Sbc 400

Hi, im gonna drop a 400 in my pickup, and i was wondering if anyone knows how safe it is to bore it .040 over, because i want it to be a 409. thanks

Hi, im gonna drop a 400 in my pickup, and i was wondering if anyone knows how safe it is to bore it .040 over, because i want it to be a 409. thanks
Welcome to AF. Any automotive machine shop can tell you if that is safe on that block, but you may not be able to get 40 over pistons and rings, better check that first.

i have already found 40 over pistons and rings, but i have also found 60 over and have heard that those are not safe. i do not know of any automotive machine shops in my area, and the machine shop i work at doesnt do automotive stuff.

i have already found 40 over pistons and rings, but i have also found 60 over and have heard that those are not safe. i do not know of any automotive machine shops in my area, and the machine shop i work at doesnt do automotive stuff.
Ok, someone has to bore and hone it for you, again any auto machine shop has the info you need. This is a thin wall cast block so be careful.

Ok, someone has to bore and hone it for you, again any auto machine shop has the info you need. This is a thin wall cast block so be careful.
Going off that reccomendation by maxwedge, if the machine shop says it's all right to bore it , Be sure to upgrade your cooling system. Since the walls are already thin, boring will make them thinner. If possible, install a 4 core radiator in the vehicle and use a higher performance cooling fan to draw more air through the radiator. I took a 1970 Chevy sb 400 and bored it out .030 (406 cu.in.) and first put it in a 1976 Monte Carlo. then a 1978 Monte Carlo, and then finally putting it in a 1964 Bel Air. Each vehicle I installed it in had a 4 core radiator put in along with a high performance cooling fan (which stayed with the engine and fit each vehicle it was in without any problems or modifications.) Make sure the machine shop also properly cleans the block including the coolant passages.

I have to agree w/everyone's replies.
All of my project cars have been built w/s.b.400s. I have built them 0.030 over and 0.040 over. I have seen others that were 0.060 and didn't have any problems. My brother had his 0.060 over and ran a 150 shot of nitrous. The bad thing was that the machine shop screwed up and bored it too big. You could hear the pistons rattling when the engine was cold, after a few hard stomps on the gas, the pistons would heat up and the engine would get quiet (freaky). I guess instead of 0.60 over, it was more like 0.062.
Come to find out that the cheepie tach he had wasn't calibrated correctly. After he upgraded to a better tach, he realized that the shift points were set at 6500 rpms instead of 5500, and that was w/stock (short) rods.

If it was mine, I would keep it 0.040 over just to leave some extra meat in the cylinders. When you find a machine shop, make sure they can hone it with torque plates.
What heads/cam/intake do plan to use?

I have a 406 in an 80 elcamino running the stock 3 row radiator and have had no problems keeping it cool. A 4 row isnt always better. Had a 75 caprice with factory 454 that had a 3 row in it and not one problem. Also if you are running forged pistons they run more clearence and will rattle until hot. Building a 396 and 427 that will have .0045 piston clearence so I expect some noise just like they came from the factory.

The forged pistons in my 406 are quiet when cold. I never had any probs w/all the other engines that I have built over the years. The ones that are noisy usually come from less dependable shops. I think it just depends on how good the man is that's working the machines.

Thanks for all the input. i was looking at trick flow heads, and the edlebrock performer TBI intake, with a Holley throttle body. i havent figured out a cam yet, but i am going for torque over HP, as it is going in a 1992 k1500. i want to keep the stock computer and everything, but get a chip burned so it will work with the new engine. everyone says im an idiot for not goin to carb, but this is an experiment that i want to try. any input is welcome, good or bad. thanks a lot.

Tommy

It's amazing how much torque a mild 406 can produce. I had one in an 84 Monte Carlo years ago. It was an every day driver and frequently made long-haul highway trips. I had the
primaries jetted down for mileage, which produced almost 20mpg running a 700R4 and 3.42 gears. Anything over 82mph, and the secondaries would start to crack open. then I could almost watch the gas gauge fall. The first time I hit the mountains (more like big hills) in the TX hill country, I realized how good the combination worked. It could effortlessly pull steep grades in 4th gear with the torque converter locked in. It really had good low-end grunt, even with the Victor Jr. It was no slouch in 1/4 mile either. 1st gear was useless w/o good traction, all my friends seemed to like it.

