Dove High Riser Tunnel Wedge Problem
 

Does anyone have experience using the Dove 9424B High Riser Tunnel Wedge Dual Quad Large Plenum Intake ? It has the raised port floors and I raised my iron intake ports to match (about 1/2"). Heads now flow a lot better (315 at .600). I also have 2" high square hole spacers under my 750 Double Pumper Pro Form carbs. Engine is just rebuilt and runs beautifully except for one problem. It just does not make the power it should between 3000 to 6000 rpm. It runs smoothly, has great AFR readings (not lean or too rich) but just does not pull hard like it should. I am suspect of possible loss of signal due to the large plenum plus the added effective plenum of the 2" spacers but want to know if anyone else has had this type problem. Just for info it is 427 with 10.5 to 1. Cam is flat tappet 254,254 on a 108 with .625 net lift. I need the 2" spacers to have the front carb bowl clear the distributor in my setup.

You might get a better response here:
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You will not have a tremendous amount of power (relatively speaking) in that range because that's a very large cam for a 427....

Comparatively speaking, I did a 428 with a set of Edelbrock heads and a Tunnel Wedge with a 248° @ .050" solid cam and the horsepower peaked at 6500. Torque peaked at 5500. Adding a larger intake combined with a quite a bit more duration will make it a lot softer through the bottom end and mid-range.

IMO, for that 3000-6000 rpm range, the intake is too big, the cam is too big, and the carbs are too big.

I had a Dove MR TW so I can relate. But I'm not understanding what you wrote.
First off, this is not in a Cobra right? Way too tall for that??
The part about raising your iron head ports-how did you do that?? Do you mean you have MR heads and you made them fit the HR intake? How?
My SO was a 427" too, had a hair more cam and the Shelby heads pulled 320 at .600 with 2.250" intakes. The difference was a MR TW with 650cfm, 1850's. It ran 11's and pulled like a freight train.
IMO, the 2" carb spacers are no help at all. You also have too much carb for the cam and heads. The 750's are only feeding a 427-they're asleep on a small combo like that. They would do better on a 482, 496 or 511 with roller cams.
I'd go smaller to get the velocity up with less additional plenum from the spacers and what ever you have to 'raise' the head ports. Unless you have actual HR heads, you should have a MR TW.
Sorry for not understanding but please clarify.

427 cid at 8000 rpm and 100% VE would pull in 988 CFM of air. 1500 cfm is half again what you need. Too much carb may cause low rpm throttle response issues, but as long as the AFR is correct, it shouldn't matter above 3000 rpm.

You should be around 12.5:1 AFR at WOT to make maximum power. Timing should be in the 35-38 deg range all in by 3500 rpm at WOT. If these are correct, then it is flow issues. It is my opinion that you just do not need a radical cam with good flowing intake, heads, and exhaust. The better the engine flows, the more a radical cam kills the low end, often without gaining anything at maximum rpm.

i've used that intake before but only with high riser heads and 12:1 CR

without knowing alot more about the combo, hard to give a direction.
like for instance the cam specs probably calls for a specific gear to use. also may specify a compression ratio.

the intake, head , cam, and carb combo seems workable but with other factors left out hard to say. with just the info you gave seems the CR is too low for the big plenum and that cam.

i have a .630 lift flat tappet ona highriser with the dove dominator intake and opened up port iron heads.....gotta wind her up tight to make power, 7500 plus, your cam may just start making power at 3k.....

my seat of the pants tells me to have 433 or 456 gear behind yours

Compression is a bit light for that cam in a "real" 427. It'd be stronger through the midrange with either a shorter duration stick of some more squeeze. I normally run a 254ish deal on the street at 482 cubes for a peak around 6200-6500.

The 750 cfm carbs are perfectly fine. If they are vacuum secondary they will run like a 750 double pumper until the primary airflow is sufficient to open the rears up.

