Author Topic: Mild 396 build  (Read 7355 times)

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blykins

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Re: Mild 396 build
« Reply #15 on: November 12, 2019, 04:00:53 PM »
Yes, 289's at 8000 rpm :)

But, on a more serious note, do you agree that the mid range can be cleaned up and produce more HP, using air corrector jetting?

Street engines are way different than all out race engines but, even race engines, need the right A/F, in the range they run in, even if it's only 1500 rpm.

For a race engine, you give it all the carburation you can, until the HP drops off, in the range your working in. In the engines that I had dynoed, they jet for max HP and then, come back with the air correcting jets, to bring the mid range in.

For giggles, I popped the specs into Holley's site, based on a 6000 rpm shift point.  There were a couple of 680's on there, but the majority (like 15-20) carbs were 750-780 cfm. 

I see nothing wrong with this size carb on an engine that's almost 400 cubic inches.  As a matter of fact, I personally would not run anything smaller. 

We tune on the dyno for idle, cruise rpm with a load, and WOT.   The OP's entire dyno session was rich.   I wasn't there, but it could easily be brought into spec with jetting and air bleed changes.  This was not a scenario where the engine couldn't use the carburetor because it was too big; it was just a tuning issue.   In most cases I love to see fuel being pulled out of a carb during a dyno session.  It means the engine is efficient and is "pulling hard" on the carb.
Brent Lykins
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Drew Pojedinec

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Re: Mild 396 build
« Reply #16 on: November 12, 2019, 04:01:17 PM »
650's are for 289's.

That is why Ford used a 780 for the Boss302  ;D
Debating carbs on the internet is fun.... lol

To Frnkeore:
Cfm is not THE determining factor in the fuel curve.

Sand hauler

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Re: Mild 396 build
« Reply #17 on: November 12, 2019, 05:08:37 PM »
The carb is a vacuum secondary 750
Bobby-   Carlsbad, NM

Joe-JDC

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Re: Mild 396 build
« Reply #18 on: November 12, 2019, 05:52:19 PM »
My recent 303 cubic inch Y Block for Engine Masters was run on the dyno with a 650 DP, 750 DP, 860 DP, 930 DP, and it made the most torque and horsepower with the 930 Barry Grant carb.  It made 453.7 hp.  We adjusted each carb for best AFR, and it responded with each one.  Last year's EMC with 375 cubic inches and tunnel ram ran best with two 860 Pro System carbs at 595 hp.  We actually dyno tested the 375 with the same intake used this year and the 930 BG carb made 581 hp, and then we tried a 1250 Dominator, and it made 582 hp/564 tq.  An engine size is not nearly as important as its efficiency when selecting a carb for proper cfm.  Look at the vacuum during the dyno pull, and if it is still pulling over .5" of vacuum, the engine can use a larger carb, or larger multiple carbs.  Being able to use a larger carb is not necessarily the best carb for street use, but a 750 cfm size is a non-issue on anything that is expected to make over 300 hp IMO.   Joe-JDC
Joe-JDC '70GT-500

Sand hauler

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Re: Mild 396 build
« Reply #19 on: November 12, 2019, 06:05:47 PM »
Also,thanks to Wes Adams for recurving the distributor  :)
Bobby-   Carlsbad, NM

frnkeore

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Re: Mild 396 build
« Reply #20 on: November 12, 2019, 07:54:01 PM »
The engine, falls flat on it's face at at 5400 and doesn't have the power of a street 302 @ 5500, why are you talking about 6000 rpm shift point?

Ford used the 780 cfm carb, not for the street version of the Boss 302 but, so that it would be legal for the 8000+ rpm Trans Am engine.

"Street engines are way different than all out race engines but, even race engines, need the right A/F, in the range they run in, even if it's only a 1500 rpm band. (Edited to read band, I wasn't referring to a race engine running at 1500)

For a race engine, you give it all the carburation you can, until the HP drops off, in the range your working in. In the engines that I had dynoed, they jet for max HP and then, come back with the air correcting jets, to bring the mid range in."

As you can see in this part of my reply, I'm agreeing with you guys, regarding a all out engine.

For the guys that reference the large carbs, are the engine build as streetable 5200 rpm engines and what was the power like at 2500?

