Question on Timing

331 Views 6 Replies 2 Participants Last post by TJHikr, 19 d ago

TJHikr

Discussion Starter · 21 d ago

We got a RV recently, It is a 1983 E350 with the 460.
It was purchased from the original owner who was a drag boat racer.
He did not like to be passed on the hills while towing his drag boat.

So he did the following Stock carb mounted ( he lived in Calif so did not change carb to pass smog check) on an Edlebrock Performer intake Manifold along with a Edlebrock performer cam #2167.

The stock heads were ported and a set of Thornley Tri Ys installed. 3inch collector about 12 inches long going to dual with cross over and2.5 inch pipes with a set of sorta straight thru mufflers.

I have been thinking of going to 3in all the way back with a set of Magna flow straight thru mufflers..

Stock Duraspark ignition. Might change to a HEI module I did this with my FSJ Jeep 360 and it ran much better than with the Duraspark.

It pulls a 6% grade at 65-70 mph with no knocking ( Running 87 gas), but my normal driving is 55-60mph @ 15 in of vacuum.

I am looking to find out what timing I should set it at? Do I plug the vacuum lines when setting the timing?

My goal is to improve gas milage as even a slight bit will help.

Thanks

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The Mad Porter

· #2 · 21 d ago

TJHikr said:
We got a RV recently, It is a 1983 E350 with the 460.
It was purchased from the original owner who was a drag boat racer.
He did not like to be passed on the hills while towing his drag boat.

So he did the following Stock carb mounted ( he lived in Calif so did not change carb to pass smog check) on an Edlebrock Performer intake Manifold along with a Edlebrock performer cam #2167.

The stock heads were ported and a set of Thornley Tri Ys installed. 3inch collector about 12 inches long going to dual with cross over and2.5 inch pipes with a set of sorta straight thru mufflers.

I have been thinking of going to 3in all the way back with a set of Magna flow straight thru mufflers..

Stock Duraspark ignition. Might change to a HEI module I did this with my FSJ Jeep 360 and it ran much better than with the Duraspark.

It pulls a 6% grade at 65-70 mph with no knocking ( Running 87 gas), but my normal driving is 55-60mph @ 15 in of vacuum.

I am looking to find out what timing I should set it at? Do I plug the vacuum lines when setting the timing?

My goal is to improve gas milage as even a slight bit will help.

Thanks

Do NOT install 3" dual exhaust on an RV it will hurt torque and Throttle response AND throttled torque. Actually 2.5" is a bit big for a near stock engine.

Did the previous owner install straight up timing set?

D3 heads need about 35 to 36* total timing for best power. In an RV delay that until about 3200 ish.
If no EGR vac advance limited to about 10 to 13* to start adding more after testing.
180f stat

OEM cam would mean that 12 to 14* initial timing is fine.

RV's are one use where we use the OEM style dual stage advance springs when we set the distributors up on our Sun machine.

Recurve procedure from our porting and BBF info website.

Duraspark_distributor_recurve_instructions_index

Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
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TJHikr

Discussion Starter · #3 · 20 d ago

Yes the cam was set at straight up.

It has plenty of power, will climb step long grades no problem.
Trying to squeez a mile or two more to the gallon.

Thanks

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The Mad Porter

· #4 · 20 d ago

Proper distributor timing curve including vacuum advance is about efficiency, driveability and economy.
An assumption that the suggestion was for "power" would be only part of the equation.

Vacuum advance helps economy by adding advance when the throttled engine's flame front speed is slow.
Most duraspark distributors are set up with EGR in mind and when removed need the dash pot readjusted.

You don't mention your initial timing, mechanical advance curve or vacuum advance. You would do well to check and properly adjust them.

Economy, driveability and best or maximum brake torque.

Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Parkland Auto Machine

See less See more

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TJHikr

Discussion Starter · #5 · 20 d ago

When checking my base timing do I disconnect the vacuum to the dist?

It still has the ERG on the engine. because he lived in Calif all the smog equipment is still on the engine.

Thanks

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The Mad Porter

· #6 · 20 d ago

TJHikr said:
When checking my base timing do I disconnect the vacuum to the dist?

It still has the ERG on the engine. because he lived in Calif all the smog equipment is still on the engine.

Thanks

Yes base timing with no vacuum.

Most OEM style distributors offer max mechanical advance at 4500+ rpm.

Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Parkland Auto Machine

See less See more

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TJHikr

Discussion Starter · #7 · 19 d ago (Edited)

In my search for maximizing mpg would swapping out the Motocraft 4180 for a Edlebrock 1403 500cfm for more vacuum?

Using the cfm calculator at 4000 rpm a 460 pulls 452 cfm.

I rarely exceed 3500 rpm as I try to keep maximum vacuum on the vacuum gauge.

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