and hose for my ram air setup. And flattens out the floor for more air flow.

The next cheapest option is to use an open element 10"x2" air cleaner, and just work on keeping underhood temps down (wrap the exhaust, cooler thermostat, electric fans, front air dam for negative pressure).

Here's the air cleaner I got recently:

http://www.ebay.com/itm/12-Oval-Polished...7274992?vxp=mtr

Looks pretty good in my humble opinion.



No problems with hood clearance on my 68 Camaro. Didn't measure but it's likely the same as MShaws's above.

The thing is if you look at the sizing calculations our engines only need a 10"x2" circular filter at most. Even mine is way oversized. ...but it looks cool so...

http://www.onallcylinders.com/2013/11/27/match-air-filter-size-engine/

Yeah, for street application the factory actually got the filter size right. If I'm going to run open element, that should be all I need. And I can get by reusing my K&N filter in a $20 raised chrome air cleaner. But I'd like to use a snorkel and duct if I can manage it. I'm just concerned about the restriction of the stock air cleaner around the air filter, and restriction of the dropped base. I figured a bigger V8 air cleaner would give me the closer to the air flow of 10"x2" open air cleaner. But I can't make it clear the valve cover and it will be pretty close to the hood. I may not be able to improve the stock air cleaner around the filter, but I could take out the drop base part and adapt it for a 4bbl with an old air cleaner base, for no cost but a bit of work. Then I can avoid sucking hot engine compartment air. But it might end up being the same net effect either way, as neither is a perfect solution.

I suspect 1st gen and 2nd gen Camaros have close to the same hood clearance. They ran the same engines, intakes, carbs and air cleaners.

note some of your height difference is due to the rim of the carb overlapping with the air cleaner. Personally, I think I got lucky with it all fitting under the hood. I never looked under the car with the hood down to see how close I am.

I've helped a college-aged friend put a snorkel with a big round air filter into a VW Jetta. He claimed his performance went up. It went down near the wheel to get fresh air. And got a lot louder too, most important!

These open air filters are a lot louder than the original air cleaner. Combine that with the headers and exhaust and it's a big deal. I even asked for the quietest muffler too.

But who wants to talk when your foot is to the floor???

I just use Play-doh on top of the air cleaner and valve cover to measure hood distance. I have 1" clearance on the air cleaner with the stock setup.

The '78 and '79 Camaro inline setup ('75 to '77 may be the same) has the intake hose conveniently come out behind the left turn signal. This makes for a great way to put together a ram air scoop:

I was rereading over the thread to make sure I had all the numbers right. So to summarize what was learned here, the clearance on the intake manifold pad of a 250 in a 2nd gen Camaro (probably the same for 1st gen Camaro, 2nd gen Nova, and 3rd gen Nova) is 8.5" from the mount to the bottom of the hood.

The stock height of the Monojet carb and 10"x 2" snorkel Thermac air cleaner are 7.5" tall.

The height of the Offy manifold plate, 0.5" spacer, Holley 8007 390cfm carb, and 2" raised air cleaner is 7.75" tall. Which assuming the Offy plate is 0.5", the 0.5" spacer, and 3" for the air cleaner; means the Holley is 4.25" tall.

Another option I've played with is using the Rochester 2G 2bbl carb instead. I'm not sure how tall it is, but my memory of the one on my '76 305 Camaro is that it was pretty short. But it was also used on the 229cid 90 degree V6 that replaced the 250 L6 in the passenger cars. The air cleaner for that used a 2.8" x 9.6" air cleaner. I'm not sure if it had a dropped base like the V8 2.5" x 12" 2bbl air cleaner, but the extra air filter may help overcome restrictions of the closed snorkel air cleaner. And it probably wouldn't need a spacer for linkage.

Looked it up, 4.125" height on the 2G carbs. Mounted on an Offy, the adapter is 0.5" tall. Mounted on a Monojet manifold, it needs at 1.625" tall adapter. I'm not sure on the height of the Chevy 229cid stock air cleaner. Somebody else also recommended machining the stock Monojet manifold to accept the 2G carb. I forgot who was working on casting a 2bbl manifold?