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V8-350 Swap 92 Astro

24793 Views 60 Replies 14 Participants Last post by  gwd
The old 4.3 in my 92 Astro made it to 282,000 original miles! A recent tick that developed into a knock turned out to be a broken piston skirt...not sure how it happened. Oil pressure still strong.

I'm swapping with a 350. I have no intention of using the computer. The 350 engine is carbureted, and is originally from a very low mileage 70 Caprice. (No emissions in Fla) The engine has a nice rumpity-rump high torque cam and intake installed, gets great mileage and runs AWESOME!

I have already purchased the custom swap V8 motor mounts, and Hedman shorty headers.

Here are my initial questions:

1) I assume the only issue with the 700R4 will be the lock-up converter (assuming I want to use it)? I've been told to either add a toggle-switch, or possibly a vacuum switch to operate it... assuming the converter is sufficient to use behind a V8? (I have a nice new TH350 with B&M 11" Holeshot converter, but I think I'd miss the overdrive).

2) The stock A/C system runs on a serpentine belt, the older engine is V-belt of course. I assume I will need to swap water pumps with a proper reverse pump that will work with serpentine system. What pump will I need? Will the V6 pump interchange? I'm assuming the powersteering and alternator will bolt up ok?

3) I also assume I will have to do something with the cooling system, fan, shroud, radiator, etc.

I will be pulling the motor from the front (working in my home garage)

The motor will be naturally aspirated (carbureted)... using HEI distributor. Fuel delivery will be stock system, with a regulator.

The other mods seem fairly obvious to me. I will have ALL the accy's available from the stock V6... if any are needed and can be used.

I have been waiting for many years for the V6 to finally die, the V8 has been patiently waiting! I just couldn't bring myself to pull a perfectly good running engine... but now the time has come.

I plan to run full dual exhaust as well.

I know there is a wealth of info here on this site... which I will be reading. I'm excited about my new advanture... as I have been a hot-rodder all my life! My last G-van had a supercharged 502. This current V8 was in my '69 Chevelle convertible.

Now it's the Astro's turn for an upgrade! It's a shorty with wide-tires and Centerline rims... and should be a perfect match!

Thanks for any advice and suggestions!
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chevymaher said:
...The 70 V-8 has the exact same engine mount holes in the block and head, as the V-6. Everything will bolt right on. Water pump, aluminum brackets, pulleys the whole nine yards...
That sounds awesome! I sure hope your right!

Thanks for the support and encouragement guys! The swap is not something I needed in my life right now... but then again there is probably no better time than now to do it. I am very glad to hear that most everything will bolt up! That is a HUGE relief!!

I was aware there could be a potential issue with a missing bolt hole on the head, or that it could be fine. The heads and block are still stock. You say the brackets, as well at the water pump will bolt on... that would be awesome!

The van is actually used to haul DJ sound equipment, and lives in the garage. I recently replaced all the clutches in the 700R4 with new, when I was replacing a broken sprag. I don't really intend to beat it up (like I used to)... so I'll give the 700R4 a shot behind the V8. If it fails, I'll throw the TH350 in it... which has a really tight shift and new holeshot converter.

The motor originally came from a 70 Caprice driven by a little old lady, and had very low mileage. When I pulled it (and junked the car)... I replaced a crappy 307 in my Chevelle with it. I've always called 307's "dumpster motors". I grabbed a bunch of crap lying around the garage, an old Erson Stage II Cam, headers, Edelbrock intake & 4bbl carb, and threw it all together. The motor came to LIFE!!! I've never had a more torquey crisp little motor than this one. The car would burn rubber as long as you layed on the thottle! It has a real choppy rumpity rump idle to about 1500rpms, thens hits a strong torque range.

The Chevelle wound up being stored outdoors in a field for many years, and fell into rough condition. Eventually, I sold it to a good friend a few years ago, who is in process of full ground up restoration, but I kept the motor and trans (saving it for the Astro). I knew the V6 couldn't last forever... but I was starting to wonder. It really was running perfectly until it developed the tick, and never burned any oil. Oh well... I got my money's worth on that one!

I'm in the process of prepping workspace in my garage, as well as prepping the 350 with new gaskets ... which is all it needs. Low mileage, but 44 years old! LOL

Here's a photo of the Chevelle it was in (photo taken at Fiesta Key, Fl)
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New question: (don't know if I should post here or start new thread, but I'll try here first)

As stated, I will be using carburated engine in place of my 4.3 which on my '92 I believe has TBI?
I would like to continue using the stock fuel pump (located in tank).

1) What is the fuel pressure from the stock pump? I've read the pressure is not the same as fuel injection?
2) What regulator do I need?

