Blower designations ...

[Ken]

Being the drag racing fan that I am, I've had somewhat of a clue as to what the various roots-type blower designations mean, but it appears that I'm not entirely clear on the subject yet. And what better place to ask than my back yard, the Corvette Action center.

Take the 6/71 blower for example, the one we're most likely to see on an older hot rod. I know the 6/71 number is not a model number - there are a number of 6/71 models. I also know that a GM "71-series" engine has a cylinder displacement of 71 cubic inches; hence a "6/71" engine has 6x71 for a total of 426 cubic inches.

I know that in addition to the inline 6-cylinder versions, the 71-series engine was also produced in 2, 3, and 4-cylinder inline versions, as well as 6, 8, 12, 16 and 24-cylinders in the "V" configuration.

What I don't know is where the 14/71 designation comes from that you'll find on the Top Fuelers and Funny Cars. Were there 14-cylinder variations of the 71-series engine as welll? :confused

 

[bill5674]

Hey Ken, been around diesels many years.Never came across a 14/71 don`t know about that one. Bill

 

[KOPBET]

It only represents a larger blower case and longer rotor up to a 16-71. Only the older 6-71 and 8-71 designations equate to a 6 and 8 cylinder diesel respectively. Designations larger than 8-71 have no equate to cylinders.

 

[Ken]

Ah! Thanks guys. Yes, NHRA is specific about the length of the rotors, as well as the case. The rules for Top Fuel and Funny Car state:

Restricted to a Roots-type supercharger, rotor helix angle not to exceed that of a standard 71-Series GM-type rotor. Maximum size: 14-71, 19-inch rotor case length, 11 1/4-inch case width; maximum rotor diameter is 5.840 inches including fixed stripping.

 

[JohnZ]

Also note that all Top Fuel and Funny Car blocks have to be forged this year; cast blocks are no longer legal (too much TV time lost to oil-downs last season).

 

[Ken]

Are you registered at Nitromater, John? There's a couple of interesting threads going on now regarding oil downs; I liked this guy's explanation of what happened recently with Paul Romine and the NHRA officials:

After Romine's 11th oildown of the season, Mr. Light requested his presence to discuss the issue. Paul referred to it a being "called to the Principal's office."

:L

There's another thread discussing whether or not Spec nitro engines will change our sport.

Good site. :cool

 

[JohnZ]

Hadn't seen that site before - will have to snoop around over there. Oildowns weren't much of a problem when I was running my AA/FD in 1961; I ran cast iron Chrysler Marine block and heads, a Moldex crank, and Carillo rods, and only had one single-stage pump to feed the Hilborn/Enderle injectors. We also seldom ran more than 65% nitro (especially those of us that were touring far from home base on an open trailer without spare engines), regardless of the "100% NITRO!" screams from the track announcers to get the spectators "juiced up" when the money runs rolled around

 

[Ken]

From what I understand John, there are several of the professionals registered at that site, and will take the time to participate if the subject is itself professional. You won't find any juvenile behavior there.