The 90s Chevy 3/4 ton trucks w/the 454 used a throttle body that was bigger than the ones on the 1/2 ton 4.3/5.7. You need to check and see if the Holley unit is the same c.f.m. as what you now have or if it's the bigger design. I have used the Performer TBIs on stock trucks and they seem to work fine, but I can't recall if the throttle inlets were of stock size or not. No sense in buying a Holley unit if it's not any bigger than the stock one.
I installed an Edelbrock intake manifold on a TBI Camaro. I made an adapter plate to mount a big holley throttle unit to the Performer RPM intake. It looked good and ran great.

Keep the compression to around 9 to 1. I know people talk about having 10:1 w/the use of aluminum heads, but that is border line between pump gas and race fuel. If you plan on using regular unleaded/unlead+, then go mild on the compression. I low-balled my Monte, it had dish pistons and 82cc heads. I never did the math, but I figured it was close to 8:1. It never pinged, rattled or had a hard time cranking.
If you have flat top pistons, you will need big chambered heads. I'm sure the Trick Flows have small chambers (68 to 72c.c.s ?) so call around and see what's available. Don't go wild on big intake runners either. If you want torque, then mild runners will make more torque than wild runners will. With mild runners and medium compression, you need to pick a mild cam. Competition Cams makes really good quality stuff, I have a 292H cam in my Biscayne's 406 but it's too radical for a mild combo. I have used 268H cams in farm trucks w/good results. W/bigger cubes, you can go bigger on everything else w/o bad results. A 272H or a 280H cam would probably work nicely and not interfefe w/the ecm.
A chip? See if they offer one that is programmed for an egr delete and 160* thermostat (that's what I have in my Vette, and I like the cooler temps).
Oh yeah, if you get heads that are assembled, don't get dual springs. See what the cam calls for and get what's recomended. Dual springs are for big roller cams, a small flat tappet cam needs 100lb+/- single springs.

Something else that makes a difference is rod length. Using the shorter 400 rod will actually bring peak power output lower in the rpm range, compared to the longer 350 rod. The short rod makes the piston come off of t.d.c. faster, giving the cylinder a faster (deeper) breath. The 350 rod slows down piston acceleration (less side-loading), moves the power/torque range higher in rpm range and is intended for high rpm.
If you have any questions or need any tips, just ask. It's more than just bolting pieces together.


Good luck.

thanks. would it be a terrible idea to use mildly worked 882 heads until i can afford nicer ones? The holley TBI is 670 CFM, and stock is 420, so it is a vast improvement. i was thinkin about gettin an intake for a carb and making an adapter/spacer at work to bolt up the TBI. the edlebrock TBI intake is about double the price of the same intake for a carb.

thanks. would it be a terrible idea to use mildly worked 882 heads until i can afford nicer ones? The holley TBI is 670 CFM, and stock is 420, so it is a vast improvement. i was thinkin about gettin an intake for a carb and making an adapter/spacer at work to bolt up the TBI. the edlebrock TBI intake is about double the price of the same intake for a carb.

If you keep in mind that the 882s were a stock, smog-type head with 76cc chambers and fairly restrictive intake runners, they should be ok in the short time. There's nothing wrong with 76cc heads on a 400, as long as you have flat top pistons (if you want it to make power). 70cc '993' heads would be better if you can find them (they were stock on some older 400s). These have a better intake runner arrangement and can be made to accept 2.02 valves just fine.

One other thing to keep in mind is that a TBI intake is going to have different angles for the four bolts in the middle than what the 882 heads have.

