4bbL vs weber or stack for max hp from 302

[Ross Nicol]

I will admit to performing a stupid act. I took a 4BBL EFI / single plane Victor Junior induction system off my new 302 race motor and fitted the 8 stack injection system from my previous motor. Now why was that stupid? I hear you say, well here's my story.
I've always been under the impression that individual throttle bodies/ 8 stack injection was the ultimate in induction systems, probably because they replicate the sexy look of the IDA Webers but use modern technology with all the tuning advantages. Therefore it took me a quite a while to appreciate that I can get more HP from a 4BBL.
Now I'm a lateral thinker but my background is electronics not mechanical so I rely on this forum a lot for Ideas and information.It didn't surprise me then that in my thread titled "Max power & torque for a 302" I posted a week or so ago, that Jac Mac would respond with a one liner " Try a 4BBL Ross ". Now when Jac Mac speaks you should listen, but I got him to explain further by PM so I could prove to myself that it all makes sense.
I spent a few days with my books and on the website (GT40s.com) of course, and then it dawned on me I should load Dyno 2000 simulator onto my computer (purchased way back in 2002 and never used) to run some simulations.
Well how surprised do you think I was when I read the user manual and it described individual runner induction limitations.Absolutely backed up Jac Mac's theory (Ross' mental diary,never question that man again) and the simulations I ran proved I will have more top end power at the next race meeting.
Here's the theory in simple terms.A typical Weber 48IDA / or similar sized stack flows about 330 cfm per barrel.While the sum total of all 8 barrels is over 2600cfm, the important difference is that each cylinder can only draw from 1 330 cfm barrel.With a 4BBL on a single plane manifold each cylinder has access to 4 barrels, reducing restriction during peak flow and increasing high speed horsepower.

Adam C another respected technical man on this forum made this statement " I love the look of Webers especially on a GT, but they really don't make much sense to me ".

My next race meeting is at Sandown 12th and 13th of May after which I will be able to describe the results of returning to the 4BBL.

Ross

[Dean Lampe]

Ross, you are right with respect to the top HP number. On that software with my specs the 4 barrel was 656 @7k and the webers were 639 @7k but the story is in the torque curve. At 3500 the webers are at 570tq and the 4brrl is only 483. At 5k the 4brrl is at 558 and the webers are at 590. I think for road racing it is important to be able to pull strong out of the corners and for that you need the brutal torque of individual runner, and they look cool! It just depends on where in the range you want to play.

[chuck smith]

another thought. When I changed from my Victor intake and 750 Demon on my 427SO to the 48 IDA, the throttle response improvement was drastic and the seat of the pants low end torque was definitly better. I do not doubt the high RPM HP numbers based on CFM for the Holley system. Were your figures based on 37 mm chokes?

[Gordon Levy]

Ross, I have been saying that for years. There is no way a 48mm t-body on an IR intake is going to keep up with a 4bbl on a single plane intake.
Here's another way to look at. a 50mm t-body is equal to 1.97", if you have 2.08 intake valves how will the t-body keep up. You number on 330cfm is a bit high. If you base the CFM purely on atmospheric pressure at will actual only be about 180cfm.
I discovered this about 20 years ago working on Parnelli's 69 Bud Moore T/A car. It ran a Boss 302 with 2 dominators on top of a IR manifold. 2500cfm and we were running out of air above 7000 revs. I figure it takes about 350cfm of air on an IR intake to rev a 302 to over 8000 revs.

[Dean Lampe]

I am going to be dyno tuning my engine in a couple of weeks. Then we will see how the numbers look. I think the problem with your comparison is that the valve in the middle of the intake runner is much more restrictive to flow than a wide open thottle plate in the weber choke. I have seen the flow numbers of the weber 48 IDA with a 37 mm choke quoted many times at the same 330 cfm number mentioned above but I have never ran the test myself. I am using 40 mm chokes in my set up. Again, the proof is in the numbers. We will see when we get the dyno numbers. The desktop software shows my set up seems to peak between 6500 and 7000rpms but even at 8000 I am still over 600hp. I think most of us spend more time between 3500 and 6000 than over 6000. I just think the webers "feel" faster.