I'm sure it needs a fuel return, but I'm confused on the pressure ratings and what I need.

New parts ordered for the v8 on their way!~ Thanks again.
Thanks guys, you confirmed exactly what I needed to know... thanks.
Ok... the V6 is stripped down and coming out today!
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Astrofarian said:
If you haven't already....I would take the bumper off AND unbolt the master cylinder from the booster....leave the lines in place but give the master a bit of wiggle room. :2:
Thanks for the suggestion... I considered it. I think I will try and see if it clears... I will let you know. I intend to drop the V8 in with the headers already attached.. so I will need the clearance both ways.

Everything is off the V6... bolts are all out! Time to lift it out! I can't believe how much I had to disconnect to finally get to the engine! Most of it won't be going back in.

More photos coming soon...
chevymaher said:
I took my bumper off. It may come out with it on but it will be in the way...
IT'S OUT!!! I've pulled a lot of V8's (in cars and vans)... but this was my first V6!

I did not need to pull the bumper, it was not in my way at all! My cherry picker arm has the ability to extend out, but I didn't need to go too far. I think my cherry picker is much larger than some (see photo).. maybe that's why I didn't need to pull the bumper.

I did unbolt the master cylinder as well from the booster (just to be safe), since it was only 2 simple nuts and very easy to do. Turns out the engine would have cleared, but this was too easy and why chance the lines getting banged up (sometimes the motor can twist a little with a tight hook). I just pushed the master cylinder slightly to the side.

I did strip the engine down about as far as you can go... particularly EVERYTHING on top! This mainly includes distributor and TPI unit, as well as everything else... only leaving the manifold. This is done for clearance reasons.

I've always pulled van engines from the front, and this Astro was no problem either!

Yes, you have to put the cherry picker arm in place as tight against the engine as possible. I turn the arm upside down and pull the hook into the arm almost as far as it will go... so it barely sticks out. Then I attach the chain to the engine at opposite corners of the heads, with it as tight as I can hook it across the manifold. The manifold did not need to come off either, but the clearance was close. The van (front end only) also has be be lifted and angled as high as you can get it with a floor jack and jack stands. My jack stands were fully extended under the lower control arms.

Then you simply start lifting, pull forward some, lift some more, pull forward more... essentially stepping it up and out! Everything cleared easily!

I did it by myself and it was a breeze! There was way more than enough clearance for the exhaust headers too! I did not have a single issue! It took only a couple minutes to actually lift it out.

Anyone considering a front pull on a Gen I van, I highly recommend it!


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Well, most of the work is unhooking all the stuff from the engine! You have to do all that regardless of which way you choose to go. The grill comes off easy enough. The crossmember above the radiator unbolted very easily... everything 13mm and easy to get to. Shroud and radiator, easy. That leaves the front wide open! As I said, no need to pull the bumper, although that doesn't look all that difficult either.

Again, the hardest (and messiest) part was all the wiring and stuff attached to the engine itself.

Since I did most of the work in my garage, I completely ruled out lifting the body. It looks like too much work, plus I didn't have clearance to lift the van either. It clearly looks like a two man job, and I work alone. Also, NO place to store the entire subframe with engine on it after it all comes out, which has to be rolled somewhere. And then, you're still going to have to lift the engine off of it anyway.

No, out the front is simple and clean... just pop the engine on a stand and your done.

Probably the one major advantage of lifting the body would be keeping the A/C system in tact and charged. I had to open the system and pull the condenser, so I removed the compressor and attached lines too. It wasn't really that bad, and I have everything to recharge it.

I'll have plenty of photos of the V8 going in!

Here's the front of the motor after you pull the radiator, shroud, and fan:


Here's the unbelievable MESS from the back side (before I pulled it)

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Save yourself a lot of grief, and buy them already made! They are adjustable, which will probably make a huge difference at show time!

(they are very high quality stamped steel now)

Here is what I got: ... ounts.html

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By the way... here is a photo of the donor 350 motor (before cleanup), with a few years worth of neglect!

Since this photo was taken, the engine has been completely cleaned up, all new seals & gaskets, high volume oil pump, chrome covers, dress up kit, etc. Performance goodies include Erson Stage II cam, gear drive, Edelbrock Performer intake, Holly 750 carb, Hedmen shorty headers, MagnaFlow dual 2 1/2 full stainless exhaust system.

Just want to show how it looked before! Ugh!
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icebrrg3rd said:
I see you're running a carb, why not stick with TBI (or were you CPI)? And did you re-use that thermostat outlet or are you going to switch to the van's one? The van one is almost straight up out of the manifold, I re-used the stock upper hose with it.
Andrew, there are several reasons why I'm running a carbureted engine...

