Suburban K20 1986 Silverado - "Silvester"

[kikkegek]

Originally Posted by will scratch

Please tell more about the natural gas system for fuel is that you originally installed.

Its a Propane system from IMPCO. I currently have the bi-fuel setup with a IMPCO 300A mixer that goes on top of your quadrajet. The mixer is connected to a IMPCO model E evaporator type 50&70.

I have switch under the dashboard in the cabin so I can switch from gasoline to LPG and back. When I run gasoline an electrich switch blocks the supply of gasoline between the pump and the carb, so the pump never runs dry.

The only problem with this setup is that the carb is empty when running LPG. This can cause the floaters to get damaged and carbs just dont like being dry and warm all the time.

we ave more then enough places to get LPG in Europe, so I am switching to an LPG only setup with the IMPCO425 carb.

got any more questions?

[kikkegek]

I did it. replaced the 300A with a IMPCO425 mixer. Our suburban is now Propane only...

everything fitted fine. Adjusted the idle CO to 2,0

havent done any big road tests to see if I need to adjust the MAX setting on the mixer.






I need to shorten the bolt on top of the mixer, because that is too long now.

Lost some more weight:
- mechanical fuelpump
- all fuel lines rubber and metal
- finally removed the EGR valve from the intake, replaced it with some bling-bling blind plate
- still need to remove my 24L spare gasoline fuel tank

1 qurestion left. there was a hole on the quadrajet-adapter and I wasnt able to fine a bolt that fitted the hole.So I took one that was just too small, taped it with a lot of teflon tape and screwd it in. what is this holes purpose? and what thread should I use?

[kikkegek]

I have to add some information to the previous post.

The hole on the front of the adapterplate has a connection to a small hole near one of the two primairies. But I dont know what it is for?

here a picture with some arrows of my adapter:


this is a clearer picture of the hole in the adapter


I got a picture of the web of a quadrajet baseplate and my hole seems to line up with some hole in the baseplate. it seems to line up with the hole near my arrow...what is that for?

[ericjon262]

how far does the 'burban go on propane? miles/kilometers per pound? I really like this idea, got any links to the parts used on the conversion?

Thanks-

262

[kikkegek]

Originally Posted by ericjon262

how far does the 'burban go on propane? miles/kilometers per pound? I really like this idea, got any links to the parts used on the conversion?

Thanks-

262

I live in the Netherlands. So I bought all my parts over here.

there are two great websites for America:

alternatives fuels:
http://www.rasoenterprises.com/

alternatives fuel forum with Propane department:
http://fuelsforum.rasoenterprises.com/

webshop:
http://autoparts.rasoenterprises.com/

There is really good information on their website and forum.
On the forum FRANZ and STEPTOE are real guru's.

My setup is pretty simple:

IMPCO425 carb on the throttleplate of my Quadrajet 4bl.
the IMPCO gets is propane from an type-E Evaporator from IMPCO

ask for a conversion advise on the forum and I am very sure they can help you.

I have a 100liter tank under the rear of my Burb. there is a 80% filling safety so I can get only 80 liters in it.

I get about 3.7 km/l (~9 mpg)

so my maximum radius is 80x3,7 = 296 km ~ 184 miles

[kikkegek]

I made a big decission today:

made an offer on a TH700R4 and NP208 transfercase.

this will replace the Th400 we now have and give us a OD without loosing the 4WD option.

so excited...

hope we can fix it before half july. Because then we are cruising to south of france for 1000km...

[kikkegek]

the guy agreed to my offer. I am picking up the 700 soon. so excited.

I am getting the torque converter revised, but the trans did 84k in miles so far. I am also replacing the filterkit. Any other things I should look into guys?

[Edahall]

Originally Posted by kikkegek

the guy agreed to my offer. I am picking up the 700 soon. so excited.

I am getting the torque converter revised, but the trans did 84k in miles so far. I am also replacing the filterkit. Any other things I should look into guys?

