1973 Chevy 3/4 454 - 496 build + more

[RPOZ11]

1973 Chevy 3/4 454 - 496 build + more

After some thought... considering my current vehicle stock, It came to me that I needed a parts mover, tow vehicle, and completely reliable truck to finish off the rest of my stable.

Thus, my 73 is getting the once over mechanically front to back.

It's a complete #'s matching motor & transmission set-up; so once pulled, it will be sealed up and placed in the corner of the garage for safe keeping!

I will be installing a 496 stroker kit; a 4.250 scat crank, a set of scat 6.385 7/16" cap screw rods, and a set of .030 over KB Forged Pistons.

I just picked up a Gear Vendor unit for the TH400.

Will be rebuilding the rear axle last.

Now, I am looking for some comments on a set of Doug Thorley Tri-Y Headers for this BBC application.
I have a set, but I am 50-50 on keeping the stock cast iron manifolds in place for this truck.
Does anyone have any pros or cons on fit, installations, any adjustments to factory parts surrounding these headers????

I am also considering searching out someone who is making aluminum reproduction radiators. I thought I had seen someone somwhere who was offering these with original appearing GM style Harrison side tanks.

Also, with the Gear Vendor install, anyone have any suggestions regarding these????

I will post as progress comes along...

Thanx guys!

[1Ton]

I say use headers let that heart pump!!

[RPOZ11]

I like it.

I am concerned about the fit of those, and maybe alt/PS/A-C bracket issues and as well maybe the clearancing of the sgifter linkage for a column shift automatic.

[RPOZ11]

Well, I received part of my Gear Vendor today.

The Adapter casting wasn't machined enough to my liking so I am going down to my friend's machine shop to Jig & square this thing up, check it all out, and do some minor fixes to the machining flaws that exist as received.

I'll post our results as they come in.

If this process works out, I could effectively have yours repaired if you so choose to use this brand.

[RPOZ11]

Gear Vendor Unit :

[RPOZ11]

Got the Heads back today from the cylinder head shop.

These are 781 heads, 2.19 / 1.88 valves, Hard Seats, New Guides, Valves, Seals, everything new!

Gotta get the bottom end balanced next!

[RPOZ11]

Radiator dimensions for a 454 Radiator in a 1973 :

What is the General consensus of this dimension???



I think I have mine measured at :
21-1/2" Tall pad mount to pad mount where the side tank are soldered on.

28-1/2" Wide from the inside Tank to Tank measurement where the CORE ends at the Tanks.

[RPOZ11]

Ive gone back and forth on using the Aluminum Radiators.

My choice for now is to try the Brass Harrison Unit, re-core it keeping the original Tanks, and testing it out for results before I move on the Aluminum one.

[RPOZ11]

Originally Posted by 1Ton

I say use headers let that heart pump!!

OK, well I picked another set of the BBC Thorley Smog Tri-Y's.
They were in Excellent shape and a great price.

Now, I left these with my friend and we are going to massage these out to flow even more than they are staright from Thorley, as they made them.

Should be 2 weeks before I get them back.

I will post up what we did to them then!

[RPOZ11]

Also picked up a 3:21.1 14-Bolt rear axle.

I think I have finally found my freeway flyer gears!

Got this axle drum to drum.

I am very lucky to find this gear set!

[RPOZ11]

Time sometimes I think is against me.

I spend more than time that I have available.

Here is the Block in the Prep stage work:



The 4.250 Crank after being fixed and Balanced!
This was a Brand New out of the Box crankshaft and it desperately needed Mallory to fix it!
At least it's Balanced now!





Still waiting to do the Exhaust system.

Should be taking the Truck in at the end of this month for this to be made and installed.

[67shortie]

Great build

I am doing the same thing to my Chevelle soon, buying SCAT parts as well. I wonder why that crank took so much mallory to get balanced? Is that a externally ballanced crank that you wanted internally ballanced?

Looking good

[RPOZ11]

I purchased this as advertised: an external balanced 4.250 SCAT cast crank.

I bought a brand new Damper and Flex Plate.

It must be in the casting process where the weight isnt close across the crank.

The finish machine work on the journals from SCAT all checked in correct so it has to be prior to this process where the problem is.

The H-Rods didnt weigh too much more than the I-Beam rods so it still ended up on the crank side.

When it was spun, he told us it was like this crank was trying to jump off of the machine.

Being this is for a street and tow use application i didnt see the need to go with the internally balanced crank.

However, I have twice the money into this crank now after fixinig it that makes me believe I should have bought a billet piece or a more precision crank for the same money.

It is what is.
It's fixed now and I can move on to the assembly.

[77BBGMC]

I'm going to be building a stroked BBC as well. I have the block and a good set of 781 heads, now I'm in the process of saving some $$ for the build. Out of curiosity what cam are you going with?

