500 cfm holley on blow thru turbo

[kirkallen143]

Howdy,

Has anyone used the 500 cfm in a blow thru set-up on a stock 200? Does 10s, you still are using the 350 cfm in the falcon, on your 250 right? Mind if I ask what jets you are using now after the dyno? Have you tried to switch or thought about the 500? I propose one could jet the 500 lean at idle then richen up enough to run at boost, pull manifold vacuum for advance (I believe you are running none at all) to lessen the bog off start, set full advance to knock off any denotation at upper rpms, etc...I'll play with it some more. The "super 60" should be here next week. Later.

Kirk ' 73 bronco

 

[66Sprint6]

No, but I plan too...well, it wont be a stock 200. I was runnin a 500 on a stock 200 bottom end and loved it
Matt

 

[xctasy]

Summary is that a stock 200 has 90 flywheel hp. Add a too big 500 cfm Holley with no mods, it will work poorly, but will still work. It needs a 60 thou jet to work with the venturi. Best power is about 105 with a 500 #4412 carb


When you turbo it with 9 or 12 pounds of boost, you'll get 165 to 190 hp if you still run the stock stump puller cam. If you use a 500, you won't gain any power. If you use a 350 Holley, you won't loose any power. The reason Does10's has over 300 flywheel horspower on a good day is that he uses boost to blow appart the rules of carburation.

The carb rules are.

Venturi size, divided by 23 = Minimum jet diameter in inches,
Venturi size, divided by 16 = Maximum jet diameter in inches,

A 500 has a 1.375" venturi. The min jet is 60 thou, or 60 call size Holley. The max jet is 86 thou, or a 77 call size Holley Jet


A 350 #7448 runs a 1.1875" venturi, and can run 51's minimum, and 71 call size maximum.

I think Does10'Ss runs 78's, which is a massive 89 thou diameter jet


When you go turbo things change. You can jet up tiny carbs with bigger jets that plain wouldn't run on a car without a turbo.

There are a few important things to remember.

1. A 350 Holley atmomises (turns fuel into little dropletts of liquid gasoline) better than the 500 Holley. Jetting is 3.7 times the flywheel net hp.

2. The 500 Holley makes more power at the expense of fuel economy. It looses large amouts of part throttle fuel efficency down low for much better horspower (if the engine can use it).

3. A turbo car can cope with a 350 Holley becasue the pressure helps atomise fuel better.


On a non-turbo car, the optimum jet size for a 350 holley is between a 51 jet for a stocker, and up to a 74 jet. After that, it fails to operate properly at the low ranges. This is a law of carburation. Stock jetting is 61.

On a blow through turbo car, the 350 can run over the 74 jet level and still function because the huge pressure helps break the fuel up.


The 500 #4412 is designed for big V8's, and can come with 74 or 79 jets. It can cope with as little as a 60 jet, and as much as the jets over 79 are really getting too big unless the car is on a big 460 cube car.



Why?


.On a 2-bbl Holley, horsepower is made by only two jets, and two power valve channel restrictions (pvcr). The jets flow rate is rated by Holley at cc's per minute at a 80 atmospheres pressure drop. The flow through the pvcr is equal to a similar amount. Most pvcr's are 21 thou or so, and thats equal to a change to two jets four jet sizes bigger. In the case of a 500 Holley, it comes with two 74 jets which flow 542 cc/min each, and the 21 thou power valves are less than 100 cc/min total.

If you do the sums, a 74 jetted 500 with 21 PVCR's will yield 1184 cc per minute. The most efficent engine around, a Cosworth V8, could make 365 hp from this. Our sixes can only make about equal to 216 hp with the wildest street cam. I've seen a 289 give a reported 352 hp with this carb and 86 jets!

For 500 cfm carbs on sixes, the rules are flywheel hp (net) needs 5.5 times the hp in cc/min jetting. I prefer to use holleys aggreed jet recomemdation, and forget about the PVCR sizes.

