[Jim Hand]

BG,
I have not had the chance to try the plenum mods on a Performer. But I would expect to see an improvement in upper end power with it. The idea is to allow each cylinder to see part of both sides of the carb at full throttle, similar to what happens with the single plane intakes. And if the engine needs more upper RPM airflow, this mod should help.

I know it sure works on my Pontiac iron stock intake on my engine.

But this sort of mod has to be considered as experimental on each engine. Some may not respond favorably - that is why we like to try it on cheap home made spacers. Then if it doesn't help, we can pitch the spacer without having to repair the intake plenum. But it is easy to repair the intake divider. Just make a tapered saw cut on each end and make a filler plate to fit. Here is a photo showing a complete divider for my RPM. (I have since made an opening only across the secondaries that works great).

Jim Hand

[berrygoat]

Originally Posted by Jim Hand

BG,
I have not had the chance to try the plenum mods on a Performer. But I would expect to see an improvement in upper end power with it. The idea is to allow each cylinder to see part of both sides of the carb at full throttle, similar to what happens with the single plane intakes. And if the engine needs more upper RPM airflow, this mod should help.

I know it sure works on my Pontiac iron stock intake on my engine.

But this sort of mod has to be considered as experimental on each engine. Some may not respond favorably - that is why we like to try it on cheap home made spacers. Then if it doesn't help, we can pitch the spacer without having to repair the intake plenum. But it is easy to repair the intake divider. Just make a tapered saw cut on each end and make a filler plate to fit. Here is a photo showing a complete divider for my RPM. (I have since made an opening only across the secondaries that works great).

Jim Hand

Thank You !!!

[slowbird]

Why not just run a 1/2" spacer instead of cutting the divider?

[Skip Fix]

I think that was Jim's point, try the spacer mods first, easier than modifying an intake and alot easier than unmodifying one.

I will also add that my roller motor idle smoothed out and produced more vacuum with less idle mixture screws with a single plane over a dual plane and an open spacer/adapter.

A case in point about motors like or not liking spacers. My RAIV 400 with an HO intake and 73 SD replacement Qjet picked up 6-8 hp with a 1/2 Q jet spacer (all that the Shaker would take). Lloyd's 455 HO motor with similar intake and carb lost hp with the exact spacer when we tried it. Each combo is unique and needs to be tuned that way.

[slowbird]

If you try the spacer and it works why cut the intake then?

[Guy,mn.usa]

GTOKARL uses a Victor intake. A spacer uses flat heads screws to mount to the Victor intake, The spacer is designed to accept a Qjet...nice set-up for a high winding 400? Also Good to see Jim Hand is in pretty good health again after a tough bout with the Doc! Welcome back Jim!!!
So Jim what think about this Victor set-up? Kinda looks like a Qjet flanged Warrior...these intakes worked well for drag racers right?
thanks,
Guy...
Katrina sucks!

[Skip Fix]

Correect Slowbird.

You can also use Allen head bolts for adapter/spacer bolts if you loose those fat headed screws that come with them. GTOKARL has a slick looking adapter for the Victor.

[Ducks Goat]

Jim, do you have a part number for the cam you're using or was it a custom grind? Thanks.

[Jim Hand]

SB,
It is more practical and easier to test the effects of plenum cuts using spacers. However, if hood clearance is not available to use a spacer, then a cut in the intake is the next step. In my case, I initially tried a full front to back cut in the plenum divider in my RPM, due to lack of hood clearance. A filler plate was made (as shown in the photo above to allow back to back testing at the track). I quickly found that the full cut lost more power in low/mid RPM range then it gained at upper RPM.

Further testing showed a cut across the secondaries only gained about .07 seconds on my 11 second car. The opening in the crossover, or divider, allows some of both sides of the carb to feed each cylinder, rather then only one side of the carb working with a standard dual plane setup. And if the carb is too small, or marginal for any given engine size/RPM, allowing air from both sides of the carb will usually add top end power.

The stock iron intake is short enough to allow a 2” spacer, and that is where I have the crossover cut for the secondaries. A photo should be attached.

Again, on both the stock iron and the Performer RPM, I see substantial ET improvement with the divider cut at the secondaries. On the RPM, it is cut in the plenum, and with the stock intake, the cut is in the spacer. It turns out the 2” spacer on the stock intake provides the same height and runner lengths as the RPM, and that is why the performance between them is so close.

Guy,
All intakes are RPM sensitive. The Victor is designed to provide best performance when it is not loaded until well up into the RPM range, and the engine shifted at relatively high RPM. The factory rating is 3500 to 7500. With the multitude of intake tests we have done over the years, I have no doubt my car would have worse ET with the Victor as compared to the stock intake/spacer I am using. Here are some numbers that cause that:

I stage at 1800-2000. The converter flash/stalls to 3200. The power from stage RPM to flash stall determines how hard and how quickly the converter hooks. There is no question the stock setup would provide vastly greater power then the Victor in that range.

