Basic Blower Measurements
This page is for basic blower measurements and is not intended for blueprint making or for specifics of any one individual blower.

Blower Type/Manufacturer Named Size C.I.D./Rev (approx) Style Of Rotor Center Case/Rotor Length Center Case Height
Detroit Diesel "GMC" Straight 71 series 2-71 136 c.i.d./rev 3 lobe 30º helix Ball/Roller bearing 4.875 inches Non-standard case side inlet

Detroit Diesel "GMC" Straight 71 series 3-71 210 c.i.d./rev 3 lobe 30º helix Ball/Roller bearing 7.500 inches 7.500 inches

Detroit Diesel "GMC" Straight 71 series 4-71 280 c.i.d./rev 3 lobe 30º helix Ball/Roller bearing 10.000 inches 7.500 inches

Detroit Diesel "GMC" Straight 71 series 6-71 approx. 353 c.i.d./rev (Small Bore) 3 lobe 30º helixBall/Roller bearing 15.000 inches 7.500 inches

Detroit Diesel "GMC" Straight 71 series 6-71 420 c.i.d./rev (large bore) 3 lobe 30º helix Ball/Roller bearing 15.000 inches 7.500 inches

Detroit Diesel "GMC" Straight 71 series (converted 8v71 to aftermarket case) 8-71 448 c.i.d./rev 3 lobe 30º helix Ball/Ball bearing 15.900 inches 7.500 inches

Detroit Diesel "GMC" "V" 71 series 6V71 338 c.i.d./rev 3 lobe 30º helix Ball/Roller bearing 12.000 inches 7.500 inches

Detroit Diesel "GMC" "V" 71 series 8V71 448 c.i.d./rev 3 lobe 30º helix Ball/Roller bearing 15.900 inches 7.500 inches

On this page you will see buttons linking to useful performance engine technical information.

Click to access.

At $400 it is not cheap, so if you can live will more noise $220

Use these figures as a fuel line sizing standard: if your feeding a carburetor with the typical 8-10 psi fuel pump feeding to the fuel pressure regulator

* Up to 250 HP = 5/16" or -04 AN
* Up to 500 HP = 3/8" or -06 AN
* Up to 700 HP = 1/2" or -08 AN
* Up to 1000 HP = 5/8" or -10 AN
* Up to 1500 HP = 3/4" or -12 AN

How big a fuel pump do you need?

The average advertised weight of a gallon of premium fuel is 6.34 lb/gallon.
Brake Specific Fuel Consumption or B.S.F.C.
Brake Specific Fuel Consumption or B.S.F.C. is the amount of fuel required to produce 1 HP for 1 hour. This means that an engine with a B.S.F.C of .5 will burn 1/2 or .5 lbs of fuel to produce 1 HP for one hour. Determining exact B.S.F.C for a specific engine is complicated and requires an engine dyno.
Based on industry standards the B.S.F.C for:
Normal Aspirated Engines is .45 - .55
Supercharged Engines is .55 - .60
Turbocharged Engines is .6 - .65

Therefore to calculate fuel required:
Target Hp * B.S.F.C. = Fuel required in lbs/hr
600 X 0.55 = 330 lbs/hr
Most fuel pumps flow rate is advertised in gallons per hour:
Lbs/hr / fuel weight per gallon = gal/hr
330 / 6.34 = 52 gal/hr
but remember pump losses, and a fuel pressure regulator and a return line fuel feed system designs flow requirements ?

Why pushrods fail

Today the Michigan firm Trend Performance is the largest manufacturer and supplier of pushrods in racing and in the performance after market. But in 1988 when Bob Fox founded his pushrod company, after working the phones as a tech rep at Diamond Racing, things were different. During his time at the piston company he noticed that the performance of competition pushrods was little better than adequate—their lengths varied and their ends failed—both ends!

Manufacturers would reduce the material thickness of the cup ends in order to form them, and as a result they would crack. Further, their lengths were so inconsistent that each pushrod had to be inspected and graded accordingly. It was this encounter that caused Fox to contemplate life as a pushrod maker. 1. If its seat is heat treated to a very hard condition, it will eventually pound its V-shape into the pushrod ball. Much more desirable is to set the pushrod ball end in a radius cup and reduce the point loadings.

