SBC intake question for the experts

[Warp Speed]

Yeah.. most street rodders and entry level guys looking for dumbed down 9.7:1 crate motors usually are content with 90's tech and power levels. If that's the way you have me pegged then so be it but you couldn't be further from the truth because I cut, grind, modify, and weld most everything of my own. Hell, even my little lowly 302 mule motor is far beyond most guys race motor from a tech and modification standpoint. Cut manifolds, port welding, coatings, bigger lifters, handbuilt headers.. far from average and just how I do. Plus.. I can actually tune my junk to make things come together.

And regardless of decade being discussed.. the physics involved comparing duals to single remains a constant. Runner size and length changes will only tweak final results so much. All about carb signal dude.

You pretty much contradicted your views in your last statement.
If you think "Runner size and length changes will only tweak final results so much".
Then why must it have a dual plane to be effective?
Carb signal????

[Warp Speed]

Speaking of towing and 90s technology (Mine anyway!Lol) in 1990 I built a 402 bbc. It had 048 heads, 11.1 compression and a 23x/24x on a 110 cam with about .560ish lift hydrauluc flat tappet if I remember right. It went into my 76 4x4 with a th350 and a 2200 stall, 3.73 gears and 36in tires. It was used to pull an open trailer with our super late model on it, and all of our tools and pit equipment in the back. It pull that load with ease over Snoqualmie pass as fast as you ever would want to go (typically 80ish) and with that same load would spin the tires no problme from a dead stop. It had a single plane Edelbrock torquer (carb slightly sideways) with an 850 holley. Bottom end was no problem, and would pull strong high enough to spit the v belts. Actually drove 5 miles with my shoe laces operating the water pump once!
My point being, why did this mismatch, poor combination (in your eyes) work so well?

[Frankshaft]

And that intake was literally one of the worst intakes ever conceived by an aftermarket company. Imagine if you would have had a dual plane on it. Just imagine how much better the transient throttle response would have been.

[Warp Speed]

And that intake was literally one of the worst intakes ever conceived by an aftermarket company. Imagine if you would have had a dual plane on it. Just imagine how much better the transient throttle response would have been.

Ya, they were a good idea on paper, they just never ran that well from what I've read.
It was what happened to be hanging on the wall at the time! Lol

[RevTheory]

Frankshaft got back around to what I was going to ask stat before things got squirrely again. I've got an engine in the planning stages where I could probably go either way but I'm torn.

4.03 x 3.5 SBC
~10.75:1 compression
AFR 195 "Race Ready" heads
Hyd/roller 225/229 at .050, .650/.590 lift, 109 LSA
2,500 to 6,500 rpm

Jeep CJ7
Muncie close-ratio M21 (not set in stone- maybe...)
33 x 13.5 tires
4.10 gears- maybe a 5-speed stick and 4.56s

If I were sure a single plane could take a WOT stab below ~3,000 rpm and it wouldn't be down the roughly 15 to 20 ft.lbs that every single dyno test I've ever seen seems to show, I'd be all over it. I don't have the luxury of leaning into a converter and I sure as hell don't want to be sidestepping the clutch all the time.

I'm thinking: Holley/Dorton 300-110, epoxied floor, ported runner entries, burr-finished plenum, 1.5 inch Wilson tapered spacer, Terminator EFI (the one with the annular discharge ring below the throttle plates.)

Is this the kind of thing that needs to be done to have your cake and eat it too?

I'm guessing they didn't use a run-of-the-mill Holley with low-gain boosters on that crate engine but I can't see where it was mentioned.

[groberts101]

Yeah.. most street rodders and entry level guys looking for dumbed down 9.7:1 crate motors usually are content with 90's tech and power levels. If that's the way you have me pegged then so be it but you couldn't be further from the truth because I cut, grind, modify, and weld most everything of my own. Hell, even my little lowly 302 mule motor is far beyond most guys race motor from a tech and modification standpoint. Cut manifolds, port welding, coatings, bigger lifters, handbuilt headers.. far from average and just how I do. Plus.. I can actually tune my junk to make things come together.

