1986 Dizzy Swap Questions

[jeroundt]

Let me start by saying hi to everyone (being my first post and thread)! I had an 81' K5 right out of high school and loved every second of ownership. Due to being a broke a$$, I couldn't afford to keep her on the road. Well now 11 years later, I have the funds and much better mechanic abilities. So long story short, I bought a 86' K5 blazer from a friend for a smokin deal ($1,800). Its got a rebuilt 350 eninge (25,000 miles ago), 700r4 trans (done at the same time as the engine), NP208 transfer case (new), and GM Corporate 8.5" 10 bolt 28 spline front and rear axles with 3.08 gears. I plan on making it into a good four wheel drive that I can take to the trails and to work. First thing on my list is to upgrade the engine. I noticed after I bought it that the thing is freakin gutless. So I crawl under the hood and find that I was lucky enough to get the electronic quadrajet and computer controled dizzy . These have got to go. Anyways the reason the truck feels gutless right now, is because my secondarys are not opening. Rather than fix this pain in the a$$ setup, my plan is to get an Edelbrock performer rpm cam, hydraulic flat tappet lifters, an Edelbrock performer rpm intake manifold, a none electronic quadrajet, a set of long tube headers, supper 44 mufflers, and a vacuum advance hei dizzy. Whew that was long..... sorry. This brings me to my question. Can I run a vacuum advance hei dizzy on this engine? If I can, what if any changes do I need to make? And lastly, does this sound like a decent setup so far to get decent horse power and torque numbers (Just trying to be around 300 on the hp and 300-350 on the torque. If I get more it won't be the end of the world hehehe)? Oh and P.S. the suspension lift, gears, locker, and other misc items will come imediatly after I get this engine going right. Thanks for taking the time to read this thread, it won't be my last.

 

[496truck]

Do you have to pass an emissions test in your place of registration? This is the most important thing to think about before you start upgrading. Hate to see someone do all that stuff just to find out they can't drive it.

 

[jeroundt]

Do you have to pass an emissions test in your place of registration? This is the most important thing to think about before you start upgrading. Hate to see someone do all that stuff just to find out they can't drive it.

No not at this time. Hopefully never. If that happens I'll just make it my toy and start driving my deisel back and forth to work again.

 

[Fordum]

Before you do a lot of engine work, be advised that this has a lot to do with it being gutless...

GM Corporate 8.5" 10 bolt 28 spline front and rear axles with 3.08 gears

I mean, those are car ratios......

 

[jeroundt]

Before you do a lot of engine work, be advised that this has a lot to do with it being gutless...



I mean, those are car ratios......

Yeah I know. I'm still deciding between 4.10's and 4.56's. Heck i still might through a set of dana 60's under it. I'm not %100 on that just yet. I do know what I want to do to the engine, so I figured I would start there first.

 

[Fordum]

Always remember you have to consider the whole vehicle when you start modifying. One of the reason the old military Jeeps and the early CJs got the reputation for being so tough, was because the system was well balanced.

Sure the axles drive shafts and transfer case were relatively weak, but the Hurricane F-head engine only put out 90HP on a good day, so nothing broke.

You add a couple hundred more HP to the mix on your truck, and stuff downstream will complain.
Expensively.
The 700R4 will handle it, but DO NOT drive one foot without properly adjusting the TV cable if you do any carb work that might disturb the setting.

The problem with new gears, is that the axles may be replaced in the future. But, I suspect that there are a lot of people here with 10 bolt gears that they are never going to use, so you might get a set cheap.
Maybe just for the shipping.
Putting in a set of 4:10s or 4:56s will take a lot of the load off the shafts. It will transfer that load to the axles and carriers, of course, but if you can put in a set cheap, you will then be able to tell how much work the engine really needs.

And have a nicer driving truck in the meantime. Just more gas usage most likely.

 

[jeroundt]

Always remember you have to consider the whole vehicle when you start modifying. One of the reason the old military Jeeps and the early CJs got the reputation for being so tough, was because the system was well balanced.

Sure the axles drive shafts and transfer case were relatively weak, but the Hurricane F-head engine only put out 90HP on a good day, so nothing broke.

You add a couple hundred more HP to the mix on your truck, and stuff downstream will complain.
Expensively.
The 700R4 will handle it, but DO NOT drive one foot without properly adjusting the TV cable if you do any carb work that might disturb the setting.

The problem with new gears, is that the axles may be replaced in the future. But, I suspect that there are a lot of people here with 10 bolt gears that they are never going to use, so you might get a set cheap.
Maybe just for the shipping.
Putting in a set of 4:10s or 4:56s will take a lot of the load off the shafts. It will transfer that load to the axles and carriers, of course, but if you can put in a set cheap, you will then be able to tell how much work the engine really needs.

And have a nicer driving truck in the meantime. Just more gas usage most likely.

Thanks for the replies. I agree %100 with what you are saying. If anyone has a set of 4.10s or 4.56s that are just collecting dust shoot me a pm. I might as well run the 10 bolts until I break one. I was cleaning out the glove compartment at lunch and found paper work for brakes and bearings at all 4 corners. Might as well run them while they are good. If I swap the gears I might as well throw a locker in while I'm at it. Who makes a good locker that is not to heavy on the wallet? Oh and with the engine combo that I posted at the top, what kinda numbers do you think I would be looking at? I was kinda thinking close to 300 hp and 325trq.

 

[Fordum]

Oh and with the engine combo that I posted at the top, what kinda numbers do you think I would be looking at? I was kinda thinking close to 300 hp and 325trq.

Getting a little out of my area of expertise. There are plenty of folks here who can tell you for sure. GM engines are not my thing.

