My P30 project

[cncsparky]

The old joints didn't feel bad, but they were definitely stiffer to turn than the new ones on now.  Based on the angle of the driveline, it doesn't look like the joints have to work much back and forth.  But the load of these heavy rigs makes me nervous when I can't service or grease a critical component like these. 

[cncsparky]

After most of the emission related stuff out of the way, the next logical step is to get the engine's timing back to where it can make some useable power.  Over a year ago I bought a new GM ZZ4 distributor with the intent of having the ignition curve set up for this RV.  I researched and did a lot of reading on timing and came to the conclusion that it bears most of the responsibility of the woes of 454's in the P30.  Poor economy, driveability, overheating, and busted manifolds are the result of timing curves meant to better emissions than to create a better driving experience for owners. 

The ZZ4 distributor only runs less than $150. (A parts store rebuild is around $100) For that, a new cap and rotor, coil, control module, and new weights and springs.  The distributor provides 22 deg. mechanical advance at approximately 4000 rpm.  I sent mine to Dave Ray to have the curve backed to 3000 rpm, limit the vacuum advance canister to 10 degrees, and reset the distributor endplay.  Cost was $50. 

My timing will look like this initially (may play around with it some later)
10* initial + 22* mech + 10* vacuum = 42* total while light on the throttle running down the highway. A big benefit occurs when the throttle is mashed, the vacuum advance goes away but left with up to 32*. Factory setup is less than 20* which is essentially retarded timing under load, spitting unburned fuel into the exhaust manifolds causing them to overheat and crack. The factory used smog pumps to inject oxygen into the manifolds to burn off the fuel, somehow reducing emissions     

I will probably start running premium, around here it is typically 91 octane. 

ZZ4 distributor GM pt#  93440806
http://www.amazon.com/ACDelco-93440806-Distributor/dp/B0013G0J9W/ref=sr_1_1?ie=UTF8&qid=1400201880&sr=8-1&keywords=93440806

http://www.davessmallbodyheis.com/

New distributor after mods.  One of the advance springs was changed along with an advance limiter on the vacuum cannister. 



I marked the original distributors housing and rotor position in order to get the new on installed as close as possible.  Pull straight up, the rotor will rotate slightly to the left.  The new distributor will drop right back in, correctly engaging the oil pump driveshaft. 



Notice the huge difference in distributor shaft endplay, original on the top.  I was slightly taken aback at how much endplay was in the original compared to the new.  Can you say irratic timing  Hm?   

[ClydesdaleKevin]

I did notice a little pressure coming out of both sides with the hoses off.  Not sure what to do yet.  May try plugging off with a piece of hose and plug.  I believe those are supposed to be one way check valves that may be bad anyways.  I do have a serious exhaust leak somewhere, haven't completely pinned it on the manifolds yet.  The exhaust donuts seem to be missing!

Do want to install headers, but running low on cash now, may have to wait till this fall.  Haven't decided which ones but am leaning towards the Hedman Elite series that would be without the smog line connections. Maybe the Thorleys. They do both have an extra thick exhaust flange.  Not worried so much about warpage after I do my timing modifications.  The exhaust should run much cooler. 

Do me a favor and explain exactly what you mean by timing modifications...and when you do them, please explain the process in plain and simple English for dummies...lol!

Kev

[ClydesdaleKevin]

Oops!  That's what I get for not reading ahead...lol!

Okay.  So explain in layman's terms exactly what benefit replacing the distributor gains, and every part needed to make it work.  So from what I understand, you bought a totally different distributor, a GM ZZ4, and then had to send it out to a specialist to have it recurved?  Was that better than just sending out the stock distributor to have it recurved?  Also, is the new distributor also HEI?  You said you had to replace the cap and rotor and control module and weights and springs.  Was that because they are different on the ZZ4, or because yours were worn out?  Does it take the same coil?  What were the part numbers for the weights and springs, and did you do that yourself, or did the shop that recurved it replace those parts? And lastly, although I'm sure I'll have more questions, what were your exact instruction to the shop, and what was the turnaround time?

