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Old 07-10-2020, 09:21 AM
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Default dual plane intake with 4-7 swap

My buddy is fighting a stumbling problem on his 406. he currently has a edelbrock rpm, ported kre ds and a hydraulic roller with 4-7 swap, forged ohio crank and on e85. fairly new combo but not entirely.
Previously had same intake, non swapped cam, unported heads and pump gas and tad too much compression and his N crank paid the price. car had been 11.60s shifting it in his 65 gto.

he has been playing with carb and timing, and even swapped carbs, and distributors. No results, except issue not as bad with less fuel (jetting etc). but car is now a dog and lean.
No one considered the intake and the cam swap until now.
has anyone run into a similar issue with dual plane and a 4-7 swap, where the dual plane is optimized for a different firing order? It makes sense that this is the problem the whole time. We are just looking for correlating experience.
Next change will be a north wind or another single plane.

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Old 07-10-2020, 09:56 AM
tom s tom s is online now
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I think it also effects the clocking of the headers?Tom

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Old 07-10-2020, 10:13 AM
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i think that does apply for max hp if seeking every last drop. I guess with the scavenging effect, it could be pulling some charge into the exhaust before its being used, due to the lobe swap. This thing sits and idles fine, as soon as you jump on it it flutters

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Last edited by mysticmissle; 07-10-2020 at 10:49 AM.
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Old 07-10-2020, 10:47 AM
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I have no experience but I just watched the Engine Masters do a Dino fest on it. They used a 572 Chevy.
The performance results were inconclusive but they did see it cause a large change in mixture distribution. May be the case in your friends car. It would probably take a lot of testing to figure out what’s going on.
I’d think at least trying a single plane might be a good start.

Murf


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Old 07-10-2020, 11:05 AM
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Id have to study it closer but i'd think a dual plane would like the 4 7 swap better. It's possible it's the issue but id be surprised. I am wrong a lot though


Last edited by slowbird; 07-10-2020 at 11:16 AM.
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Old 07-10-2020, 11:32 AM
"QUICK-SILVER" "QUICK-SILVER" is online now
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If you stay in it, does it start to pop and crack out the exhaust?

Clay

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Old 07-10-2020, 11:43 AM
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Was the cam installed properly? Any intake gasket leaks? Valve adjustment? Valve train issues with new cam?

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Last edited by ta man; 07-10-2020 at 11:54 AM.
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Old 07-10-2020, 12:19 PM
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no pop out the exhaust, lifters are a little noisy but 1/4 turn past zero lash, We have also considered an intake leak.
i cant speak to the cam installation, but he is pretty sharp young fella, and this was not the first time througe the process.

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Old 07-10-2020, 06:53 PM
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Has the cam been checked to confirm that it was ground with the 4-7 swap. I know one person on this board who fought problems with his engine only to find out he didn't get the swap he paid for. If I remember right it was mainly sluggish, didn't pop or backfire.

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Old 07-10-2020, 07:18 PM
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"Tanzi also noted that “to yield the greatest gains requires header design work....Matching primary tubes with regard to the intake manifold and cylinder head ports is also necessary. This usually relates more directly to applications that use a single-plane manifold, and tunnel ram manifolds in particular. In terms of fuel distribution, we see greater benefits with single-plane manifolds as compared to dual-plane manifolds, since dual-plane manifolds are less prone to
reversion and negative pulsation.”


https://www.motor.com/magazinepdfs/032009_07.pdf


.

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Old 07-11-2020, 09:04 PM
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Not to hi-jack the thread, but my new cam has the 4-7. And I believe 3/2. Swap. Do i need to worry about my header tube arrangement?

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Old 07-11-2020, 09:50 PM
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I dont know about worry but if they were clocked properly for a std cam it could have some effect.Maybe a questions for the guys on SpeedTalk?Tom

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Old 07-11-2020, 10:45 PM
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Imo no worries with a 4 into 1 collector, a 4-2-1 collector yes worry

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Old 07-11-2020, 11:21 PM
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Thanks for the replies. Maybe " worry" was a little strong of a word. But I dont want to leave much of power potential on the table. I am assuming it will be minimal. But have no real experience with it.

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Old 07-12-2020, 12:09 AM
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4/7 swap in mine. Had a dual plane first and it seemed to run ok for that season. Next season went to FAST 2.0 and ended up changing to a Northwind. Single plane seemed to wake it up in low end all the way thru top end. Happy with how it runs.

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Old 07-13-2020, 02:43 PM
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You probably already tried it but my stumble problems almost always were the fault of small shooters or small accelerator pump/cam. I like the 50cc pumps.

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Old 07-13-2020, 04:11 PM
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Check valve under the squirter sometimes gets stuck as well.. That could make someone walk in circles ..

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Old 07-13-2020, 09:00 PM
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Got at least 12V going to the distributor? Cylinders not firing cause o2 to read lean.

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Old 07-22-2020, 08:15 AM
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Received an update from my friend. He thinks he found some improvement with the squirter cams and shooter size. He also believes the butterfly’s may have been a little bit too open. I assume out of the transfer slot.
He is going to put wide name on it and continue to tweak it

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Old 07-23-2020, 08:22 AM
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Quote:
Originally Posted by mysticmissle View Post
Received an update from my friend. He thinks he found some improvement with the squirter cams and shooter size. He also believes the butterfly’s may have been a little bit too open. I assume out of the transfer slot.
He is going to put wide name on it and continue to tweak it
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Last edited by Half-Inch Stud; 07-23-2020 at 08:39 AM.
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