And regardless of decade being discussed.. the physics involved comparing duals to single remains a constant. Runner size and length changes will only tweak final results so much. All about carb signal dude.

Have you used one of the "new" carbs from one of the good carb guys? They are so much better than the "old" stuff its crazy. They truly work unbelievably well. Idle, throttle response, power, fuel usage, etc. They turn a 289-314 at .050 cam into something almost tame. Idle at 800 rpm for an hour if you wanted without loading up, coughing, bogging, flooding, etc. Absolutely INSTANT throttle response, that is literally better than efi. Like idling at 800 rpm, wack the throttle, it INSTANTLY is at 7000 rpm, and INSTANTLY idling again at 800 rpm. We are talking 2.4 to 2.8 inch throttle blades, with venturis sized to match, BIG. Keep in mind, a H.P. 1250 Holley dominator has a 2.08 throttle blade. The drivability is borderline amazing. On an intake that is big enough to drive a bus through. One of the 4150 versions are even better. They aren't cheap, but, they absolutely work. The right amount of fuel at the right time, makes up for A LOT. In a lot of cases, that is the issue.

I have one question for you Groberts, why a 302? Why not a 347 or a 363. And just tell everyone its a 302. Not to be a smartass, just curious.

I don't mess with big or really stout race type motors like you guys do, so all my stuff has been with typical cookie cut 750-850 cfm throttle bore/venturi sizing. Messed with a few older dommy's and couple 950's when tuning others rides but Holley's XP series is my personal favorite, which I typically like removing/correcting and race stepping the boosters. I currently have a cut horn/modded 1850 600cfm and 750DP I may use temporarily but will likely end up with a 650-750 Ultra converted to 50/50 mix or full E85 on this little motor. Since this is a dual plane setup(cut down/reflanged 351W air-gap) I may change over to a progressive linkage and run the 750DP. Only reason this motor stayed small CID is because, mainly I don't street race anymore, I got the used Eagle pendulum cut forged 3" crank for cheap and don't want to start breaking cheaper parts, stock block, 8" rear gears or otherwise. Longer 5.4" rod softens things up a bit too. Almost offset ground this crank and went with custom aluminum rods but decided to put the cash elsewhere, Innovators West belt drive and dampener that could be transferred over to my other bullet down the road. I like really light recip's no matter the power levels.. just my personal preference, is all. The car, 71 Mercury Comet GT(Ford Mavericks big nosed cousin) is pretty light too(sub-3k) so no need for 500+ horses at this stage of its build evolution. Several years from now when I cage it and build my fab 9" and add weight reduction I will turn up the wick. By then my two boys will likely be out on their own two feet and might even eventually grow a bigger pair and add twin turbo's.

But yeah, I do know what you mean about carb tuning because I've been cutting up, drilling, boring and converting 4150's and even lowly 1850's for many years now. Being a big compression ratio advocate, especially for E85 and even on pump gas, really helps push boundaries and EFI guys are sometimes stupified at how crisp the throttle response and tire reaction is to light throttle jabs. Some have even said seeing mine makes them want to keep tuning what they thought was good enough. lol I usually do well enough with my tunes to wet the manifolds plenum and they fire right up and idle without chokes. My last 383 Chebby's 750XP was sometimes driven without a choke during our MN winters and after about 15-20 seconds of throttle nursing would idle just fine on its own during warmup. And if the diisty's not locked out I also typically run buttloads of base timing, short mechanical sweeps, and modded vac advance pots. My last 2 motors have both had MSD programmable 6 and 7 series boxes with MAP's.. probably just run the 6 series unit on this lower budget deal and sell it off when I convert over to IR COP EFI on my bigger 342" all-aluminum Kaase headed SBF bullet.

I do agree with most that you guys have to offer around here but will never be a "bigger is better" convert when it comes to induction/plenum style/sizing for street type deals. Street/strip oriented type stuff.. sure, move the power band up.. give it some more gear and converter and deal with the compromises of one towards the other and let it eat. But not on part throttle/lower rpm/driver type deals which are often being talked about around here. Wack the throttle on those kinds of deals and the pressure differentials change far too suddenly for all those street oriented weights and gears to deal with. I do agree that a single plane can certainly help traction for tire limited cars and make them faster, and that in itself should be proof enough that single planes most definitely kill lower rpm torque enough to soften the tire hit, but I still almost always prefer to leverage today's suspension and tire tech rather than running a poor mans single plane style traction control. On my own personal rides.. I build as much power from idle to redline as I possible can and just learn how to work the pedal to make them ET the fastest.

