70 duster race car(drag), fenderwell hdrs

[motorhead440]

i'm building a 70 duster for qtr mile, i will be using fenderwell hdrs, comp. engineering front motorplates, is there a certain height to set motor, or do i just trim plates untill all fits? other info as follows... 69 440 stock from chrys 300, low miles, frame conn., rebuilt 727 with turbo action manual vb, tci clutches, turbo action 3800 stall 10" conv., 4:30 U.S. gears, spool, moser axles, hurst qtr stick, i hope to run low 13's, hi 12's this year with the stock motor. any carb suggestions?

[Christopher]

We have a similar setup in a 71 Demon.We use the old Doug Thorley headers with 1 pipe on each side that wraps around the frame rail and the other 3 are in the frame.The fenderwells usually limit the size of the front tire,we use a 7.10x15 Moroso frontrunner.I don't know what cam you are using,but I would use a Holley 750 Double Pumper,it's what we are using and it works great,in fact it has for 27 years.We are using the same converter as you,we bought it in 1977.We are using a 5.12 gear,but we will switch to a 4.88 later this year.You should be well in the 12's with your setup,we had a junker 440 that we used to sort out the car with a street hemi grind cam and ran 12.20's with a 4.56 gear and 10.5x29 tires.We use a motor plate too,we just had to trim it a bit,about 1/16 inch.Good luck with your car.

[This message has been edited by Christopher (edited July 03, 1999).]

[This message has been edited by Christopher (edited July 04, 1999).]

[Bryant Fields]

I might be wrong,but I think M.P. has an old bulletin on this swap. When I bought my k-frame they sent it w/ instructions, and it referred to the measurements of the crank centerline in relation to the frame rails. If you can't find anything, e-mail me & I'll go measure mine.

[Richard Reardon]

Motorhead 440, I agree with Christopher on the et's you should get. I was all set to reply and then I saw C's reply, so I will just 2nd his motion! With that many cu in's and hp in a '70 Duster, if you can get it to stick you should be in the low 12's no sweat. Don't be suprised if you better this a tad. For some reason 750 cfm doesn't seem like enough for 440 cu in's. ( The '71 340 had an 800 cfm Carter Thermo Quad on it.) My engine is ~ 150 cu in's smaller and a 650 Holley double pumper is suggested for the strip. Of course I will be winding it up to 7 to 7,200 rpm. If you're running a stocker, as mentioned, 6,000 is probably as hi as you'd want to go. If I had access to an 800, I wouldn't hesitate to try it. My buddy is running an 800 dp'er on 100 less cu in's and it screams.
Oh well, my 2 cents worth, Richard

[Christopher]

Normally I'd agree and say a 440 would need a bigger carb.But...we have a 750,850,and a 830cfm Holley double pumpers and both the 383 and the 440 run better with the 750.Why I don't know.We even asked Holley why.They asked us why we run a double pumper with a automatic trans,said we should use a vacuum secondary,but still never answered our question on why the 750 works better than the other two carbs.I don't have a 800,but it makes good sense to me to try one.

[This message has been edited by Christopher (edited July 12, 1999).]

[Richard Reardon]

MotorHead 440 & Christopher, this is getting interesting! Where you guys are talking a racing application I'm assuming you're both running some sort of moderate to hi-stall converter behind your automatics. With this in mind and considering the vacuum operated 2ndaries vs mechanical 2ndaries, one would think that the 2ndaries in the vacuum job would already be open ( to some degree ) upon launch, same as the mechanical ones. So, there is only one differance, the extra squirt of fuel into the 2ndaries vs the transitioning mode in the vacuum operated unit. My buddy that races went from a 750 cfm vacuum operated Holley to an 800 mechanical unit and he dropped something like 3/10ths of a second and went from ~ 116 mph to ~ 124 mph in the 1/4 mile. It must also have something to do with what you have and what combinations you're using = try it before you knock it, it may work for you and not the other guy & visa versa. Of course some givens never change, like nobody runs used lifters on a new cam - right! Rich

[Christopher]

The 750 was bought new in 1972 and had been on the Road Runner I have now.It is a 4-speed car,hence the mech.secondaries.When we ran it as a automatic in 1977,we left the engine as is.I do have a high stall converter,a 3800 turbo Action unit.I've always had very good results with Holley double pumpers,when I got the Road Runner from my Dad,and put it back on the street,I bought a new 750 and I was getting 16 mpg with 3.91 gears,which I didn't think was too bad.

[motorhead440]

I DON'T KNOW IF I WILL PUT A CAM IN THIS YEAR, ALL THIS CARB TALK IS A BIT CONFUSING , I HAVE NOT RESEARCHED THE SUBJECT MUCH. SOME MORE INFO ON THIS PROJECT AS FOLLOWS, 3200LBS. S.S. SPRINGS, COMP ENGINEERING 3 WAY SHOCKS, HURST ROLL CONTROL, DRIVE SHAFT LOOP, I CONVERTED STEERING TO MANUAL, I WOULD LIKE TO RUN M.T. E.T. STREET 28" TIRES, I'M NOT SURE HOW THEY WILL WORK, A FRIEND HAS HAD GOOD LUCK WITH THEM. ANOTHER FRIEND OFFERED TO LEND MSD 6AL SYSTEM FOR IGNITION. FOR THE SAKE OF CONFUSION, I'LL RUN STOCK MOTOR WITH MSD IGN., 750 TO 800 DP CARB, HOOKER FENDERWELL HEADERS, ALL THE TRANS AND CHASSIS MODS MENTIONED AND A LITTLE LUCK I SHOULD RUN IN THE 12'S. I'LL BE INSTALLING ALL OF REAR END COMPONENTS THIS WEEK. THANKS FOR ALL REPLIES AND SUGGESTIONS, KEEP THEM COMING IF YOU THINK OF ANY THING ELSE. I COULD NOT FIND INFO ON MOTOR PLATES INSTALL, I DO HAVE MOPAR CHASSIS BOOK, IT MIGHT COVER THIS SUBJECT. I'M NOT SURE HOW TO E-MAIL WITH THIS FORUM YET, AND THIS APPLE IS A BIT SLOW ON INTERNET, PLEASE BEAR WITH ME, THANKS TO ALL, MOTORHEAD440

[Christopher]

Generally,if you have a motor plate or the one piece "elephant ears" like I have,the engine will drop into place.Use the trans mount as a guideline.And as a side note about carburetion,I read a article about a Ray Barton SS/AA engine on the dyno.It said that at 8500 rpm,the engine was making 800 hp and that it was only consuming 1000 cfm at this speed.Now a race hemi has 2 770 cfm Holleys on it,that have a combined cfm rating of 1540 cfm.I'd say that that engine is a bit overcarbureted.