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Sun May 08, 2016 6:41 pm

1965 double cab. 1500 single port. 30/31 carb. 009 distributor with pertronix, set to 29 degrees total advance. Stock trans and big nut RGB. 27x9.50 tires.

From a stop the truck pulls well up to about 57, and will touch 62mph. Then it hits a wall and will not pull beyond. I have a tach and it's at about 3500 rpm at 60. In other gears it will pull to 4000 rpm easy. I can maintain 60 at around 3/4 throttle.

I'm not looking to go super fast, but other reports have this setup capable of 70/4000 rpm in 4th. I'm fine with cruising at 65, but the ability to get to 70 if needed would be nice.

I've swapped distributors, checked for dragging brakes (all new everything ), and have been through all of the normal troubleshooting. Throttle is opening all the way. Head temp measured on number 3 hangs rock solid at around 300 degrees. New fuel filter at the tank.

I'm running out of ideas. I feel like it must be starving for fuel at the top end, but the fact it pulls hard otherwise and will hit 4k in other gears makes me question that. [/b]

Sun May 08, 2016 7:02 pm

What kind of distributor did you swap to? What brand of distributor and what country of origin?

I would first put my money on the distributor- get yourself a quality vacuum advance to match that 30/31 carb or at least a Glenn Ring restored 010 that will give you more advance and therefore, better power and rpm response.

Let me just tell you this for reference- my dad's 21 has a stock height 21 with a freeway flyer 4th big nut trans and a 1776 dual port and a single 34 carb and it will pull 75 if you make it, but cruises at 65 comfortably. My 58 panel is lowered with a stock ratio small nut center section and long axles and a stock 1600dp with a 34 carb and that will do 70 with the pedal on the floor uphill and 70 on flat ground. A 1500 in a stock ratio bus might not be enough to get 70 out of it, but I think the distributor could be the problem with not being able to pull 4000 in 4th gear, but it could also be a lack of torque. My 58 had a 40hp in it for a while and pulled great in 1st through 3rd but would lose all power in 4th and top out at like 52. We thought it was just really tired but it turns out it didn't have enough torque to fight the wind resistance of the van at 52 mph.

Just my $0.02
James

Sun May 08, 2016 7:10 pm

Both are german bosch 009. One with pertronix. Other with bosch points and condenser. The both are pulling full advance so I don't think that ignition is the problem. Both also were used in my dp 1600 bay and worked fine. I know the 009 isn't the most ideal setup but for now it works fine.

Sun May 08, 2016 7:13 pm

In that case, I personally think its an issue of a lack of torque, but Id wait until someone else chimes in.

Does it pull well all the way up to 3500 rpm in 4th or does it struggle and once it gets to 3500 does it flatline or do rpms vary?

James

Sun May 08, 2016 7:23 pm

Plenty of torque. It accelerates up hill at 50 mph pretty easily. Just reaches 3500ish rpm and that's it. It's almost like 3/4 to full throttle are the same thing.

Sun May 08, 2016 10:09 pm

Maybe you arent getting full throttle at the carb.

Mon May 09, 2016 5:18 am

Throttle is opening all the way. New cable. New linkage at pedal.

Mon May 09, 2016 7:02 am

you might not want to hear it..but 62 might be your top speed with your current set up. A 1500sp is not very peppy, and if it is at all tired, it will be even slower.

Mon May 09, 2016 7:51 am

maybe his 4th gear is taller than original stock for that trans? or his R&P is a 4:12 instead of 4:37? not every big nut trans is geared the same.

Mon May 09, 2016 8:03 am

Ohio_Style wrote: 1965 double cab. 1500 single port. 30/31 carb. 009 distributor with pertronix, set to 29 degrees total advance. Stock trans and big nut RGB. 27x9.50 tires. ...............

I'm running out of ideas. I feel like it must be starving for fuel at the top end, but the fact it pulls hard otherwise and will hit 4k in other gears makes me question that. [/b]
How fresh is the motor? Compression check?
Since it pulls to 4K in other gears, but not in 4th, I'm wondering if the motor is just getting tired?
Or, how does the tire size 27x9.50 compare to stock size?

Putting on a tall tire effectively raises the gearing. It can make the bus overgeared for a stock 1600. This will have the effect you found, rather than allowing a faster top speed.

Mon May 09, 2016 8:17 am

Ohio_Style wrote: 1965 double cab. 1500 single port. 30/31 carb. 009 distributor with pertronix, set to 29 degrees total advance. Stock trans and big nut RGB. 27x9.50 tires.

From a stop the truck pulls well up to about 57, and will touch 62mph. Then it hits a wall and will not pull beyond. I have a tach and it's at about 3500 rpm at 60. In other gears it will pull to 4000 rpm easy. I can maintain 60 at around 3/4 throttle.

I'm not looking to go super fast, but other reports have this setup capable of 70/4000 rpm in 4th. I'm fine with cruising at 65, but the ability to get to 70 if needed would be nice.

I've swapped distributors, checked for dragging brakes (all new everything ), and have been through all of the normal troubleshooting. Throttle is opening all the way. Head temp measured on number 3 hangs rock solid at around 300 degrees. New fuel filter at the tank.

