Trick flow intake mods

When we dynoed my engine a few(?) years ago, the Trick Flow intake I decided to run instead of a Victor was pretty much out of the box, except a few minutes cleanup of some casting goobers and sharp edges.

Since I also have a bone stock TF to compare against, I did some -- not a huge amount of -- work on the dynoed intake before the engine went back into the car:
- a fairly deep port match to the standard-port Victor heads, since the TF runners were still a bit undersized; left the cuttered finish, FWIW
- some plenum cleanup and blending, but no polishing
- "bevel edged" the 5/7 divider as recommended by David Vizard to help keep #7 from robbing as much #5 since they're back-to-back in firing order

At some point when the car's been baselined, I'll swap the intakes to see if my work actually shows up on the ET slip. And then... ?

Dividers simply rounded off of casting "stuff", except putting bevel of 5/7 to help direct air/fuel mixture into #5 while discouraging #7 from robbing #5

I like it.
W/r/t beveled edge between 5 and 7: I agree, flow reversal is aided by an large radius in the "V", a sharp edge reduces cross-flow.

Harley-Davidson learned this in the opposite direction. In the the 1940s with a "Y" shaped manifold feeding both 45 degree cylinders (315-405 degree split), the V split was sharp. Material was added on outside and removed from inside to re-shape into a radius, this allows charge already in the non-intake manifold leg and port (up to the valve) to reverse, follow the vacuum source and flow back to the cylinder on intake.

I get the theory, but wouldn't you want to direct flow to #7 since #5 starts pulling on the plenum first? Does David Vizard have data that corroborates this method ( I'm guessing in a SBC ) ?

A curved divider edge...?

The timing is that 7 starts pulling early enough that it robs from 5 before 5 is done drawing in the air-fuel charge. So ya' gotta keep as much on the 5 side and try to inhibit 7's tendency to pull from 5, too.

IIRC, he says it reduces the need to stagger-jet for that corner of the intake. Makes me wonder if something should be done for the 2/1 divider, even though they're on opposing sides of the plenum.

That makes sense....
but has anyone seen Wilson do that to a manifold??

Crude diagram with original divider on top vs modified

Not me, but Wilson is big on extending the runner dividers, which I can see doing something similar

Brad, think about airflow in a small plenum, how hard will cylinder 7 have to suck on the plenum under the carb. to get the airflow to change directions from the # 5 intake runner to change it to go into the #7 runner: work: Maybe it is time to increase the intake lobe duration on # 7 cam lobe

Yeah, I can see where cutting a bias in the divider would work, just not sure if #5 is the one that needs help.

Good point on #1 & #2.

Vizard covers this mod in one of his books; stagger jetting is discussed in his "How to Super Tune and Modify Holley Carburetors" book. I haven't messed with the jetting approach, though.

I think it would be more duration for 5 and less for 7, since 7 robs from 5...

I think you are thinking backwards on that, #7 is the hardest cylinder to get the mixture correct on a single plane intake with one four or two barrel carb
#5 intake runner and intake valve are closer to the throttle blades also
Put a tunnel ram on it with two Dominator carbs and forget about it

To me, that's just standard port matching....I do that to all my intakes. After that, I find the more I open up the plenum, the better the HP...

Dragula - looks good

Yeah, it's basic stuff and -- as I mentioned -- isn't a lot of work that I did. However, since I have a bone stock intake to swap, it'll be interesting to see if this minimal amount of work shows up on the ET slip. Then as the mods go from there (more plenum work, etc.), it's another level to compare against.

EDIT - Pic of plenum mods that worked well on a Victor intake. I think the TF intake probably needs a short spacer to raise the carb mounting surface to achieve the same type of approach to the top of the runners, though.

Brad,

With a single plane manifold, the same exact thing happens with the 2-1 firing pulse i nthe front of the motor between the banks, the cylinder drawing first has the advantage over the second pulse because the momentum is already moving in the earlier port.

I would liken it to a Bernouli effect so the "band Aid" is to first make sure the plenum is charged (which is is at it's optimum RPM) and the second is to help the second port pulse get more of a shot at the good charge.

But I think whenever the manifold is tuned and the Peak torque is matched well to the heads and induction , the plenum receives a charge which is the best guarantee all the cylinders are filling,

I used to modify Street Dominators by making the second port entry from the plenum more Trapezoidal (I used to call it "Gumby's head" lol) when looking at them side by side and with slightly more square area to the second port. It's seemed to work because the SD would usually pick up 1.5 MPH and drop the ET .1-.2 tenths on a typical low 12-high 11 B or E body.

Most recently I modded a Victor 340 in a similar way and it too picked up in terms of performance.

Interesting thread

Even if it's just interesting to you and me?

You "Gumby Headed" the #7 and #1 ports? Trying to get my mind wrapped around that idea...

I wish I still had pics of the mods I would do, I think there is a bit of give and take between the adjacent ports throughout the rpm range, at low piston speeds/higher vacuum the 7 pulling from 5 may be more prevalent, but at higher speeds the velocity of the charge from the leading ports air/fual charge is going to have so much momentum as the later cylinders intake valve is just starting to open it seems far more likely the second cylinder is more likely to be starved of effective filling "duration' until the 5 intake valve is closing.

Was it #1 and #2 intake ports or #2 and #4 intake ports you're talking about?
I had never thought about the potential cross flow interference between #2 and #1 being 90 degrees away from each other on the firing order on a single plane single carb intake
Thanks for opening my mind, a tiny bit

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The thing Vizard keeps stressing is the exhaust pressure wave of the subsequent cylinder (1 after 2, 7 after 5) starts pulling against the first cylinder before the fill cycle is over...

What's confusing to me is he says the adjacent cylinder robs from the first one as a result, but you need to make sure the second one still can pull adequate air-fuel mixture if you can reduce the cross-flow issue. Maybe I need to speak "British English" instead of "American English" to fully understand him. Or maybe it's all just me...

Brad,

I actually have met David a couple times through a mutual friend.

He's much more lively in person,

Something to consider is at 90 degrees after TDC through maybe 115 ATDC (depending on the stroke and rod ratio) that first cylinder is at or very near peak piston velocity so I can fully visualize how the second cylinder is getting a bit "ripped off"....this is how I interpret what's going on anyway. I may be completely 180 off...or at least 90 off, lol. So if the second pulls on the first somewhere in the cycle....as the english would say...."Fair Play to #7" lol

Again when the engine is approaching peak torque there should be a slight "ram effect" in the plenum which should minimize...or "balance" the port flows to all cylinders, so the gains are probably slight and only over a relatively small part of the powerband.

come to think of it, Mark GY3 runs one of my old street Dominators on his Stroker big block, he picked up about what I quoted on his motor...as far as I know he still runs it and seems happy with it.

Yep, picked up exactly what you said it would on back to back weekends.

The cylinders seem to fill pretty equally with it, too, as I keep an eye on plugs since we run nitrous now.

I love it because it's stealthy and fits under my stock hood.