What I'm suggesting is that the 1500 - 4000 rpm number, just might pick, w/o loosing the 5200 max HP. It stumbles, right out of the gate, on the print out.

As for my own experience with a race engine, the car in my avator is a twin cam Cosworth, it produces 200 hp, out of 96 CI, at 8500 rpm and has a pair of 600 cfm Webers so, I do know what large carbs can do for a race engine but, idles over 1600 rpm and stalls if given any load under 3500. If I where running it at 5200, I'd probably run 150 cfm, not 1200.

I'm only suggesting that it could be tried, as street engine and we won't know if it would produce better lower end numbers, w/o that.

It looks to me like the cam is what restricts it's air flow not the carb.

 
Frank

blykins

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Re: Mild 396 build
« Reply #21 on: November 13, 2019, 06:34:38 AM »
The engine, falls flat on it's face at at 5400 and doesn't have the power of a street 302 @ 5500, why are you talking about 6000 rpm shift point?

Ford used the 780 cfm carb, not for the street version of the Boss 302 but, so that it would be legal for the 8000+ rpm Trans Am engine.

"Street engines are way different than all out race engines but, even race engines, need the right A/F, in the range they run in, even if it's only a 1500 rpm band. (Edited to read band, I wasn't referring to a race engine running at 1500)

For a race engine, you give it all the carburation you can, until the HP drops off, in the range your working in. In the engines that I had dynoed, they jet for max HP and then, come back with the air correcting jets, to bring the mid range in."

As you can see in this part of my reply, I'm agreeing with you guys, regarding a all out engine.

For the guys that reference the large carbs, are the engine build as streetable 5200 rpm engines and what was the power like at 2500?

What I'm suggesting is that the 1500 - 4000 rpm number, just might pick, w/o loosing the 5200 max HP. It stumbles, right out of the gate, on the print out.

As for my own experience with a race engine, the car in my avator is a twin cam Cosworth, it produces 200 hp, out of 96 CI, at 8500 rpm and has a pair of 600 cfm Webers so, I do know what large carbs can do for a race engine but, idles over 1600 rpm and stalls if given any load under 3500. If I where running it at 5200, I'd probably run 150 cfm, not 1200.

I'm only suggesting that it could be tried, as street engine and we won't know if it would produce better lower end numbers, w/o that.

It looks to me like the cam is what restricts it's air flow not the carb.

If the engine produces a sufficient signal, it really doesn't matter what number is stamped on the carburetor. 

A few comments about the dyno sheet:

1.  It didn't "stumble right out of the gate".   It was rich all the way through the pull.   This was not an issue with carb size, it was an issue with *the tune* of the carburetor.  If you read the OP's follow up post, the carb was leaned out and gained even more horsepower. 
2.  The first couple hundred rpm of a dyno pull and the last couple hundred don't really mean anything.  It's at these rpms where the operator is loading or unloading the engine and many different things are happening to skew numbers.   The engine does fall off, but I'm not convinced that it's a function of the engine.  I think it's from a situation where the operator/computer knew where the peak hp rpm was and there was no reason to pull the engine higher.  *Even so*, I don't know the OP's intention of using the truck, but if he plans to "play" a little bit, you would shift higher than 5200 rpm. 

A comment about the engine itself:

The camshaft is not the limit here, it's the cylinder heads.   That camshaft on an aftermarket head that flows 280-300 cfm would produce a peak hp rpm closer to 6000 rpm.  I spec'd that camshaft knowing that there is a fine line between getting the most from the entire combination and taking power away from the engine because the camshaft was inefficient at the rpms that the OP would see. 

