[xMLMx]

To sum up what could be a four paragraph explanation as to why I'm writing this, I'll give you the summed up version: I have a bunch of junk that I want to bolt together to get my Nova driving instead of sitting.

Long version:

I have a complete, running, relatively low-mile 400 small block at my disposal (block casting 3951511, out of an early 70's Impala) with some weirdness added in. It was plucked from a running and driving plow truck that my father scrapped; he installed the engine some 20+ years ago and daily drove the truck for 5+ years in what he thought was box-stock form. I, myself, drove the truck with this engine in it, even though it always ran half-ass.

The plan is (or, was) to take this engine, toss a little cam in it, and then plop it between the fenders of my Nova for the sake of being able to drive it around town and have some low-buck fun. I don't care that it'll be a wheezing, low-revving turd; I just want to be able to cruise it around with my family and have fun while I build the 350 the "right way" while the missus is in school (read: I have a lunch money budget, so the wild drag motor is going on a stand until I can afford good heads to make it live on pump gas). This past weekend, I decided to do some forensics on the 400 to have some data points... to which the weirdness began.

As previously stated, it's a 3951511 block, crank, rods, and pistons. Or, so it appears. The heads, though... the heads aren't the same. One is a factory 997 casting (76cc boat anchor), and the driver's side... is a 601 casting (H.0. 53cc off of a 305). I have absolutely no idea when, or where, this occurred, but like I said previously... the motor ran and putted a 3/4 ton truck down the road for years. So, at least the shortblock is usable, I hope.

Now, the proposed solution.

I have a pair of complete, refurb'd 291 heads with 2.02/1.60 valves in them ready to go (were gone through years ago and sat on a shelf). Yes, I know they suck compared to modern heads. Yes, I know the intake ports are small for the bigger-inch 400. Yes, I know I need to drill steam holes. But, they're what I have for free, and they're usable. My question is, will they work well enough to add a little life into this engine to go down the road?

I planned on robbing parts off of the 350 to get it completed (750cfm 4160, Pertronix distributor with VA, headers, Weiand single plane, and the accessories). The 350 in the car now has wild compression (read: 12.25:1 static / 9.5 dynamic) and cut heads (62cc 461's), and it genuinely needs something like a pair of 72cc aluminum heads to knock the squeeze down.

I'm not after a fire-breathing engine, I genuinely just want to put something together using nothing more than a gasket set, a dual plane intake, and maybe a small cam kit. All off the above parts are available to me, completely 100% free.

Am I ****ing crazy?

Photos for your attention.

The car.

The existing 350.

The questionable 400.

Head casting on the driver's side.

Head casting on the passenger's side.

The spare 291 heads.

 

[sbc1320]

Those little 400's run good. My buddy had a big cammed lazy 283 and was getting a 400 stock. He was blown away how much better that car ran with it. My last 511 casting was a replacement which is the two bolt. Regular 511's are 4 bolt. I have a 509 2 bolt casting on my engine stand right now for my little winter project if I get some money(lol). Good little cam and those heads you will have lots of fun and the perfect little street engine to go play.

 

[Repointer1]

Yep what he said. A 76 and 53cc head. no wonder it ran weird. Probably be pleasantly surprised with that "little" 400 and those 291's. Just don't go crazy on the cam.

Oh I have 2 of the '509' standard bore blocks in my garage. Always planned on a drag motor with one if I ever get around to it.

 

[xMLMx]

Thanks for the replies, guys. I've been peeking around to see what cams seem to be popular with similar builds, it appears that the Comp Cams CL12-600-4 is a popular front runner, along with the Lunati XXX12224; both at the cost of needing valve springs though.

Trying to grab the most cam I can for the stock valve springs that are in it, while not throwing money away is proving trying. I'm open to any suggestions.

 

[Repointer1]

https://www.summitracing.com/parts/lun-10120702/overview/


Hydraulic Flat Tappet. Mid-level performance street cam with excellent drivability. Exceptional replacement for muscle car type cams with automatic transmissions. Works well with stock type exhaust manifolds and dual plane intake with mild 4 bbl carb. This is an Awesome 4X4 and performance marine cam.

 

[hrlyrdr]

Am I ****ing crazy? You asked this question to a bunch of car guys? I say, at times, we all are. But, you are not crazy for wanting to get your car on the road. All the stuff we go through to get to ride down the road is amazing. Good luck with the engine.

