I was considering doing something like this myself... something that replaces the adapter that sits between my spread-bore intake and the square-bore carb. I was thinking something 2 inches tall that slowly makes the change from square-bore carb to spread-bore intake, while increasing plenum and insulating the carb.

I figured CFM could help me with this process, maby you have the solution. Where can I find some of the Richlite you used?

 

Richlite Material

We use it around work due to it's excellent machining properties. It's a man made synthetic, epoxy based board like material that is non-impervious to petroleum products and is non-thermally conductive, (which makes it an excellent candidate for this application). Don't know where you'd find it in the commercial market. An internet search maybe? Also Jegs offers a similiar spacer, however a bit pricey.

I made mine using a Q-jet gasket as a pattern, hole sawed and drum sanded the bores and outline. Important thing is to ensure that when installed it is a perfect "flow through" match with the carb and intake. Don't want to create any "reversion" steps or ledges due to minor mis-alignment that would interrupt flow.

Dave

 

DLR -

I'm assuming you have a Quadrajet carb too. Did you just make a 4 hole spacer? How tall is it? Maybe I can give some insight to why it worked.


AFBryan - going from a squarebore carb to a factory GM spreadbore intake with the 4 quadrajet bore holes on top is a bad transition, no matter which way you do it. Going up to 2" will make the transition smoother (less abrupt changes to airflow + fuel direction) than a 1" but is still a band aid. If forced to keep the intake machine the top of the intake to look like an aftermarket spreadbore intake - ie: cut out the bore holes and leave a center divider. Then just get a squarebore to spreadbore adapter that is made to adapt the bolt holes, not the throttle bore holes which makes a normal transition (ie: straight thru) from carb to intake.

 

Home made carb. spacer

DLR -

I'm assuming you have a Quadrajet carb too. Did you just make a 4 hole spacer? How tall is it? Maybe I can give some insight to why it worked.


AFBryan - going from a squarebore carb to a factory GM spreadbore intake with the 4 quadrajet bore holes on top is a bad transition, no matter which way you do it. Going up to 2" will make the transition smoother (less abrupt changes to airflow + fuel direction) than a 1" but is still a band aid. If forced to keep the intake machine the top of the intake to look like an aftermarket spreadbore intake - ie: cut out the bore holes and leave a center divider. Then just get a squarebore to spreadbore adapter that is made to adapt the bolt holes, not the throttle bore holes which makes a normal transition (ie: straight thru) from carb to intake.

CFM,

Machined the spacer out of "Richlite." It's 1" thick. I was sure to pattern all 4 venturi holes exactly the same as the carb, ie; When viewed through the Q-jet bores the transition is smooth, (with no steps or ledges, between the carb, spacer and intake), that would interrupt flow, (reversion). (4 seperate holes).

I suspect I'm benefitting from the reduction in intake charge temp as well as increased intake plenum volume and charge velocity.

DLR

 

Ok, so it's a standard 1" high 4 hole spacer. Got it. Thanks.

BTW: I am familiar with that material. It does work good for carb spacer applications.


Yes, it will add plenum volume but I don't think that is what is helping you. Plenum volume helps more in the actual plenum where the air fuel from the throttle bores are collected as one unit.

Yes, the air will have a little more velocity under the throttle bores but the velocity going to the intake runners will only be marginally increased. Why? Plenum again. The plenum is the storage area for the individual runners. Although I'm saying this generically you'll see my point - the carb fills the plenum area and the plenum feeds the cylinders. They are not totally seperate of course but do cause some seperation of each other.

So, I'm thinking that since a 4 hole spacer will make an increased "pull" under a carbs boosters thus drawing more fuel out of the carb your engine had an original A/F ratio that was not rich enough to make the most power.

Said another way, this slight velocity increase in air has a much bigger effect on fuel than it does actual air volume.

Yes, this material does block heat well. The Quadrajet's can be effected by heat. This may of helped somewhat, but impossible for me to answer. This depends on air source, engine compartment heat, etc, etc.

Anyway, this is fact on how this type spacer works and theory why it helped in your application.

I know spacers better than most. This does not mean that I know 100% on all applications what will add what for hp.

On yours, I would have said "it's worth a try but don't expect much." The carb calibration is not something I can guess on, of course. Again, I feel that this is probably the case. "Feel" and "probably" is stating theory, not fact.

Anyway - I'm glad it worked for you. I like when people try different things and don't 100% go by what others say (including me) and don't always suspect a gain when doing it. Experimentation leads us to better and better performance.

Let us know how the other mods go.

 

Carb spacer ?

DLR,
My SB project last winter included a 1" Phenolic spacer, from Jeg's ( Mr. Gasket) was only $29.95. I used heavy coat hanger wire to connect ckoke to carb. Bends easy and is soft enough to cut a groove to install a clip on ends of the new rod.
Not sure if the spacer added any power, but isolating engine heat between aluminum intake and carb helped
loss of power in the summer.

