Dual 40 DCOE

[ConreroGT]

Would anyone be interested in buying my dual 40 DCOE Webers? They would include a K&N (oval) filter setup and the cutom made adapter to fit the the thermostat housing (if needed...depends on the intakes you use)

They have a 30mm choke and have already been used on a 2.0l GT.

-Kyle

(I'll be taking pictures of them w/o the engine and posting on eBay soon.) Starting at $250

[calvin]

hmm I just had a one year old set of 40ies rebuilt. I was looking at how the last person had the linkage hooked up. I also just had the cannon intakes welded up and redrilled to be straight. What intkaes do you have? why are you getting rid of the 40ies? Are you not going to run duals anyone?

They finished my engine today. Compression is 220 so I think it is about 11 to one. It seems I used 30 over 305 pistons.

[calvin]

I didn't, they did... I just stood there grinned foolishly and nodded

but I will find out how the number came to be tommorrow. I didn't grin so much when they said i most likely will have to use 104 or some other additive because of our 92/3 low octane here in Mo.

Funny the guy at advance auto parts said the same thing when I told him the compression was about 220 he said 10 and a half to 11 also just with that number. This is the kind of question that bob could answer with his eyes closed.

I think I will need one of those houseing with my cannon intakes...

[ConreroGT]

I found some 45's off eBay for $550. I use Risse manifolds (I think that's how they're spelled.)

[ConreroGT]

I look at it this way:

Going from a 32/36 to a 38 DGAS is a big differance. Especially if the motor is built up. I remember I had to go back to the 32/36 to pass emissions (I had a 38 DGAS on my 2.2) and there was a world of difference in power loss. And I really noticed it when I passed emissions and went back to the 38's. Remember the 32/36 is a single barrel that only opens the second 36 barrel about halfway thru the throttle travel. A 38 is a two barrel design that feeds all 4 cylinders at the same time.

Let's look at some numbers:

On average, a 32/36 is providing 17mm of "air/fuel" flow at a time. And thats assuming both are open.

A 38 DGAS is providing about 19mm of "air/fuel" flow all the time to 4 cylinders.

(38 x 2 barrels / by 4 cylinders.)

This gives us a difference or increase of 2mm per cylinder.

Dual sidedrafts provide 4 barrels to 4 cylinders. This is an amazing 40mm per barrel! An increase of 21mm over a 38 DGAS!

Going to 45's increase this further to 26mm over a 38 DGAS or 5mm over dual 40's.

Were talking a 5mm increase. Remember is was only 2mm that made a huge difference over a 32/36 and 38 DGAS.

So the answer to your question is: It will make a big difference in performance.

(anyone wanna back me up on this. This is probably a crude way to look at from an expert engine builders standpoint. And I'm no engineer either)

And besides. The 45's I bought are brand new. So they look prettier too.


-k

[TGSI Racing]

What you say is true as far as carbs go. But remember, after the carbs are the manifolds, the port runners, the valves, etc. Consider that a 45 mm side draft that has to go through a 40mm intake valve... and if the valve is only 1/2 open (as it is twice as much as it is full open), then the velocity through the side draft is really low. Also, the plenum of a stock manifold has an effect vs a single runner of side drafts.

So, I guess what I am really saying is that bigger is not necessarily better. It's the total set up that counts.

Oh yea... pretty new carbs are always good

[ConreroGT]

yea, good point.

Man...I have a feeling the carbs alone will give me hours of time wasting enjoyment. But then I've never really learned much from doing it right the first time. That's whats so much fun about the unknown.



-k

[Travis]

Notavette,

You've missed the effect of the length of the intake system.

Especially in a GT which has very little room for carbuetion, you must run a very short intake system. This will seriously reduce your low end torque. If you're racing and are keeping the RPM up above 5k or so this isn't a problem, but if driving on the street you'll be giving up a good deal of low end power over something like a DGAS. Conversly, if you run a DGAS you'll be giving up some high RPM power both due to the long intake length and breathing that isn't as good as the sidedrafts...

Bob's intake porting article does a good job of showing how significant the effects of intake length are. Look for the part where he experiments with carb spacers. Just 1/4" can make all the difference.

-Travis

[ConreroGT]

Yea, I have a few velocity stack sizes to try. I'm aware, from what I understand, the distance from the opening of the velecity stack to the head makes a big difference in performance. Like you were saying: For street you want a longer run and for racing a short run. I'm not using the short Irscher intakes. I use Risse intakes that are "normal" size. The only other way to control the distance is the stacks themselves. So I have a few different sizes. The longest I have is 2 1/2 inches. I figure I can't use too much longer or else I'll have to cut the fender out and have it hang over the wheel!

I know, I know...I still have a lot to learn!

thanks for the input!

-k