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Old 05-21-2019, 09:41 PM
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Vortec head 406 build - brain storming

I just picked up an 89’ caprice police car with a tired tbi 350 but the 700r feels good. I have a 400 sbc that needs a rebuild. My buddy has some Vortec heads for sale for 100$.

I’d like to build a budget 400 with some midrange power. The car has 3.42s. I’ve read over some magazine builds . The Vortec heads are stick and need a trip to the machine shop. The machinist says he’ll do the valve job, resurface the heads, machine the spring seats for 350-400$

Premium gas here is 90 octane.

I have a 750 q jet and a 750 Holley vac secondary boat carb off a 502

I’m not dead set on using either of those carbs

I do want a peppy cruiser with some passing power. I have a seized up good wrench 454 also that might be rebuildable

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Old 05-21-2019, 09:49 PM
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Eric has some good recipes for the 400 torque monsters
probably using offshore aluminum heads not Vortecs ( a bit small for the 400 cube beast)
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Old 05-21-2019, 09:54 PM
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Pick a piston that puts the compression between 9.5-10:1. Keep your quench below .045", grab a set of long tube 1 5/8" headers and a Performer RPM, Team G, Holley 300-36 intake, a cam along the lines of an XE274, and you'll have a torque monster for a NA build that will make for plenty of tire burning smiles.
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Old 05-21-2019, 10:22 PM
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On top of what Nailhead said, don't expect to turn any RPM above 5200-5400 rpm, as the heads will become a choke by then even as good as they are. It'll rev past there, just won't be making any more power.
Make sure your machinist shortens the top of the valveguide, as that stock valveguide height is the reason stock Vortec head won't accept a cam with more than .440-.460" valve lift....the valvespring retainer crashes into the top of the guide and the valve seal unless you machine the guide shorter.

don't forget you need to put at least the lower row of steam holes in the head to match the 400 block...top row is not as needed and is up to you if you want to add them.

It'll make enough torque to really test just how good of shape your 700R4 is in.

Long tube header would be better, but a mid-length won't hurt you much if that's all that is easily available.
You can find some real good deals in stainless headers in mid length for that chassis on Ebay in the $90-120 range. Made somewhere Asia/India/China but nicely made and often better than a lot of the hooker, Hedman/Patriot/Flow-Tech basic headers....the set's I've bought have been nicely TIG welded, thicker than average American header flanges at just over 3/8" thck, and fully polished tubing.
I'm notot sure if this is the right one, I'd compare tube routing with a Hooker, Hedman or Patriot listing to see if it is in fact the same. Might be a different ad similar to this, you'll just have to do some detective work at an Caprice/Impala forum to know for sure, but here is an example:
https://www.ebay.com/itm/STAINLESS-R...sAAOSwZmJcmKxM

Just took a look at the Patriot header for this chassis shows it is the same.

Last edited by ericnova72; 05-21-2019 at 10:34 PM. Reason: more info
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Old 05-21-2019, 10:36 PM
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Awesome! Thanks for all the quick replies. I was thinking 268 or 274. I ran a xe284 in a 383 with dart aluminum pro 1 heads and a Scat rotating assembly with flat top srp pistons and a 3310 Holley. I locked the timing advance on a stock Hei with an MSD drop in coil and control module with a rev limiter. It was good for low 12s in my old s10.

I’ve built 18 dodge 47/48re and 727 trans . I have a 2wd t400 and t350 cores but I would like to keep an auto with overdrive in the car . I haven’t tried building a gm trans yet.

Would keeping the compression below 10.0 affect cam choice ? The gas in Ak is crap. Some of my buddies run around with higher compression and iron heads and they back the timing off. 100 low lead is easily available though.

Would stock rockers be fine ? What about rods ?

Would the Rochester work with the cams mentioned ? It’s in the best shape of the used 4 barrels I have in storage
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Old 05-21-2019, 10:45 PM
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Here is the car.
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Old 05-21-2019, 10:48 PM
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Here’s Another pic
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Old 05-22-2019, 12:58 AM
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Either the 268 or the 274 cam choices would be fine with a 9.5 to 10.0: 1 compression ratio.

Stock rockers would be fine if they are in serviceable shape. You asked about rods, not sure if you meant pushrods or connecting rods??

Would be better to use a better than stock pushrod with the bigger than stock cams, you can usually find welded ball end hardened pushrods in the $25-35 range easily enough. Stock are not hardened at all.

if you meant connecting rods, and are planning a rebuild of the engine that includes boring it and new pistons, then the smart move is to get an aftermarket Sportsman level connecting rod in either 5.700" or 6.000" length, and pistons to match, rather than use the short, weaker stock 5.565" long rod.

You can get your basic SCAT or Eagle entry level I-beam rod for not a whole lot more than the cost of cleaning, magnafluxing, replacing the stock rod bolts with ARP bolts, and resizing the bore of the weak stock rods. The aftermarket rod is a lot better material, already has an ARP capscrew, and it's longer length allows for a lighter piston and helps to not thrust load the cylinder wall as hard as the short rod does.

