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  #1  
Old 09-15-2007, 11:59 AM
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mrbill426 mrbill426 is offline
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Cry LD340 intake modification

My humble apologies if I am (probably) repeating this subject but I am looking for a diagram of the modifications that can be done to an LD340 to make it a spread bore manifold. Someone posted and/or sent them to me long ago but I lost them in a PC crash. Can anyone help?

Thanks!
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Old 09-15-2007, 12:25 PM
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I've seen one LD 340 hogged out to take a spreadbore and the transition into the plenum looked pretty severe. I put a TQ on a Torker and used an adapter to smooth the flow as much as I could. I did open the intake a little to minimize the change in size/shape, but it was minimal. I will probably have hood clearance issues though (my excuse for a hood scoop) but maybe a thinner adapter would give you the best of both worlds without having to carve up the intake.
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Old 09-16-2007, 09:40 AM
dhochsprung dhochsprung is offline
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I believe the modification is in the back of the MOPAR Performance Engine Handbook. You can buy one at any dealership for about $10 or $15.
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Old 09-16-2007, 10:27 AM
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http://www.moparchat.com/forums/atta...7&d=1040948024
http://www.moparchat.com/forums/atta...3&d=1041746838

Mill center divider down to 3/8 and round of the edges.
A T-Q gasket or MoPar T-Q spacer like pictured can be used to bolt down and made as a template to use a scratch all for a guide.

This is a race type mod. Made to help bring up the RPM range of the dual plane. MoPar sells 1/4 inch plastic spacers (as shown in the picture) to raise the carb up. A decent spacer wouls help any sharp turns though a few min.'s with the die grinder to produce more of a curve would help a tad.

This mod is recomended by MoPar for what they called, "Cams over .550 lift." Which back in the day ment large street or smaller race cams. Typically, cams of this description were over 244* duration @ .050

I like this mod and it works well with the T-Q for explosice top rpm power.
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Old 09-16-2007, 11:43 AM
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Quote:
Originally Posted by dhochsprung View Post
I believe the modification is in the back of the MOPAR Performance Engine Handbook. You can buy one at any dealership for about $10 or $15.
By golly, I have one of those books (8th edition) and there it is on page 141! Thanks, dhochsprung
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Old 09-16-2007, 12:02 PM
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Thank you, Rumblefish 360

You say this is a racing modification? My intent is to use this LD430 in place of the stock iron manifold which is also a spread bore. It is more of a stock restoration with a few little "hidden" kickers. I also have a set of higher compression pistons. To maintain appearance I will be using the stock exhaust manifolds. I want to put in a cam that is a step above stock, and maybe some steeper gears. It has 3.23 gears now and I am thinking 3.55



Quote:
Originally Posted by rumblefish360 View Post
http://www.moparchat.com/forums/atta...7&d=1040948024
http://www.moparchat.com/forums/atta...3&d=1041746838

Mill center divider down to 3/8 and round of the edges.
A T-Q gasket or MoPar T-Q spacer like pictured can be used to bolt down and made as a template to use a scratch all for a guide.

This is a race type mod. Made to help bring up the RPM range of the dual plane. MoPar sells 1/4 inch plastic spacers (as shown in the picture) to raise the carb up. A decent spacer wouls help any sharp turns though a few min.'s with the die grinder to produce more of a curve would help a tad.

This mod is recomended by MoPar for what they called, "Cams over .550 lift." Which back in the day ment large street or smaller race cams. Typically, cams of this description were over 244* duration @ .050

I like this mod and it works well with the T-Q for explosice top rpm power.
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Old 09-20-2007, 03:23 PM
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Thanks, I needed this too!
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Old 09-20-2007, 08:51 PM
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Quote:
Originally Posted by mrbill426 View Post
Thank you, Rumblefish 360

You say this is a racing modification? My intent is to use this LD430 in place of the stock iron manifold which is also a spread bore. It is more of a stock restoration with a few little "hidden" kickers. I also have a set of higher compression pistons. To maintain appearance I will be using the stock exhaust manifolds. I want to put in a cam that is a step above stock, and maybe some steeper gears. It has 3.23 gears now and I am thinking 3.55
Sorry for the delay.

You can open up the intake for a T-Q, but just do not mill the divider down. Thats the race mod.
A spacer to raise the carb up so the open butterflys are flush (At a min.) to slightly above the base of the intake would help some. (Approx 1/2 inch.)