1. What are the biggest challenges that face today’s competition pushrod maker? “Racers seeking to exploit every tiny advantage tend to select lighter and lighter weight oils, many of which are impaired or even deficient in lubricity at high loads and high revs. Also, installing pushrods positioned between lifters and rockers with contact surfaces rougher than 1Ra expose the pushrod ends to severe abrasion. For example, a rocker arm adjuster ball with a rough, hard contact surface can act like a file. Plainly, it’s prudent for the engine builder to inquire about the surface finishes of the parts that operate in conjunction with the pushrods. “Another factor that leads to premature failure occurs when pushrod balls are bound in tight cups. It’s imperative they have sufficient operating clearance. A further problem arises when you set the ball end of pushrod in a V-cup. The V-cup presents a very narrow contact seat which significantly increases the loading on the pushrod ball end. If its seat is heat treated to a very hard condition, it will eventually pound its V-shape into the pushrod ball. Much more desirable is to set the pushrod ball end in a radius cup and reduce the point loadings. “Recently, I was reminded by Jon Kaase, the race engine builder, of the severe environment in which the pushrod operates. ‘Assume,’ he said, ‘you have an open spring pressure of 1,400lb and a rocker ratio of 1.9:1, therefore, the loading on the pushrod equates to around 2,660lbs. This is then transmitted through the tiny area of the pushrod ball. If the surface area of a V-cup is 100th of a sq. in., the loading could be somewhere around 300,000psi!’ “In addition to these loadings, increased rocker ratios and engine revs further increase surface speeds on the ball ends.”

If they begin to turn blue from excessive heat, it’s time to replace them.

2. How long do pushrods last in racing engines? “In Sprint Cup, the top teams might use them only once or twice and then switch them to their Busch Series engines. Other Cup teams will run them much longer. In NHRA Pro Stock, most of the teams will run them until they show signs of wear. The same is true in Top Fuel and Funny Car, except those pushrods might show signs of discoloration on their ends instead of wear. If they begin to turn blue from excessive heat, it’s time to replace them. In short track oval racing, engine builders will use the same pushrods for several seasons—often six to eight thousand laps—providing they are not bent and show no signs of wear.”

3. What percentage of your pushrod business is racing? “Probably ninety percent of our production is devoted to racing. But Trend also produces piston pins and tool steel flat tappets for racing, particularly NASCAR. About one half of our valve train production serves professional race teams; the other half is dedicated to the weekend racers and to the high-performance street users.”

4. Do you make single-piece or three-piece pushrods? “Trend doesn’t make three piece pushrods, but we do manufacture two-piece. These allow the engine builders to cut the pushrods to length and install the tips as required. Our tips are pressed into the pushrod using a hydraulic press and an installation tool. But a few years ago, when we introduced a Quickship program, we discovered most engine builders preferred one-piece pushrods. These were finished to size and length—they required no more work—and they’re shipped within 24 hours.”

5. From which materials do you manufacture pushrods? “The biggest proportion is made from chrome molybdenum, a type of alloy steel known as 4130. This material possesses an excellent strength-to-weight ratio and is considerably stronger and harder than standard 1020 steel. Sprint Cup engines use it as do much of Pro Stock and Pro Mod. In contrast, Top Fuel and Funny Car teams use H13 tool steel in solid bar form. The 4130 pushrods are produced from thick-wall tubing. Their hollow center passage is pressurized by oil destined to lubricate the rocker adjuster.” The most recent troubles we encountered derived from galling in the top cup of Pro Stock pushrods, which we overcame by introducing a bronze insert.

6. What do you consider the biggest recent failures in valve train? “As long as racing engines continue to produce more power, failures will soon follow. But failure isn’t too concerning—as long as you learn from it. The most recent troubles we encountered derived from galling in the top cup of Pro Stock pushrods, which we overcame by introducing a bronze insert. When similar troubles afflicted ball-ball pushrods, we succeeded in eradicating it by replacing the top ball with one made of a special self-lubricating tool steel.” 


This is the same engine with a Procharger and intercooling.

Now you can see the benefit of E85 without the increased cooling effect.

It also reveals how much better a Procharger works.

This graph shows the huge benefits of using E85 compared to racing gasoline in a Roots supercharged engine.

Much of the increase came from cooling the blower.

Quick Formula: HP X .55 :- 6 = GPH.

600Hp X .5 = 330 :- 6 = 55 GPH

Holley Blue pump flows 70 gph at 9 psi and includes a regulator.

(HP x BSFC = pounds of gasoline)
500 hp x .5 BSFC = 250 pounds of gasoline.
500 hp x .75 BSFC = 375 pounds of gasoline.