1) The engine is a 1970, and is already carbureted. It has a nice high performance Edelbrock aluminum intake... perfectly matched to the Holly carb. It's a hot-rod engine.
2) Nothing fits. The TBI unit does not fit the carbureted manifold, nor does the V6 TBI manifold fit the V8.
3) The 350 runs so unbelievably awesome, I have NO intention of changing anything!

I'm old school... simple works for me! No need for computers, or all the crap that messes up the performance and operation of a good engine. I'd have to go find and buy a V8 TBI manifold, swap manifolds, install TBI unit, install O2 sensor (and any other possible sensors) and then there might be a chance that something would still need to be reprogrammed for a V8? No thanks.

The thermostat outlet I intend to use is a chrome stock replacement.. aimed more forward in typical fashion. I haven't really looked at my hose options yet... might just use a simple flex hose or high performance aftermarket.

By the way... I see in your photo what looks to be an answer to a question I had regarding the harmonic balancer. It looks like you were able to just mount the serpentine pulley on the V8 balancer. I wasn't sure if it would be positioned correctly on a V8 vs V6 pulley, or if bolt holes lined up too. I just haven't got that far yet...
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Well... sorry to say I'm not moving very fast! It's 95+ degrees out every day and I'm not feeling very motivated.. although I'm doing some of the current work in my garage. The middle of July is NOT when I had intended to do this work!

While I have the engine out, I have been prepping the empty engine compartment... pressure cleaned it last week (along with all the accy's and brackets), and today I replaced the motor mounts and upper control arm bushings. This is SO much easier to do when there is no engine in the way!

Regarding the motor mounts... I had originally purchased a set of cheap "Anchor" motor mounts... got them from Summit for $5/ea. Apparently most of the local stores carry them too. When I finally pulled the old mounts out and went to put these in, I realized how cheap and crude they looked. The old mounts even looked better, but have over 100,000+ miles on them. I did some research and found a lot of complaints about the cheap Anchor mounts and premature failures. Also discovered that other dealers were putting their name on the same cheap crap.

I decided it wasn't worth the risk of having the new cheap mounts fail early on me, so I bit the bullet and purchased a set of OEM mounts from the dealer. I got them for $53/ea. That's certainly a lot more than the $4.95 I paid for the low budget crap. But I can sleep now knowing I got a quality mount that should hold up for some time. Didn't want to chance early failure with the added load of the V8.

Of course, I have the "JTR" custom stamped V8 conversion mounts for the engine side! Painted and ready to go!

Here are some photos taken this weekend.

Anchor vs GM

Engine compartment with new mounts installed


Sorry I don't have something more exciting to post yet.

Once the control arms are back in tomorrow, my next step will be to clean up the wiring and make final preparations for the V8. Most of the factory TBI system wiring will not be needed any longer. I will replace loom and possibly re-route what I do need. I may completely cut out and remove the wiring I don't need.. since I have no intention of ever putting the V6 back in. This should be completed this weekend or next.

Next weekend, I also plan do final prep on the V8... and I expect to drop it in!

Stay tuned....
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While the engine is out of the way... it's a good time to swap out bad upper control arm bushings! The old rotted rubber has 20 years on it... and 282,000 miles!

Removing the old control arms with nothing in the way is a piece of cake!

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Well, you haven't heard much from me on this project as we slowly move forward dealing with the south Florida summer heat. But I made some real progress recently!

The final preparation the 1970 motor needed before install was the drilling and tapping of the PS cylinder head for the 92 serpentine system accy bracket. The stock 1970 head only came with only one hole, so another would be needed. Fortunately, there was a raised boss where the mounting hole is needed. (the 3rd hole would not be possible where the head curved)

Seen here with a mark where hole will be drilled on the stock head:
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Accy bracket (this side holds the alternator and pulleys):
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Initially I was concerned about hitting the water jacket. I took measurements to determine how far I might want to drill. The head with one single hole was .7 deep, the heads with 3 holes were all .9 deep. My goal was to drill .9 deep.
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The hefty and thick bracket would serve as the template for alignment and drilling of the hole. It was important to temporarily sleeve the large bracket holes to get an accurately centered drill point. The sleeve and thick bracket would also allow me to drill straight in as well, since I would be doing it by hand.
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Remove bracket to double check my work before I continue:
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At first I drilled and tapped for a 3/8 stud. I bought a long 5/16 drill. I had not hit the water jacket at .7 depth, but did hit it at .8. At this point I drilled completely through. This turned out to be a good thing, as it would allow me to tap deeper threads.

