How much space required above air cleaner?

[Whiplash]

I'm wrapping up the rebuild before I send the car out for paint. Got the body back on and am making all the connections before firing her up. My question is about the required clearance between the top of the air cleaner and the hood.

I've got an aftermarket L-88 Hood. The motor has an intake similar to the Edelbrock Air Gap (It's a Professional Products intake but I can't remember the name.), a 1 inch spacer, Speed Demon 650, and a Billet Specialties large oval air cleaner with 2 inch filter. It's a fairly tall stack.

The hood fits and actually closes. There was only about 1/8th of an inch of clearance. I decided this wasn't enough. I cut about a 1/4 inch off the ring at the base of the air cleaner so it just clears the adjustment screws for the fuel bowls on the top of the carb. So now I have at most 3/8ths of clearance between the top of the filter and the hood.

My question is this enough? How much will the engine spin up when it revs?

Thanks.

Whiplash

 

[Whiplash]

Here are some pics that illustrate the question

 

[Scott Winebarger]

Playdough ! Silly Putty! When you get it all assembled, place some on top of the air cleaner and it will tell you all you need to know without any damage to anything.

 

[Whiplash]

Playdough ! Silly Putty! When you get it all assembled, place some on top of the air cleaner and it will tell you all you need to know without any damage to anything.

Thanks the clay idea is great to measure the clearance I have. Is there a rule of thumb for how much space I need however?

 

[vett boy]

No just do what the man says.Surely you must have playdough .3/4 of an inch will solve your problem as it did with my 69.I had the same question and wished i'd tryed playdough it would have saved a lot of time.

 

[Whiplash]

No just do what the man says.Surely you must have play-dough .3/4 of an inch will solve your problem as it did with my 69.I had the same question and wished I'd tried play-dough it would have saved a lot of time.

Vett Boy,

Thanks. I'm not arguing against the play-dough. I appreciate the advice and I get it 100% but it doesn't do me any good if I don't know how much space I need. I already know the hood doesn't touch the air cleaner. I can see the entire cleaner when I look down the hood through the scoop from the windshield and I can see the front from under the car. The hood closes no problem.

3/4 of an inch is a good rule of thumb. Thanks for that information. I'm probably in trouble as at most I have is 1/2 an inch, more like 3/8ths (the 1/16th to an 1/8th I had at first plus the 1/4 I cut off the base of the air cleaner. When I finally start the car I'll be able to see if it hits the hood. I'd rather not hit the new hood.

I checked how much the motor on my Z06 twisted up when the engine revs and it doesn't seem like that much but these old style motor mounts might let the engine twist more than I'd like.

I'd appreciate any more feedback anyone else has on how little clearance I can get away with.

Thanks everyone.

Whiplash

 

[revitup]

Don't know how much you need but you can probably figure out if you have enough clearance with the clay. I'd put a few blobs all around the outside edge of the air cleaner and then rev the engine a little. Check how much contact you get with the clay. Then drive it sedately at first then thrash it more and more, checking the clay after each run. Should be able to figure out if you're going to get contact.

 

[74bigblock]

Be sure to account for motor rocking on WOT. One good twist, and your nice hood is cracked.

 

[RodsnRides]

Poly

You could also go to polyurethane motor mounts to subdue any engine twist.

Rick

:gap

 

[Evolution1980]

I don't know, but any more than .75" rocking sounds a bit excessive. Another way to check is to power brake it (if you have an auto trans). Since you'll see your aircleaner without the hood one, hold down the brake, put the car in drive, and get on the gas a little bit. The engine will torque to about it's max under full brake. You don't need a lot of RPMs to check this either. (They used to use this method to determine proper stall speed for torque converters. Hell, some might still do that!)

 

[Whiplash]

I don't know, but any more than .75" rocking sounds a bit excessive. Another way to check is to power brake it (if you have an auto trans). Since you'll see your air cleaner without the hood one, hold down the brake, put the car in drive, and get on the gas a little bit. The engine will torque to about it's max under full brake. You don't need a lot of RPMs to check this either. (They used to use this method to determine proper stall speed for torque converters. Hell, some might still do that!)

