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1978 Blazer/Jimmy projects

mac907

mac907

1/2 ton status
Joined
May 11, 2013
Posts
147
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0
Location
Alaska
Hello all, I'm fairly new to the forum and have only posted a few questions here and there. I made what I now consider a mistake and left my 78' K5 Blazer in the hands of a professional to install about $5000 in parts for a 1 ton axle conversion that ended up being a "replace everything from the frame to the tires" upgrade as I kept ordering parts while the shop took their time at getting around to my truck. Long story short, after having to dish out nearly $10,000 in labor I'm ready to take advatage of current living conditions with a heated garage and bust a knuckle or two doing all feasable body and mechanical mods/restoration myself. Any suggestions or advice would be greatly welcomed from here on out. I'm still waiting on my 78' Blazer to be finished after nearly a year, just waiting on final touches on the brakes, shock mounts, and twin stick np205.

While waiting, I currenly have a running/driving 78' Jimmy that I aquired as a "parts truck" to gain my wifes approval. The following items need to be immediately address in order to make it a safe driver:

1-smashed and leaking fuel tank
---I have a 31 gallon tank off of another 78' K5 that came with a skid plate, after hitting it with a wire wheel I've uncovered a few pin holes in the bottom of the tank. Should I restore the tank with a POR15 fuel tank cleaner/sealer for $87 or get a new tank for $160?

2-engine RPM drops significantly when the TH-350 is shifted from park to drive
---It never stalls, but the truck shakes badly until I give it a little throttle the then everything runs smooth. I've notice the TV cable isn't hooked up to the carb since the pin or rivet that mounts the cable to the carb is missing. Once I re-attach the TV cable is it likely this issue will go away?

3-small amount of coolant pooling on the intake manifold
---No oil in the mix, so I'm starting with replacing the intake gaskets. I have checked the numbers and confirmed the engine is a 400SBC. It runs smooth/quiet and starts easy but I have heard that the 400SBC overheats easily. Is it an engine worth keeping in the event that my "parts truck" convenietly disappears to my remote property as a trail rig?

1978 2.jpg

1978 3.jpg
 
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a couple more pics

Passenger seat and rear bench are like new. Carpeting is original and minimal rust is detected with what I can see of the rocker panel and a look at the underside. I'll be ripping out the carpet later this week and grinding/priming whatever surface rust I find while I wait for either my POR15 kit or new tank to arrive (haven't decided which one yet).

The current plan for this truck is to be a mechanically sound donor truck that can be driven safely and supply my 78' Blazer with all the odds and ends it may need. I don't mind investing time in it, but money in terms of parts has a priority to the 78' Blazer. That being said has anyone repaired a tank with pinhole leaks, or will I regret not spending the extra $70 for a new fuel tank?

Also, can anyone identify the item sitting on the fender on the right side of the top picture? Factory cruise control module maybe?

1978 5.jpg

1978 4.jpg
 
10k in labor, just got that vomit taste.

Gas tanks are cheaper than that from rock auto or advance auto online.

Rpm drop, choke settings, carb issues, timing, vac leaks, mech advance in dizzy comes in too soon then drops out when put in gear. Etc

TV cable for trans kick down, nothing to do with idle.

Cruise control yes.

Coolant pooling where? Front back, thermostat gasket, hoses.

400 sb can be more sensitive to overheating, but usually overheat do to neglect, or not using heads with steam holes, I'd keep it.
Proper cooling system is a must.

That should get you started.
 
I noticed maybe a couple ounces of coolant on the front driver side of the intake manifold near from behind the thermostat housing to about halfway down the driver side of the intake manifold. I drove the truck home about 10 miles and no additional coolant has leaked out. The leak doesn't appear to be spilling over or causing me to lose coolant so fast that I have to top off on short drives. More of a seap than a leak I guess, but I'd like it to stop regardless. Mentioning the thermostat does make me want to use this as excuse to add a low temp t-stat and re-seal it up, even if it doesn't fix the leak I'll at least get a cooler running engine.

Thanks for the input on the other issues. I'll check out rock auto, but autozone's free shipping to Alaska at $160 may be hard to beat for the fuel tank (some stores want $60-$110 for shipping)

.........and rockauto save $60, but then charges $132 shipping. One things that sucks about living in AK :(
.... advance auto $110 shipped, we have a winner!
 