Yeah, make sure it's a 1987 or newer 700R4. My Suburban kept eating 700R4's until I installed one from an 89.

You may also consider installing a shift improvement kit. I recommend one by Transgo.
www.transmissionpartsusa.com
or
http://www.ebay.com/

Getting the torque converter worked on is a great idea. Have a torque converter shop open it up and braze all the fins so they can't break off. Have the rivets replaced with something stronger. My dad had several 700R4's get torn apart by a rivet breaking off and sending metal pieces through an otherwise pristine 700R4.

[kikkegek]

I have looked at several websites, but none seem to have information on the trans I am about to buy.

its supposed to be out of a 87 K5 Blazer. So I was hoping its a 87 model transmission, since they were a improved model from 86 and older models.

numbers on the trans:

CMZ109093


1krm2250


8663548

[Edahall]

Take a look at this link to see if the transmission you're interested in is the updated one with the auxiliary valve body.

http://www.thirdgen.org/replace-700r...c-transmission

[kikkegek]

Originally Posted by Edahall

Take a look at this link to see if the transmission you're interested in is the updated one with the auxiliary valve body.

http://www.thirdgen.org/replace-700r...c-transmission

thanks, already read that. I'd have to open her up, and I dont have her over here yet. So I need to go by the pictures.

[Edahall]

Auxiliary valve body looks like the following.

[kikkegek]

Originally Posted by Edahall

Auxiliary valve body looks like the following.

ok, but isnt that only visible when taking of the pan?

[Edahall]

It appears that transmission is out of a 1991.

[Edahall]

Around 1987 the THM 700-R4, now know as the 4l60, was introduced with an auxiliary valve Body. There is an easy way to find out if your 700R4 has an auxiliary valve body. As illustrated in this picture, look for the casting mark where the arrows are pointing to. If your 700R4 has this casting mark you have an auxiliary valve body 700-R4.

[kikkegek]

Originally Posted by Edahall

Around 1987 the THM 700-R4, now know as the 4l60, was introduced with an auxiliary valve Body. There is an easy way to find out if your 700R4 has an auxiliary valve body. As illustrated in this picture, look for the casting mark where the arrows are pointing to. If your 700R4 has this casting mark you have an auxiliary valve body 700-R4.

thank you thank you thank you....that makes me very happy...

funny though that my tranny comes of a 87 K5 Blazer. So it must have been replaced...still would like to know what the rest of the numbers mean

[Edahall]

Originally Posted by kikkegek

thank you thank you thank you....that makes me very happy...

funny though that my tranny comes of a 87 K5 Blazer. So it must have been replaced...still would like to know what the rest of the numbers mean

It was common for these transmissions to be replaced behind a V8 engine or even more so behind a diesel engine. They were just not very strong (in stock form) when coupled to a powerful engine. There were many variations of this transmission made and many different applications as well. They were used behind small V6 engines all the way to high torque 6.2L diesel engines. They were very reliable behind V6's and it was common for them to last 200k+ miles, but behind a diesel, they often were very short lived. The last 700R4 on my 1982 Suburban lasted 10k miles so that's when I upgraded to a newer 1989 700R4. I had all the upgrades done to it at a very reputable shop and so far, it has lasted admirably well. It's wonderful that the aftermarket took a hold of this transmission and developed upgrades that make it much better than in stock form.

[kikkegek]

okay guys, some feedback,

the TH400-NP2808 swap to TH700R4-NP208 went fine.

- crossmember fitted perfectly
- axles didnt need any work, fitted perfectly
- speedo cable fitted perfectly
- shifter only needed only small adjustment
- OD now connected via Lockupkit from Bowtieoverdrives
- needed to cut the balance-pipe though and weld it back in later (stupid location btw)

will only add a vacuumswitch for turning off lockup under load...we will go to France this summer and the highway has some really big slopes/hills in them...dont want to ruin the lockup by steppin on the throttle...

highway mileage went up from 9 to 12.23 mpg on last trip over 126 miles...yihaaa...

still need to install the extra oil cooler for the tranny and the vacuum switch.