Since a gallon of fuel weighs about 6.2 pounds, we find that in our first example, 250 / 6.2 = 40 gph (gallons per hour) and 375 / 6.2 = 60 gph.

700 X .7 :- 6.2 = 79gph

Use 110gph or bigger.

Narrow Lobe Separation really helps make Tq in the mid range

Long duration cams increase valve overlap, this reduces vacuum for the power brakes at idle.

There are a few solutions.

Here is a good one.

This is a reprint from a forum.

I spoke with Yates before building my headers because I had the same Tri Y questions. First off, other than the roller camshaft and 950QF carb, my engine is right out of a Cup car. I had my C3 headed Cup 358 on an engine dyno with 1 7/8" tri Y's off an on old Cup car. The engine signed off early and made hp 741 hp at 7800 and peak tq at 6400. After speaking with one of the Yates engine R&D techs, he told me that the tri Y headers were used on the road race car and on the shorter tracks. They were willing to sacrifice peak hp numbers for better torque and hp under the curve. Even though the tri Y's killed some of the power, their lap times were better. On the super speedway engines, they used mostly triple stepped headers with a merge collector because the engine lives at or close to peak hp all of the time. Yates recommended for my setup and cam profile not to use a tri Y header on my engine and build triple stepped headers going from 1 7/8" to 2" to 2 1/8" going into a 3.5" merge collector. He was very specific on the length of each tube and the total length of 29-30". He also said that my engine would gain 60+ hp.

I built the headers exactly to Yates specs and put the engine back on the same engine dyno with the same dyno operator. With no other changes, the engine made 817 hp at 8400 and peak tq at 7200.

The person I spoke with at Yates explained things that were well beyond my level of knowledge. Basically, he was trying to explain to me port CSA vs port volume vs intake valve size vs intake runner design vs cam events and a bunch of other stuff that I didn't understand. Anyway, it's hard to believe that a header could make that much difference in power but he was right.

CVR electric vane-style vacuum pumps offer less noise and vibration with more vacuum. These precision-machined, self-contained units will increase levels to 20 in. of vacuum when it drops below 15 in. of vacuum—automatically and quietly. They can be mounted in any position and the installation is easy; simply connect the positive/negative power. Keeping your brakes pumped up with the appropriate stopping power is a good thing. Maintain vacuum levels and proper braking performance with CVR electric vane-style pumps.

 Carb Size

 CID x RPM x V.E. / 2820 = CFM
 418 x 6000 x .9 / 2820 = 800 CFM

Cars with big cams may run a little short on vacuum for their power brake boosters. For all of the vacuum that you need, just install one of our Summit® electric vacuum pump kits. They include a shiny 12 V pump and all of the vacuum line, fittings, and hardware required for installation. These units are completely self-contained, with no need for the additional wiring of relays or switches—simply supply power to the units and they regulate themselves. When vacuum levels drop below 15 hg, the electric vacuum pumps activate and increase brake vacuum to 20 hg.

Best View On Desktop

US Recommended Bolt Torque

Size Recommended Torque
Grade 2 Grade 5 Grade 8 18-8 S/S Bronze Brass
Coarse Fine Coarse Fine Coarse Fine Coarse Fine Coarse Fine Coarse Fine
#4* - - - - - - 5.2 - 4.8 - 4.3 -
#6* - - - - - - 9.6 - 8.9 - 7.9 -
#8* - - - - - - 19.8 - 18.4 - 16.2 -
#10* - - - - - - 22.8 31.7 21.2 29.3 18.6 25.9
1/4 4 4.7 6.3 7.3 9 10 6.3 7.8 5.7 7.3 5.1 6.4
5/16 8 9 13 14 18 20 11 11.8 10.3 10.9 8.9 9.7
3/8 15 17 23 26 33 37 20 22 18 20 16 18
7/16 24 27 37 41 52 58 31 33 29 31 26 27
1/2 37 41 57 64 80 90 43 45 40 42 35 37
9/16 53 59 82 91 115 129 57 63 53 58 47 51
5/8 73 83 112 128 159 180 93 104 86 96 76 85
3/4 125 138 200 223 282 315 128 124 104 102 118 115
7/8 129 144 322 355 454 501 194 193 178 178 159 158
1 188 210 483 541 682 764 287 289 265 240 235 212
* Sizes from 4 to 10 are in lb-in.
Sizes from 1/4 up are in lb-ft.
† Fine thread figures are for 1-14.
Grade 2, 5, and 8 values are for plated bolts.