125 hp needs 125*5.5, or 687.5 cc/min, or two jets that flow 344 cfm or 64 jets.

fwhp______total cc/min______each jet______ Holley Call size
90______________495________248______57
100______ _______550________ 275______59
110______ _______605________ 303______61
120______ _______660________ 330______63
130______ _______715________ 358______ 65
140______ _______770________ 385______ 67
150______ _______825________ 413______ 68
160______ _______880________ 440______ 70
170______ _______935________ 468______ 71
180______ _______990________ 495______ 72
190______ _______1045________523______73
200______ _______1100________550______74
210______ _______1155________578______75
220______ _______1210________605______77
230______ _______1265________633______78
240______ _______1320________660______78
250______ _______1375________688______79
260______ _______1430________715______80
270______ _______1485________743______81
280______ _______1540________770______82
290______ _______1595________798______86
300______ _______1650________825______84
310______ _______1705________853______85
320______ _______1760________880______86
330______ _______1815________908______86
340______ _______1870________935______87
350______ _______1925________963______88
360______ _______1980________990______89

These are rich jet sizes sized for 12:1 air fuel ratios. If you are planning on economy, you can use 15.6:1 on todays fuel, and could run jetting 27% leaner. That is down 6 jet sizes if you can tune with a gas analyser. Wisely, Holley jets are much richer to avoid problems.



Here is the rated flow rate at 80 atmospheres for Holley jets. Each step is a 4.5% gain in power.

198 cc/min or 50 thou nominal, 51 call size jet
205 cc/min or 52 thou nominal, 52 call size jet
212 cc/min or 52 thou nominal, 53 call size jet
221 cc/min or 53 thou nominal, 54 call size jet
230 cc/min or 54 thou nominal, 55 call size jet
239 cc/min or 55 thou nominal, 56 call size jet
248 cc/min or 56 thou nominal, 57 call size jet
257 cc/min or 57 thou nominal, 58 call size jet
267 cc/min or 58 thou nominal, 59 call size jet
285 cc/min or 60 thou nominal, 60 call size jet
298 cc/min or 60 thou nominal, 61 call size jet
311 cc/min or 61 thou nominal, 62 call size jet
325 cc/min or 62 thou nominal, 63 call size jet
341 cc/min or 64 thou nominal, 64 call size jet
357 cc/min or 65 thou nominal, 65 call size jet
374 cc/min or 66 thou nominal, 66 call size jet
392 cc/min or 68 thou nominal, 67 call size jet
411 cc/min or 69 thou nominal, 68 call size jet
429 cc/min or 70 thou nominal, 69 call size jet
448 cc/min or 73 thou nominal, 70 call size jet
470 cc/min or 76 thou nominal, 71 call size jet
492 cc/min or 79 thou nominal, 72 call size jet
517 cc/min or 79 thou nominal, 73 call size jet
542 cc/min or 81 thou nominal, 74 call size jet
566 cc/min or 82 thou nominal, 75 call size jet
587 cc/min or 84 thou nominal, 76 call size jet
615 cc/min or 86 thou nominal, 77 call size jet
645 cc/min or 89 thou nominal, 78 call size jet
677 cc/min or 91 thou nominal, 79 call size jet

In total, if you know how much power you need, you can work out the maximum rich jetting to the nearest call size. If you live at a high altitude, go down a jet call size according to this site


http://www.bgsoflex.com/holley.html

if you have a poor intake manifold design, you'll need to go up a size becasue the fuel will wet the intake manifold more. Sixes need more jetting than V8's of the same size. A stock 250 or 265 I6 needs as much jetting as a 302 or 318 of the same year.

 

[66Sprint6]

What about runnin the 500 with a 274 cam, low compression with Forged pistons and 10-12psi boost? Would the cam change things or am I running the wrong carb? Im pretty much gonna stick with it either way, but I would like to know what Im missing/gaining usin it.
Matt

 

[Does10s]

After the dyno we're running a #72 jet in the 350cfm Holley. I do believe that I could lower it a bit more but we're running fairly "safe" with the tune we have. Although we blew a head gasket last time out becuase I got greedy by adding to much timing, and boost (18lbs!).
As for the timing/vacuum adv., we're using a modified Duraspark distributor. No vac. adv. Just mechanical. We modified the rotor shaft by welding on the tab so it will only advance the timing 10* or so. So we're at 17* initial and 27* total. This setup is very simple. easy to work with and very effective. Although I don't think it's perfect. It does have a nice "off idle" acceleration with this setup under normal street conditions. At the strip...who cares! By the time Kelly releases the brake, all the timing is in, boost is quickly building up to 16lbs, and she's gone!
Later,
Will