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I've had no luck trying to seal up a leaky gas tank,not for long anyway--tried J-B Weld,Fiberglass cloth and resin,etc,and in a few months it's dripping again..its worth the extra money going with a new tank IMO...around here you can usually find a new one for about 100 bucks...J-C Whitney used to sell plastic tanks too,which are more $$$ but your rust worries will end for good with one of those..

I've tried the stuff you slosh around inside the tank and had poor luck with it,its only worked well on some small engine gas tanks and motorcycles ,I think a new tank is a good investment--drop it once and put a new one in,new hoses,and never have to mess with it again..

The 400 small block is externally balanced,unlike all other small blocks,and it has a counterweighted flywheel and harmonic balancer with a "half moon" shape to it instead of a solid disc,I'd be sure both are intact and that someone hasn't put one from a 350 or other internally balanced small block on it,I have seen that many times...that'll make it shake and vibrate like crazy at certain rpms and do it no good at all..

The TH350 has a detent cable,it only makes it downshift when you floor it to pass someone,its best to have it hooked up and properly adjusted,but you can leave it dissconnected without doing any real harm to the tranny,its not like a 700R4 where the cable controls line pressures and shifting speeds and firmness..I'd guess your engine is out of tune judging by the symptoms,it might have a vacuum leak,check all the rubber hoses,the brake booster ,and the steel tubing going to the vacuum modulator on the rear of the tranny,if any vacuum leaks are present it will idle crappy and want to stall in gear,and stumble when taking off from a stop..

I would leave the 195 T-stat too,especially where you live..your engine will not run any cooler with a lower temp one,it will simply open up faster and let the coolant get to the radiator quicker...your oil will sludge up faster if you do keep its operating temparature under 195 degrees and the gas mileage will suffer too...just about every Chevy V8 I have owned oozes coolant from the t-stat housing after they sit awhile,it seems to be a common dilema..even if you use RTV or gasket sealer it still shows a bit of green antifreeze after it sits awhile,but the level in the radiator never seems to drop any..sometimes the t-stat housing has a hairline crack in it,they sell cast iron ones to replace the die cast crap oem ones..
 
I've also had the mystery leak on the intake also, never could see it but would just appear. Cured it with a new cast thermostat housing, not a cheap chrome one.

Check your rubber filler hose to the gas tank, might want to replace your tank sender unit and rubber hoses while your there with methanol rated also. I use fuel injection hose, 6 bucks a foot tho.

Blow out your metal fuel lines also, could be rust etc in them. Replace your fuel filter.
 
Thanks a ton diesel4me and blazer74! That gives a little bit of relief regarding the coolant leak. I was told the truck was sitting a year before I picked it up and drove it home so it probably did just seep during storage. A 195* t-stat and quality cast housing sounds like the plan. I only thought of dropping it to 180* because that's what I use on my supercharged car to keep the KR down (a whole different animal from naturally aspirated I suppose).

As far as the idle goes, vaccum lines will be thoroughly checked as soon as I get home. Another problem I forgot to mention is the brakes barely work, so a new brake booster will certainly be on my list of parts once my lines are checked over. Do either of you know if it would be possible/worthy to upgrade to a 1 ton brake booster? I've seen with my 1st gen K-5s that getting a heavier duty vaccum booster was a simple and effective mod.

Lastly, I had no idea about the balancing of a 400 SBC. I'm keeping my fingers crossed that when I get home in a few days I find the right balancer under the hood. I'll check the flexplate if vaccum lines and all the more simple stuff doesn't fix my shakey idle.

Thanks again, now I have plenty to look into while I wait for my new gas tank to arrive. :thumb:
 
mac907 said:
As far as the idle goes, vaccum lines will be thoroughly checked as soon as I get home. Another problem I forgot to mention is the brakes barely work, so a new brake booster will certainly be on my list of parts once my lines are checked over. Do either of you know if it would be possible/worthy to upgrade to a 1 ton brake booster? I've seen with my 1st gen K-5s that getting a heavier duty vaccum booster was a simple and effective mod.
Click to expand...

The brake booster, if bad, will just make the pedal really hard to press.

If the pedal is soft, that's a hydraulic problem (and far more likely.)

The 1-tons used hydroboost, i.e. boosted by the power steering pump, not vacuum, so it means changing the booster, master cylinder, power steering pump (or at least the reservoir), brake pedal, and lines.