I'm running out of ideas. I feel like it must be starving for fuel at the top end, but the fact it pulls hard otherwise and will hit 4k in other gears makes me question that. [/b]

My 1500 sp (same exact setup, 009/H30-31/Big Nut) runs basically the same. The motor is a bit tired so I never expected it to do more. It will run fine up to about 62 if pushed but will run all day in the 58-60 range.

Mon May 09, 2016 9:43 am

sled wrote: you might not want to hear it..but 62 might be your top speed with your current set up. A 1500sp is not very peppy, and if it is at all tired, it will be even slower.

I'm leaning toward that being the case. This is the first split bus with RGB and 1500 that I have driven, all my other stuff have been bays, beetles, or non RGB busses with beetle trans.

volksheime wrote: maybe his 4th gear is taller than original stock for that trans? or his R&P is a 4:12 instead of 4:37? not every big nut trans is geared the same.

RPM and speed pretty much jive so I thing that's not the case. I'm running out of steam and not RPM.

Clara wrote:
How fresh is the motor? Compression check? Since it pulls to 4K in other gears, but not in 4th, I'm wondering if the motor is just getting tired?
Unknown history on the engine, it was in the truck, which had been parked for many years. I got the truck in pieces, but was able to get the engine running with minimal work, and it runs so well, that I didn't mess with it. Sitting at around 105-110 psi on all cylinders.

Clara wrote:
Or, how does the tire size 27x9.50 compare to stock size?

Putting on a tall tire effectively raises the gearing. It can make the bus overgeared for a stock 1600. This will have the effect you found, rather than allowing a faster top speed.

I took that into consideration as well. My speedometer is about 6% off so I would guess I raised the final gearing by that amount.

srfndoc wrote:
My 1500 sp (same exact setup, 009/H30-31/Big Nut) runs basically the same. The motor is a bit tired so I never expected it to do more. It will run fine up to about 62 if pushed but will run all day in the 58-60 range.

Thank you, I have not had any other similar setup to compare to.

I'm not expecting this thing to run 85mph, but everyone I have talked to makes it seem like I should be able to pull 4k rpm in 4th. I guess I'm more interesting in diagnosing an issue before it becomes an issue, and this is one of those things that when all I hear about are that they can pull 4k rpm and mine cant, something must be wrong.

I did pull the fuel pump today and found that the pushrod was about 1.5mm short? Odd. I replaced it and it did pep the truck up a bit, but still hangs tight at 62.

The engine runs so nice, cool, uses no oil, I'm not going to dink with it.

Mon May 09, 2016 11:13 am

Stock comments:
The stock big nut Buses could go 65 with a 1500cc engine and big nut so no way is 62 the top speed unless there is something else at play here.

My old '64 that was bone stock would do 65. I can't recall if I tried to go faster as I didn't drive it a ton on the freeway. It was a dog on big hills or with a headwind.

You said your tires are larger.
Are you really going 62? If you have a smart phone try a GPS speed app to double-check things.

As you mentioned, maybe the big tires are bogging things down.

Mon May 09, 2016 11:16 am

The 62mph is GPS speed. Speedo reads about 58 at that speed.

Mon May 09, 2016 7:42 pm

If his 1500sp is functioning as is expected and he has 15" wheels, what would be the difference in top speed if he had a 4.12 versus 4.37 in his big nut?

How would the top speed RPM differ 4.12 versus 4.37?

Mon May 09, 2016 8:48 pm

nlorntson wrote: If his 1500sp is functioning as is expected and he has 15" wheels, what would be the difference in top speed if he had a 4.12 versus 4.37 in his big nut?

How would the top speed RPM differ 4.12 versus 4.37?

Formula - RPM=(MPH*336* (R&P*4th*1.26))/Tire Diameter in inches

So with a .82 4th, stock rgb's and 27" tires at 62mph:

62 x 336 x (4.375 * .82 * 1.26)/27" = 3487rpm

62 x 336 x (4.12 * .82 * 1.26)/27" = 3295rpm

Mon May 09, 2016 9:59 pm

Your speeds seem about right to me. I have a new 1600 single port that I built with a 4.12 R/P bus trans. The engine is happy at 62-64 mph. I can push it further, but temps rise quickly.
I just drove nearly 600 miles, and 62 mph (on the gps) was about average, unless it was uphill or a headwind area.
You could try a bigger main jet if you think you may be running lean (not revving past 3500 rpm). Or check the adjustment on the accelerator pump. But your speeds sound right to me.

Tue May 10, 2016 8:37 am

If you go down a long hill can you get past 3500rpm in 4th?

Wed May 11, 2016 10:36 am

Now that I've seen the gigantic tires you are using (your truck thread), they are definitely bogging you down. Original VW tires were tall and skinny, you went taller and pretty wide. Lots of rolling resistance, weight, and I would guess that long term you will find parts wearing out faster as well. They do look cool though

Wed May 11, 2016 11:28 am

nlorntson wrote: If his 1500sp is functioning as is expected and he has 15" wheels, what would be the difference in top speed if he had a 4.12 versus 4.37 in his big nut?

How would the top speed RPM differ 4.12 versus 4.37?
Ha... I got to this post and thought... "Holy crap... where is srfndoc when you need him?"
Ta-da!... right on cue Brother!