Jr Fuel tire diameter

[Scottmech]

Anyone know what diameter tire was typically used on mid to late 60's JF cars? Thanks. 

[JrFuel Hayden]

Scott are you building a 60's type nitro JrFueler ? or just want to know details.
My 1963-69 nitro SBC JF car was about 30" with 9" wide M&H
Have Fun,
Jon, 805-444-4489, cell

[Scottmech]

Just finished a mid 60's Woody JF.  Has been modified for a glide and updated for 7.5 specs.  Getting ready to test soon. 

I had mocked it up with 33's for several reasons, but to me they just look too big. It came to me with 30x10.5 which just seem more proportional.  Gonna go back to them.

[JrFuel Hayden]

a 60's Woody car has the motor further back towards the rear end than current built cars, because in the 60's they had no VHT, and no slipper clutches, just rev-it-up pop the clutch and smoke the tires to keep the RPM up to where it was making good power. So depending on your HP you may need a bigger/better tire, but maybe not a 33x12 tire unless you are making over 1000 hp.
Feel free to call me with any questions.
Jon, 805-444-4489

[retroboy]

Howdy I have a 155" early 1970's car with updates and 31x13 M/T which are too big visually for it.

[Scottmech]

John.....Yep...that's the way my car was set up originally.  Motor was set back 7 inches from it's current position.  They pushed it out for the glide at some point. 

I ended up going back to the 30 inch tire.  Tried the 33's to gain ground clearance and lower rpm at line, but the car looked like a cartoon. Lol. Tires were too tall which also made the tire too wide.  Ended up going back to the 30 inch tire.  Looks much better, and it handled great.

Car ran good first time out. Did a good shakedown run then opened it up after. Wasn't hitting it hard off the line cause still getting used to it, but ended up running 9.3 at 152.  Basically they were high gear runs cause I didn't go WOT till it was in 2nd about 1.5 sec into the run. 

This pic is the car with the 33's....



Here it is with the 30 inch tires. 

[JrFuel Hayden]

Your high gear launches should be hard on your PG clutches, just try 1'st gear launch then shift early, like 60' out, while you are getting used to the car.
What 30x10.5x15 tire are you using ? And any idea what kind of HP you are making ?
Have Fun !
Jon

[Scottmech]

I'm not launching in 2nd gear, launching in 1st.

I considered the first runs "high gear" runs because by the time the front end got loose, I let off the throttle let it settle, and then got back into it, the car was all ready into second gear at which time I was WOT.

The trans is a fresh BTE unit with SFI case and was built to handle a blown alcohol 7.0 car.  I doubt there's much my little NA 355 can do to it.....lol.

Estimated hp from weight and trap speed is 410-425 at crank.  Which matches other testing I did when engine was in my other car. 

Slicks are M/H 30x10.5x15. 

Ran the car this past weekend.  Was happy with the progress, but it has a slight intermittent miss that's been there since I built it.  Think I know where the problem lies and have a plan to address it before the next time out.

Here's a pic from this weekend.  A few feet off the line. 



Had some goals for the car before the build began.  Wanted something that looked mostly period correct (minus the updated chassis and clothing).  Had to be able to run it on my own (self start), which means it's driven to the lanes and back to pits.  Didn't want a cooling system or batt on the front of the car, and under no circumstances will it run it with a wheelie bar.  Yeah, I know it wont be able to push the limits coming off the line without one, but I'm willing to accept that for the sake of looking a little more period correct.

The plan is to run it on an 8.5 or 9.0 index.......the latter being more likely on straight alky, and 8.5 with a little pop, which the motor will easily handle.  It was making and easy 650+ hp in my Fiat with a blower....so I figure there's plenty of room for a 20% load....and possibly as much as 40%, which is about as much as I can run being a self starting car (as per recommendation from Spud). Though I doubt I'll ever run it with 40...

So far most of my goals have been met.  Am confident the remaining goals (better ET) will come around as I get used to the car and learn what it likes. 

[JrFuel Hayden]

Scott, it sounds like you need to add some ballast to your front axle, to help balance your car to keep the front wheels down. You can't win races if you can't steer your car. I would run a wheelie bar until you get the  car balance figured out. You may also be running a converter that is too tight [ not enough stall speed]. Basic idea is your stall should be 1500 rpm below your shift point. You can try changing your slick air pressures. With my Goodyear 31x12x15 , I lower the pressure to 5 1/2 to 5 3/4 when I looking for more tire speed, and raise it to 6 1/2 looking for more bite. Call M&H to get some suggestions on tire pressures.
My thought is you might be dead-hooking your tires. Looser converter hits the tires softer, lower tire presures or allot high presures [ 7+ lbs] should allow more tire spin to keep your motor in the RPM range your motor is making good power.
Without using a wheelie bar you have a good chance of sending me your front wheels to fix.
BTW I know FED running in the 7.60 class running on pure alky, some with only 355 ci SBC injected.

Feel free to call me, 805-444-4489
Jon

[Scottmech]

Jon....thanks for the advise.

I agree with you on some points, but respectfully disagree on others (which might be due to my lack of experience...lol)

Ballast...agree and all ready have some for the front axle
Converter...agree but will probably have to wait for next season
Contact M/H....agree and all ready have

Wheelie bar....disagree.  Is there a chance of it doing a wheel stand?? Depends on how the car is set up to run. Not going to go into detail as to what my set up is, but results from the second time I took the car out proved that the set up is working.  60 ft times weren't anything to write home about, but quick 60 times don't win races..... consistent 60 ft times do.  And as I said before, I'd rather be slower and look more period correct than push the 60 ft limits of the car and have a bar hanging off the back of my car. May not be the popular choice...but it's mine.