I have a couple questions about my new Trick Flow 11R head 50 or maybe 52° seat mod's was hoping you could steer me in the right direction on and will PM you to avoid even more off-topic clutter around here. Not looking for gospel.. just some input gathering to know where I want to end up is all.

[groberts101]

Yeah.. most street rodders and entry level guys looking for dumbed down 9.7:1 crate motors usually are content with 90's tech and power levels. If that's the way you have me pegged then so be it but you couldn't be further from the truth because I cut, grind, modify, and weld most everything of my own. Hell, even my little lowly 302 mule motor is far beyond most guys race motor from a tech and modification standpoint. Cut manifolds, port welding, coatings, bigger lifters, handbuilt headers.. far from average and just how I do. Plus.. I can actually tune my junk to make things come together.

And regardless of decade being discussed.. the physics involved comparing duals to single remains a constant. Runner size and length changes will only tweak final results so much. All about carb signal dude.

You pretty much contradicted your views in your last statement.
If you think "Runner size and length changes will only tweak final results so much".
Then why must it have a dual plane to be effective?
Carb signal????

That's the problem with text, Warp. I only meant modifying a SINGLE planes architecture could do so much. Dividing the plenum is another aspect all on its own. Which then allows us to run an even larger carb and cam to make up any top-end deficits that may have come about from its use.

Case in point. I have an old 302 Ford original torker single plane intake here with small plenum and runner sizing. Great little manifold on mildy mod'd motors "way back when" and still made decent low-end torque and maintained throttle response due to it's smaller than average single plane sizing. Put a bigger runnered air-gap on the same motor and it crushes it EVERYWHERE.. AND idles better too.

[Warp Speed]

Yeah.. most street rodders and entry level guys looking for dumbed down 9.7:1 crate motors usually are content with 90's tech and power levels. If that's the way you have me pegged then so be it but you couldn't be further from the truth because I cut, grind, modify, and weld most everything of my own. Hell, even my little lowly 302 mule motor is far beyond most guys race motor from a tech and modification standpoint. Cut manifolds, port welding, coatings, bigger lifters, handbuilt headers.. far from average and just how I do. Plus.. I can actually tune my junk to make things come together.

And regardless of decade being discussed.. the physics involved comparing duals to single remains a constant. Runner size and length changes will only tweak final results so much. All about carb signal dude.

You pretty much contradicted your views in your last statement.
If you think "Runner size and length changes will only tweak final results so much".
Then why must it have a dual plane to be effective?
Carb signal????

That's the problem with text, Warp. I only meant modifying a SINGLE planes architecture could do so much. Dividing the plenum is another aspect all on its own. Which then allows us to run an even larger carb and cam to make up any top-end deficits that may have come about from its use.

Case in point. I have an old 302 Ford original torker single plane intake here with small plenum and runner sizing. Great little manifold on mildy mod'd motors "way back when" and still made decent low-end torque and maintained throttle response due to it's smaller than average single plane sizing. Put a bigger runnered air-gap on the same motor and it crushes it EVERYWHERE.. AND idles better too.

Ya, I understand what your saying to a point, but your everything small with a big cam is really old school technology. You don't have to buy into it, but don't expect everyone else too also! That's the only point myself and others are trying to make to the magazine crowd. Don't get upset by that comment unless you fall into that category!
It's been brought up many times, but LS engines prove it!
You never did elaborate on the "carb signal is everything dude" deal........

[groberts101]

You pretty much contradicted your views in your last statement.
If you think "Runner size and length changes will only tweak final results so much".
Then why must it have a dual plane to be effective?
Carb signal????

That's the problem with text, Warp. I only meant modifying a SINGLE planes architecture could do so much. Dividing the plenum is another aspect all on its own. Which then allows us to run an even larger carb and cam to make up any top-end deficits that may have come about from its use.

