I'm Gonna Build A Dragster!

[bob w]

We made 3 runs today at Brainerd. Cool, cloudy, perfect weather for good e.t's. The dragster shed 120 lbs. over the winter. We made it into the 10's. A 10.93 @ 115mph. It ran terribly rich so better time are a possibility. Included are some shots other racers and a few from the car show too.

 

[offroadrolls]

10's! Old28 was right....Doc would be proud, Well done [cl

 

[soltz]

Glad you you’re under 11! Does it sound as good as it looks [S
Thanks for the pix! Like the Buick[cl

 

[Dave1946]

It sounds GOOD!

 

[Old Iron]

As long as you're cutting times off of the runs it's the right way to go.

 

[smallfoot]

Great news and good work! Next runs will be better too...Congrats!

 

[old28]

Bob & Dave,
Well no doubt that shedding that 120# was a big part of getting into the high 10's. 10.93 is a good starting point for jetting down a bit so that bullet drops into the mid to low 10's. I new you guys could get that rig into the 10's, congratulation on a team effort & a job well done. [cl[cl[cl

 

[Dave1946]

We made a fourth pass after Bob left. We raced a friend of ours with a 37 Chev gasser powered by a blown 502. We were side by side till about 1000 feet when our buddie’s cubic inches got the best of us, but only by a length or two. Another [email protected].

 

[old28]

Bob & Dave,
Well a 10.94 & 10.93, verry close times, shows the car is more consistent than it has been before. That 125# was a big part of the Consistent passes.

As Dave said the car was running very rich you might want to try going to smaller primary jets ( say 2 jet sizes) & making sure your two carb floats are set at the correct setting. Only way to see if you can get into the mid/lower 10's is to make some changes.

Never be satisfied with the current 10.94 & 10.93. It will go quicker with a few changes, keep at it, I would love to see 10.25 - 10.50. It will do it.[cl[cl

 

[bob w]

Tom, we are launching at 4,000 rpm with 750cfm of carb. wide open (two 750 cfm Holleys with the primaries wide open). I think that is too much. So, a change is in order. I agree, the car has quite a bit more potential. That's the only reason I stick with it. Oh, and the fact that Dave and Jerry and Dave's son Al enjoy it so much.

Also, I think the improvement is from the weight reduction. The engine improvements have not resulted in a horsepower gain yet. Needs the carb correction and some fine tuning.

 

[old28]

I'm as thrilled as Dave, Jerry & yourself.
I new it would run in the 10's right along.[cl[cl

4000 leave is good for a motor that tops out around 6500 in the form you have it in today. I agree you have not got all the motor HP to the track yet. If it is running rich you will have to install smaller primary jets. If you think the amount of air taken in buy the 750 primarys, it should not be running rich.

Next change will fore sure be in the carb setup. You are real close but the bullet will run 10.35 - 10.55 fore sure.

Without a dragster of my own, I follow the bullet real close. [[
I think if it would run a 10.35 - 10.55 and we all would be happy with that.

Keep up the good work Bob & the good driving Dave.

 

[old28]

Bob,
What is the next move with your pair of 750 Holleys?
Some carb tuning will get the bullet into the mid 10's.[cl[cl[cl

 

[BlueNorther]

2 x750 is a bunch too big. On an all out race motor I would use 3 x cubic inches = CFM.
In your case that would be 900CFM. While there was a few odd-ball 450cfm carbs built, finding 2 of them would be just plain luck.

better yet use all the parts off the existing 750's, putting all of the parts onto a matching pair of 600cfm bodies, like a LIST-1850, and put in the stiffest secondary springs made (the black ones) like in the holley race tune packs.

you'll end up with 2 carbs f;owing roughly 650cfm each and a the black springs will make full throttle come on further down the track.
the base plate and jet blocks and float bowls all are a perfect match for the 1850 600cfm body.
jet it like a 600 and it will fly.
I ran 2 carbs built like described on a 327 with a tunnel ram and we picked up 10 mph over a single 800cfm carb went from 118mph to 128mph back when I wore a younger man's clothes

 

[old28]

BlueNorther, great carb information, but at this point I think Bob is tired of working on the bullet. It is my quess that they will stay with the two 750's and jet them up or down as needed. Dave said the setup was running on the rich side. It would be of some help if we new what the primary & secondary jetting is?[S

 

[bob w]

Here's what's been going on: The sooty plugs were a sign. However, we ran record e.t.'s and MPH went up also. But, I made another plenum top plate that works with two Autolite 2 barrels. After thinking about it, that isn't enough. we ran 3 of those carbs last year. Then, I dug out an 1850 600 cfm Holley and got another from a friend. Began dismantle/rebuild all the while thinking abut the existing set up. With the 750's I doubt the secondaries are even opening. But, I did have power valves in the primaries. I suspect they were at full flow while Dave was on the trans brake. So I turned the power valves into block offs with a bit of modification. Changed the primary Jets from 72 to 77. I know that seems like the wrong way, but if the power valves were open with the 72's and it ran 10's and common wisdom is with block offs you jet up up to 10 sizes, I figured 5 sizes was conservative. I'll put tattletales on the secondary vacuum diaphram push rods to see how much they come into play. Like I said I doubt there's any contribution. We run next weekend and I don't want to make it run worse. Dave is having too much fun. I'll fire it up tomorrow and evaluate.

Thank you, BlueNorther. Very helpful information.

 

[old28]

Bob,
Very interesting carb & power valve information. Please let use know how it runs with the new setup (driveway test).

 

[bob w]

Finally, no leaks. lots of changed carb parts. All power valves deleted. I have some 600 cfm bodies to use based on BlueNorther's experience.

Had to change the trailer to fit the narrower frond axle on the dragster. Too many projects.

 

[old28]

Bob w,
I missed asking you if you were going to run plugs in the power valve hole?

Trailer looks real nice. [

When will you have the 600 carbs ready for a driveway test run? [cl

Wish I could provide more carb information but I ran blowen & injected setups the last few years. I think you got all the setup from BlueNorther.

 

[bob w]

We will be racing this Friday & Saturday at The Fall-Out in Eau Claire, WI. Fired it up yesterday and it sounds real crisp. Little black smoke on start up. A lot less. All power valves are blocked. The 600 carb bodies will not be used until next year. Record registration for this nostalgia meet. Should be great for spectators.

 

[old28]

Bob w,
Best of luck this weekend. With the power valves plugged off & the jet
change the bullet might have mid to low 10 in it. It sure should be running
much cleaner.[cl[cl[cl