Thanks everyone. I guess I'll just have to find out when I fire her up. It's a stick so I'll have to find an extra foot to test it in gear

I'd just go with a drop base filter and solve the problem all together but my wife picked out the air cleaner for my birthday, my son picked out the flames, and I really like the look of the oval cleaner. Worst case scenario I'll cut the entire ring off the base and drill 2 holes in the base to let the adjustment screws for the bowls fit through. That will give me another half inch. I don't want to remove the 1 inch spacer necessarily as it will give me grief with the the vacuum fitting on the back of the intake. Although some would argue the spacer actually hurts low end torque.

I've got options so we'll see how it turns out. I might get her fired this weekend but probably 2 more weekends of work. I've spent 8 months on this body off so far and I don't want to rush things.

 

[motorman]

you need 1/2" between the tops of the carb bowl vents and the under side of the air filter top or the carb will not run properly

 

[Whiplash]

you need 1/2" between the tops of the carb bowl vents and the under side of the air filter top or the carb will not run properly

Motorman,

Thanks. I'll double check the clearance on the vents. I've got a 2 in element on the base. I'll make sure I've got the 1/2" clearance.

You had me worried for a second. At first I thought you meant the adjustment screws on top of the bowls. :W I've got so much going on in my head to get this done it's hard to keep straight. Even with my checklist my brain is going non stop on what needs to be done.

Any thoughts on clearance requirements above the top of the cleaner to the hood? From your signature I'm guessing you have a bit of experience

Whiplash

 

[Crimson Thunder]

What kind of motor mounts are using.If you are using solid then you would be fine with 1/2 inch.How about getting rid of the 1 inch spacer to solve the problem.

 

[motorman]

Motorman,

Thanks. I'll double check the clearance on the vents. I've got a 2 in element on the base. I'll make sure I've got the 1/2" clearance.

You had me worried for a second. At first I thought you meant the adjustment screws on top of the bowls. :W I've got so much going on in my head to get this done it's hard to keep straight. Even with my checklist my brain is going non stop on what needs to be done.

Any thoughts on clearance requirements above the top of the cleaner to the hood? From your signature I'm guessing you have a bit of experience

Whiplash

if you are close cut the vent tubes on a 45 degree angle as most all corvette carbs have. the way to check is to slip a piece of rubber hose over the vent tube that is 1/2" longer than the vent and then set the air cleaner top to see if it will go all the way down

 

[Whiplash]

What kind of motor mounts are using.If you are using solid then you would be fine with 1/2 inch.How about getting rid of the 1 inch spacer to solve the problem.

They're replacement mounts like stock. I read in one of the rebuild books that these are the best for most applications.

I'm pretty sure the vent tubes have more than enough clearance. I just got home tonight. I'll measure tomorrow to check. Motorman, thanks for the advice on the 45 degree cut if necessary.

Regarding the 1 inch spacer I may pull that off and be done with it. The dyno sheet that came with the motor spec'd out a 1 inch spacer. The torque curve is like a table from 2,000 on up to red line. I'm not sure if removing the spacer will increase the low end torque or ruin the profile. Also the vacuum adapter in the intake needs some space to clear the back of the carb.

I've got some playing to do with everything. Thanks for the advice. At least now I have a few paths to go down as I discover how things are working once I fire her up.

Whiplash

 

[Crimson Thunder]

Holley makes a low profile vaccuum adapter that will clear the rear fuel bowl on the carb.I just used 2 base gaskets to clear mine.

 

[Whiplash]

Holley makes a low profile vacuum adapter that will clear the rear fuel bowl on the carb.I just used 2 base gaskets to clear mine.

Well I got a 1/2 inch spacer at a local speed shop. The cleaner now has .830 inches of space in the front and 1.125 in the rear. I used Play-Dough to get the exact measurements. This confirms I had a little less than 3/8 of an inch in the front before I dropped the carb.

Now I just have to get the darn throttle cable hooked up. I modified the original bracket but it doesn't hold. I'm sending it with a friend to his shop to get some support welded to it. I don't want to change the cable if I can avoid it and all the aftermarket brackets have the square retainer instead of the round one that works with my 71 cable.

If the modified bracket doesn't work I'm going to have to change the cable out.

Thanks for everyone's help. .830 has got to be fine. If the engine is jumping more than that I've got another problem.

Whiplash