Your thoughts are in the right direction. If you plan on upgrading to better heads later on, then build it w/the better heads now. There's no use building it twice.
The 882 heads? Big chambers make for lower compression and would work good w/flat tops (like what Silicon stated). I still have parts from my Monte's 406, including the 882 heads. I spent many hours w/a die grinder getting the ports/runners opened up to perfection. I used a valve seat cutter and widened the seats to accept 2.02/1.6 valves. I was cautious not to take out too much material in the bowls (in fear of punching a water jacket) but camparing these to some modded camel-humps that I've seen, I'd say that mine looked better. I had a holley 850, Victor Jr., 1 5/8" headers (should have used 1 3/4") and a Comp Cams 280H. For "crappy" 882 heads, it ran really strong. Better heads would have been nice, but for the price, my reworked swap-meet heads saved me a bunch of money.
Good idea on the carb'd intake. I did the adapter trick and it worked great, and to save money over the TBI Performer, why not.

What rods do you plan to use?

i was thinkin about 5.7s, just because they are easier fo me to get, but if i could find some good stock length ones id rather do that.

Actually, the discussion about rod length is backwards. The longer the rod, the better. Rod/stroke ratio is an important parameter for longevity. The 5.7 rod is the best "compromise". 6" rods are better, yet. A rod/stroke ratio between 1.6 and 1.8 is optimum. 5.565" rod yields a R/S of 1.48. A 5.7" rod gives 1.52:1, which is outside the "envelope". A 6" rod yields a R/S of 1.6. All the "best" rotating kits use 6" rods.

The longer rod will "dwell" longer at TDC and BDC. This allows for higher cyliner pressure on "fire", and a better intake charge, as it "fills" better when the piston is at BDC a bit longer (a degree or two).

The best aspect of a longer rod is less rod "angle" (in relation to the crank pin at full "swing") is the reduction of thrust on the side of the cylinder wall.

An engine with shorter rods will tend to catch revs quicker, but the torque curve average will be lower.

FWIW

Jim

Everything Jim said is basically what I said. So how can what I said be all backwards?

The "average" mechanic doesn't realize that choosing rod length is as inportant as picking the proper cam and header size. The main considering factor on how the engine should be built, is how it will be run.
Be careful when purchasing stock 350 rods. The back sides of the rod bolts will hit 2 or 3 of the lobes on the cam, when using a 400 crank w/stock 350 rods/bolts. It depends on cam timing and lobe size, but parts will iterfere. There are special rod bolts on the market to solve that problem, or the rods can be modified and shorter bolts used. In extremely radical combos, custom small base-circle cams are needed.

There has been no talk about clearancing the block.
Reliefs are cut into the sides of the block for rod bolt clearance. You need to decide if that is something you can do or the machine shop will have to.
Oil pumps too. If you want to nit-pick, even oil pumps make a difference. The correct pump can free-up a few extra horses.
Plug the oil drain-back holes ablove the cam. Drill a small hole into the oil galley behind the cam gear to lube the thrust plate. Tap and plug the big coolant holes in the deck surface. Drill steam holes (at the needed angle) in the heads needed for the 400 block (and using the special gaskets). Plug the small coolant hole under the right side water pump port. Etc, etc,... It's more than just bolting aprts together, it's the little tricks that make the difference.

Why are you blocking off the thermostat bypass hole? Fine for a race motor that only uses a coolant restrictor but not for a street engine with a thermostat.

If you keep in mind that the 882s were a stock, smog-type head with 76cc chambers and fairly restrictive intake runners, they should be ok in the short time. There's nothing wrong with 76cc heads on a 400, as long as you have flat top pistons (if you want it to make power). 70cc '993' heads would be better if you can find them (they were stock on some older 400s). These have a better intake runner arrangement and can be made to accept 2.02 valves just fine.

