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Winter Projects

  • Thread starter Deleted member 21878
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Ahhh. winter time and no yard work… what to do with your time?


last year it was my attempt at installing a PCV valve/system to my car. i can’t say it helped anything.. or hurt anything for that matter. but it took up some time and was a fun project. in the process i learned a little about PCV systems. So what this year?


My projects have a few goals:

  1. do not hurt the car
  2. can be removed
  3. and this is important… get me out of the house


After some thought i decided this years project would be a cold air box. After all they were good enough for a 100M. these cars have a cold air hose already incorporated to the front of the car. Albeit for the cockpit. i had not seen one for a tri-carb so it was basically a start from scratch project.


My first thought was to build it around the existing air breathers and have them hold the box to the carbs. connect the other side of the box to the cold air hose and done…i soon realized the problem… space! the air breathers are too big to build around and have the box fit in the space allowed.


So then i needed to figure out what i would use for an air filter. Most modern cars use the round filters at the front of the hose. i decided i did not want to look at the filter in the engine bay. i hoped i could reverse the round filter and put it in my air box. then have the butt end stick out of the box and connect my cold air hose to it. Again the size of the filters and the room available did not seem to work out. the filters were too deep and/or too wide.


that left me with a flat filter. Now, how big? time for some research. there are a few websites to figure out how many Sq inches of filter you need for an engine. one being the K&N website. after trying a few formulas on different sites i determined the amount of sq inches or sq cm, i would need. from there i went to Autozone and started looking over the wall of filters. i knew from some initial measurements i would like to keep the filter to no more than 4-1/2” high. this allowed me to miss the fender brace and also stay below the hood. once i found a filter with a width i could use, i looked at some different lengths. i felt i would be ok with a 12.5 inch length but i went to the next longer one for a little safety factor.


then it was time to start building. knowing my filter width gave me the final height for my box. from there the length of the box was decided by the carbs. the depth was then the biggest factor. this is where starting with cardboard becomes a good idea. you tape up a box; see if it fits; then make some cuts and try again.

C5DBCFC0-0594-41AE-80FA-C63E875524AB_1_201_a.jpgA6F2E59C-60DA-4AAB-B074-20C2D4098E3B.jpg149821A2-4DF8-457E-A729-3581D2DDB133_1_201_a.jpg






 
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Re: winter projects...

first picture above is the very beginning. i started out with the holes in the middle of the back piece but soon found that would not work after adding the bottom. offsetting the holes lower and making a few other adjustments got me away from the braces. rerouted the fuel line a little (mainly because i have a filter in the line) and move the horn back a little. i added a spacer to the horn bracket and drilled a new hole in the bracket to allow me to swing it a little lower. problem solved. with a few more box adjustments, i could get the box in and out as well as mount it to the carbs.

View attachment 62010View attachment 62011

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Re: winter projects...

Then came the transition to metal. i took the cardboard apart and used the pieces as patterns for the metal. each time i cut and bent a piece, i put it back in the car to be sure it fit. i used the old gaskets to mark out holes for the carbs.
View attachment 62012View attachment 62013
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to mount the box to the carbs, i ended up tacking nuts to the back plate and running bolts thru them. i wanted to drill the bolts and put cotter pins thru them instead of using nuts. anyone with a tri-carb knows what a pain it is to tighten the nuts on the old filters. this is a little easier because you can tighten the bolts from inside the box and just hold the nuts. but still it is tougher than just pinning with cotter pins. i did end up with a nut on the very back bolt. only because i can’t see the bolt to put a pin in it.


you can also see from the pic 7 that i used a 1/2” self-stick foam seal at my seams in the box since i was not welding the box together. still trying to learn welding. just not enough practice yet for this part of the job.
 
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Re: winter projects...

View attachment 62014View attachment 62015
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on the bottom of the box i added some self-stick duct insulation. may help some with the radiant heat from the pipes below. figure it can’t hurt and it isn’t seen.

To this point the only thing i had done on the car was just take off the air breathers and set the horn back. before i made any real changes i wanted to make sure i would be ok with the look of the box.. first and that the system might actually work.


with 3 carbs i could not be sure they line up perfectly. after some test fitting, bolting and unbolting, i ended up using a different number of gaskets at each carb to make a tight fit. if i was to do the box again i might make the back plate stiffer by either using a thicker metal or adding in a stiffener.