The big plenum intake is pretty huge - I suspect that many of the responders have never laid hands - if even eyes - upon one. Adding two inch spacers makes a big plenum even bigger and will theoretically move the tuning window up into the stratosphere. Might not be the whole deal but certainly a contributor.

Why would you need the spacers? I've run several of these and never needed a spacer unless you're trying to run the carbs in the normal "front to back" orientation or trying the run a 4150 style secondary metering block instead of a 4160 type plate. Both of those are good pure race modifications but really unnecessary for any sort of street build.

Thanks for the all the info. Barry, I am the person who you were trying to find BT HR heads for. I gave up and redid my original iron HR's. I raised the bottom of the ports approx 1/2 inch and increased the flow about 50 cfm at .600. I have an excellent custom Ray Tirri valve job with 2.25 and 1.75 yet not shrouded. I do run the (true double pumper) Pro Forms front to back with dual primary metering blocks in each. I did this so I could use a power valve in the secondary side and therefore keep the secondary jets smaller to help the drolplet size. The carbs have 76 primary jets, 80 secondary jets with dual 55 power valves. The AFR's are excellent with this combo. I had to make the spacers to keep the front bowl above the distributor. The front spacer hole is sloped 3/4" to move the front carb forward since the Dove intake is closer center to center than the original Ford dual plane HR intake. It also matches the hole in my hood and the custom fuel logs on each side of the carbs that I use (i use 2v bowls to get dual feeds without the crossover tubes). The car is a 66 Fairlane with 4:11 posi, 26" drag ardials, and a 2:84 low gear (Tremec TKO 600). I tried 34 and now 38 degrees timing with 100 octane but noticed almost no difference. I am an old timer (67) so I drive it daily since life is short. My low power issue is in comparison to my pre rebuild much worse head flow, dual plane ford intake. I had a Comp Cams 256/266 on a 108 with .595 net lift before so I have cutback the overlap with the new profile. I used a single duration for both intake and exhaust since my heads exhaust flow is about 78% of the intake flow. The previous combo pulled hard starting at about 3500 almost like a passing gear, but I don't feel that at any rpm now. I am thinking about putting a wedge shape filler in the intake ( to reduce the plenum volume) if you think that may help (think of it as a mountain range running front to back under the carbs. Also wondering about redsigning the 2" tall carb spacers to each have 4 holes rather than 1 square hole to maybe help with the signal.

Adding some turtles is probably a good idea, but I don't think it will help much. It doesn't seem like you need a "signal", I suspect you're just having velocity troubles because every volume is just so large.

What happens when you get it up over 6000?

If you can't change the spacers, could you go with a steeper rearend gear?

I was thinking the same thing.

I can see how too much plenum area could cause fuel droplets, poor idle, poor throttle response, etc. I do not understand how it could cause low torque in the mid rpm range. I would think the runner length and area would be the biggest factor, as far as the intake manifold goes.

I do not know many things and would be pleased to learn more on this subject.

No velocity.....the same reason why the fuel can fall out of suspension. A large amount of air has momentum and inertia. It takes a lot to get that air moving and to keep it moving.

I've also seen carb spacers cause the fuel to fall out of suspension and pool, especially on some dual plane intakes.

Thanks for all your comments and help. I first tried disconnecting the secondaries on each carb but that had the same lack of power, only worse. I then reconnected the secondaries and put a wood filler down the middle inside the intake. it is a wedge shape 3-1/2" wide by 2-1/2" high by 13-1/2" long. It definitely amde an improvement but not to where it should be. It did show me the problems are with the intake manifold. I will now go back to my stock Ford HR dual quad intake which now has raised ports to match the raised floor ports in my heads. I still want a single plane eventually and may have a Thunderbolt friend modify a stock dual plane (if I can find one) to make it a single plane like he runs on his real Thunderbolt or wait until Jay Brown makes his PSE type FE intake adapters and find or make a single plane intake to fit up to it.
Thanks again for the helpful advice.

Turles, or your wooden wedge gizmo.

An offset distributor drive and lose the spacers.

JMO