He actually said that he did try a dual plane/600 and a single plane/750 and decided to stay with the 750.  We can sit here and discuss "what ifs" all day, but in the end, if it works, it works.   Many of us here have built and dyno'd enough combinations that we have a really good feel on what works well, even on low rpm "street" engines. 
Brent Lykins
Lykins Motorsports
Custom FE Street, Drag Race, Road Race, and Pulling Truck Engines
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Sand hauler

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Re: Mild 396 build
« Reply #22 on: November 13, 2019, 07:32:19 AM »
Thank you Brent,well said . I'm very pleased with the cam and feel that it works very well with the entire combo,even though an after market head would be better , I tried to set the combination up with the intention of up grading the heads in the future for my son when he's ready,yet deliver a good solid and reliable motor that should last him a very long time. I believe that with your help and everyone else involved that has been accomplished. Is there still some left on the table? Yes of course ,there usually is but that's the one of the things I love about the Fe, it's versatility, durability
And this motor has responded well with every tweak and change and should also with better heads in the future without having to change alot of other parts in the process. Again thank you for your time and help
Bobby-   Carlsbad, NM

Falcon67

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Re: Mild 396 build
« Reply #23 on: November 13, 2019, 10:48:50 AM »
650's are for 289's.

Hahahahaha  ;D

My dragster 393C went 5.80 something @ 119 on gas with a 800 home brew using QF parts.  Put the 650DP on it as a test and it ran...5.80 something at 119. 

frnkeore

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Re: Mild 396 build
« Reply #24 on: November 13, 2019, 01:01:25 PM »
Bobby & Brent, I am not criticizing the build, AT ALL! It has excellent numbers in it's rpm range, especially for how rich it is.

What I'm trying to say, is that it does not need that 750. What I'm trying to get across is that for this street build, the engine would probably produce a higher average HP, between 25K & 52K, using a 600 or 650 carb and a 600 VS, should give better gas mileage.

One other thing about the 750 VS, the secondarys when fully open and as they are opening, may not have enough air flow across the boosters, to fully atomize the fuel.

Regarding Bobby's wording about the 650 dual plane, it sounded to me like he thought it might be better but, decided to keep the SP & 750.

I like this forum because I like FE's. They were top of the line when I was young but, I only had two, a 300 HP 352 and a LR 427 before I started formula racing. The other reason I like this forum, is the knowledge, dyno testing and attention to detail.
Frank

blykins

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Re: Mild 396 build
« Reply #25 on: November 13, 2019, 01:41:45 PM »
What I'm trying to say, is that it does not need that 750. What I'm trying to get across is that for this street build, the engine would probably produce a higher average HP, between 25K & 52K, using a 600 or 650 carb and a 600 VS, should give better gas mileage.

I highly disagree.
Brent Lykins
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frnkeore

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Re: Mild 396 build
« Reply #26 on: November 13, 2019, 02:56:48 PM »
So then, what your telling me, is that fuel atomization and intake track velocity has no effect on HP, either good or bad and that it doesn't need to be optimized, for best results, either in MPG or HP?
Frank

blykins

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Re: Mild 396 build
« Reply #27 on: November 13, 2019, 03:47:07 PM »
So then, what your telling me, is that fuel atomization and intake track velocity has no effect on HP, either good or bad and that it doesn't need to be optimized, for best results, either in MPG or HP?

They absolutely do!  Fuel atomization and intake track velocity have effects on everything!  However, *I do* optimize it on every single engine that leaves here and that doesn't mean, in any way, shape, or form, that I have to bolt on a smaller carb to do it.   The old internet wives' tale that you have to bolt on a small carb to get good  throttle response is a bunch of bunk. 

I will tell you, based on experience, that a 750 vacuum secondary carburetor is not a detriment to horsepower or mileage on an engine such as this.   This engine is pretty much at 100% volumetric efficiency and uses a camshaft that will pull very hard on everything above it.   

I will also tell you that unless it's an extremely gross negligent error in carb sizing, you will not see any differences in average horsepower.  I'm looking at two dyno sheets right now, on a 390 that I built, where I tried a Quick Fuel 750 and a Holley 1050 Dominator. 

This engine made 539 hp with the 750 and 540 hp with the 1050.   This engine was not a 3/4 ton truck engine by any means, but looking at averages between 4000 and 6000 rpm, the average HP and TQ for the 750 were 497.5 and 498.5.  The averages for the Dominator were 497.9 and 499.3.  At 3750 rpm, the 750 was making 327.1 hp and 458.1 lb-ft.  At 3750 rpm, the Dominator was making 329.7 hp and 461.8 lb-ft.   

I didn't turn a screw on the Dominator and basically just bolted it on for giggles. 

