Hello there

A friend of mine is going to give me 2 IDF 36 (i think) carbys from a alfa 33. I am thinking about bolting them (fabricating a new stainless steel intake manifold and a new steel exhaust manifold) into my car A12 engine. What do you think about it?

The engine is begining to burn some oil and so i am considering a major overhaul. If i need to replace the engine pistons and you advise to me?

I would like to know if i can bore the A12 engine block to get something like 1400 cc and if there are some suitable pistons.

Thank you

Ricardo

Dual IDF carbs would be sweeeeet! I'm assuming they are the downdraft version of the DCOE. My first thought was "too much carb" but then I thought about all of those dual 40mm DCOE setups running around. Sounds like a good plan.
As for the bigger pistons in an A-12 block, A-14/15 pistons with an A-12 crank will yield around 1270cc. Unless you buy shorter rods, you are stuck with the A-12 crank due to the short deck height. One other thing, the A-12 rods will have to be resized at the small end to fit the A-14/15 wrist pins. (But if you have an A-12A, the wrist pins should be the same. A-12 & A-13 have 17.4mm wrist pins where A-12A, A-14 & A-15 have 19mm wrist pins.)
I know all of this because that is what I'm building for my turbo car. Haven't gotten any of the parts back yet so I don't even know if any of this is going to work.

hey ricardo,how are you.the 36 idf's will mean making a new manifold,as they are definitely downdraughts,but you probably knew this anyway.the biggest piston you could squeeze into the block is a 77 mm piston,which is one mm oversize for the a14.this will then be 1308 cc's.an a14 crank with a10 rods will fit,but how many good a10's rods are there still floating around.i'd suggest to rebore to 76-77 mm with the stock crank & a mild cam.as for the webers,downdraughts on an inline motor has been done successfully,so no problems.

Thank you for the information

Tim

Yes, they are the downdraft version of the DCOE and they are 36 (smaller than 40), the alfa 33 engine was around 1300 cc and so i think that the jets will be quite similar if not the same.

Paul

I am doing fine, and i am in a great mood for cars since another friend of mine give me (i am still waiting) four aluminium wheels (however they are 13s and i am looking for something like 15s or 16s to put at the car rear). When are you going to post your car photos? I need new ideas...

For both

The guy who is going to give me the alfa 33 IDF carburetors works here with me, at one of our workshops. Everybody around here likes my car and they think that it is cute (around here we only have BMW, Mercedes, VW, Porsches, etc...), so I asked them if they can help me doing the new manifolds and they said imediately yes.

The intake manifold is going to be made of stainless steel. However i am a litle worried about the curve that they must have (since the webers must be vertical) and about the brake servo system. I think that the vacuum from one of the cilinders will be enough???????????

The vacuum advance controler is another issue...

The exhaust manifold will be made of construction steel (i would love it to be stainless too, but then it is more probable for it to brake due to the thermal expansion, stainless alfa is bigger). The exhaust mani. shape will be mimetized from one that i saw at datrats (sorry, i would buy it but i am on other side of the world). The exhaust muffler is one that a cousin of mine is going to give me from a bike (something like GSXR1100, i think)

Regarding the piston rods, is it safe to oversize the small hole? Have everyone ever done that? I don't want to brake a rod at the midle of the night in nowhere street...

I am now working on a very simple gizmo for increasing the engines power, if it works I am going to post some photos and maybe even some CAD drawings, if not I am not going to talk about it anymore.