After I started shopping for studs, I decided to go overkill with a 7/16 tap and stud, since I would only be using 2 of the 3 mounting points. The hefty bracket has over-sized holes already, perfect for the larger studs. The cylinders were very easy to drill and tap.

A drill extension (which I fabricated) was needed for the larger 23/64 drill bit :
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The Harbor Freight tap and die kit (China) was a huge waste! I was struggling turning the tap so hard, I expected it could break, despite oiling. I aborted using the garbage tap, and purchased an Irwin 7/16 "bottoming tap" from Ace, which I would need anyway for the first original blind hole. I tapped the 2nd hole was tapped all the way through. Turns out, the new tap cut the head like butter!
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I wanted to use larger studs for extra strength, again since I would only be using 2 of the 3 mounting points. The 3rd mounting point would not be possible, since the head was curved at that point. The good news is that the bracket still rests firmly against part of the head at this point, and is being pulled toward the head at this point anyway, so I don't consider it critical. The PS bracket only holds the alternator and pulleys, and in addition to the over-sized studs, rests firmly pulling against the block as well. (The DS accy bracket (A/C and PS) bolt up without mods)

I found the PERFECT studs! These 4.350" ARP cylinder head studs are made from 8740 chromoly steel with 190,000 psi tensile strength.. thread-rolled to Mil-S-8879 specs... and should be way MORE than adequate for the job! Nothing like OVERKILL!
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It should be noted that I found many forums with discussions about hitting the water jacket. But I was happy to note that the lower right water pump bolt is ALSO in the water jacket... completely normal! I never even noticed before, have never used sealant in the past, and never had one leak over all the years I've installed pumps. Despite that, I have procured the proper thread sealant and expect to have NO issue whatsoever.

The job came out perfect and I am very delighted! This was the LAST thing I needed to do before dropping in the V8!
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Happy Labor Day! It's ready... today I'm doing my final prep work before dropping it in!

As stated, it's a low mileage engine from a 1970 Chevy Impala... and a while back I had added an Erson Stage II cam, Edelbrock intake, Holly carb, gear drive, custom 2.02 valve heads, hedman shorty headers, HEI ignition, hi-volume oil pump, new gaskets and seals, etc. This little V8 runs unbelievable! Tons of torque... goes "rumpity rump" on idle and "rump rump" cruising around the neighborhood up to about 1500 rpms. Then it smooths out really strong! I have a FULL stainless MagnaFlow DUAL exhaust system to go behind the headers.

I decided not to re-paint, just clean it up... since I figure most of it will not be visible behind brackets and accessories. It's really clean, and I replaced all the rusty trim with new! It ran so unbelievable awesome in my Chevelle, I didn't want to change ANYTHING else!

Here's a photo of the 350 motor. Not real pretty or fancy... just the things that count!
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Here is a shot of the amazing JTR V8 swap brackets! High quality STAMPED steel.. and completely adjustable!
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The only thing I can't figure out is if I'm supposed to use the one stock "spacer plate" that is used against the block with the stock motor-mount shells? I assume I'm not supposed to use it since the new bracket appears to not only adjust from front to back, but from left to right as well.
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As opposed as I am to electric fans... I have a nice shrouded Black Magic electric-fan (from another hot rod project) I intend to use. I also have the thicker stock radiator, which always ran cool.. as well as the motor.

But I will make observation on what mods would have been required to keep the stock fan...even if I don't use it. Considering how much closer the fan will now be from the engine to the radiator, a good electric fan seems to be a good choice.
The JTR mounts are awesome! Not expensive.. but worth every dollar! Fully adjustable too!

PS: They worked perfectly! (you'll see in next post)
Hooray!!! The V8 is finally in!!! It dropped in easily (this past weekend). It went in like it was made for it! It was a one man job too!
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I installed it complete with headers attached, new plugs, water pump, harmonic balancer, pulley, and oil filter all in place. The headers measured almost exactly the same distance as the stock exhaust coming out, and went in easily with NO clearance issues whatsoever! Also, NO need at all to pull the bumper... just angle back the motor and keep stepping it down and in! You only need to have the van angled up high on jack stands to match. Simple!