Thanks!

Kev

[legomybago]

I did notice a little pressure coming out of both sides with the hoses off.  Not sure what to do yet.  May try plugging off with a piece of hose and plug.  I believe those are supposed to be one way check valves that may be bad anyways.

I pulled these hoses out, left one cut end in, and installed pipe plugs with hose clamps in the existing rubber hose.

The timing re-curve, cold air intake, and exhaust work is a must if you want some ponies in these four five fours..Would love to do that to our 86', but when I only weigh in around 14k towing a dingy, it still rolls pretty good right now. My Beaver coach had all that done to it, it was a differant animal than our Komfort, and a lot heavier.

[tiinytina]

I did find that when I put a naked KN assembly on top of the carb without snorkel/RAM air and removing the exhaust input... in 32F or below driving (also was wet snow so high humidity) I got carb icing and 3.2MPG vs 6.4-7.6mpg seen normally regardless of weather (at this point). 

[cncsparky]

Oops!  That's what I get for not reading ahead...lol!

Okay.  So explain in layman's terms exactly what benefit replacing the distributor gains, and every part needed to make it work.  So from what I understand, you bought a totally different distributor, a GM ZZ4, and then had to send it out to a specialist to have it recurved?  Was that better than just sending out the stock distributor to have it recurved?  Also, is the new distributor also HEI?  You said you had to replace the cap and rotor and control module and weights and springs.  Was that because they are different on the ZZ4, or because yours were worn out?  Does it take the same coil?  What were the part numbers for the weights and springs, and did you do that yourself, or did the shop that recurved it replace those parts? And lastly, although I'm sure I'll have more questions, what were your exact instruction to the shop, and what was the turnaround time?

Thanks!

Kev

Kev, I'll try to answer all your questions as best I can.  The ZZ4 distributor is a GM HEI just like the one in your rig, same cap, rotor, connections, etc.  Its the same distributor that comes with several GM crate engines from SB to BB.  What makes this one nice is it is already setup with the correct center and outer weights to get the total advance timing needed.  The curve is a little slow for most applications, more GM conservative tuning to keep the average enthusiast from damaging anything. 

Correct aftermarket weights (I believe #375 center and #41 outer, stamped on top) are not available.  Up to a couple of years ago one could purchase just the center distributor repair shaft from GM that contained the correct parts.  I tried ordering one and had on backorder a couple of months before they cancelled the order due to being discontinued.  The alternative is to scour the salvage yards for a distributor with the correct weights, if you luck out and find some you still have used parts that wear over time.  There is talk amongst various performance forums of somebody trying to get these made but I haven't heard of any yet.  Also, you can pick up a nearly new used ZZ distributor on ebay, peeps buy a GM crate motor and think an aftermarket MSD is better then sell the HEI. 

To get the same timing out of your distributor, you would need to push the initial up to around 16*+  resulting in starter kickback and possible hard starting. Thats assuming you have the stock distributor, which I understand only puts out around 16* mechanical.  The vacuum can could be changed to an adjustable or get one that only puts 10* out.  Have you checked the weight pivots on your distributor?  Most likely they are worn, sloppy, and rusty resulting in irratic timing.  Mine were a little loose at 65K miles and you can see my comment about the shaft endplay. 

Dave Ray at the link I posted is very familiar with this distributor and needed modifications.  Just let him know before sending it to him.  Turnaround was very quick, like a week or so.  He may be willing to explain the need for the changes a little better than me also  .

[DaveVA78Chieftain]

Here is some light reading on Ignition curve timing:

http://www.hotrodders.com/forum/distributor-tuning-theory-part-1-a-59033.html

http://www.73-87.com/7387garage/drivetrain/hei.htm

http://www.summitracing.com/parts/crn-99600-1/overview/


You need to grasp the basics first so you can understand the goal of adjusting the curve.

Dave

[cncsparky]

I pulled these hoses out, left one cut end in, and installed pipe plugs with hose clamps in the existing rubber hose.