Besides....if the car does wheelie and wheels get bent...you'll make some money off me....lol

I'm aware there are faster SBC's in FED's running alky, but that really has nothing to do with my car.  They may be running 7.60's, but they aren't doing it on my budget....lol.  Fact is my current motor is only capable of 410-425 hp in current config (not gonna tear down a perfectly reliable, proven motor just to go faster).  With everything perfect (right converter, best launch, good weather, maybe even a better cam since the blower cam is still in it, etc...)......the car should run 8.5.  But most times conditions aren't perfect, so that's why i'm shooting for 9.0 index with the current combination. Will easily be able to do that even in June at Bowling Green with 95 deg weather and REALLY bad air.  lol

Have no illusions about the car setting the world on fire. I know it won't.   Just wanted to build something that had the looks of a mid 60's FED (which my car doesn't just look like one....it actually IS one) but easy to maintain/operate, be reliable and reasonably consistent and take me a few rounds (which would be a step up from my last car...lol). So far, I'm right on target. 

Again, I appreciate the help.

[ricardo1967]

Without using a wheelie bar you have a good chance of sending me your front wheels to fix.

Wheelie bar....disagree.  Is there a chance of it doing a wheel stand??

Sorry for being repetitive with this video, but I really wished I knew better (that was three months before the start of this forum). Like you, I dig the look and stance of old diggers, but I wished I had the wheelie bar installed during that shakedown pass, at least as a 'safety net' (the fire bottle ended up doing that job, kinda).



Scott, you have a great looking car. Keep it looking good. But you can rest assured that Jon is the best on the planet to restore your wheels   (mine look better than new now)

[Scottmech]

Thanks for the vid.  I've got a similar one of a friends car doing a wheel stand similar to yours during a test session. Always interested in the factors that lead up to incidents like this and what can be done to prevent them.

In accidents that I did sort of a case study on...seems human factors are the major cause. 

In my buddies wheelie, lack of judgement (trying too much too fast in a new car) led to the wheel stand and damage to the car.

In the second one, an experienced driver was unfamiliar with a new car,  lack of test runs (from half track runs on alcohol to full sub 7 second pass on a 95% load of nitro in a 115 inch car......in 4 runs)and pushing a car to performance levels it had never been run at  led to the car hitting the wall and flipping.

In the third, rushing to build the car and lack of test runs led to the car hitting the wall.  They finished the car the night before the race (new car chassis and all), and with no test runs tried to make a full pass.  The front of the digger narrowly missed the back of the car (and the driver) in the other lane. 

IMO, if proper procedures (with a healthy doser common sense) are used, the chances of an accident are drastically reduced.  I work in an jet engine test cell....so maybe it comes from that.  In any case, I've tried to follow that same methodology with my car.  Didn't rush the build, proper prep before heading to the track, and small steps in testing the performance of the car at the track.  So far its worked out well. Car went through the shakedown runs without incident and allowed me to gain confidence the car. Still haven't made a full clean pass (8 runs on the car) but it's getting really close to it...

Best thing is...I'm having a BLAST!!

[ricardo1967]

Thanks for the vid.  I've got a similar one of a friends car doing a wheel stand similar to yours during a test session. Always interested in the factors that lead up to incidents like this and what can be done to prevent them.

In accidents that I did sort of a case study on...seems human factors are the major cause. 

In my buddies wheelie, lack of judgement (trying too much too fast in a new car) led to the wheel stand and damage to the car.

In the second one, an experienced driver was unfamiliar with a new car,  lack of test runs (from half track runs on alcohol to full sub 7 second pass on a 95% load of nitro in a 115 inch car......in 4 runs)and pushing a car to performance levels it had never been run at  led to the car hitting the wall and flipping.

In the third, rushing to build the car and lack of test runs led to the car hitting the wall.  They finished the car the night before the race (new car chassis and all), and with no test runs tried to make a full pass.  The front of the digger narrowly missed the back of the car (and the driver) in the other lane. 

IMO, if proper procedures (with a healthy doser common sense) are used, the chances of an accident are drastically reduced.  I work in an jet engine test cell....so maybe it comes from that.  In any case, I've tried to follow that same methodology with my car.  Didn't rush the build, proper prep before heading to the track, and small steps in testing the performance of the car at the track.  So far its worked out well. Car went through the shakedown runs without incident and allowed me to gain confidence the car. Still haven't made a full clean pass (8 runs on the car) but it's getting really close to it...

Best thing is...I'm having a BLAST!!

I understand your points. In my case I rushed to get the car ready for the last track day of the season, spent almost all night in the garage taking car of last minute details...

Your car seems to have a similar combination to mine... I wished you were closer, it'd be fun to match race! (that is, once I learn to drive)

[AWAG]

I had a fed that I had bracket raced for over a year and a half. It was just a simple cheap built 302 Chevy in it. One day I added a carb spacer to it. I made a t&t pass not much changed so the next t&t I raised the rpm 200 at the line and when I took off I drug the push bar on the ground. The next time out it had a bar on it.

[dreracecar]

If one is running an index, the only thing that matters is to leave ahead of the other guy and the ability to run right on the number, if you can do that, 60ft times dont mean $%#@.  Never go by the 60' time of others unless the front end is set up exactly like yours, a car with 30" of overhang will always 60' better because the overhang shortens the 60' clocks 24"