With the 3.31 gear and 3200 converter, my car passes the 60’ timer before it even hits peak power in first gear. In other words, the engine has to work hard for a long time simply gaining RPM through first. And that would also favor the stock setup.

Finally, I shift at 5500, and that is barely in the mid-range of the Victor. In other words, my engine would spend little or no time in the superior upper RPM range of the Victor.

The Victor is an excellent intake, but it is not designed for use in a low RPM street car pulling 3.31 gears that is shifted at 5500 or lower! If we had a loose converter, or manual trans, and launched at or above 4500 and ran to 6300 or higher, it would certainly be satisfactory, especially with lower gearing. And yes, it will run/operate at lower RPM, but its efficiency won’t be very good in a low RPM application.

Jim Hand

[P@blo]

Jim i was only kidding........I have a great ammount of respect for you and hope i can learn as much as i can from your posts........

[Guy,mn.usa]

P@b....if thats a picture of you I'm selling my Pontiac!

[Guy,mn.usa]

Jim that intake is done so dam nice...great pic!
I'd really like to see you go after a 400, like you did with your 455.

[Z Code 400]

Jim...I am curious about the work required to remove the exhaust crossover on the iron intake. Was welding required, or was this just careful cutting??? What did you use to perform the modification.

Also...it has been a long time since we exchanged e-mails and I recall you were facing some real challenges back then. Great to see you posting again!!!...Robert

[grandville455]

Jim How far down did you go down your plenum on your rpm?
thanks!!!

[Jim Hand]

Robert,
The original was done with a torch and angle grinder. A better method is probably some sort of chop saw, and an angle grinder. No welding is/was necessary providing the intake floor is not broken.

GV, I cut the RPM down about 6/10". It needs at least 1/2", but more then .75" doesn't seem to help.

While it is hard to see, the openings at the top of the spacer (on the Q Jet intake above) exactly match the Q Jet throttle plates openings, while the openings at the bottom of the spacer taper out to match the intake plenum sides. This will slightly help flow through the carb. However, it means the spacer has to set in the correct location or it will "hook" the secondary throttle plates!

Pablo - I was also joking. Appreciate the kind words.

Jim Hand

[grandville455]

Thanks Jim Do u have a pic of your new modified RPM... I used to have it but i dont anymore!!

[Jim Hand]

Ducks Goat,
Sorry, I missed your question. The cam I run is a copy of the original Wolverine 5059. I had Bullet Racing grind one. The specs are:
234 intake duration with a .338 lobe
244 exhaust duration with a .340 lobe
The lobe separation is 112, with the intake indexed at 107.

http://www.bulletcams.com/

This is a great cam for a 455 but is too much for a 400 that will be run on the street (for best all around performance). I also use Rhoads lifters in order to have a good idle and great low end power and controllability. And higher ratio Harland Sharp 1.65 rockers are used to emulate the faster valve action of roller cams.

Here is a photo of my currect RPM setup. Since I had cut the full divider in earlier testing, had to restore the area across the primaries. I did that with fuel resistant epoxy that has wire backbone within. And unseen are two pieces of allan wrench (for strength) protuding down from the epoxy into matching holes in the intake divider. It is easily removable and when removed, the intake is as the photo above. While I don't have hood clearance for real spacers, there is room for the 5/16" spacer/gasket shown. And the epoxy filler was shaped to match that spacer.

If starting from scratch, simply draw a line across the front edges of the secondary throttle plates, and where that line crosses the divider, cut down from that point to the rear, and round/smooth all edges.

[Z Code 400]

What about a full-length divider in a single plane???...Robert

[pastry_chef]

Hi Jim,

Glad you are feeling better.

Are these the lobes you used to create your 5059 copy?

From the bullet master catalog.

*Intake*
H282/338 282 233 145 .338 .000 CTA
OR
H285/338 285 235 145 .338 .000 CTA

*Exhaust*
H298/340 298 244 150 .340 .000 CRA

Just curious.. obviously they are close to the .338 and .340 you stated, but often close isn't good enough. Does not seem to be a 234 duration .338 lift, say if someone desired to duplicate your copy.


Thanks.

[Jim Hand]

P.C.
I did make an error in the lobe lift of the 5059 style cam ordered from Bullet.

I used the Bullet 284/335 lobe for the intake, which has .335 lobe lift.

And used the Bullet 298/340 lobe for the exhaust, which has .340 lobe lift.

Jim Hand