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Old 11-02-2016, 05:13 PM   #1
SilverMiner
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Upgrading a stock 400sb

I recently acquired a small block 400 out of a 1975 truck (T0505TLS casting, presumably a 2-bolt) which was rebuilt .030 over to stock specs approximately 20K miles ago. I got to hear it run, and everything was fine. It is now sitting on the engine stand in my garage awaiting installation.

Back in the mid to late 80's I owned a 76 Blazer that had a 400 which had been given the standard 70's performance upgrade: a cam, headers, and an intake. That engine had the most snort of any squarebody I've ever owned, and I've always wanted to recreate that experience and I'm hoping to get that again by replacing the tired original miles 350 in my 1980 suburban.

I'm looking at installing either a COMP Xtreme 4x4 X4250H cam or whichever package Lunati recommends to me. I already have the Edelbrock 2101 Performer and a well tuned and rebuilt Q-Jet. Headers will probably wait, and I'll run with the stock cast iron logs initially as I've never had many good experiences with headers.

What do you think of my cam choice? Is there a better or more universally approved cam out there for a 400 small block with stock compression, cast manifolds and original heads? Later on I might entertain the idea of going with Vortec heads, but if I can achieve similar performance to what I had with my old 76 I'd be more than happy, and obviously it didn't have Vortecs (who knows what the heck it might have had).
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Old 11-02-2016, 06:19 PM   #2
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Re: Upgrading a stock 400sb

That cam would make that a toque monster, but it will run out of breath quick.. You could go a little bigger, as that is a cam that I'd run for a torquey 350. The extra 50 cubes will handle more cam, so the X4254 might be better. If you had headers, I'd say even jump to the X4262.
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Old 11-02-2016, 06:31 PM   #3
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Re: Upgrading a stock 400sb

Even without headers (which I'm not a fan of on a street vehicle) the bigger displacement of the 400 will suck the duration out of a "350 rated" camshaft. You could easily step into a 262 or (if it were me) the 268.
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Old 11-02-2016, 08:17 PM   #4
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Re: Upgrading a stock 400sb

I build a 406 about 15-16 years ago that was a torque monster. Nothing crazy bout it either. I used 350 rods, KB pistons, boot 10:1 compression. Stock rebuilt TBI heads, flow tech headers, y-pipe and single into dual muffler. I used Comp Cams Extreme Energy 268, regular hydraulic flat tappet. This was also TBI. I didn't have a tach in when I did the motor, but had it well past the 85 on the speedo with the moon gauges, think it went to 35, so guessing well over 100. It was still in 3rd, chasing down and mustang. If I ever were to build a small block it would be a 400, the same as that motor. maybe a roller cam and better heads. I can't imagine how insane a motor it would be!!!!
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Old 11-02-2016, 11:45 PM   #5
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Re: Upgrading a stock 400sb

You need to go with a bigger cam that what would normally be used in a 350. I would go with the X4262. Here is some info for you to look at.

http://www.67-72chevytrucks.com/vboa...d.php?t=612016
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Old 11-03-2016, 01:09 AM   #6
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Re: Upgrading a stock 400sb

Maybe consider some of the excellent Lunati Voodoo cams ?
The small ones are on a 112* LS and that works well with iron manifolds.

The #10120702 is very similar to the Comp X4262 , but on a 112* VS 111* lobe separation.
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Old 11-03-2016, 02:29 PM   #7
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Re: Upgrading a stock 400sb

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Maybe consider some of the excellent Lunati Voodoo cams ?
The small ones are on a 112* LS and that works well with iron manifolds.

The #10120702 is very similar to the Comp X4262 , but on a 112* VS 111* lobe separation.
Yes! I just heard back from Lunati this morning, and they recommended the following cam:

Part Number: 10120700
Previous Part Number: 60100
Advertised Duration (Int/Exh): 250/256
Duration @ .050 (Int/Exh): 207/213
Gross Valve Lift (Int/Exh): .437/.454
LSA/ICL: 112/108
Valve Lash (Int/Exh): Hyd/Hyd


Chalk it up to good marketing (TV shows, Internet, who knows where I picked it up), but I'm very inclined to select Lunati over Comp, Crane, or any others. No idea why, I just think better of them for some reason.
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Old 11-03-2016, 02:30 PM   #8
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Re: Upgrading a stock 400sb

That's a very mild cam......
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Old 11-03-2016, 03:48 PM   #9
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Re: Upgrading a stock 400sb

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That's a very mild cam......
Yup, especially for a 400. That's more like an RV style... little above stock
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Old 11-03-2016, 04:03 PM   #10
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Re: Upgrading a stock 400sb

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Originally Posted by SilverMiner View Post
Yes! I just heard back from Lunati this morning, and they recommended the following cam:

Part Number: 10120700
Previous Part Number: 60100
Advertised Duration (Int/Exh): 250/256
Duration @ .050 (Int/Exh): 207/213
Gross Valve Lift (Int/Exh): .437/.454
LSA/ICL: 112/108
Valve Lash (Int/Exh): Hyd/Hyd


Chalk it up to good marketing (TV shows, Internet, who knows where I picked it up), but I'm very inclined to select Lunati over Comp, Crane, or any others. No idea why, I just think better of them for some reason.
X's 2 on the 10120700 being a small option. I'm running the Voodoo 10120701 in my stock rebuilt 350 for 2-1/2 years now and I love that thing! Motor has a Performer intake with a Quadrajet and headers with a heavy duty 350 Turbo-Hydramatic. I use it to tow a tandem axle trailer with another LWB 72 C/10 with a big block under the hood. She pulls hard from idle right up through 5K and passes many of the loaded or towing late model 1 ton's on the interstate. I'm very impressed with the Lunati Voodoo cam in my small block!
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Old 11-03-2016, 04:06 PM   #11
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Re: Upgrading a stock 400sb

Yes, it appears to be the most basic "entry level" Voodoo that they make. I filled out their online request form but had to leave a couple of the entries somewhat vague as I didn't know what the CR might be or the exact volume of the combustion chambers other than to shrug and enter "stock". So perhaps given my vague answers they finally responded with the most conservative cam choice they had available?

I must say I'm inclined to select a Voodoo up a notch or two higher like the 10120701 or 10120702 as suggested above. What bad consequences might happen if I do?

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That's a very mild cam......
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Old 11-03-2016, 05:12 PM   #12
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Re: Upgrading a stock 400sb

Not enough compression will result sluggish bottom end, and might fight a stock convertor. But I ran a 230 duration cam in a 400, stock TH400 and convertor and was fine. Thing had 200k plus miles and it ran pretty good....only other issue was the heads were the limit on lift, and every now and then I would snap a rocker arm...so I just kept spares and a small tool kit with me. Got pretty good and changing after a while lol...
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Old 11-03-2016, 06:50 PM   #13
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Re: Upgrading a stock 400sb

For what it's worth, I just confirmed that the heads on my barn find 400sb are the original 458642 smog-era boat anchors, rebuilt with a 3-angle valve job and hardened seats.

The hot 76 with a 400 I drove back in the 80's almost certainly had the same or similar heads, so I believe I can recreate that level of performance without the expense and hassle of going Vortec. What sort of lift will these heads tolerate? Will the .454 Int and .468 Exh of the Lunati 10120701 cause problems?
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Old 11-03-2016, 08:21 PM   #14
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Re: Upgrading a stock 400sb

Coil bind can happen to any head, it's easy as changing the springs. Bang for the buck it's hard to beat vortecs. Bump compression, better flowing heads, more power!!!! I talked to someone bout the motor I was gonna build using vortecs and XE268 cam, and was told it would be around 425 horse. Now if that's true I dunno, but either way would be an awesome motor..
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Old 11-04-2016, 12:13 AM   #15
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Re: Upgrading a stock 400sb

I would step up to the 10120701 cam. Regardless you should really upgrade the springs and check for retainer to seal clearance. That is not difficult to do with the engine on a stand.
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Old 11-04-2016, 06:45 AM   #16
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Re: Upgrading a stock 400sb

Quote:
Originally Posted by SilverMiner View Post
Yes! I just heard back from Lunati this morning, and they recommended the following cam:

Part Number: 10120700
Previous Part Number: 60100
Advertised Duration (Int/Exh): 250/256
Duration @ .050 (Int/Exh): 207/213
Gross Valve Lift (Int/Exh): .437/.454
LSA/ICL: 112/108
Valve Lash (Int/Exh): Hyd/Hyd


Chalk it up to good marketing (TV shows, Internet, who knows where I picked it up), but I'm very inclined to select Lunati over Comp, Crane, or any others. No idea why, I just think better of them for some reason.
That cam has just a whisker more lift than the cam in my 400. A 400 will eat that right up. It should run just like a stock cam and run out of breath at 4500 rpm. If I was doing it again I would go a little bigger.
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Old 11-07-2016, 11:18 AM   #17
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Re: Upgrading a stock 400sb

Well, I've decided to install the Voodoo 10120701 kit with new lifters. I also wish to replace and upgrade the springs, but I'm not sure what to buy. It's a case of Summit offering TOO many options, and as an uneducated buyer I'm lost. One nice thing about the Crane and Comp kits are that they offer one complete with springs.

Is there any reason to also replace the pushrods? My existing ones appear fine, although I haven't measured them yet. But new ones seem cheap.
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Old 11-08-2016, 12:56 AM   #18
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Re: Upgrading a stock 400sb

You should use the springs recommended by Lunati. Their website doesn't seem very user friendly for fins=ding the recommended components. According to an old cataloge I have the correct springs should be #73943 and retainers #75704. The locks are #77003. You can also buy what they call a valvetrain kit, which includes everything but the cam. That is under #73943K1LUN. I would suggest contacting Lunati Tech dept to verify those numbers.