Jerry G. aka Raptureman :yak: :yak: :yak:

 

Phonelic Carb Spacer

Jerry,

My spacer added 2 mph on the top. I also wired the choke plate in the open position so it is invisible to the incomming air flow. The coat hanger sounds like a great idea. Strong enough and easy to form. What did you do to capture the end of the new choke rod at the cam at the chock plate shaft to keep it from falling out? That's the only obstical I'm battling. If I can't figure it out, I'll just use a shot of either to speed up cold start ups, I guess.
Dave

 

I give it two pumps and a shoulder roll. :bigsmile: :bigsmile:

I have the choke wired up too. My intake is too high to re-use the choke rod.

A couple of pumps and get idle to around 800-900 rpm for about 20 or so seconds. Idles fine for the rest of the day, even if turned off for an hour or two.

 

Phenolic spacers have been around for a long time. I
had them on every boat with a carb. My first experience
with phenolic came when I bought my 1972 Challenger
with the Thermoquad carburator .Mr Gasket has them
1" 2" and you can stack them to 4" if space is not an
issue . Back in the 70's Robinson Ford had a 6" spacer
to enhance bottom end torque , on their 9 hour Parker
enduro winner boat. Ps; I've machined a 1" spacer for
the plenum of my 96 Mustang GT . The extra factory
"O" ring needed still cost ca $ 16 cdn

 

Carb spacer?

DLR,

I bent the new rod in the same profile as the shorter rod, only 1" longer. Cut a notch on the end going into the choke cam and installed a small wire clip. Choke works great. Prior to making my own rod, I called Edelbrockcause they make these rods ,but they were all too short. No provisions for carb spacers.
Spring can't come too soon. :yak: :yak: :yak:

Jerry G.

 

Carb Spacer

Jerry,
I still have the OEM clip. I'll have to experiment with the groove and see if I can use it to retain the choke rod. Thanks for the advice. We're in the midst of a snow storm here in the Northeast as I write this. You're right, Spring can't get here soon enough.
Dave

 

DLR,
Not to burst your buble, but keep in mind outside air temp, humidity, and chop as you progress. I went out last fall on a 65* low humidity type day and went 2 to 2.5 mph faster than the boat ever went before. No changes to anything...just went faster. I have to believe it was weather related.

Not saying the spacer doesn't work, just that there could be more to it.

Hey, if it does work, maybe you can teach cfm { aka Cape Man} a thing or two :winker:

 

My ears and mind is always open. The more data I see and hear helps give me better advice to those I talk to and sell to.

Now kid, how about a 500+hp Nitrous plate/spacer combo. That should wake things up a little ? :bigsmile:

 

Normally it takes about 15HP to gain 1 MPH in most boats. So you'd be looking at a gain of almost 30HP. Not to say that this is impossible, but that would seem to be a very large gain on a stock application. Weather conditions, ballast, and lots of other variables can, and will affect the top end performance.

If you have the time, and you're really bored you may want to set up a little test so you could back to back it on the same day. This would let you see what is really going on, but that being said if you've got it on already, and you're not have problems no real reason to.

 

My ears and mind is always open. The more data I see and hear helps give me better advice to those I talk to and sell to.

Now kid, how about a 500+hp Nitrous plate/spacer combo. That should wake things up a little ? :bigsmile:

Nitrous .......now cut that out :

Actually, I have been day dreaming about lower comp pistons and a minor blower

 

On the air temp changes, don't they say 10 degree is good for 2% up or down? How about the water density? As water is cooled can it become more dense providing less prop slip and maybe more buoyancy for the hull so you displace less water? In regards to increasing intake velocity, a six inch spacer with a blower on top also works!

 

Nitrous .......now cut that out :

Actually, I have been day dreaming about lower comp pistons and a minor blower

Not in your boat.

Stop it ! :bigsmile: :bigsmile:

 

On the air temp changes, don't they say 10 degree is good for 2% up or down? How about the water density? As water is cooled can it become more dense providing less prop slip and maybe more buoyancy for the hull so you displace less water? In regards to increasing intake velocity, a six inch spacer with a blower on top also works!

10 degrees air temp is typically near 1%. If, the A/F ratio is kept constant - meaning calibrated for the temp change. Switching gears, each 100lbs of weight is the same or many times more of an effect than each 10 degrees of air temp. This should not be overlooked!

A spacer will not change air temp going into/thru carb, into motor much if anything. The temp thing is more about fuel - which is more of an issue after a vehicle is turned off where there is no airflow and no fuel flow. Thus, hard starting from percolation/vaporization/etc

If you want to change air temps somewhat use an intake gasket that blocks off the exhaust heat crossovers. On small blocks this usually means a Fel-Pro 1204 gasket or equivalent.