 

[kirkallen143]

Xtaxi,
Your info is superbly gracious, I take my hat off to you. So if I run the 350 (which atomizes the fuel better) and are looking for 175 hp (wishing) at the flywheel I would need to run 63 jets:

3.7*175=647.5/2=324=call jet size 63.

This also is obtained from a previous post you had about Holley jet sizing, in which also doing the math comes out to be the same number (or jet size in this case).

Again, using your formula for the 500 equates:

5.5*175=962.5/2=481.25=71 or 72 call jet size.

Just as you have in the chart. So really it is a matter of what you are gaining for...daily driver w/ good performance, the 350 cfm, or "hold on to your britches, I'm lettin' her loose," the 500 cfm (at the expensive of fuel economy). What do you think? I am just trying to understand myself, as it is. We sure do appreciate ya, though.

Kirk ' 73 bronco

 

[kirkallen143]

And here, Will is proving the breaking of the laws of carburation under pressure...the 350 cfm running 79 thou. jets(72 call size), which only supports 266 hp at the flywheel, and he has about 300 hp (caculated from dyno) at the flywheel.

492*2=984/3.7=266 hp supported at those jet ratings from chart.

Kirk ' 73 bronco

 

[Anonymous]

do you think it could be done to turbo the 300 in my pickup? I have bumped the compression to 9:1, is this a problem? would twin turbos be cooler?! you could run them in series or run dual carbs or............?

 

[xctasy]

The 72 main jets alone can support packages worth 266 hp net at 12:1 l air: fuel ratio. When you add in the power valve channel delivering fuel at low vaccum (wide open throttle) you can get well over that.

The power valve channels on a 350 are small, and only add about 27 hp if they do indeed flow 100 cc per minute at wide open throttle. That's about 293 hp at a 12:1 fuel air ratio augumeted by extra fuel.

If Will can run it lean with out detonation, perhaps at 13.5:1 or 14:1, then he may get 330 to 343 hp. The Holley 350 jet selection is always peak flywheel hp at 12:1, multiply by 3.7, there's you jet flow is cc per minute.

500 takes 48% more fuel because the venturi area (1.485 sq in verses 1.108 sq in is 34 % bigger) and throttle area (2.20 sq in verses 1.77 sq in, 25%) is on average needing at least 30% just to compensate. Bigger carbs atomise fuel worse than smaller carbs. To be safe, it need just on 48% more fuel to balance the increased air flow leakage. Similarly, the PVCR need to be a similar size bigger to cover the bigger amount of air flow.

Since fuel is incompressable, the the signal the jet and PVCR's sees is the method of increasing flow. In a 16 pound turbo, the pressure is blowing against the jet, and the fuel pump is provding the additional shove.

When you got to a #4412, I think the PVCR is bigger on the 500 than on the #7448 350. The smaller ones have 21 PVCR's, the bigger ones have about 52 or so. I've not measured it.

Holley balances the power valve fuel delivery for every application. That's why I have a conversion factor for each type of Holley carb configuration.

Second matter is that the formula is based on Holley jet recommendatiosn, which has been set in stone for 15 to 30 years. I trust there judgement, and the formula follows Holley's selection process. I don't tell Holley how to jet there carbs becasue I don't dyno engines or do drivability testing and mobile data logging like they have to.They publish there info, I read it, calculate and interpolate jetting from documented, known combinations.

No black magic.

 

[gravelrash]

have you guys modified the holleys at all to enable to run blow-through.

 

[xctasy]

No, no mods.

Above 9 pounds per square inch boost, it pays to Boost Referenace the throttle body in the manner Dave Emanuel suggested in the Holley Performance book dating from 1980. Holley 2-bbl throttle bodies in good condition can cope with lots of boost beyond 9 psi. The steel throttle trunion sets in a cast aluminum alloy throttle body.