Then i sat back and took a good look at the box. would i be ok with it? it looked ok to me and it could work. So i went ahead and pulled off the cold air hose from the cabin. this is the big commitment because it is hard to get that hose back on. No turning back now…i took some foam i had and packed it in the bulkhead to keep any air from going in there. i also plugged the vents on the inside.


My plan was just to bend the hose around and on to my air box flange. HA! not a chance. i had forgotten that these hoses do not really bend. So out came the knife and i cut it off just behind the horn. i would get a 4” metal elbow and make the bend with it. Wrong again! the hose just has no wiggle room and my outlet on my box was too high and at the wrong angle. So back to Lowes… again… i ended up buying a dryer vent hose. not the wire/foil type but the flex metal type. i cut about 18” off one end and made my bends from that. looked good. painted it flat black and attached it to my cold air hose. it is virtually out of site anyway. hidden by the box.


next came the mounting procedure… first i slid the box in to position, sort of, and attached my hose to it. then lifted the box a little and got two end bolts in thru the carb holes. from there i ran each bolt thru until the cotter pin hole just came thru the carb flange. pushed it up tight and shoved in my pins
 
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Re: winter projects...

Next i slid in my filter. (remember the filter from Autozone… many words ago) Well now i decided it was too thick for my box. it did not leave much room for air movement behind the filter. it would probably have been ok but it just did not look right. i found a cross reference with Spectre filters. they are like K&N but half the price. the high flow filters are also about 60% as thick as a paper filter. in the pic you will notice an aluminum channel at the top and bottom of the filter. i made those out of some scrap sheet alum i had to keep the paper filter from flexing. added more foam on the edges to make sure they seal in the box. the Spectre filters have a hard plastic frame and probably do not need them but i already had them made.
View attachment 62016View attachment 62017
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put my top on and that was that. Added an old “Austin” sticker to the top and all done!…
View attachment 62018
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Re: winter projects...

well not quite. i felt like the top just needed something. My paint job was ok but i wanted something with a little more shine to it sort of matching the carb tops.


i ended up going to a local metal place and asked about a small piece of aluminum. long story shorter… ha! i bought a piece of SS for 9 bucks. heck i could have made the whole box out of that piece and saved myself 20 bucks in sheet metal in the process. anyway replaced the top with the new piece.
View attachment 62019
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summary:
i am fine with the look. at least for now. Certainly not a look for the purist. And i really like the original look. However, i ruined that long ago with the alternator, the PCV valve, among other things.


So this was one winter fun project. in the process i got to read about sizing filters, do a little welding, and maybe even help the engine a little. Assuming all works as planned at least i have a better filter system. heck you could have small pebbles go thru those original filters. Cooler / cleaner air in the carbs has to be a good thing right?


As soon as it gets warm i plan to run a test. pull the hose to my PCV valve and hook a vacuum gauge to the manifold. run the car at various rpm’s and check my readings with the filter in and with the filter removed. this will tell me if the filter is restricting air flow.


Wait… it is still cold out. now what? guess i could practice welding…

 
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Garrym

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Re: winter projects...

Very nice write up of an interesting project. Unfortunately I couldn’t get the attachments to work.
I recently finished the restoration of my 100, including changing the sock type filters to something that looks more original. The car doesn’t seem to have as much power as before, and as this was the only thing I changed I may have to do something similar.
Thanks for the inspiration.
Garry
 
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Re: winter projects...

Not sure the attachments were all done the same way. The first three still show up. The rest did when I first entered. But when I went back they did not. Maybe I can edit and try again.
 

nevets

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Re: winter projects...

Nice work! Compliments your very clean engine bay. I assume you checked clearance required for engine vibration/movement.
 

gonzo

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Re: winter projects...

Hey DD, nice write up with detailed pics of a splendid job. Probably not an issue, but does the new Cold Air Box result in more induction noise? With air intake modified, do the carbs need to be adjusted and balanced again? The Corvair Corsa I once owned had 4 carbs - 2 / head - and was sensitive to air intake modifications e.g. run issues with individual air cleaners. Switching back to the common stock air intake modified with a ram forced (cold) air tube, similar to your's, made it run much better at speed. Keep up the good work! GONZO
 
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Nevet,
that makes two of us. i assume i left enough room also. well curiosity got the better of me this afternoon, so i fired it up. no rattles or banging. i do have new motor mounts; put in when i did the motor. my engine shakes very little, if any, except maybe at 1/2 choke on warm up. but even then, today, no banging. may not be the case as the mounts get older. will have to watch that. i do have a couple of options if i need to adjust a little. good news is the engine torques away from that side on throttle.

