[C-10]

What to do, what to do....

Well I have NO problem ditching the points in this dump truck. Zero sentimental value... The fact that it has no tilt nose my sway my decision. The thing is a real SOB to work on under the hood.

The distributor has this 1/4 inch line that runs to the carb, possibly vacuum or pressure for the governor'd Holley.

I tore down the carb mentioned in this thread:
Holley Carb GMC truck List 6929 info needed

It's a pretty complex little booger. It appears to have an OIL capacity on the topside of 2 of the 3 diaphragms. Strange....

If anybody has messed with these or knows how the hell it works, please post up.

Here's what I may do. I have a nice gently used Holley 3310 750 on the shelf. Also I have a spare HEI that will need a going through. I might just get a rev limiter module for the HEI and bolt on the 3310 and call it 'good'.. What do you guys think?

[blue54]

That will work, but isn't a 3310 a little large. I would lean toward something in the 600cfm range. The rev limiter etc will work great.

[cobalt327]

Originally Posted by C-10

What to do, what to do....

Well I have NO problem ditching the points in this dump truck. Zero sentimental value... The fact that it has no tilt nose my sway my decision. The thing is a real SOB to work on under the hood.

The distributor has this 1/4 inch line that runs to the carb, possibly vacuum or pressure for the governor'd Holley.

I tore down the carb mentioned in this thread:
Holley Carb GMC truck List 6929 info needed

It's a pretty complex little booger. It appears to have an OIL capacity on the topside of 2 of the 3 diaphragms. Strange....

If anybody has messed with these or knows how the hell it works, please post up.

Here's what I may do. I have a nice gently used Holley 3310 750 on the shelf. Also I have a spare HEI that will need a going through. I might just get a rev limiter module for the HEI and bolt on the 3310 and call it 'good'.. What do you guys think?

I've never worked on that Holley. But using a different carb sounds like a good idea to me. The governed carbs are a PITA from the get-go, and were used to keep non-owner operators from abusing them. If you just stay mindful of the redline of the engine, you don't even need a rev limiter.

If you are the worrying sort, use a tach w/a shift light or even a shift light alone to let you know when to grab a gear.

The 3310 carb will only give you what the engine demands (vacuum secondary) so being "too big" isn't a problem- even on your "industrial" TD 427.

The HEI distributor is another matter. The TD block takes a longer distributor than a 'normal' SBC or BBC engine. There are aftermarket HEI distributors that will work fine, though. Or you can add an electronic points replacement that uses the original distributor.

[blue54]

Originally Posted by cobalt327

I've never worked on that Holley. But using a different carb sounds like a good idea to me. The governed carbs are a PITA from the get-go, and were used to keep non-owner operators from abusing them. If you just stay mindful of the redline of the engine, you don't even need a rev limiter.

If you are the worrying sort, use a tach w/a shift light or even a shift light alone to let you know when to grab a gear.

The 3310 carb will only give you what the engine demands (vacuum secondary) so being "too big" isn't a problem- even on your "industrial" TD 427.

The HEI distributor is another matter. The TD block takes a longer distributor than a 'normal' SBC or BBC engine. There are aftermarket HEI distributors that will work fine, though. Or you can add an electronic points replacement that uses the original distributor.

I agree with everything above excepth the carb size. Even though the vacuum secondaries will not open until needed and unly as much as needed the primarys are larger than a 600 and as such will not deliver the throttle response that the smaller primarys will.

[C-10]

Originally Posted by cobalt327

The HEI distributor is another matter. The TD block takes a longer distributor than a 'normal' SBC or BBC engine.

Well hmm.. This is puts me in a pickle sort of...

Read more on the distributor length deal and it appears that the TD427 (& 366) even has a different oil pump drive shaft 'interface' -as in, Car and light truck is slotted, and TD/industrial/marine is round with 2 flats.

While I have the carb and ignition torn down, I'm going to pull the distributor for a checkup anyway. Then I will know for sure the difference in length, and if it's even feasible to MOD a typical HEI to work. (slip collar, shaft and or gear)

[cobalt327]

Originally Posted by blue54

I agree with everything above excepth the carb size. Even though the vacuum secondaries will not open until needed and unly as much as needed the primarys are larger than a 600 and as such will not deliver the throttle response that the smaller primarys will.

Guy- the engine is a 427 cid- a 750's primary is not too large.

[C-10]

Thought I'd share a few photos on the difference in distributors between a '75 TD427 and a mid 80's BBC distributor. My findings is that the LENGTHS are identical. The reason a regular ol HEI won't simply drop in a tall deck is due to the oil pump drive as mentioned above.

The medium duty truck's 427 distributor housing is cast iron. It has no wear a'tall.

If a guy really wanted to, he could grind the rivets from the TD427 gear and then grind the drive tab off the HEI shaft and fasten the TD427 gear by either re-riveting or roll pin. If a guy wanted to...

on edit: Found some n.o.s. Blue Streak parts and they're on the way. Cap, points, condenser, rotor and coil. Sometimes ebay works out for the better.

BTW Echlin is now Standard Motor Products stuff (bought out) SMP still does the Blue Streak line but Echlin is the lower line SMP. (as per NAPA counter guy)