The float needs to be changed to a solid plastic foam filled item rather than brass.

The needle and seat may need to be upgraded to cope with the fuel flow demanded by the jets.

 

[XFlow_Fairlane]

I thought will was running a drilled power valve?

That is the only blow through mod I have really heard that people make. allows a smaller jet to be ran while allowing the high fuel flow needed for boost

 

[gravelrash]

xecute,
you sound like the man in the know. i have a 600dp on my 250 2v in nat aspirated form it works great, i have now put a turbo on the 2v using a blow through type setup. apart from the nitrophyl floats what other mods should i do to it, the jets in it are standard 600dp list 4776-3.
btw: where can i get some nitrophyl floats holley pt#116-3

 

[XFlow_Fairlane]

on a side rant my 350 holley came yesterday.....has 40 jets in it!! tore it down since I want to put a solid float in it for later this month and prob chang out the jets in it.

 

[Does10s]

62Fairlane170,
Nope! Our Holley 350 still has a standard Power Valve. No holes drilled or any other modification to the valve.
Here are our mods to the Holley:
1. Nitrophyl solid float. We're using a circle track float that has a beveled "rear" portion that allows fuel to flow under hard acceleration. This is due to the carb sitting sideways.
2. Removed choke and choke horn. Filled in choke rod hole.
3. Jet'd up. Currently at #72.

THAT'S IT! It's not brain surgery!
Piece of cake!
K.I.S.S.
Later,
Will

 

[Anonymous]

Hey Will,
you wanna borrow my PLX 300 wide band? You may find out that by drilling your power valve channel restrictors,, you will be able to jet down your mains for better cruising economy,

and still have enough fuel flow (through the PVCR's) under power.

 

[Does10s]

Mmmmmm.....maybe!

Will

 

[Anonymous]

hey you boost gurus,
what would it take to turbo a 300 in a pickup? I have rebuilt it and rodded it to a supposed 300hp and 300ftlbs, would like about another 100 horses and ft lbs. I ported the head, had a cam custom ground for my application, had the ignition set up to match, have a offenhauser dualport and a 450 holley 4bbl, hedman hedders, x-pipe, dual 3in exhaust, MSD 6a box, Fischer balancer, 3 angle valve job, arp studs, 9:1 compression, etc.
will the compression hurt me for a daily driver? are roller rockers worth the money? how hard would it be to retro-fit roller lifters in it, and would it be beneficial?
I'm pullin 35" mudders with 3.54 gears, lots of torque makes it ok around town, jus want more, you know how it is.

 

[Does10s]

Scott,
Piece of cake! It's just a lot of work. Your C/R is fine for a turbo motor. You'll just have to watch the timing if you're going to run 89 octane.
The hardest part by far is fab'ing up the turbo header and associated piping. But in a truck it should be a little easier. There's a lot more room to put stuff!
That intake and carb will work fine for blow-thru. Just swap the floats for solid Nitrophyl ones.
Find one T04 with a .69 A/R housing, 57-64mm, or a couple of small T03s and have twin turbos.
Later,
Will

 

[Anonymous]

Will's advice is right on.

If you plan to stay with pump gas, you can use a "Boost timing retard" box or a good water/alcohol injection kit. They operate only when under boost. You can buy a good one for around $300 - $400 or build your own from info found on the 'net. Also, get "turbochargers" book from Hugh McInnes.


I used this guide:

from this article:

http://www.hotrod.com/techarticles/engi ... 312_turbo/

and was LUCKY to find just that on ebay, for $275, brand new in the Garrett box.

You could also run a Holset HY35 or HX35 from a Dodge Cummins. The HY35 will be getting close to its limit at 400 HP, but the HX35 should be fine. Even better is an HX40, but those are getting hard to find at a decent price because the Dodge guys can get more power form a HX40 than from a HY or HX35 and they buy them as soon as any come up for sale.

BE CAREFUL buying a used turbo. They get damaged very EASILY, and a lot of people would like to sell you their burned up junk. You can get great help from Kevin at Majestic Turbo here in Waco, TX or in Dallas.