Stock crankshaft will be fine, get it polished or reground if it is needed.
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Old 05-22-2019, 10:02 AM
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Quote:
Originally Posted by ericnova72 View Post
Either the 268 or the 274 cam choices would be fine with a 9.5 to 10.0: 1 compression ratio.

Stock rockers would be fine if they are in serviceable shape. You asked about rods, not sure if you meant pushrods or connecting rods??

Would be better to use a better than stock pushrod with the bigger than stock cams, you can usually find welded ball end hardened pushrods in the $25-35 range easily enough. Stock are not hardened at all.

if you meant connecting rods, and are planning a rebuild of the engine that includes boring it and new pistons, then the smart move is to get an aftermarket Sportsman level connecting rod in either 5.700" or 6.000" length, and pistons to match, rather than use the short, weaker stock 5.565" long rod.

You can get your basic SCAT or Eagle entry level I-beam rod for not a whole lot more than the cost of cleaning, magnafluxing, replacing the stock rod bolts with ARP bolts, and resizing the bore of the weak stock rods. The aftermarket rod is a lot better material, already has an ARP capscrew, and it's longer length allows for a lighter piston and helps to not thrust load the cylinder wall as hard as the short rod does.

Stock crankshaft will be fine, get it polished or reground if it is needed.
X2

Bogie
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Old 05-22-2019, 01:06 PM
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Quote:
Originally Posted by 5.7s10 View Post
Would keeping the compression below 10.0 affect cam choice?
Camshaft intake lobe closing point and static compression ratio go hand in hand. The later you close the intake valve, the more static compression ratio the motor will tolerate because you are leaking off some compression with the later closing (the intake valve is still open, with the piston coming up the bore to compress the mixture that was just pushed into the cylinder by atmospheric pressure). Depending on the actual closing point of the intake valve, you could leak off quite a lot of compression by allowing the ascending piston to push some of the mixture back up the intake tract before the valve closes. This is the balancing act faced by everyone who has ever changed the cam in a motor.

Quote:
Originally Posted by 5.7s10 View Post
The gas in AK is crap. Some of my buddies run around with higher compression and iron heads and they back the timing off. 100 low lead is easily available though.
The generally-accepted limit using iron heads and pump gas is to build at no more than 9.5:1 static compression ratio, unless you have some really killer fuel to run. For instance, if you had E85 available to you, then iron heads and 15.0:1 on the street could work. Then it would just be a matter of how much cam and how much torque converter could I fit into the project. The one specific about your situation is that you live basically at sea level (actually 102'), where the atmospheric pressure is right at max for the planet (14.7 lbs per square inch at sea level). Since it is atmospheric pressure that loads the cylinders with air/fuel mixture, you fellows up there on the coast are getting maximum cylinder filling and therefore the biggest bang. That's why your buddies are having to back down on ignition timing (and killing power when they do).

Quote:
Originally Posted by 5.7s10 View Post
Would stock rockers be fine ?
L31's used "rail" rockers to keep the rockers centered on the valve stem tip. If you'll look at the rockers here (click on the photo for a magnified view)......
https://www.summitracing.com/parts/nal-12495490
you will see that there is a raised portion on each side of the rocker. These are the rails that keep the rocker centered on the valve stem tip. If you use these stock type of rockers, you cannot use guideplates with them because you would have two systems fighting each other and something will bend or break. Either use the stock rail rockers or use conventional rocker arms together with guideplates. If you use guideplates, you will have to mill the pedestals down on the heads to make room for the plates and also for threaded rocker studs. Pressed-in studs will begin pulling out of the heads at 260-280 pounds of valvespring force.
If you will use stock rail rockers with an aftermarket cam, you will want to pay attention to the holes where the pushrods come up through the heads from the lifters. The pushrods will need additional clearance to prevent scuffing on the heads. There is a tool, called a Louis Tool,
https://www.summitracing.com/parts/pro-66485
that is used to clearance the holes a little if, for instance, you were going from 1.5 to 1.6 ratio rockers using conventional (non-rail) rockers. There are no 1.6:1 rail rockers in the conventional stamped configuration that I am aware of. This is a good place to upgrade your heads with 7/16" threaded rocker studs, guideplates, enlarged pushrod clearance holes (with a Louis Tool or a burr in a drill motor or drill bit in a drill motor or via hand with a rat-tail file), hardened pushrods and full roller rockers such as those offered by Scorpion.

Here are two examples of the procedure to add steam holes to 350 heads so that you can use them on 400 blocks........

https://www.gregsengine.com/converti...ds-to-400.html

https://www.enginelabs.com/news/stea...-small-blocks/

You fellows also need to pay attention to the squish/quench when you are building these motors. A clearance of 0.035" to 0.045" will go a long way toward preventing detonation.

.

Last edited by techinspector1; 05-22-2019 at 01:27 PM.
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