I run Fords. I only hang around here out of pity and to try to help the less fortunate.........

 

[jeroundt]

Getting a little out of my area of expertise. There are plenty of folks here who can tell you for sure. GM engines are not my thing.

I run Fords. I only hang around here out of pity and to try to help the less fortunate.........

Lmao! I love both Chevy and Ford. In fact my main vehicle is a 2006 Super Duty 6.0 PSD FX4. I love it. But I have a soft spot in my heart for Chevy's too. I just love what can be done with a 350. They are amazing engines.

 

[jeroundt]

Oh and by the way, the first thing I did to the blazer was adjust the TV cable. The whole reason I couldn't keep my first blazer was because I smoked the trans and I couldn't afford a new one. I put a new carb on and I didn't adjust the TV cable right and smoked the trans in like 200 miles.

 

[496truck]

I run Fords. I only hang around here out of pity and to try to help the less fortunate.........

hahaha!!! And you've got the programmed responses to beginner questions too!

Seriously though, my stock TBI 350 would burn rubber with 3.42 gears and 33s. And that was doing a brake stand style burnout and the gov lock engaged turning both rear tires with properly adjusted and fairly new rear brakes. It still gets up and goes now with the 35s and 4.10s.

If you have some money burning a hole in your wallet, put it towards better axles and gears first. Bolt in 3/4 ton axles can be had cheap and can be found with 4.10s pretty common. Start there. If you plan on wheeling this thing, bigger tires and pushing more power from the engine don't waste time with that rear 10 bolt.

 

[diesel4me]

I'd bet dumping the 10 bolts for the 3/4 ton axles with 4.10's will amaze the driver with the increase in performance just by having lower gears,without even touching the engine...then your worries of breakage can be put to rest also....a salvage yard should have a pair of axles in decent shape (or look on craigslist)--I see them going for as low as 400 bucks for the pair,even less at swap meets or private party sales..
why mess with 6 lug stuff when it wont save you much,if anything in the long run,and you'll always be fearing breakage..

The engine could have its carb swapped for a non-electric Q-jet and a vacuum asvance style HEI with the good old 4 prong module ,that would put it back to pre-emission standards pretty much..Something an old hot rodder told me was to always buy timing gears for a pre-72 engine,as they retarted the timing after that year...at first I thought it was BS but he was right,just replacing the timing gears with "old" spec ones made a difference I could feel driving my truck...he also said sometimes an engine actually runs best with all the "emission crap" intact,rather than have some of it disabled,because GM designed the cam lift and duration and compression ratio to work with the emission controls,and defeating all or part of the system can make it worse,not improve it..

I have a '81 Chevy van that has 2.73 gears,you want to talk about sluggish--it was a slug with the original rear ends 3.08's and a straight six,after I had to replace the old rear end ,I was disgusted with it,it was so gutless,so I swapped in the only carbed V8 I had available,a '73 307...it didn't improve much,the 115 hp 307 that year was actually LESS hp than the original 250 six was--acceleration went from sluggish to barely acceptable!!...I have driven a nearly identical van with a 250 six and 4.11 gears with a 3 speed manual and that thing felt like a rocket compared to my van...gearing does a lot to enhance a vehicles performance,and sometimes lower gears will inprove gas mileage,if the engine was lugging too much with the taller gears...I think lots of engines get the blame for poor acceleration when its the gearing and big tires that are the real culprits..

 

[jeroundt]

Thanks for everyones responses! I have started to get things sorted out. I found a brand new, but damaged, msd distributor with the vacuum advance (just needs a new cap) at the local Carquest for $150 bucks. The guy at Carquest is also gonna throw a q-jet together for me for $100 bucks. I also found an 80's model K5 that is just a roller. The guy is going to sell it to me for $500 bucks. It has the 3/4 ton 14 bolt axles front and rear with 4.56 gears allready in them. Plus it has a set of long tube headers that come with it, a 6" lift (new springs up front with all the steering parts still intack, with blocks and shackle flip in the rear), front and rear drive shafts, and a good set of 8 lug aluminum wheels (tires are rotted). The axles look like they are in decent shape, but I'm gonna go through them and throw new bearings seals and brakes at them. I will probably throw new u-joints at the drive shafts too. The only problem is that the rear axle is locked. He said he didn't know if it had a spool or if the gears had been welded. Will I be ok with a locked rear end? I will probably only put 8-9 thousand miles on the blazer a year on pavement, and maybee 4-5 thousand offroad (I'm lucky, I can drive down the street from my house and be wheelin in less than 3 minutes). Thanks again for the help guys.

 

[496truck]

In that case, a welded or spooled rear will be fine. You can always swap it out later on if you don't like it.

 

[jeroundt]

Well as soon as I pick the blazer up next week, I will take as many pictures as I can to share with everyone here on the build process. Thanks again for all the responses.

 

[Fordum]

Will I be ok with a locked rear end?

I had a friend who ran a minispool in his Ford 9inch for over a year as a DD. He scrubbed a lot of rubber off his rear tires, and had to change them more often than normal.
Plus, cornering in the rain was interesting.

But, despite my misgivings, it did OK, until one afternoon he was helping a friend re-roof his house.
He ran down to the store and bought a large amount of roofing materials. Really loaded the truck down.
Heading back, he made a sharp turn on the highway, under power, and snapped the housing in two!
Said it just sorta exploded.

Put in another 9inch he had, but did not put the spool back in........

As long as the tires can slip, and their friction does not exceed the strength of the rear end, you should be fine.
Just don't do a lot of heavy hauling on pavement.