[Russ Noble]

I love bench racing, it's so cheap! It's just a matter of finding who puts out the program that will get most power out of your existing setup!

Dyno's seem to vary too although they shouldn't, but they are good for the ego to be able to say my motor was dynoed at 634.2 hp @ 8400 rpm. But their main advantage is for back to back comparisons for development purposes. Now if Ross, or anyone, was to do a dyno comparison of both setups on the same dyno on the same day by the same operator that would be a real life result that would mean something.

The other real life result is lap times and straight line comparison with competitors that you are racing closely with. At the end of the day that's the only one that counts. Gordon's obviously been there, so I'll go with his experience over a computer program or theoretical hypothesising any day! So go for it Ross I'm sure the 4bbl will win hands down. We're watching this space!

I'm not even going to dyno my motor, the spark is going to be set to the head manufacturers recommendation and the 4bbl will be jetted on the track using a lamda sensor. What else is there?

FWIW, if you want a penis building exercise, give me a CanAm type setup with massive throttle bodies, looks cool and delivers the horsepower and the torque! That could be the way to go Ross!

All the above IMHO!

Cheers

[Paul Thompson 'Hooligan']

When I first met Roy Smart his GTD had a 4-barrel carb (not Holley) but I can't remember the make... The car ran well but once fitted with Kinsler throttles (58mm) on injection, it ran even better. We would regularly pull cleanly to 7500/8000 rpm on hill climbs and throttle response was very good. I don't know what the flow rates for 58mm would be but they certainly didn't seem to restrict top end power.

I also agree with all said re dynos, real and s/w, great for direct comparison of 'ideas', but on rolling road types, a lot comes down to operator skill in keeping the playing field 'level', as peak/flash readings can be quite inaccurate (sometimes not in error! ) to give a very incorrect result, which in turn is then meaningless. Actual timeslips from repeated 1/4 mile / timed events or carefully recorded laptimes can be a far more realistic guage of whether something works or not.... (IMHO too!)

Fot those who know him, I spoke to Frasier Mackellar recently, (The most knowledgeable MOTEC GURU you could ever meet) and his soon to be complete GTD made serious numbers on the Knight Racing engine dyno recently... Can't wait to see (and hear) that one on song!

Apologies if I've veered a little off track....

[Peruch]

Originally Posted by Russ Noble

I love bench racing, it's so cheap! It's just a matter of finding who puts out the program that will get most power out of your existing setup!

Dyno's seem to vary too although they shouldn't, but they are good for the ego to be able to say my motor was dynoed at 634.2 hp @ 8400 rpm. But their main advantage is for back to back comparisons for development purposes. Now if Ross, or anyone, was to do a dyno comparison of both setups on the same dyno on the same day by the same operator that would be a real life result that would mean something.

The other real life result is lap times and straight line comparison with competitors that you are racing closely with. At the end of the day that's the only one that counts. Gordon's obviously been there, so I'll go with his experience over a computer program or theoretical hypothesising any day! So go for it Ross I'm sure the 4bbl will win hands down. We're watching this space!

I'm not even going to dyno my motor, the spark is going to be set to the head manufacturers recommendation and the 4bbl will be jetted on the track using a lamda sensor. What else is there?

FWIW, if you want a penis building exercise, give me a CanAm type setup with massive throttle bodies, looks cool and delivers the horsepower and the torque! That could be the way to go Ross!

All the above IMHO!

Cheers

331cu,holley vs weber carbs
@Peruch
Normal User
Joined: Mar 05, 2004
Posts: 25
Posted: 4/30/04 7:02pm
--------------------------------------------------------------------------------
Engine specs:
stroke 3.250,5.400 rod lenght,crower ultralight crank 11.0 CR
Head:Victor JR 301.5/200.5 @.600,Victor Jr manifold
Buddy Rawls flat tappet cam:.592/.544,262/264 @.50
Holley Weber carbs
Tq Hp Tq Hp
4000 338 257 382 291
4400 371 311 400 335
4800 398 364 449 411
5200 411 407 441 436
5600 413 440 438 467
6000 412 470 434 496
6400 400 488 422 515
6800 401 519 399 517
7000 390 534 386 514


Back to back dyno test weber vs holley same date ,same operator (superflow 901 )

[Doc Watson]

On this data Webers look better...