I'd look at the hydraulic side and/or turn the rotors and scrub or replace the pads are good LONG before I dinked with all of that.

-- A
 
Thanks for the input dremu. I want to say it sounds like the booster then because the truck will stop, but I do have to press the pedal pretty freakin' hard to get it to do so. When I checked the pads they looked almost new and the rotors are clean with no noticable distortion. The E-brake cable does hang down pretty loose though and doesn't seem to do much of anything when I press the E-brake pedal (in case that could be causing any of this).
 
mac907 said:
Thanks for the input dremu. I want to say it sounds like the booster then because the truck will stop, but I do have to press the pedal pretty freakin' hard to get it to do so. When I checked the pads they looked almost new and the rotors are clean with no noticable distortion. The E-brake cable does hang down pretty loose though and doesn't seem to do much of anything when I press the E-brake pedal (in case that could be causing any of this).
Click to expand...

Other than a sticky cable causing the brakes to drag (not the case here), the E-brake cable should not be able to affect the pedal brakes.

Booster is a good guess, assuming the vacuum lines are intact and sucking properly. I feel for ya...My suburban (hydroboost brakes) came with a non-functional Power Steering pump. Stopping (and steering) that truck has been a real task! :(
 
The parking brake may indicate the rear shoes are out of adjustment. They're supposed to float just inside the drums, but the auto adjusters never work.

It can be possible to adjust them in situ, through the hole in the backing plate. I always seem to have to pull the drums. At the very least I'd remove them once, clean and lube the star adjusters, and reassemble. Not like the adjuster will AUTO adjust, but it's easier to manually adjust when it's clean and greased, IME.

Otherwise, yeah, a reeeallly *hard* pedal can indicate a failed vacuum booster. Check for vacuum leaks and/or a cracked plastic fitting on the booster before you go to the hassle of replacing the booster proper though.

-- A
 
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Thanks cucvnut. Pictures of my thrashed driver seat and a moldy leather replacenent I found for $20.
Then pictures of the leather seat after being sprayed and wiped down with chonchribium. I also hit the seat frame with a wire brush attachment on my drill and removed rusty spots, then covered the bare metal with Rustoleum primer.

old chairs.jpg

damaged chairs.jpg

back.jpg

front.jpg
 
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I didn't have time to check the brakes or vaccum lines since the military cut my weekend short, but I did peek under the front end and confirm that i have the correct balancer on the engine. The gas tank is due to arrive from Autozone on the 8th (they were the only company i could find that included Alaska in free shipping).
 
Remember the flex plate or flywheel has a balance weight on it too,for the 400 small block--both the balancer and flex plate or flywheel must be the correct ones, or it'll have a bad vibration at various RPM's..
I've seen many flex plates off a 305 or 350 or other small block get re-used when a 400 small block gets installed ,and just having the wrong flywheel ,but the correct balancer,can cause problems...
 
I had just enough time to rip out the front carpet last week and do a bit of rust removal. I don't have an angle grinder yet, so I did the best I could with a 4" wire wheel attachment on my drill.

The driver side just needs a little grinding and some new paint, I removed most of the rust with the wire wheel and sealed it up with Rustoleum primer untill I aquire an angle grinder in the near future.

The passenger side will need a small panel welded in the front kick panel area. I only have an oxy/acetylene welding setup right now, so I gave it the same treatment as the driver side and will do a more thorough rust removal/repair when I get a MIG welder (also on my list of goodies as I aquire more tools of the trade).

floor.jpg

floor 2.jpg
 
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I eventually plan on Rhino Lining the interior since I really can't stand the thought of carpet going back in the truck. I may buy a prefit poly/rubber insert kit from LMC or some other vendor further down the road. Until that time comes I just cut up some pieces of 1/4" excercise mat that I had collecting dust in the garage to place between the painted metal floor and the seat brackets to act like the barrier that the capet used to be between the metal on metal contact.

floor 3.jpg
 
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diesel4me, I haven't forgotten your mention of the flexplate. I was just putting that off until I check the vaccum lines 1st in hopes that I won't have to unbolt the driveline/tranny to look at the flexplate.
 
You should be able to see the balance weight on the outer edge of the flex plate(just inside of the ring gear facing the engine), thru the starter opening--so you'll only have to drop the starter,if there is no removeable dust cover on the bell housing...
 
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