Gonzo, thanks. i really could not tell if the noise changed today on my test ride. as far as adjusting the carbs, i can't tell either. to balance them i would have to remove the air box. then how would i know... but for my short drive today it ran fine. no stumbles, lag, or anything i could tell. i have alway felt my cars ran better (let's say crisper) on cooler, dryer, days. i think any real difference i may notice will be when it gets hot out. think it is going to be a while for that test.

Last pic / had to add a little bling to my box. wanted to use a 3000 trunk emblem, but they seem to be curved and my box is flat. so for now i ended up with this. will keep looking for a better piece.
02BE94DF-228F-4369-86BD-482CBBE51D5A_1_201_a.jpg
 

dougie

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Drone Dog -

That looks similiar to the one I made for my vintage racer a few years back. Dyno numbers revealed it was way to restrictive.

Cold Air Box.jpg

Cold Air Box 3.jpg
 
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Dougie,
wow, yours looks a lot more professional than mine, as one would expect. would love to see the whole box on it and in the car.

you seem to be running larger carbs and i would expect a hotter cam, headers, etc. thus sucking a lot more air than i do.

questions:
did you have a filter in your box?
what size inlet pipe did you use?
so what do you run now? straight velocity stacks?
Also what HP and what RPM's does your engine run?

of course i have stock HS4 carbs and only do road driving.
i do plan, as i said above, to do a vacuum check to see if i am restricting air flow, when it gets warmer. with no dyno to test, that is all i have. who knows, i may be pulling it all off after that test.
 

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Correct, this is a full race motor built more for torque. Custom billet crank to run Chevy LS Clevite racing bearings, light weight longer rods, dome pistons etc. Max HP & torque about 270 depending on tune. It pulls strong past 7500 rpm, but shifting closer to 6500. The real problem with my air box was the cover was too narrow, rear carb was being starved. This was about 12 years ago and I was experimenting with a lot of performance options. Now open 2" ram pipes, which I also tested the best on the dyno.

Cold air box installed.jpg

Ruddspeed Race Motor 2019.jpg

 

wangdango

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Very nice job but I agree with Dougie, the theory is great but not that great. We have used a "stock" 100M cold air box on our vintage racer and it is too small and does not give enough flow to the carbs. From what we have learned, even a bigger "box," would not flow enough. What we have found is to fabricate round, "stubs" and then put the largest K&N cone filters on those. This is really just a backing plate to bolt up to the intakes, with a tube that the air filters bolt onto. Using a large tube/intake duct from the grill into the engine compartment will add in air flow. Just my 2 cents
 

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I have read in an old tuning book that a cold air box should have an outlet at the back (that could be partially reduced for experimental purposes). The cool air should be allowed to flow freely around and past the carbureter air intake.
 
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dougie
Thanks for the pics. do me a favor and never do a walk around of your car for this site. i may then be stuck at this computer for hours. just the couple of pics, info and race video leaves me with 50 questions. boy driving that car with 270hp around a track must be a hand full. wow!

you know i always wondered about the design on an air box that comes in from the end like the 100M. first of all the transition from what appears to be a 4" round house to a 2x4 box has it own issues. the change in shape and the drop in Sq inches creates back pressure right there and cuts air flow. also wonder if the air flowing directly down the tube to the back end will create an air pocket back there which could cause air restriction to the back carb. Maybe a longer box might be a better option or even what John said about a hole at the back. one reason i liked the idea of the air duct coming in to the middle of the box and towards the carbs. actually think i read that somewhere. surely did not think of it on my own!

guess it is important to realize we have two very different situations here. getting max HP and acceleration is different than driving around towns and probably never getting above 4000 rpm with a stock motor. My goal was to get cooler, fresher air to the carbs in town traffic or at stop lights where the build up of heat in the engine bay may be a factor.

Mandango
my one thought about just having an open hose run in to the engine bay (i see Dougie looks to have gone that route in that last picture): one thing i read many times on this forum was about the porous front of the car. the thought was that it allowed air pressure to build in the engine bay at highway speed hurting the fan trying to pull air thru the radiator. thus the engine may run hotter. So i have tried to keep as much air as possible coming in the bay thru the radiator.

As always everything is a compromise.

Dougie:
i am going to be out west the first couple weeks in July around the bay area. you all don't have any races running around that time do you?
 
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