Remember guys, the air going into the engine along with fine droplets of fuel will cool the intake air down a significant amount. To cool it down further would require outside air and secondly, cooling intake manifold. The carb's throttle bores just don't have much of a surface area to transmit much heat/cold + with introduction of fuel in this area it cools down even more.

 

Not in your boat.

Stop it ! :bigsmile: :bigsmile:

Oh alright fine, we'll see. JEEeeeeze... what a kill joy :


Back to reality ..... it seems that lowering the temp in the engine compartment would help with the overall performance especially WOT. BT and I had a discussion about this about a year ago.

As far as engine compartment venting, all most of us have is a couple of small openings on the side of the boat, and a couple of small exit holes at the rear. I'll bet on a hot summer day, temps under the hatch can easily get over 100*. Increase ventillation, lower temps under the hatch, better performance??

 

Yes sir. Not really that bad in most boats - but some really do have an issue. The old trick is to raise your hatch a few inches while at WOT to see if performance picks up. If it doesn't, than all that work to seal off the carb to get fresh air and a duct to blow at the intake may not show much of a difference.

Also, I find that people get fixated on their outside vents that lead to the engine compartment and don't notice that may have huge air passages on each side of the rear seat entering the engine compartment.

I forgot about these two until I'm lying down there doing stereo work or wiring things into the engine compartment.

 

Yup, I have those huge air passages on each side of the seat too. I also found mine messing around with wiring.

I expect those might help some. But, due to their location mine won't allow any air to be "forced" through them {at any speed} into the engine room. They do ensure plenty of air for the carb/engine though.

I thought of the hatch raising idea late last year. That would likely allow cooler/outside air to be forced under the hatch. Just have to figure out a way to keep Mr. Hatch from blowing off at WOT. Could be few cheap mph . Nice little spring project

 

I expect those might help some. But, due to their location mine won't allow any air to be "forced" through them {at any speed} into the engine room. They do ensure plenty of air for the carb/engine though.

Are you so sure?

Why is it that when sitting in the back seat of some boats your hair blows towards the front of the boat?

Just saying a visual with no test equipment won't tell you anything.

Put a string about 4 -5 inches in length in the opening. Connect the string to a tennis ball. If the tennis ball moves backward (towards the engine) you have a good amount of fresh air going in thru this 'port.'

If the ball doesn't move it is stagnant - ie: very little air flow.

If it moves towards the driver than the air from the engine compartment is rushing out of it.

You'd me amazed how many cold air kits I've seen mounted in an area that is actually under a slight vacuum at speed :shocked: Instead of being labeled as 'Cold Air Kits' they should have been labeled as "Less Air Kits" :laugher: :laugher: :laugher:

 

That makes sense. Openings next to the rear seat in the Nova are well hidden behind side panels. Front seats are ahead of the panel openings. Drop the seats down {bolsters} and air from forward movement would be further restricted.

But as you mention, that's not to say that air under the hatch would not EXIT through the openings. Hhmmm...Open the hatch about 3 inches or so, the openings next to the back seat could help the circulation process.

Another interesting thing to try would be mounting a thersmostat under the hatch just over the carb. Go for a cruise at around +,-4500 rpm for a while, then WOT for a few minutes, stop and quick jump back open hatch and check the temp. Then do the same with the hatch raised a few inches. And of course check to see if WOT rpm's go up any

 

If the tennis ball doesn't move from air use something lighter, like a ping pong ball.

You get the point.

Anyway, I mention opening the hatch for testing - not for driving all the time. Would hate to break it.

Unrelated - how to do cure a "Too many Girl Scout cookies' sugar hangover ? Man, I shouldn't have brought the whole box - I new I would eat the whole thing at once. I do it every year and with each box. :shocked: :shocked: :shocked: :shocked:

 

Running with the hatch open about 3 inches was actually what I was wanting to do. I just never got the time and ambition simultaneously to rig something up. Before becoming an "insurance guy" I was a finish carpenter by trade. And, I'm also a decent welder, with a mig. So, I'm confident I can fabricate a pair of not too ugly brackets that will fit under the front of the hatch {at the rear seat}, and hold it up where I want it to be. Just have to be sure the hinges at the rear of the hatch are secure. Fear not cape man, loosing the hatch is the LAST thing I want to do :shocked:

Only thing I can think of to cure the bad feeling after eating too many GS cookies is to eat some more, just to give yourself a lesson on gluttony uke:

They are the best, and it's real tough to stop eating them. Wifey gets about 4 boxes every year. The chocolate mints and Macaroons are my down fall. I'll eat them 'till I'm about ready to barf...love 'em