Edelbrock LD340 Intake Manifold Usable Max RPM?

-
Fast340cuda said:
I recently took my car to a local chassis dyno and ran it with the LD340 intake. Combo is 4.06” bore, 3.58” stroke, 11.1-1 compression ratio, solid flat tappet cam (252/257 @ .050, .550 ish lift, 108 LSA). Intake was gasket matched and the plenum divider was cut down 1” and 2.5” length wise. This was topped off with a 750 double pumper. Here is the dyno graph for reference.
Click to expand...
Fast340cuda said:
Edelbrock RPM’s that were touched up by Ray Barton.

I use the numbers as a reference. Was more interested in the power curve. I have tried the performer RPM, Weiand action plus, Victor 340 as well as the M1 single plane. I have been the happiest with the LD340 so far on my combo.
Click to expand...
Fast340cuda said:
The heads have only had a valve job and the bowls cleaned up. I believe the camshaft is a little small, it was ground for a 3.31” stroke but I ended up finding a great deal on a 3.58” stroke crank and some .060” 360 pistons so it is now 371 CID.

I feel the car runs pretty good, pump gas, all steel, full interior and runs mid 11’s with a 4 speed at 118 MPH. I also feel the dyno numbers are pretty good for a motor that was designed in the 1960’s as there were several late model 392 challengers and 5.0 mustangs that were putting out low 400’s on the dyno which seems to line up with what others are reporting.

I have only had the LD340 on the dyno. I have run both the Victor 340 and M1 on the track with the M1 being a little over a tenth faster. On the street, the performer RPM was great off of idle but the LD340 pulls harder up top and the power doesn’t nose over like it did with the RPM.
Click to expand...

This information is immensely helpful. Thanks.

What type and size headers are you running?
 
Newbomb Turk said:
Right not my deal.

As an engine builder I despise rule makers who think they need to limit engines to junk **** to level the playing field.

Bewy thinks you can innovate your way around ignorant rules. It shows his lack of experience.


Parity means mediocrity. I detest both.

If I sound like an 18 year old it’s because the truth hurt your little feelings.

Class rules like that are bullshit. He can run decent compression. He can have headers.

But we will **** them on an intake manifold to make it “fair”.

If you can’t see the absurdity in that statement you are just too bone headed to see.

At least FAST classes limit everything. It’s still more expensive than it should be, but at least they have rules that make some sense.

It’s damn near always the corner turners who want **** to be “fair”. It’s stupid.

As for Stock Eliminator racing, no one should lie to themselves and THINK an intake manifold other than OE would be slower than what they have are either full of **** or stupid.

Comparing Stock Eliminator to a corner turning car is overly simplistic.

They didn’t make the rule to make **** “fair”. They did it because it’s STOCK and they chose to keep that part STOCK.

Not the same.

So stop with your whining and put on your big boy pants. Stupid rules are stupid rules.

Truth is truth.

You should red X your dumb self. Or better yet, BLOCK ME. I get tired of clowns talking ****.

Bad rule, bad class. Simple as that. If the OP wants to run the class then who cares what the “real world” experience is? The OP will need to PAY to out innovate everyone else if he wants to win.

That burns through money. Fast.
Click to expand...
I agree, and using the intake manifold to add parity to a class with multiple manufacturers is about the worst way to do it.
 
TT5.9mag said:
Ask em what the .050 intake duration is. I’m betting you won’t get an answer. Maybe @GTX JOHN can chime in.
Click to expand...
Yeah that ain't limited. That's where cheater cams come into play. I've built lots of dirt track engines under the stock lift rule.
 
GTX JOHN said:
Duration is on Intake 260+. That is as specific as
I want to be. Exhaust is well over that.

The engine on our 340s will run 7500 thro
the lights.
Click to expand...
That’s about as specific as I thought you’d be.
:thumbsup:
 
All info from ( John ) about 8 months ago hope it gives you some needed info !!!