[Ron Earp]

Originally Posted by Doc Watson

On this data Webers look better...

But you never know all the details on the carb sets, who tuned it and set it up for the motor, so forth and so on. If the owner and builder isn't 100% out to get objective results, and are willing to do 100% of the work needed for both sets of carbs, which might include a cam swap to take advantage of what each has to offer, then it is relatively inconclusive.

My money is on a well-done 4bbl though (with numerous posts on various aspects of them and why I think that). In the states with an abundance of 4bbl knowledge it is relatively easy to get extemely good quality builders and carbs plus knowledge of tuning and running.

R

[Doc Watson]

I dont disagree with you Ron (about the data).... I just like seeing data like that in a graph...

More specific data would be required from Peruch about cams etc.

I'm hooked into the 48IDA's but you know where I'm coming from ref originality (with a pinch of fiscal prudence).

Whatever the carb/stroke/chassis/trans combo used, deep down it dosent matter to me they are all GT40's....

Andy

[RRD]

putting this intake from the '99-2001 panoz lmp car onto my 435" yates engine. changing because the 4bbl yates intake plus carb are way too tall and present a "packaging" problem. with carb it was 649hp at 6300. will change to this intake,sans distributor and with autronic ecu and ls-1 coils. will let you know what updated dyno results are when installed and tuned. also have another to put on 8.2 deck all alum engine; maybe for fran's new "p" car?

cheers,
rd

[Andy Besic]

IMHO peak HP builds are for strip and circle track racing. In Road Racing you have to tailor the track, gear ratio's and power curve to be effective. Since our cars are generally limited to somewhat widely geared 5 speeds I would think the fattest and tallest torque curve would win.

Ross
Look at how many gears you actually use at your tracks and the rpm drops between gears and reverse engineer your ideal power curve. My guess is you use 2-4 and have around a 1800rpm drop. If you build a screaming Nascar motor that HP varies by 100 over the 2000rpm you will have some throttle modulation issues. If you could plateau the power curve through that rpm range you will be concentrating on other things than when the arse is going to step out on ya.

[Ross Nicol]

Andy - I have arrived at pretty much the same conclusion. I probably use 5th gear at 3 of the 4 circuits I race at, but the most important gears are 2nd, 3rd and 4th.I agree the 5 - ZF ratios are widespaced and because of this and the rev drop, torque is very important.The ZF ratios range from 2.23 to .704 and when you compare this to the ratios in a V8 Supercar (Australian premier category) 2.5 to 1:1 over 6 gears the need for torque in my car becomes apparent. To this end I will be building up a 347 stroker and keeping as wide a torque band as possible.
Ross

[BruceB]

All engines whether on injection or carbs should produce the same peak HP and torque figures once both are correctly spec'ed to the engine.
Where injection with programmable ign and fuel maps will win out every time is in the driveabilty. HP and torque curves can be smoothed out easily and big dips in either at certain parts of the rev range are unlikely. This is not true of using carbs.
Also when you spin on the track and stall (which will happen to the best), engines on injection will normally start a lot easier when hot.
When building an engine I would always recommend people to spend the extra money and go for injection.

[Ron Earp]

Originally Posted by Bruce Burges

All engines whether on injection or carbs should produce the same peak HP and torque figures once both are correctly spec'ed to the engine.

If both were using the same manifold this would be true. But I don't think it is true because of the fact that injection manifolds and carb manifolds differ significantly. For example there are great differences in air flow when comparing a single plane carb intake with individual runner intake (webers or EFI). Or dual plane 4bbl versus single plane intake, or a single plane injection intake versus a modern folder runner design and so on.

The different intakes with produce different intake resonances which will improve the volumetric efficiency in various parts of the engine operating curve. Most street intakes are tuned to have the resonance occur in the most used portion of the RPM range, while racing intakes optimize the upper RPM range. Some have variable tuning lengths to optimize throughout the range. All designs take advantage of the resonance effect to improve torque/horsepower where needed.

In the original question it is IR (webers/stack) versus plenum induction (4bbl). And I bet they will not have the same hp/tq curves even if both are optimized for the same RPM range, no matter if both are injection or both are carbs, and certainly not if one is carb and one is injection.

R

Ron