Case in point. I have an old 302 Ford original torker single plane intake here with small plenum and runner sizing. Great little manifold on mildy mod'd motors "way back when" and still made decent low-end torque and maintained throttle response due to it's smaller than average single plane sizing. Put a bigger runnered air-gap on the same motor and it crushes it EVERYWHERE.. AND idles better too.

Ya, I understand what your saying to a point, but your everything small with a big cam is really old school technology. You don't have to buy into it, but don't expect everyone else too also! That's the only point myself and others are trying to make to the magazine crowd. Don't get upset by that comment unless you fall into that category!
It's been brought up many times, but LS engines prove it!
You never did elaborate on the "carb signal is everything dude" deal........

Trying to multitask too much here today and phone texting seems to be better suited to teenage girls tiny fingers cause I suck at it! And some of what I was saying here has been lost. What I said in my original smart ass post, or what a tried to convey afterwards, was not what you just wrote there.

What I'm saying is that when using a divided plenum.. you CAN run a bigger induction AND carb size to help make up peak power deficits compared to another combo having open plenum and slightly smaller induction and smaller cam specifically chosen to help maintain power below its peaks. The cake stays bigger and you end up just as fat and happy.

Another way to look at it is like this. Pick a gear and converter based on the driving style and application.. then match the engines power curve to that. OD trans help greatly in what's "livable".. but this is a universal requirement for us all on the street. Generally speaking, with average sized street based 300-400" motors, the lower end of the power spectrum will almost universally prefer a dual plane setup.. and the top half will like a single plane setup with bigger induction package.

There is a crossover point, plus a few "wildcards" and many many other variables such as personal preference(me?.. I like a motor to feel bigger than it really is.. and still rev like a smaller one), driving style(me?.. I'm a friggin' lunatic and treat roads like my own personal racetracks), engine size and vehicle weight.. but that's almost always been true for a reason. Dual plane plenums tame a cam down in the lower rpm ranges and allow stronger signals allowing the boosters to come in and help the motor accelerate up onto the cams sweet spot quicker and stronger during initial acceleration. Manifold vacuum levels are better which carb's really like to improve their efficiency and tuning resolution. The various induction designs are getting better all the time and power has risen.. but that physical fact still remains a constant. Short of some newer design with a mechanically moveable plenum divider.. probably always will be that way on these old school buckets of compromises.

[swampbuggy]

I PURCHASED ON OF GM'S LS-7 crate motors in appx. 1988.....454 B.B.C. . Had to buy intake which ended up being that Eddy single plane that the carb sat about 20 degrees (clockwise) i believe it was. The iron heads were 990's i do believe, and were RECTANGLE intake ports. Actually it seemed to work quite well, 850 Holley Dbl. Pumper, changed cam to .650" lift with 272* @ .050" 108 LSA. Made 565 H.P. at appx. 6400 it went into a 1964 Pro-Street Chevelle with a 4 speed manual. Mark H. Boy how stuff has changed since then!!!

[JoePorting]

I think BigJoe said it best when he said, " The intake manifold holds up the carb".

I tested a number of different manifolds on SBC engines and was surprised how little the difference was.

Manifolds are cheap. If you're curious how a given manifold will work on your car, try it.

[RevTheory]

I'm guessing trying to burr-finish epoxy is probably a really bad idea, no?

[groberts101]

I'm guessing trying to burr-finish epoxy is probably a really bad idea, no?

It's really tough to get the same profile because the burr doesn't jump and bounce same as it does off the base material.

[groberts101]

I think BigJoe said it best when he said, " The intake manifold holds up the carb".

I tested a number of different manifolds on SBC engines and was surprised how little the difference was.

Manifolds are cheap. If you're curious how a given manifold will work on your car, try it.

Joe came from a different era with far fewer test choices. Probably more true when comparing same or very similar csa and runner lengths but if that were truly the case there would be far fewer market offerings. Maybe just depends on what amount of power you're willing to dismiss as.. "not worth the hassle".

[Carnut1]

I'm guessing trying to burr-finish epoxy is probably a really bad idea, no?

No problem Rev.