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1968 Impala Repower Thread

16K views 110 replies 7 participants last post by  FearlessAZ 
#1 ·
Hello all,
Attached is a pic of Gloria. She'll be getting a 496 stroker, T56 Magnum, and a 3.73 posi here in the next few weeks. My plan is to install the engine & trans myself and then take it to a local guy for the rear axle work when I have her running. The T56 will require some fab work (trans tunnel & crossmember) which I also plan to do myself. I thought I would start a thread so I can ask dumb questions as well as post pics and updates which may help someone else in their future build. Thanks in advance for any replies.
 

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#3 ·
Cheap way is four hose barbs and a length of three quarter inch rubber heater hose. Expensive way is a bunch of AN-10 fittings (at ten bucks or more each), and size ten stainless steel braided hose.

Four elbows at $17 each:
https://www.ebay.com/p/Russell-6101...w-Hose-End/1211846110?iid=232331907843&chn=ps

Four 3/8th male NPT to AN10 adapter ($5 ea):
https://www.jegs.com/i/Russell/799/670030/10002/-1

Six Feet of -10 braided stainless steel hose (at $22 for 3'):
https://www.jegs.com/i/JEGS/555/100...FvNCmBd4MiaiwCR3jshGknyqDQTVs-4kaAgiPEALw_wcB

Big Dave
 
#4 ·
Thanks for the reply and links Dave. My concern is that this would eliminate the ports in the intake I could easily use for the two temp sensors I need to install (Holley EFI and Dakota Digital). I guess I'll have to see what, if any, coolant ports I can tap into in the block /heads. Two more weeks until I have the engine in from of me.
 
#8 ·
A few questions regarding grounds: I want to ensure the new engine is properly grounded.

The water pump is powder coated chevy orange and I will be grounding the battery to it per the original cable routing. Do I need to grind off the powder coating from the pump where it attaches to the block?

I've also got an original ground strap kit from American Autowire. The ones that attach at the valve cover fasteners - do I need to grind the chrome off the valve covers (steel under the chrome)?

Thanks for any replies. The T56 is being delivered today. Will post a pic or two.
 
#9 ·
Chrome and steel (all metals) conduct electricity to one degree or another (there is a table in my Engineering manuals that lists the conductivity of metals (Silver, Copper, Gold, Aluminum, Zinc, Nickel, Brass, Bronze, Iron, Platinum, Steel, Lead, Stainless Steel, etc. for every known alloy, or elemental particle). Your plastic covered water pump is a different story. Plastic is an insulator (why your wires are covered in colored PVC plastic).

You can grind it off, or relocate the cable to a different grounding point like the intake manifold.

Big Dave
 
#12 · (Edited)
I'm trying to drill and tap my intake for the 5/8 line from the heater core. I drilled the correct 45/64" pilot hole and I have a 1/2-14 NPT tap, but the pic shows the furthest I can get the damn thing to go. The black mark on the tap is how far it needs to go. Any tips here? I don't want to crack a $400 intake trying to do this. Thanks for any replies.

Edited to add: I have not been using any kind of lubricant or tap wrench. Wonder if these would help...
 

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#15 · (Edited)
Look in hole for marks indicating the tap is hitting back wall of water passage. If clean keep threading in tap with oil on threads. If you are hitting then you need a bottom tap. It will have a flat bottom with full threads from the bottom tip up, like a big screw only having the flutes to hold the material you cut while threading the hole.

Big Dave
 
#16 ·
Dave, the boss on the intake I'm tapping is at least 1" thick and I'm at most maybe 1/3 of the way thru it. Not bottoming out for sure.

I got this bugger installed in the meantime. Clutch master cylinder. Had to remove the wiper motor and brake booster / master cylinder to make room. Also installed the pedal linkage. I'm hoping this was the worst part.
 

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#18 ·
With aluminum heads and intake and water pump your BBC weighs the same as an all cast Iron small block. So yes that engine stand will hold it up. Whether you can rotate it freely to work on it; well ... that would be questionable. Other issue is with the trangular legs and it being very top heavy (center of gravity very close to the edge of the base; well as you studied in engineering I would be very cautious pushing it around the shop). Any thing that gets stuck under a wheel and it will probably flip over (with a leg rising rapidly off the floor following an arc that could hook you if you are standing near it).

Engine stands are rated by weight (same as jacks and cranes). A good engineer always has a 50% safety factor in mind so a 630 pound BBC like you have probably needs an engine stand rated for a thousand pounds (945 pound load with safety factor). It is why I had in my shop a seven ton floor jack and a five ton engine crane (that and I liked the air over hydraulic cylinder), and all four of my engine stands had four legs rated at a thousand pounds with my favorite having a gear head to rotate the engine.

Big Dave
 
#21 ·
PCV is a thermal plastic. It isn't used on water heaters because it turns soft at 170° degrees and start st flow at 220° degrees. Coolant and engine oil exceed this temp easily.

I used to order custom plumbing from a company in Clearwater, FL that bent PCV pipe to order by immersing the pipe (capped at both ends and filled with compressed air) in a long thin tank of hot cooking oil, and then pulling it out and putting it on a wooden table with hundreds of holes in it to hold pins and cylinders of different diameters. Once bent around the rollers it was sprayed with cold water and the ends cut off. Voilà a custom bent pipe to fit a complex device we were building.
 
#22 ·
Installing the intake manifold. I have extra fasteners, which set off alarm bells. Holes 5,10,11, & 16 on the intake torque sequence diagram (see attached images) do not have matching threaded holes in the Dart Pro 1 heads. Is this normal? Thanks for any replies.
 

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#23 ·
If you had a SBC I could understand it, due to the difference between an early SBC head and the Vortec head. But that doesn't apply to a BBC. Every Dart head I have ever seen was fully machined for installation of an intake manifold.

Only difference in a BBC manifold is between a tall deck manifold and a standard height manifold (a bit more than three eighths inch difference in bolt spacings). A tall deck is too wide to fit between the heads of a standard deck height (kind of what you are experiencing).

Big Dave
 
#25 ·
For new engines, is it common to use some quantity of ATF fluid mixed with the oil?
NO

ATF is 10 weight hydraulic oil. You can run 10 weight motor oil in an engine but it will be subject to ambient air temps as it can become too thin to pump at high temperatures.

I run 10W30 high Zinc/Phosphate motor oil with GM EOS for break in and off the shelf motor oil afterwards as I run only roller lifters. If you run the cheaper to buy initially flat tappet cam then you must run high Zinc/Phosphate motor oil all of the time or risk loosing an engine.

Big Dave
 
#27 ·
I used to build my engines to look as stock as possible and put them in a non-obvious car body not associated with performance (like a late model four door Caprice taxi cab). It was a policy known as building a sleeper. I used stock valve covers even with roller rockers, only going to the tall valve covers if I ran a stud girdle (required for high RPM operation with a solid roller cam). So if the engine had a hydraulic roller I ran stock covers with my roller rockers.

Crane, Comp, Isky all sell "short" rocker arm stud polylock adjusting nuts to clear the stock valve covers. (they also make you buy tall polylock adjusting nuts for a stud girdle leaving middle height polylocks that they ship with roller rockers being useless. Drives me nuts to throw them away to buy either a taller set or a shorter set.

Big Dave
 
#28 ·
I'll be looking to have her running this weekend. What is an acceptable/typical level of exhaust back pressure just to have a reference? I'm running 2" shorty headers and Walker mufflers, which are close to stock. No catalytic converter (obviously), 2.5" pipe, and no resonators or crossovers.
 
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