The only initial minor trouble I had is that I didn't have the motor positioned and angled correctly on the lift, as seen in this first photo.
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It was angled too far down in front... and the hook was not tight enough. Although I was able to lift the front by hand, I still didn't have the hook tight enough for overhead clearance when I got it to the motor mounts.
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Here are some photos of it tighter on the hook, and angled better...
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The front opening of the lift plate was ideal, giving it a much better angle to go in! This is the first time I ever used a lift plate, so you see the chain as a fallback. The biggest advantage of the plate is that it kept the block strait going in.
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A few final things left... basically slide in the motor mount bolts and attach transmission. But first I had to wait for the rain to stop before crawling underneath! lol
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Adjustable JTR V8 mounts are awesome! Quality stamped steel product... seriously worth every dollar! Tighten trans up to block first.. then final tightening of mounts. Went in perfectly!!! One very important note: you will need 1/2 longer 5" Grade 8 bolts for the thicker mounts! Thank you icebrrg3rd for that tip!
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Plenty of room... everything completely cleared with room to spare!
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The ONLY unrelated issue I had was overlooking the fact that the 1970 flexplate did not match the later model 700R4 lockup torque converter bolt pattern, which I didn't notice until after I bolted the trans to the block. Fortunately, I had another later model 350 flexplate laying around that had "dual pattern" holes, which worked perfectly. A minor inconvenience caught early... fortunately.

Overall, not too pretty... and the alternator, pulleys, and A/C accessories will cover most of it. But it's a runner.. and is going to be awesome!!!
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Thanks! My biggest hurdle now is to attach the throttle cable to the carburetor. It pulls from the front, and has the wrong fitting on the end. I expect to replace it with something compatible, but I will still need a bracket or way to pull from the front. Minor stuff I have to figure out.

My other related issue is fuel. I will be using the stock pump (in tank) which is supposed to produce about 12psi. I will obtain a fuel pressure regulator (with return) to lower pressure to something the carburetor will like.

I've been removing ECM wiring and connectors that used to attach to the TBI system, and various other engine stuff... and cleaning things up a lot! The only engine wiring I kept is oil pressure, temp sender, alternator, and A/C. Starter too of course. One ignition power source for HEI distributor, and stock wiring for fuel pump (if it still sends a signal). Otherwise I will just wire it direct myself. Wiring couldn't be any more basic. I sure removed a lot of it and re-routed it nicely!

I will need a simple relay for the electric fan, and I still have to build the dual exhaust system, which I have.
I have some nice dash mounted gauges and tach already mounted, that will require hookup at some point.
I will put in a temporary manual switch for the lockup converter, unless I find another alternative.

I think that will pretty much cover it.

Hope to post a video soon of me firing it up!
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Ok... I got the poke! lol It's time to post an update!

First of all... I'm sorry it has taken so long! I somehow manage almost every weekend to find something else to do... or somewhere to go! I live a very FULL and busy life! I also love to ride my motorcycle... so I often find myself riding when I have free time.. and the V8 van upgrade keeps taking a back seat. But this is a 4 day weekend for me... and my goal is to fire it up for New Years! Realistically, I have less than a day's work left.

I found a perfect solution to the throttle cable! It is from my old carbureted 74 G10 van. The cable is about 4' long, runs out and under the floorboard, and comes in from behind as needed. I also have the factory bracket that mounts to the manifold behind the carb... which also holds the kickdown cable for the transmission. Simple... problem solved!!! It fits like it was made for (well it actually was) it and connects to the carb perfectly! I suspect just about any throttle cable from just about any carbureted van will work. The pedal side also fit perfectly.. I think they all use the same universal type.

I bought a Holley fuel regulator (with fuel return), which should work perfectly with the stock "in tank" pump. I am mounting it underneath to the frame where the two metal lines connect to the rubber TBI lines. I will post photos.

There essentially isn't anything left to figure out.

The Holley I had planned to rebuild got bumped for a much nicer (and in better shape) one of two Carter/Edelbrock carbs that I used to use in a dual-quad setup. I had forgotten that I had these boxed up and ready for future use. It's all cleaned up and ready to go!

Drive shaft is in (trans was never removed). Van is off jackstands, and new suspension is tightened up and done. Thermostat and new heater lines done. New belt pulleys.. done.

Tomorrow I finish the fuel system install... I already bought the line, angle adapters, and connectors, and placed the regulator. I will drop in the HEI distributor, wire the plugs, install the DS accy's (PS pump and A/C compressor), and lastly connect up the radiator. Then it's time to fire it up! The final dress up can come after it's running. The little things like factory oil spout, vacuum to PCV and brake booster have all been sorted out.

The last thing I will need to do is a full dual exhaust system, which I already have... a nice custom FULL stainless dual exhaust system. But this won't stop me from cranking it up with open headers. The exhaust system may be easier than I'm expecting.. we'll see.

I also have a full set of dash mounted gauges.. but can deal with them after I get the van on the road. The factory oil and temp is already wired up.

I'm excited to be in the final stage of this project!

Video and more photos coming shortly...
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