Best wishes and looking forward to hear from you

Ricardo

You pose some interesting questions. I am of the opinion that the brake booster should draw from all of the cylinders. What you could do when building your manifold is connect all four runners with a "balance tube" and take the vacuum signal from that. Having said that, I have seen several (read: all) sidedraft manifolds that only draw from the #4 cylinder. I'm guessing that since it draws a vacuum and then no more air, it doesn't effect the performance.
I don't know what the laws in Portugal are regarding the PCV system but I would suggest you run one. Once again, the "balance tube" is where I would connect the PCV valve to the block. I've used the brake booster port for this on a single side draft setup. I wasn't really happy about it but it didn't seem to hurt the performance.
As for resizing the rods, I'm keeping my fingers crossed that it will be OK. There appears to be plenty of meat on the A-12 rod to bore it out. Besides, we're only talking 1.6mm diameter or 0.8mm radius increase. In fact, the machine shop went too far on mine so it's going to be a full floater with teflon buttons.
I was also thinking about your manifold. Is there going to be enough hood clearance? Aren't those carbs a bit on the tall side? Resist the urge to have the manifold swoop down and back up into the cylinders. I think there would be a serious puddling problem with that design. They may require a very sharp radius to make the turn from vertical to horizontal and you still might not be able to get them under the hood. What I would suggest before you invest a lot of time in making a manifold, measure from the top of the stock manifold to the hood and see if there will be enough room.
Stainless will work fine for the header if you allow it room to grow. The bolt holes on the ends of the flange need to be bigger than the ones in the center and a flexible mount needs to be incorporated at the bottom. Of course it could still crack so, use what you like.
Well, I guess I've rattled on long enough.

Tim

I have already been doing some measurements and my opinion is that it is possible to fit the Webers under the hood (including the velocity stacks) and doing the manifolds with a minimum curvature radius similar to the original manifold. I am planning to make a special air box, but i think that the clearance is enough.

I dont want to do the manifold tube bends to sharp since that will "choke" the flow inside of it. If you have a sharp corner the flow will not follow the wall and a recirculation zone will appear after the bend reducing the "efective" manifold diameter.

Someone over here "throw the idea into the air" of cuting the hood, leting the velocity stacks sticking out. However, that is not possible, since I don't want to do it. I have just killed the guy.

I think that you are correct regarding the PCV (nobody gives a damn about it around here, most of the thecnicians at inspection centers doesn't even what is it for), the advance control and the brake booster. You will get a more equilibrated engine (i think).

Regarding the exhaust manifold I think that your idea is quite good and I am going to calculate some figures about the flange dilatation.

Regarding the rods, can you estimate the outer diameter of their heads?

Thanks

Ricardo

Aside from the law, isn't still a good idea to run a pcv? help seat rings, help prevent oil leaks.
I'd love to see those carbs poking up through the hood too but the truth is that when the car starts moving the air flowing over the carb will start to suck out the air/fuel thats trying to go down the carb.

If they will fit with a good radius bend then that will be a very cool setup.
As for the distributor advance, I think there is some dispute as to what that does and how necesssary it really is. I have run both Gil and the Chickenhawk without any vacuum advance mechanism for years. I've never noticed any ill effects.
I've been told that the A-series engine needs the vacuum of the PCV system to help draw the oil down from the head. Like the drain holes are not big enough and need a little help. I'm not sure how true it is but the one engine I ran without a PCV line to the intake, started burning quite a bit of oil soon after. I had a little K&N breather on the valve cover and another on the pipe sticking out of the block.
Hopefully you have an A-12A. If so, you will NOT need to resize the rods. Where is your distributor? Is it at the front of the engine right over the oil pump or is it near the middle of the block? Also, what is the distance from the timing cover to the head? Are they a few millimeters apart or quite a few inches? These things will help to identify it.

If you really want a stainless exhaust do it, just be careful of the grade you use. Most muffler shops use a 400 series grade which is magnetic. If you have more money use some 304 don't be tempted to use 316 as it will crack. I have built many exhausts and headers in 304 and never had a problem. It also polishs up really nicely. To make life easier for your polisher just tack every thing together and then break it into each branch to make it really easy to polish. And don't forget to make the flanges out of the same grade SS as the tubes..

Hello everyone

Tim, regarding the distributor position it is located in the midle of the block. You can see two pictures of my car engine bay on Photos/Misc/B310 Radiator. Is it a A-12A ?

Wayne, hopefully that you advise me on that, since i was planing to use 316 stainless steel.

Thanks

Ricardo