20241017_224710.jpg
 
Fish Bite said:
Thanks for taking the time to find and post the numbers, which are very helpful. I'm glad John's contribution continues on.
Click to expand...
Absolutely , he was a Happy content man and it showed in all his endeavors & tasks !
His contributions will carry on well past many of us members to say the least.
 
I took NewbomTurk's advice and ignored him. He talks more sh*t than a fertilizer salesman.
 
As others have said, 7000 rpm is about peak, and I only ran to about 72-7400 through the lights but it was dropping off. I ran an LD340 modified same as yours and a very similar engine combo except bigger flat tappet cam. 5.57 gear (car was an E-body, so heavier). Switched to a single plane and picked up 2 tenths, but you are playing within the rules so that's out. Kept that LD340 on the shelf for a long time before I was willing to part with it because it's a great intake!
 
TheRacerDave said:
As others have said, 7000 rpm is about peak, and I only ran to about 72-7400 through the lights but it was dropping off. I ran an LD340 modified same as yours and a very similar engine combo except bigger flat tappet cam. 5.57 gear (car was an E-body, so heavier). Switched to a single plane and picked up 2 tenths, but you are playing within the rules so that's out. Kept that LD340 on the shelf for a long time before I was willing to part with it because it's a great intake!
Click to expand...
Thanks for more empirical feedback.

Do you happen to have the cam profile you ran?
 
Fish Bite said:
Thanks for more empirical feedback.

Do you happen to have the cam profile you ran?
Click to expand...
I don't know if this is any help, as it t was an old Cam Dynamics. I believe Crane now has the masters from Cam Dynamics, but I'm guessing as old as this is (1980s) there are much better profiles available now. if your rules package is lift-limited I'd talk directly to one of the cam companies, as they can make up for lack of lift with longer duration, like they do with stocker cams.

cam tag-edit.jpg
 
Last edited:
The most interesting info on the above cam card are the modest spring pressures for a cam of 310 duration & nearly 600 lift. 130 lb on the seat.
I have the CD catalog. That cam had 275 @ 050 & quoted rpm range was 4800-7800 rpm.
 
I know, right? Anything near those specs today they want about 170# on the seat and over 400# open. Stock spring diameter is 1.430" and I cut the seats to use a 1.480" diameter spring installed at 1.750. I don't recall who made the springs - I bought all that stuff from Ed hamburger way back when and trusted his recommendation. I set it up just as he said and never once ran into valve float even with only 130# on the seat.
 
Fish Bite said:
I'm hoping to get feedback from people who know firsthand (or can point me to others' results) about the RPM limits of the LD340 intake manifold with the plenum divider removed per Direct Connections' instructions and an exact deep-port gasket match.

The racing class rules I'm bound by restrict my intake manifold to either a factory cast-iron or LD340, and I know the intake will limit performance compared to a quality single plane. I'm trying to get an idea of the RPM range the engine can practically use with the LD340 to help me in considering cam profiles. The engine is a 360 gas race engine (no street use), 12.5:1 static compression, headers and unrestricted exhaust, four speed, and low rear gearing. I'm restricted to a Holley 4150 750 cfm.

The ported heads flow the following:
Lift Intake CFM Exhaust CFM
.400 256 171
.500 277 189
.600 285 195
.700 281 197

Can anyone give input on their experience of what RPM the power flattens out or starts dropping off with the LD340 on a race engine?
Click to expand...
I have no idea about the intake but I'm guessing you are building a SVRA or HSRA racer? If so that is great. I have a shell here I am very tempted to do that with when I'm done with my main one.
 
What was that movie where the pursuit cop says his top end is unlimited...? oh yeah Dirty Mary Crazy Larry...:thumbsup:
 
I shift at 6300-6400 and cross the strip at 6800 with a massaged stock 340 intake. Your intake is better. For cam, I would talk to a reputable cam company and tell the exactly what you are doing. As an example, we share a somewhat similar intake, but you don’t want my cam specs. I run exhaust manifolds to your headers. I run a bunch of lobe separation.
 
You must log in or register to reply here.
-

Back
Top