 

[g2072]

The 291,461 and 462 heads were probably the best head GM came out with until the vortec head came along. The 186 heads were also along the same lines. I think unless you can put aftermarket heads on or a good set of vortec's the 291 heads should work fine. Not crazy about the camshaft but there are many that will work. For a fun engine just to sport around in I'd tighten up the lobe separation to around a 108 or maybe a 110. If I was going to put a lot of miles on it I may go 110 to 112. I'd stay mild on duration and lift but may try to find a 1.6 rocker to help make it breathe especially on the exhaust side. You can build decent HP and have a amazing sounding engine fairly cheap. If the heads have been sitting a while I'd probably check the valve seals.

 

[Squigie]

Crazy? Yes. You have to be, to play with old cars.

...But not for considering using the 400. I also have a 350 under the hood, with a 400 on the engine stand. I'm still trying to figure out how to get that 400 in the car without costing an arm and a leg. (It doesn't help that I also want boost when the 400 goes in... But that's another - and more expensive - subject.)


I agree with g2072 on the cam: Keep it tame. The 400 will make good power in stock form, and should respond well to mild upgrades. You don't need to throw a big cam, springs, or anything else at it. It may not be a good idea, anyway, since the engine isn't being rebuilt.

I think something like the classic 'RV' cam might be a good fit.
204/214 @ 0.050", 278/288 advertised, .420/.433 lift, 107/117 LSA. (MC1730)

Or, for about the maximum those heads can probably handle:
224/224 @ 0.050", 290/290 advertised, .465/.465 lift, 107/117 LSA. (MC1991 --- Just a bit meatier than the OEM 350HP L-82 grind.)

The above part numbers are Engine Pro part numbers. I don't think a name brand cam is important here, and the Engine Pro cams are half the price (or less). Besides... They make cores (and ground cams) for most of the other brands, anyway. They just ship out in a prettier box, with a more recognizable name and a higher price tag.


*For totally unrelated reasons, I have used both of the above cams and was happy with them. The 'RV' cam was particularly impressive. Torque. Torque. Torque. -From an engine that was fairly turdy and unremarkable before. There's an MC1991, lifters, lube, a gasket kit, and more actually sitting on the roof of the 4-door right now. It'll be going into the 350 in the car some time this winter...

 

[Duntov]

well, i hate to be a devils advocate but I think I'd enterntain a slightly different route.

The 350 is running now but too wild with compression? What about figuring out an economical way to run that motor with less compression, might be a lot less work and still a kick-ass motor. If I read things correctly, might be simple as a fatter set of heads.

THEN..... Use the 400 to build a nasty 377!!

 

[xMLMx]

https://www.summitracing.com/parts/lun-10120702/overview/


Hydraulic Flat Tappet. Mid-level performance street cam with excellent drivability. Exceptional replacement for muscle car type cams with automatic transmissions. Works well with stock type exhaust manifolds and dual plane intake with mild 4 bbl carb. This is an Awesome 4X4 and performance marine cam.

Oooh... I like this cam. That would be fairly easy to street with a 112 LSA, and the duration favors the fairly lazy exhaust ports the 291's enhibit. I was also looking at Comp Cams XE262H cam in very comparable specs, albeit with a slightly wider 110 LSA for a little bit more of a bumpy idle.

Am I ****ing crazy? You asked this question to a bunch of car guys? I say, at times, we all are. But, you are not crazy for wanting to get your car on the road. All the stuff we go through to get to ride down the road is amazing. Good luck with the engine.

I guess I need to remember my audience, I am among friends here. :yes:

My dad is getting a good laugh at the fact that I'm doing the same antics he was doing at the same age, kids and the house included. We'll see if I get to laying 11's on the street more, though.

The 291,461 and 462 heads were probably the best head GM came out with until the vortec head came along. The 186 heads were also along the same lines. I think unless you can put aftermarket heads on or a good set of vortec's the 291 heads should work fine. Not crazy about the camshaft but there are many that will work. For a fun engine just to sport around in I'd tighten up the lobe separation to around a 108 or maybe a 110. If I was going to put a lot of miles on it I may go 110 to 112. I'd stay mild on duration and lift but may try to find a 1.6 rocker to help make it breathe especially on the exhaust side. You can build decent HP and have a amazing sounding engine fairly cheap. If the heads have been sitting a while I'd probably check the valve seals.