[retro69]

That is the first I have ever heard of a SCAT crank being bad, I have heard of some eagles being off a little. I am in the process of having a 496 built buy local performance shop that dynos. The owner says he only uses SCAT and swears by them. I choose the 049 heads for my build. I am curious about the gear vender setup and install. If you post gotchas on the setup it would be nice.

[RPOZ11]

"Out of curiosity what cam are you going with? "

I was relying on my motor guy on this more than my choosing one.

I typically stay around 500" to 520" on lift.

I will share a small suggestion of his thoughts ...

"we want to reduce a small bit of cylinder pressure from idle, so adding a little bit more duration should slow down any detonation and or pinging."

He is very High on using the EGR valve system to help with the same issues as well as our current gas available here in California.

With sooo much torque, he wants this motor to work inside the available octanes we use as well as the California gas additives incorporated into our gas.

Slowing down the temperatures off of idle.

[RPOZ11]

Originally Posted by retro69

That is the first I have ever heard of a SCAT crank being bad, I have heard of some eagles being off a little. I am in the process of having a 496 built buy local performance shop that dynos. The owner says he only uses SCAT and swears by them. I choose the 049 heads for my build. I am curious about the gear vender setup and install. If you post gotchas on the setup it would be nice.

I cant explain the issues with this crank other than it must be in the casting processes that this crank was run in.

Does SCAT spin these prior to packaging to determine the bulk of cranks from a "said" casting pour to determine consistencies/irregularities???

I dont know.

This is how it was straight out of the sealed box we opened from SCAT.

The results are what you see in the Mallory installed to Balance this thing back to a usable piece.

049 HEADS

I really wanted to use my set of 049 heads that I have here.

Being this is just a tow motor and my 1st 496 build, I had these 781 Heads laying around and these 781 Heads are nearly identical to the 049 ones.

Beings that I was going to do the work to them that I intended to, whether 049 or 781, they werent stock castings amymore once the port work, bigger valves installed, and seats as well, even the backside of the valve area cast-iron was massaged.

They arent stock in comparison anymore once all this work was done.

So I saved my 049's and used the 781's in this build.

GV set-up

Ill post them as soon as we start this part of it.

I have a brand new wiring harness, adapter, and a rebuilt unit as seen above.

Gotta build this exhaust system and factor in the GV added length for adding the X-OVER pipe.

The Doug Thorley Tri-Y Headers were cut and we added a larger 2-1/2 Collector to get this to breathe more.

It takes so long to do this right the first time.

Sorry for the long timeline.

[RPOZ11]

Also, I posted a wanted ad but havent gotten any results so I am going to add it to my build thread here in hopes someone might have what I need here:

http://67-72chevytrucks.com/vboard/c...ct=3767&cat=19


I need the Bracket and a correct GM used working EGR unit for my 73 Chevy truck.
looks like the one in this picture below:



OR, If you have the very same intake with the EGR that I need as shown, PM me as I might take it.

[turbo350]

You have a great looking truck! As far as headers go they win hands down for exhaust flow but also depends on what kind of sound you want. With a full exhaust and some nice say, hemi turbo mufflers, your truck will have a nice powerful sound but not obnoxious. I recall reading an article in Car Craft several years ago where they did a test with some hogged out exhaust manifolds and ran them against some headers. The headers had better flow but not by much in that contest. The cost of getting manifolds to flow better may be more than most guys would care to spend considering you get better results in general from headers right out of the box.

Good luck with your build!

[RPOZ11]

I have picked up 2 extra sets of smog manifolds; and both sets have the cast iron webbing between the exhaust ports where they bolt onto the heads.

Good core candidates for what you are suggesting.

I thought of sending a set out to do this process to them, but since I already have the Thorleys and that they are already cut up and changed at the collector, I decided to give the headers a shot first.

I am still very interested in massaging out a set of the stock manifolds!

Maybe on my LongHorn, when I do this same 496 swap install, I will try it on that build.

[RPOZ11]

Here are 3 simple shots of the Thorley Tri-Y's being increased to 3" collectors.

I am going to have these "Jet Hot" type coated to look new again.

Looking at a 3" or a 2-1/2" pipe system with either an H or an X system incorporated into it.

Small steps.

[munger]

what are your r's with that 3.21 rear end

[RPOZ11]

Gas mileage???

I havent installed all of this yet.

That will happen in February as I need to complete the exhaust system first before we R&R the drivetrain.

If you want a guess on the final ratio with 4'th engaged, with a set of 3:21's, I will take a guess at somewheres around 2:50 as a final.

Its only a guess.

I plan on driving this more than towing but the cubic inches will make up for the weight pull and I can flip in and out of the GV as needed.

[munger]

no before you did anything to it

[RPOZ11]

Originally Posted by munger

no before you did anything to it

Could you be more specific in your request?

The truck is a Factory 454 motor, TH400; Factory gears intalled by GM are 3:73's.

All this is to increase my towing capabilities, find more power within what I am using, and seek to obtain Maximum gas mileage.

Trying to take advantage of the extra cubic inches, sorta borrow from that bottom end torque, and create an efficient running combination.