Wayne Brooks who owned JE Pistons at one time with Barry Calvert. Barry now owns CP Pistons, which is my preference for high performance pistons.
Wayne and Barry weren't the "original" owners of JE Pistons. The story goes like this: A guy named John and his brother began a piston manufacturing business, back in the 1950's. The brother was only interested in producing OE and aftermarket replacement pistons and had no interest in the high performance market. So John started a separate company and named it John's Engineering, a short time later the name was shortened to JE Pistons. Harvey Crane actually owned JE Pistons at one time and he sold the company to Brooks and Calvert. The current location of Race Tec was the home of JE at one time, until they moved into a larger facility a few blocks away.

Cylinder Wall Thickness Recommendation.

For a street engine .125 on the non thrust side and .170 on the thrust side. you can trade this for .156 to .160 all the wall around if you luck out with concentric walls.

If going over 6000 RPMs or racing .170 on the non-thrust side and .2 on the thrust side is safer. This also works if concentric at about .185-.190 all the way around.

High RPMs, nitrous, blower all require a thicker wall to hold the pressure and temperatures without distorting. A wall approaching failure will show cracks in the direction of the perimeter, usually forming near the deck or in the side wall lower in the cylinder at the point of greatest piston side thrust.

Guys have been known to go thinner and survive at least for a while.

Naturally aspirated engine BSFC between .45 and .55 lbs/hp/hr.
Nitrous combinations BSFC from .5 to .6 lbs/hp/hr.
Forced induction engines BSFC ranges from .6 to .75 lbs/hp/hr.

(HP x BSFC = pounds of gasoline)
500 hp x .5 BSFC = 250 pounds of gasoline.
500 hp x .75 BSFC = 375 pounds of gasoline.

Since a gallon of fuel weighs about 6.2 pounds, we find that in our first example, 250 / 6.2 = 40 gph (gallons per hour) and 375 / 6.2 = 60 gph.

Stroker Engine V8 Engines

I use a Plasma-Moly Ductile Iron Top Ring

and a Napier Second Ring.

Click on the image above to learn more about Rings

As a performance Engine Builder, I know a little about other builders.

Here is one I greatly respect even though we have never spoken to each other.

Arron Johnson

302 verse 602

408 Short verse Long Duration!
- Gasoline is what most of our cars came setup so it's usually what we stick with. Gasoline is a mixture of hydrocarbons. The petroleum distillate fraction termed "gasoline" contains mostly saturated hydrocarbons usually with a chemical formula of C8H18. The air fuel ratio, A/F Ratio, for complete combustion is 14.7:1, stoichiometric. The A/F ratio for maximum power is approximately 12.5:1 - 12.8:1. This means that our engine at max power, 12.8:1, consumes 12.8 pounds of air for 1 pound of fuel. Gasoline has approximately 18,400 BTU/lb . Using the air flow calculator with the default inputs we get our 355 SBC consumes 567.53 cfm @ 6500rpm which is 42.64 pounds of air and consumes 2.89 pounds of fuel. Therefore if we are using gasoline our engine is producing 53,176 BTU's of energy at 6500 rpm.

Alcohol (Methanol) - Alcohol is usually used in the form of Methyl alcohol or methanol. CH3OH is the chemical formula. Methanol burns at a much richer mixture than gasoline does, between 5.0:1 - 6.0:1. That's 5 lbs of air to one pound of fuel. Methanol has approximately 9,500 BTU/lb. Using our 355, example above, SBC consumes 567.53 cfm @ 6500rpm which is 42.64 pounds of air and now at 6.0:1 ratio for Methanol is 7.11 pounds of fuel. Therefore if we are using Methanol fuel our engine is producing 67,545 BTU's of energy at 6500 rpm.

Nitromethane - is a fuel that is used mostly in specialized drag racing classes, "nitro funny cars" and "top fuel". Nitromethane's chemical formula is CH3NO2. The oxygen in nitromethane's molecular structure means that nitromethane does not need as much atmospheric oxygen to burn, part of the oxygen needed to burn nitromethane is carried in the fuel itself. Typical A/F ratio for nitromethane is 1.7:1 and nitromethane has an energy content of 5,000 BTU/lb. Using our 355, example above, SBC consumes 567.53 cfm @ 6500rpm which is 42.64 pounds of air and now at 1.7:1 ratio for nitromethane is 25.08 pounds of fuel. Therefore if we are using Nitromethane fuel our engine is producing 125,412 BTU's of energy at 6500 rpm.

