TQ on LD340 or Air Gap

-
71duster06

71duster06

Well-Known Member
Joined
Jan 23, 2008
Messages
639
Reaction score
74
Location
West Michigan (GR)
Hi everyone,
I know there has always been the battle between the LD340 and air gap. Overall it typically leans towards the air gap as the preferred intake. I have both intakes on hand and was wondering if anyone ever used the air gap with a thermoquad (with adaptor). I have not seen this combo before.

I am sticking with the TQ as my 340 saw a noticeable increase in the 1/4 mile over the holley 750 so I'm not changing that.

Any insight would be great. If not I might just try the air gap afor the trip to Mopar Nats in August and see how it runs.
 
The air gap might be 2/3 hp better not sure how it would be with a spacer or if it would even fit under the hood with a spacer. The LD can be hogged out for the tquad just use the base gasket as the templet. I would be more inclined to use the LD over the gap with a spacer. I would not run the heat crossovers open and I would use the 1/4 plastic spacer under the carb.
 
Agreed. Somewhere on the World Wide Web is a picture of the very thing your considering. It did not fit under the hood of my'73 Cuda and I doubt very much it will fit under your hood. Do a mock up and see. I could be wrong here.

I also still have my LD340 and TQ set up. A wonderful dual duty set up.
Have you tried a larger Holley?
 
rumblefish360 said:
Agreed. Somewhere on the World Wide Web is a picture of the very thing your considering. It did not fit under the hood of my'73 Cuda and I doubt very much it will fit under your hood. Do a mock up and see. I could be wrong here.

I also still have my LD340 and TQ set up. A wonderful dual duty set up.
Have you tried a larger Holley?
Click to expand...

Fortunetly i have a six pack hood going on the car so clearence will not be an issue. I always go back and forth on if the spread-to-square adaptor is a restriction or a benefit since its an inch think and spacers seem to work very well. depending on what intake i settle on the plan was to bolt the adaptor to the intake and then cut out a long transition from the carb into the intake... thought is it would reduce the abrupt transition.

Again, just a thought.
 
I do think that LD-340 will like the extra plenum. While it is a high rise dual plane, the fuel could use that extra inch to atomize a little better. A lot depends in the set up of course!
Some where here, at the forum, I measured the heights of the two intakes and posted them. I do not remember which one was taller and by how much.

I do remember that the RPM's runners where smaller and more stream lined vs the larger more volumous runners of the LD340.
 
rumblefish360 said:
I do think that LD-340 will like the extra plenum. While it is a high rise dual plane, the fuel could use that extra inch to atomize a little better. A lot depends in the set up of course!
Some where here, at the forum, I measured the heights of the two intakes and posted them. I do not remember which one was taller and by how much.

I do remember that the RPM's runners where smaller and more stream lined vs the larger more volumous runners of the LD340.
Click to expand...

Do you think my idea of improving the transition will make any difference ?
 
If it is done correctly, I see no reason why it would not improve unless the current combo doesn't need it. Adding a spacer doesn't all ways mean added power.
 
Yup, i have seen that mod before. The TQ has been mounted to my LD340 for a few years now but i never cut into it since i wanted to make sure that was the long term intake...

That has forced me to use the spread-to-square adaptor. my question now is if that adaptor effects the operation vs a straight shot (like the intake mod).
 
Yea it does but don't worry about it.
What is happening is the air and fuel are being necked down to fit into the square opening. The less the air and to a higher degree, the fuel have to bend and turn the better it will be for the engine. Fuel needs to atomize and turning left right up and down allows the fuel to collect on the floor and walls of the intake. This will cause puddles and big droplets. In this state, it burns poorly.

If you can take one less bend out of the intake or relax the sharp bend, the better it will deliver the fuel In a better state to burn. With that said, then you can see why the RPM makes a few more HP even though the runners are smaller. Though smaller runners add velocity, which can help in some cases. To small a runner and you restrict power. Which doesn't seem to be the case at all with the RPM. Judging by some members running very well with it on top of strokers.

If I were you, I'd just run the TQ on top of the RPM and let it rip and see how it goes.
Have fun swapping parts out, tinkering with it to see what works best and what you like best.

I'm curious, what are the engine specs?
 
Good deal. Thats the way i was leaning for a bit was trying the Air Gap just to see if there was any improvement. owrse case the LD would go back on...

The motor is a 69' 340
Steel crank and rods, forged pistons (.030 over due to corrosion on the cylinder walls)
4-speed w/ 3.23s
Lunati Voodoo 60403 was the number at the time, heads cleaned up along with intake and header port matching.

The car ran mid 13's with a 2.5 sec 60' time at 103mph so once i improve my launch im hoping for high 12's.
 
Just keep on focusing in on the best launch and lowing the times at the starting line. Finding a half second or more is a lot of time and power. Good luck and have fun.
 
rumblefish360 said:
Just keep on focusing in on the best launch and lowing the times at the starting line. Finding a half second or more is a lot of time and power. Good luck and have fun.
Click to expand...

Yup. I should be in good shape there. The car about died and I still was in the mid 13s so I think the power is there. Now it's dealing with the 3.23s.

Nice driving the car to the track hense why I have them.
 
You must log in or register to reply here.
-

Back
Top