Good suggestion on the LSA and the valve seals, I could measure what the valves will clear with some newer positive-sealing units for grins.

Fate has a strange way of doing things, the 291's in question have been sitting on the same shelf for some 20+ years, and I've known they were there. I have a picture somewhere of the H22 4-holer from a Honda build I did in my youth, with a 291 resting on the top of the short block. No shortage of ball busting when you're a sport compact fan in a Chevy household growing up.

Crazy? Yes. You have to be, to play with old cars.

...But not for considering using the 400. I also have a 350 under the hood, with a 400 on the engine stand. I'm still trying to figure out how to get that 400 in the car without costing an arm and a leg. (It doesn't help that I also want boost when the 400 goes in... But that's another - and more expensive - subject.)


I agree with g2072 on the cam: Keep it tame. The 400 will make good power in stock form, and should respond well to mild upgrades. You don't need to throw a big cam, springs, or anything else at it. It may not be a good idea, anyway, since the engine isn't being rebuilt.

I think something like the classic 'RV' cam might be a good fit.
204/214 @ 0.050", 278/288 advertised, .420/.433 lift, 107/117 LSA. (MC1730)

Or, for about the maximum those heads can probably handle:
224/224 @ 0.050", 290/290 advertised, .465/.465 lift, 107/117 LSA. (MC1991 --- Just a bit meatier than the OEM 350HP L-82 grind.)

The above part numbers are Engine Pro part numbers. I don't think a name brand cam is important here, and the Engine Pro cams are half the price (or less). Besides... They make cores (and ground cams) for most of the other brands, anyway. They just ship out in a prettier box, with a more recognizable name and a higher price tag.


*For totally unrelated reasons, I have used both of the above cams and was happy with them. The 'RV' cam was particularly impressive. Torque. Torque. Torque. -From an engine that was fairly turdy and unremarkable before. There's an MC1991, lifters, lube, a gasket kit, and more actually sitting on the roof of the 4-door right now. It'll be going into the 350 in the car some time this winter...

Greatly appreciate the input, as well as the suggestions! Oddly enough, I was poking around Rock Auto and saw the Engine Pro brand pop up. Glad to know you've used them with success!

well, i hate to be a devils advocate but I think I'd enterntain a slightly different route.

The 350 is running now but too wild with compression? What about figuring out an economical way to run that motor with less compression, might be a lot less work and still a kick-ass motor. If I read things correctly, might be simple as a fatter set of heads.

THEN..... Use the 400 to build a nasty 377!!

I've been beating my head against the wall for the better half of a year trying to figure out how to make the 350 safely usable on the street, but I've come up empty handed without "hacking" things. I've entertained the idea of lower compression pistons... but then I'm left with the added cost of good pistons, rings, and balancing the rotating assembly again, while still being stuck with the same camel hump heads. I've tried finding a set of affordable heads for the motor with large chambers (70cc+ in order to work; I've done the math for both dynamic and static compression), but a GOOD set of heads is still north of $800 after machine work. Aside from those things... there isn't much to be had.

All told, I'm into this project for $500 or less for the winter. I may be able to squeeze a little more out of it, but not double the budget.

The 400 is an attractive idea because it's already pump-gas friendly, and even the most affordable set of mediocre heads with small heart chambers will wake the motor up, while being able to run on 93 happily with ~9:1 static compression. This is even more attractive when you have the heads on a shelf and only need gaskets to follow through!

The cam and other parts are just things to "hot rod" the 400 a little bit more, and keep the whole shebang from sounding like a plow truck in distress. At the low cost of entry, as long as I don't go full-bozo, a little cam and some lifters will complete the combo, produce a boatload of torque for a lightweight car, and run on dog water with low stress.

 

[xMLMx]

Just as an update... I followed through and got this thing between the fenders of the car. The cam gets broken in Friday after I pick up some header plugs on my way home from work, and I couldn't be more excited.

I ended up stuffing a Comp Cams XE262 cam/lift/spring/timing set in it, doing a little port work on the 291's, drilling the steam holes, and put it all together. I scored a great deal on a Performer RPM intake manifold and decided that would be much nicer for a street-driven car.

The quench is going to be deplorable since the pistons are .042" down the hole and I had to use a .035" head gasket, but it is what it is. Should be right around 9.0:1 and run on 93 with a conservative timing curve.

Sincerely, thank you guys again for the advice along the way.