Fuel Engine Air Flow (cfm) lbs of air (lbs) A/F Ratio Pounds of Fuel (lbs) Energy Content of Fuel (BTU/lb) Total Thermal Energy (BTU)
Gasoline 567.53 42.64 12.8:1 2.89 18,500 53,176
Methanol 567.53 42.64 6.0:1 7.11 9,500 67,545
Nitromethane 567.53 42.64 1.7:1 25.08 5,000 125,412

Summary - As you can see from table 1 above the clear winner is nitromethane. But that doesn't mean to go out and pour nitromethane in your car and see how it runs, if you do your engine will surely blow up. Nitromethane is very expensive and dangerous to handle. The interesting alternative to gasoline is Methanol. Methanol will make more power, typically around 20% more power than a similar engine running gasoline. Some things to consider in running methanol is your fuel system will have to be completely changed / upgraded. Based on the table above the fuel system will have to flow approximately 2.5 times as much as the gasoline engine.

I guess the old saying is true. "Gasoline is for washing parts, alcohol is for drinking and nitro is for racing."

This dyno test reveals that the venturi effect generated in a carburetor will make more Hp than a EFI system. However the longer runner of many EFI manifolds will make more low RPM torque and there accelerate more effectively on the street.
This dyno test shows that there is little difference in Hp between a vacuum secondary or double pumper carb. For a lighter weight car seeking maximum acceleration I'd recommend the mechanical secondary carb, but for most applications a vacuum secondary carb will do just fine.


On this page I have posted articles and links related to engine performance I have found useful. 


Here are articles on two engines a Chev 383 and a Cleveland 383
I am trying to show the torque is directly related to CID.

What I want to first illustrate is with ported stock heads the Chev made 422lbs/ft being 1.1lbs/ft per CID then swapping to better Holley heads the air flow was improved generating much more horsepower, but torque was only increased 22lbs/ft, however the increase did begin early 3000rpm.

Because Hp is Tq X RPM :- 5252 the additional airflow dramatically increase Hp at 5500rpm by 70Hp. To accelerate through first gear you want as much torque as possible between 2000 to 6000rpm with a focus on a high average or put another way a flat torque curve.
Once in second and third gear having more Hp is important as the engine is operating through a high RPM curve say 5000 to 6000rpm then shifting.
In a drag car making high RPM Hp, a high RPM stall speed torque convertor allows the motor to begin accelerating at say 4000rpm, leaping over the loss of low RPM Tq cause by tuning the motor to make an increased Hp number.

Next by replacing with even better designed port of an AFR head Hp is farther increased, but Tq under 4000rpm remains much the same as the engine isn't "pulling" in any more air than it needs.
It does reveal why I use so many AFR heads in my combinations.
It turn what was a 230Hp/350Tq (stock head motors tend to make 1.0Tq per CID) motor in to one that made 524hp because Tq at the high RPM was substantially increased to 481lbs/ft.  

Now look at the Cleveland, same CID good heads, Trickflow in this case 480Tq 524Hp almost identical to the Chev, although you need to be careful comparing dyno figures from different dynos, the results do reveal Torque is Generated Primarily from Cubic Inch Displacement.

Understanding horsepower and why you must quote RPM.

Note that these 2 engines (see below) one a 302CID the other 602CID both make 500Hp, but one is clearly more powerful than the other.

Look at this same 408CIDengine (see below) one having a 450Hp tune up then a 750Hp.
On the street the 450Hp motor will be faster across the intersection, assuming you have traction, good luck, that the 750Hp beasty.
Why? Look at how the lower Hp mill makes more torque from 2000 RPM to almost 4000R RPM.
Ignore the difference in Hp as it is torque that accelerates a car. To get the 750Hp motor to hang with the 450Hp, you would want a high speed torque convertor.
Now take both cars to the drag strip on slicks. With the same stall speed the 450Hp car will jump out in front.
Shift into second and now the 750Hp car is catching up, and passing at some point.
Third gear, forget about it, 750Hp is making serious MPH.
Now put a higher stall speed convertor behind the 750 car and it's out in front from the get go.
But back on the street the 750Hp car has no power brakes, idles fast and rough, and struggles to drive slowly up a steep driveway.

So make sure you are not blinded by impressive Hp numbers, build an engine to do the job you need.
And remenber more CID always makes more power!