As for the pushrods. To be absolutely correct, the length should be checked once the cam, lifters, springs and retainers are installed.

Quote:
Originally Posted by SilverMiner View Post
Well, I've decided to install the Voodoo 10120701 kit with new lifters. I also wish to replace and upgrade the springs, but I'm not sure what to buy. It's a case of Summit offering TOO many options, and as an uneducated buyer I'm lost. One nice thing about the Crane and Comp kits are that they offer one complete with springs.

Is there any reason to also replace the pushrods? My existing ones appear fine, although I haven't measured them yet. But new ones seem cheap.
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Old 11-08-2016, 12:24 PM   #19
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Re: Upgrading a stock 400sb

Captainfab - thank you so much for your useful and accurate replies. I've contacted Lunati, and sure enough the part numbers you gave were spot on, and are on their way from Summit post haste.

All told this little cam project is costing more than I had originally expected what with new tools required and such, but it's the sort of thing I've wanted to tackle since I started reading Hot Rod and Four Wheeler how-to articles back in the late 70's. Now with the help of this forum and YouTube videos I'm confident I will succeed and have a rip snorting new engine in my old Suburban.
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Old 11-08-2016, 12:29 PM   #20
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Re: Upgrading a stock 400sb

I'm guessing you'll be a happy suburbanite , but please report back here to confirm these suspicions.
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Old 11-08-2016, 05:08 PM   #21
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Re: Upgrading a stock 400sb

Let me know how that cam works for you. I have been thinking about upgrading my 406 with that same one.
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Old 11-08-2016, 06:06 PM   #22
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Re: Upgrading a stock 400sb

I wonder if the cam companies have a good cam for a stock 400. It seems like everybody, me included, just grabs an off the shelf 350 cam. I hope you get that rip snortin 400 like you had before. Let us know how it goes.
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Old 11-08-2016, 06:55 PM   #23
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Re: Upgrading a stock 400sb

I will absolutely report back with my findings. I'm hesitant to set myself any deadlines, but I intend to complete the project by the end of the Thanksgiving week. There will likely be plenty of tuning involved and I'm already in contact with Cliff Ruggles to possibly re-jet the Quadrajet I'm intending to use (which came off a stock 400 engine). Lots of parts and tools are on the way from Summit, and I suspect there will be at least one more order before I'm all done.

Stay tuned, and thanks for all the help!
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Old 11-09-2016, 02:39 AM   #24
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Re: Upgrading a stock 400sb

I think you'll like the 701, they have a mild lope at low idle. Lunati provides a red syrup assembly grease but that stuff seems to run off after a bit of time. I prefer the Isky Rev Lube whenever I'm breaking in a cam & lifters, it sticks way better and is a moly based grease with plenty of zinc (ZDDP) and sulfur. http://www.speedwaymotors.com/Isky-R...4-Oz-,428.html I strongly suggest getting a 4oz can, it goes a long way and is good insurance and assurance that the cam & lifters break in properly and live. Nothing wrong with using the push rods you have but do verify the stock length works. A new set of push rods is only like $40 and again, cheap insurance. http://www.lunatipower.com/ProductGr...5&cid=24&pid=2 If your running guide plates make sure they're in good shape or replace them too. Pay close attention to the lifters instructions and get a good feel for the preload springs. Do Not presoak the new lifters in oil! Isky Rev lube on the bottoms, and that red syrup (assembly lube) on the top and sides. A new tight in the hole lifter can hydro-lock and fail to give a good preload feel or indication if its full of oil with Rev Lube blocking a hole.
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Old 05-17-2017, 12:21 PM   #25
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Re: Upgrading a stock 400sb

Finally, an update. I just recently finished installing my barn find 406sb into my 1980 Suburban and as promised I wanted to report back on my decision to install the Lunati Voodoo 10120701 cam.

Everything seems great at this point. All I've done thus far is break in the cam and then take a couple mild jaunts around my local area. No tuning to speak of yet other than setting the timing. This weekend after I've had a chance to put some miles on the block I'll install the Cliff Ruggles upgraded Quadrajet, fine tune the timing and confirm the overall timing curve. I may even complete the first 500 miles of break-in after which I'll be more confident about stuffing my foot into it. But so far I can confirm that my butt dyno tells me the new engine feels stronger, which hardly seems surprising as I am comparing it to an original 100K+ mystery miles stock 1980 350. Vacuum gauge not yet hooked up but the idle is strong and everything sounds good.

Summary - I'm glad I tackled the project even though the initial budget and time expectations were not even close to reality. Every item under the hood is new with the exception of the brake booster and the original Harrison A6 compressor. Guess I need to update my signature, too.
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