I'll do that, thanks!

[DaveVA78Chieftain]

They also sell vacuum port plugs at the autosupply

[ClydesdaleKevin]

Confused here.  You got new weights, or you didn't?  Love the turnaround time, since we are always pressed for time.

Gonna do this, but am so busy this time, I can't do my own research.  I'm relying on yours...lol!

Kev

[cncsparky]

Kev, the weights are part of the new distributor.  Its a complete unit, ready to install.  The center and weights are not available separately. 

Most on here have enough miles on their rig to justify at least looking at their distributor for wear.  The new GM distributor is not much more than a parts store rebuilt unit(that does NOT come with cap/rotor).  Get a new distributor, have it curved and setup for your application for about $200.  And that includes the new cap/rotor that comes with it(will need to pick up a new distributor base gasket).  Then swap it out in an hour. 

[DaveVA78Chieftain]

Kev, the weights are part of the new distributor.  Its a complete unit, ready to install.  The center and weights are not available separately.

Stock GM weights that is.  There are aftermaket parts but I have no clue if they are equal to what he is referring to.

First step is to determine what you currently have.  Simple to do. Timing light, degree tape (DIY or aftermarket) and vacuum tool. 
Then you can determine which way to go.

What is your current initial timing set to?  Emissions sticker

How much mechanical advance do you have?  Timing light, degree tape (or fancy timing light Actron).  Simply engine RPM vs advance.  Write ups indicate GM used around 20 degrees but better to know where it is.

DIY Masking Tape Degree tape

What is your vacuum advance?  Timing light, degree tape (or fancy timing light Actron) and vacuum pump.  Typically way to much.

Dave

NOTE:  If you live in a yearly emissions requirement state you may not be able to mess with this.

[cncsparky]

Dave, correct if you have emissions testing probably don't want to mess with this.

There are no known aftermarket advance weight kits that will give the same advance I described above. 

[DonD]

http://performancedistributors.com/product/gm-crate-engine-dui-distributors/ This is the high end!

[cncsparky]

http://performancedistributors.com/product/gm-crate-engine-dui-distributors/ This is the high end!

I haven't looked into those.  My problem with them is they don't say anywhere what the curve is.  In the FAQ section, it indicates that they can set a custom curve for you.  But you will spend another $100 above the GM HEI. 

[ClydesdaleKevin]

Cool!  I think I'll do some of Dave's "light reading", and then make this mod myself!

Kev

[DonD]

http://performancedistributors.com/product/gm-dui-streetstrip/ Better for our ap. I think.

[cncsparky]

http://performancedistributors.com/product/gm-dui-streetstrip/ Better for our ap. I think.

But mine is about $100 less and it is setup for a 454 in a MH.  Others across the web I have found using this also.

[ClydesdaleKevin]

Yep.  This is definitely on my list now!

Kev

[cncsparky]

Was having trouble getting the engine to idle down.  Found the choke wasn't opening all the way.  Also, found the choke is non-adjustable     .  The heating element inside read 31 ohms, read that over 25 ohms its bad.  Seen a few on here had put on a manual choke, so I did the same. 

Original choke



Picked up a Doorman manual choke kit.  Pt #  55104



Drilled a hole in the dash.  Found an opening in the firewall to run the cable.  This version of the choke kit has a 9' cable, plenty of length. 



Finished.  The kit seems to work fine.  The cable was a perfect length for my setup.  The engine now idles down like it should. 

[cncsparky]

Now that the choke and idle is fixed, I installed a new tach. 



Since I know the idle RPM's, rechecked the timing with the distributor vacuum line off.  Nice solid 10*, no jumping around      at 700 RPM.  Plugged the vacuum back in and now at 800 RPM. 

About ready for a test run!

[DonD]

Cool stuff  http://www.summitracing.com/parts/msd-8394/overview/year/1986

[DonD]

How'd it run Sparky?

[engineer bill]

Great stuff Sparky. I just wish I could make some of these changes but I'm afraid California smog law prohibits any of this for me.