Let me say, by no means do I expect a 2-circuit Dominator to be "fuel efficient" in comparison, but your point about a larger carburetor making less average horsepower really has no merit here.

I know you're gonna say, "Well, that's a high hp, high rpm 390 and it has nothing to do with the OP's engine."  You can say that, and I will disagree with you again.   


« Last Edit: November 13, 2019, 04:01:10 PM by blykins »
Brent Lykins
Lykins Motorsports
Custom FE Street, Drag Race, Road Race, and Pulling Truck Engines
Custom Roller & Flat Tappet Camshafts
www.lykinsmotorsports.com
brent@lykinsmotorsports.com
www.customfordcams.com
502-759-1431
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Falcon67

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Re: Mild 396 build
« Reply #28 on: November 13, 2019, 04:11:07 PM »
I will tell you, based on experience, that a 750 vacuum secondary carburetor is not a detriment to horsepower or mileage on an engine such as this.   This engine is pretty much at 100% volumetric efficiency and uses a camshaft that will pull very hard on everything above it.   

I will also tell you that unless it's an extremely gross negligent error in carb sizing, you will not see any differences in average horsepower.  I'm looking at two dyno sheets right now, on a 390 that I built, where I tried a Quick Fuel 750 and a Holley 1050 Dominator. 

This engine made 539 hp with the 750 and 540 hp with the 1050.   This engine was not a 3/4 ton truck engine by any means, but looking at averages between 4000 and 6000 rpm, the average HP and TQ for the 750 were 497.5 and 498.5.  The averages for the Dominator were 497.9 and 499.3.  At 3750 rpm, the 750 was making 327.1 hp and 458.1 lb-ft.  At 3750 rpm, the Dominator was making 329.7 hp and 461.8 lb-ft.   

I didn't turn a screw on the Dominator and basically just bolted it on for giggles. 

Let me say, by no means do I expect a 2-circuit Dominator to be "fuel efficient" in comparison, but your point about a larger carburetor making less average horsepower really has no merit here.

I know you're gonna say, "Well, that's a high hp, high rpm 390 and it has nothing to do with the OP's engine."  You can say that, and I will disagree with you again.

Agree with all this, having seen it in real world results.  My comment on my 393C wasn't meant to trash a 750 LOL.  David Vizard even says in his books that the "carb too big" thing is BS because as long as the carb can meter fuel, it's technically not too big.  Above comparison between a 750 and a 1050 backs that up.  The Holley formula that everybody quotes is their way of reducing returns.  Having sold hot rod parts over the counter, everybody with a 283 wants an 850 double pumper because thats what last weekend's drag strip hero had on his car.  Try to sell them a 600 or 750 vacuum and they look at you like you said something bad about their mother.

I am partial to my 650DP because it was a $40 swap meet deal that has performed like a million bucks in the last 20 years.  A good 750DP is an all-around good unit for any engine from a 302 to a 460.  I had a 750 VS "proformed" unit (PF center) that I loaned to a guy with a 8.5:1 454 in his street/strip car (used to run a 8-71 on it).  Had his old 850DP on it.  Kept jacking with it, car was all over the place on ET and MPH.  "Here, try thing thing."  "It's kind small for a 454."  "Well, try it anyway to see if the issue is that 850 or something in the motor."  Car immediately went 1 1/2 seconds (not tenths - seconds) quicker in the 1/8 mile.  It was like 2 months before I got my carb back.   8)

Same deal with a jet boat.  Guy insisted on buying an 850DP.  Came back to the store, "seems lazy, blubbers a lot".  Tried to sell him a 750 VS (List 3310).  Nah.  "Here - make you a deal-deal.  You take it and if it doesn't run better, I'll take it back used no questions.  If it runs better on the lake, you come pay me."  I got paid.
« Last Edit: November 13, 2019, 04:14:25 PM by Falcon67 »

Falcon67

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Re: Mild 396 build
« Reply #29 on: November 13, 2019, 04:18:17 PM »
How much grief do you think I got at the track and interwebs for running this pile of 600 CFM carbs on a .030 over 302.  Not counting the flack that they "ain't no Holley, them's trash carbs".



Same ET and MPH as a 650D and 289 Air Gap intake.