I had 2900 rpm going down the road at about 55 mph. I now have 1850 rpm.
60 mph is about 1900 rpm....









TH700R4 and NP20 going in!



she's in:


bye bye TH400 and NP208, thanks for two good years


I have only one problem left....the new NP208 is sweating ATF...damn! are there any easy solutions?

[Edahall]

You really lucked out on the drivelines fitting. Apparently, the TH400 and 700R4 are very close in length.

The new NP208 very well may be leaking out of the output shaft.

Did you install brackets on your engine for the TV cable? And did you get it all hooked up and adjusted? Getting it adjusted correctly is very important for keeping this tranny alive.

Another alternative is to use a switch in the cab to toggle the lock up torque converter.

9 to 12.23 mpg is huge 36% difference. Is this on propane? The compression ratio on a stock 350 is a little low for getting the best fuel economy out of propane.

[motornut]

yes thats a huge difference
won't take long to be worth while, $$ wise

[kikkegek]

Originally Posted by Edahall

You really lucked out on the drivelines fitting. Apparently, the TH400 and 700R4 are very close in length.

The new NP208 very well may be leaking out of the output shaft.

Did you install brackets on your engine for the TV cable? And did you get it all hooked up and adjusted? Getting it adjusted correctly is very important for keeping this tranny alive.

Another alternative is to use a switch in the cab to toggle the lock up torque converter.

9 to 12.23 mpg is huge 36% difference. Is this on propane? The compression ratio on a stock 350 is a little low for getting the best fuel economy out of propane.

yes, got the TV cable hoked up correctly. drives perfect. shiftsdown like it should and hauls ass when I put the pedal to the metal.

even did a pressure test with a gauge to check pressure at different TV cable settings. and they all seemed fine.

yes, I drive 100% propane only. I know a little higher compression would be better, especially since my engine is a former Californian smog engine...and they are supposed to have lower compression for less emission?

I dont think there is a easy and cheap way to increase compression? isnt there?

I got to get the second propane tank connected and then we have a total of 134 liters of propane that should take us about 520 - 650km before we need to get a refill, which is nice...because we will be driving 1000km to our holiday location in Southern France this summer...

there is one more thing left I wanna do...and that is tune the last little bit out of it using a wideband AFR...but that is again something like $200,- investment...that will have to waite for now...

will do some testing by increasing and dropping the timing a little 2-3 degrees and see if the mileage improves.

also I was told that the converter of the propane system I have is tune-able for a leaner mixture...will go after that too

[kikkegek]

installed an extra tranny cooler

Derale #13107
biggest I could fit easily



mounting method:


only thing I noticed is that the upper hose in my case was the return line to the tranny. anyway, I mounted it in the return line, like the instructions said.

[kikkegek]

connected a vacuum gauge to read my vacuum under several conditions.

I get these readings

idle, 400-450 rpm: 17-18 inch

70 km/h:
3rd gear: ~ 13-15 inch
4th gear: ~ 10-12 inch

90 km/h:
3rd gear: ~ 11-13 inch
4th gear: ~ 10-12 inch

100 km/h:
3rd gear: ~ 11-13 inch
4th gear: ~ 10-12 inch

If I touch the throttle gently the vacuum goes down to about 8 inch.
When I push the throttle further it drops to about 6 inch
Close to WOT I get only 2 inch

are those normal readings for a standard 350 SBC?

I guess I am gonna set my lockup vacuumswitch to about 8 inch...

and I need to check my vacuum advance and see if its all in at 10-12 inch....never checked that before

[kikkegek]

just returned from 2 weeks of France with the Suburban and family. here are some impressions:

[manimal]

Looks like you had an AWESOME time! Thank you for sharing it!