496 truck motor....
 

So I have a 72 c20 that I picked up a couple months back and it's a factory 402/400 truck. The prior owner did an RV cam (flat tappet :banghead:) and its running well but I feel like I'm on borrowed time given my past experiences not to mention its just underpowered given the 6400 ft altitude. So I'm starting to get my ducks in a row to do another engine and one of my options are as I have 90% kicking around is use my old 4 bolt main mock up block(I used to build chassis) and make a 496 CI stroker with the eagle cast crank kit and either a set of 781 BBC heads or even a pair of peanut ports that have a light touch up and better valves , either way will be oval ports with a C396 intake and a small 228/236-112+4 roller cam with 10.5:1 comp and a set of 1.72 comp cast roller tip rockers. This is ment to be a strong vacuum low RPM off idle torque engine with peak from 4500-5000 rpm a stock to 1200 stall converter and headers easy driver. Being its a 100% opposite of what I normally build and I was looking for opinions and thoughts

Re: 496 truck motor....
 

A turbocharger could be a lot cheaper? Don't need a lot of boost to get back some air pressure. Just jetting the cab for the elevation should help some.

Re: 496 truck motor....
 

Well I already have a f1A94 blower on a small block in my other c10 making 790 wheel but this I want to look like a 402 that was done in 1972-73 so all vintage visually but with some torque and power. But having grown up knowing how these should feel vs they do at altitude I want more power as it's more than a jet change to get that back.

Re: 496 truck motor....
 

That's always been one of my favorite color combos since these trucks were new.

As far as engine that will get the job done that sounds like it will work for what you want. I have a Cad 500 in my 71 because I wanted torque and pulling power along with reliable freeway cruising.

What I am wondering is if a hide under the stock air cleaner fi unit would perform better than a carb at that altitude. I've been thinking of running one on my 292 with the 4 barrel intake rather than a carb although it will probably get a carb at first.

Re: 496 truck motor....
 

I think a 496 is a great idea. But I think if you use it for truck stuff like hauling, 10.5 is too much with iron heads. I’d target just at or under 10 and an aluminum head. I spent nearly $1300 on the 290 oval ports on my 427 and I bought a set of ProMaxx 290 oval ports for $1800 on a holiday sale for a 502. For $500, I wouldn’t even consider an GM head unless I could do all the assembly and machining myself.

Re: 496 truck motor....
 

The 496 would be a great motor for your truck. That was what I was going to build first but ended up building a 511. The 511 puts out 589 hp at 5200rpm and 671 tq at 4200 rpm. It runs great for a driver.


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Re: 496 truck motor....
 

^ Monster numbers! What's the story on that thermostat housing?

Re: 496 truck motor....
 

KC is a lot higher than I remember ;-)

Re: 496 truck motor....
 

Steeveedee, I was always told the radiator cap should be the highest part of the cooling system. It's so all of the air can bleed out and leave no air pockets. The housing helped me route the upper radiator hose more directly to the radiator, keeping it below the cap. I also had to trim out the hump in the hose, that's why there is a Gates heat clamp on the hose.

Re: 496 truck motor....
 

Thanks. That's an interesting thing. Does your engine sit higher than stock? The top hose on my truck runs uphill to the radiator, about 3" up from the thermostat housing to the radiator neck. It also seems to have been installed 2" too far forward, as near as I can tell.

Re: 496 truck motor....
 

Very nice C 20, looks showroom new! I believe your problem is just in the gearing. Big block c 20's automatically got the 3.54 gear set, great for generally flatter terrain, but not so great for mountainous areas. This was a common complaint when hauling heavier campers back in the day. Here was the advice: rear gear the rear end with 4.11 gears and or go to smaller diameter tires. Just not getting enough torque at low rpms.

Re: 496 truck motor....
 

I would still go with the 496. Its bore and stroke relationship is near perfect for power. Just put the right cam, heads and intake on it. You will have a fantastic engine with plenty of power.

Re: 496 truck motor....
 

No, it's an original big block truck using the original big block engine mounts. The original thermostat housing had the hose neck tilted up which made the upper radiator hose run upwards to the alternator bracket. Then the hose went down to the radiator. The rise in the hose peaked just above the filler port on the radiator. So, I used a Moroso thermostat housing to lower the hose. Then I cut the hose and reshaped it to be in line to the radiator inlet. Now the tallest part of my cooling system is the filler neck. No issues with air pockets.

Re: 496 truck motor....
 

Thank you its a killer survivor, Yes I agree with the gearing and I plan to change it to a 4.11 and keep the turbo 400 with a gear vendor (already had) to make an ultimate hauler

Re: 496 truck motor....
 

so im going to play with the dynamic compression quite a bit to get it at 8.0:1 for what im doing my big thing is I want the truck to look like it still has a 402 when im done

Re: 496 truck motor....
 

my only thing with running a FI is I want no computers in the truck the goal is simple as possible I have an MSD (hidden ) triggered by points but with a couple connection changes go back to points

Re: 496 truck motor....
 

My 72 runs the original T400 with a Gear Vendors. I changed the 3.54 gears to a 4.11 and I run a Fi Tech fuel injection. I leave the GV alone so it will auto-shift into overdrive. The Fi Tech is a simple system that you input a few numbers and itself learns from there. It starts up very easy and goes right to warmup. It will also idle up when the AC comes on.

Re: 496 truck motor....
 

Could you share some of the specs on your engine like what is the cam lift and duration? What is your compression ratio? What part # for the Edelbrock Cylinder heads?

Re: 496 truck motor....
 

The cylinder heads are Edelbrock # 60455 matched up to an Edelbrock Performer RPM Airgap Intake. Cam is a Crane Power Max Hyd Roller # HR-296-2S-12-IG which has 610 I / 632 E Lift, 296 I / 304 E Adv Duration on a 112 LS. I also use Comp Cam Roller Tip rockers so I can keep the factory valve covers. I am not entirely sure on the compression ratio. The shop that did my machine work calculated it at 11.3 but that is hard for me to believe. I would think it's more like 11.1.

Re: 496 truck motor....
 

I wondered how the Gear Vendors did its thing..... My Model-A has a Mitchell Overdrive unit that's a manually selected gear splitter. I wasn't sure how much electronics were part of the GV set-up so I guess I should look into them.

Re: 496 truck motor....
 

Awesome thank you! Do you have enough vacuum to run power brakes? I see you have a 112 LS and that probably helps.

Re: 496 truck motor....
 

Yes, the GV works great. I can manually shift it as a 6 speed or leave in auto as a 4 speed. I can run highway speeds of 65 to 70 mph at approx 2400 rpm. Then when at lower speeds it has plenty of power.

Re: 496 truck motor....
 

I have enough vacuum, brakes work well. I think because of the motors size it softens up the cam. It's not extremely aggressive like it would be in a smaller CID motor such as 396 to 454.

Re: 496 truck motor....
 

A few more remarks:

Installing a 496 or larger motor will give you more power and torque for sure. I would also suggest a fuel injection set up. I use the Fi Tech part number 3001, and it works great. Itself learns as you drive and it will auto tune as you go. So, no matter the weather or altitude it seems to stay in tune. It is also very easy to start no matter how hot or cold it is. It will control your electric fans if you have them, your fuel pump rate if you have an electric one, you're timing if you set it up and your AC idle when it is on. When I had a carb on the motor there was times you had strong gas smell which I am sure was due to it not being tuned right. Not the case with the EFI, no gas smell.

Now for the radiator hose. The stock upper hose with the stock thermostat housing seemed to place part of the hose at or slightly above the radiator cap. So I changed it to keep the hose below the cap. See picture that I got from this board.

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