I just did 3.55's in my Magnum from 3.21's. (Pinion seal failure promted this.) Nice street gear with Hwy. abilty's. 3.91's cut out the Hwy. a bit.
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Old 09-21-2007, 11:59 AM
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Thanks, I appreciate you clearing that up
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Old 09-21-2007, 12:06 PM
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Is the spacer used to omit the need for modifying the manifold?

I wonder if that extra 1/2" would cause clearance problems with the stock air cleaner and the hood.
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Old 09-21-2007, 12:22 PM
dodger1 dodger1 is offline
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Are you referring to an additional spacer as well as the stock TQ thermal spacer?
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Old 09-21-2007, 02:41 PM
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Quote:
Originally Posted by mrbill426 View Post
Is the spacer used to omit the need for modifying the manifold?

I wonder if that extra 1/2" would cause clearance problems with the stock air cleaner and the hood.
No, but you could do that. Skip the mod of milling and just use a spacer.
Car , hood year model dependent on clearance. If you want a height measurement of the intake with carter carbs, I can do that. I have no Holleys in house anymore.

Quote:
Originally Posted by dodger1
Are you referring to an additional spacer as well as the stock TQ thermal spacer?
The T-Q doesn't have a stock spacer. It does have an extra thick gasket not normally seen on cars. So does the earlier squarebore Carters. The AFB/AVS.

In short, yes. In example, a typical aluminum square to spreadbore adapter could be hoged out to a T-Q pattern on both sides. (For example) and mounted on top of the intake with regular thin gaskets for additinal height.

Would anyone like pictures? This would be easy to take a few shots and post them up later.
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Old 09-21-2007, 07:26 PM
dodger1 dodger1 is offline
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Pics would be appreciated here, for sure.
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  #14  
Old 09-21-2007, 09:19 PM
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rumblefish360 rumblefish360 is offline
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OK peoples! Some measurements.

1st picture

Typical T-Q gasket from any store U.S.A. is approx. 1/16 thick, rebuild kit gasket, which should be OE thick (?) @ 5/16 thick, aluminum spread to square adapter, a Mr. Gasket model I think it was is 3/4 thick.

OK, Thats 1/16, 5/16 & 3/4.

2nd picture;

*Please note that I did not do the spreadbore mod to the intake and I believe the person whom did, screwed up and had to weld up the blunder and/or added the extra material to beef up the sides which get thin.
By compare of other pictures and up close and in person LD-340 intakes, the job done on my intake doesn't seem to be to far off from what was casted from Edelbrock.
Like I said, I don't know if it was a screw up in the spreadbore mod or someone was nervous after doing it.
It is not a spacer welded on top via evidence of a natural for and aft pad without mods on the intake.
I did do the plenum mods.


The intake measures 4-1/2 inchs at the front and 5-7/16 at the rear.
The way Edelbrock measures there intakes; http://www.edelbrock.com/automotive_...lds_main.shtml
Scroll to the bottom of the page for how to measure instructions and a diagram.

To the top of the T-Q air horn is 8-1/2 and with the MP air cleaner, (OE unsilenced) is 1 foot with the thin 1/16 gasket installed.

Total height can really get up there. Nearly 1 ft.- 1-3/8 inch with the thicker gaskets. Measured from the top of the block. (Not pictured. Just imagine a aluminum spacer in the 2nd picture.)

3rd picture;

You can see from the picture that the aluminum spacer helps raise the carbs butterflies above the intakes carb pad. This is helpful in fuel atomization into a finer mist which will turn corners better and faster than droplets of fuel.
The butterlies do open up alittle more, but being one handed with the camera in the other hand....I think you get the idea.

4th picture;

This is what I mean by hog out the spacer. While this may not inhibit actual cfm totals, (It may, I don't know) but the air and fuel do have an obsticle (sp) and I'd bet it hits it on the way in. Thus the reason to open up the spacer. A clean clear shot.

From running this intake and T-Q (850 larger unit), this is one kick butt street set up. Excellent!
I do have a air gap RPM and put the spacer /adapter to run a T-Q, but I could not close the hood of my '73 Cuda.
To bad Edelbrock doesn't make a RPM capable of a T-Q like the LD-340 is with a mod. Which I'd do in a heart beat to a (Capable) RPM.
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