LD4B intake on a 1969 340CID

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17remfan

17remfan

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The car I just purchased has an LD4B intake on the otherwise stock 340. Will the use of this intake cause a power lose on this engine or is an ok intake?
I have heard the LD4B is designed for the 273 - 318 engines.
Should I be in a hurry to get this intake off the engine?The cam should be stock ,same with the converter and probably 323 gears as far as I know . Any comments welcome .

I dont have the car here yet to test it and was just curious about the intake setup. Thanks
 
The LD4B is a great manifold even on larger displacement engines. The ports are small, but they are larger than the ports on my Wieand Action +.

It'll be fine with a stock cam.
 
On a stock 340 it should be OK, but no better than the factory iron (which was pretty good). Hang onto it and see if you can trade for an LD340. A Performer RPM is the modern equivalent to the LD340, and would be even better yet.
 
Ok guys ,ill keep my eyes open for an LD340,maybe at a swap meet .It will give me something to look for .Im glad to hear it should be fine for now though.Thanks
 
It'll work but the port alignment will be off the ld4b is for the smaller port 318 heads,an ld340 or performer rpm would be a much better choice,even a stock 340 intake would be better the ports will align...
 
hi, awhile back, I flow tested the stock 340 intake and a LD4B just for grins.
test pressure was at 25", flow tested through one port, blocked others.
flow numbers were, 197 CFM for the stock cast 340 Intake, LD4B 264 CFM.
hmm ,
 
Thanks for all the help . You guys are great.I feel pretty comfortable with keeping the LD4B on the engine . It seems that it has been on there for some time so I would think the previous owner was happy with it . Ill post back with how the car runs with it soon ...
 
To small of a port is better then to big of a port.

Weres Rapid340 ? He mentions testing a few intakes in his Duster and seeing no to little gain over the 71 intake and thermoquad.
 
I never tested an LD4B but I did test an LD340 on a mildly built 340 in a street/strip duster with a 2600 stall converter. What I found was a very small increase in peak power but a significant loss in low speed torque. Cold idle quality was terrible compared to the stock intake. My quarter mile ET did not improve with the LD340.

Having said that, I have no doubt that an RPM intake would be an improvement. In my opinion, the LD340 and performer RPM intakes are nothing alike. Since I play with thermoquads, I have never tested an RPM but I have seen dyno comparisons published is some of the magazines.
 
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