Wow. I don't think I've ever read the terms "'993 heads" and "better" in the same context. :D "Better" is a very relative term here. If we're talking about wheel chocks or mud anchors, that might apply

That being said, I've also ported and refit 2.02/1.60s in '993 castings - Screwed studs, guide plates, bowl porting and blending - The whole nine yards. They still don't flow worth a damn, but they are certainly "better" than what they were (I think I even still have those lying around somewhere, since I'd feel bad about giving them to anyone except for the aforementioned uses). They are probably "better" than some of the other possible smog-dog castings used by The General. Still, there are probably far better choices just sitting in junk yards waiting to be unbolted. '083s come to mind first, but the tighter 64cc chambers might boost the larger bore to more compression than you might be prepared to use. BTW - The 3998993s I had started out as 75cc chambers and finished up just over 73 after fitting the larger valves (a little shallow on the seat grind for better rocker geometry).

Since there's so many manufacturers of aluminum heads, prices have really become affordable for the back yard builder. Wasn't this thread intended for an "average" torque engine.
I surely wouldn't waste the time and effort to mod a junk set of cast iron heads any more. It's so much easier just to bolt on a set of AFRs.

Thermostat bypass?????

Texas,

Not to stir it up, but your advice is what is backwards. And what we said is not the same. The longer the rod, the better. If that means a little more effort to make clearance, so be it. It may be easier and more convenient to use the short rod, but it will not improve the engine in necessary areas. Consider, the LAST reason to use ANY part in a performance applicatioin is ease or convenience. We don't build them for ease of maintainence when we're looking for horsepower and/or longevity.

There are several good reasons for using iron heads, too. Heat-sink is one. An iron head, in the average engine, will provide more efficient use of fuel, provided the octane required to support the compression ratio is maintained.

I'm of the opinion, if you WANT aluminum heads, go for the gusto. That is, get Darts or Edelbrocks. AFR heads are alminum, and they work. Darts and E-heads, IMO, are far superior in design and in manufacture. And yes, they do cost more... Again, you get what you pay for.

993 heads are fine for a mild build. They're VERY popular among the circle track crowd, where large chambers and stock valves/ports are required. It, along with 441, 997, 336 and 487 are good heads.

There shouldn't be any "clearancing" in a 400 block as there is in a 350 when building a "383". The rod bolt-to-cam issue does exist, as Texas has pointed out. We use Eagle H-beam rods for most of those, which are "relieved" at the top of the bolt for that purpose. When using stock rods, we simply grind off part of the rod and bolt head. I know, it sounds scary, but we've never had a problem in twenty-plus years of building some stout 400 small blocks.

Jim

I have never seen a clash in advice turn into an argument. Can't you just post your advice along w/the others? Making a point on who's correct or not isn't cool at all.
I know clearancing a 400 is not needed, I was confused on an earlier 383 post. Yes, a longer rod lessens the side-loading on piston and is better for a high rpm engine. Is a longer rod better? Yes and no, it depends on the application. If the car will be raced and run hard, a long rod is better. With all things being equal, it'll produce power higher in the rpm range (as I stated before and you confirmed that). A stock length rod 400 will make the power/torque sooner, yet very capable of turning safe rpms in the 5K/5500 range. Long rod/short rod, big cam/mild cam, big runners/mild runners, aluminum heads/cast heads, etc,... IT ALL DEPENDS ON WHAT IT WILL BE USED FOR.

This original thread was meant for a stock-ish torque engine for a semi-stock Chevy truck. A stock-length 400 would work great. Good power, great torque and lower rpm levels (stock axle ratio, stock converter, stock tranny???). There is nothing wrong w/an all stock 400 w/a mildly modded set of heads and a decent cam. We're not talking about building a circle track car here. It would be a whole different combo where long rods and more attention to detail is needed. This is more for pulling hills (locked up in over drive) and towing a trailer.

I too have 20+ years in building small block 400s, as well as all forms of custom fabrication, auto/manual tranny rebuilding, turbo/blower/nitrous systems, efi tuning, paint/body work,etc... So don't come off in public making out like I'm some kind of idiot. I don't need crap from peeps like you. I take time out of my day to sit here and give good honest advice to those in who ask for it.
Send me a P.M. if you want to argue.

Thanks for all the advice. i've been lookin at GMPP vortec heads in summit and the price is right, so can anyone tell me how they would perform on the 400/409? its a mild street engine, not an all out racer, so edelbrocks and so on seem like overkill for me. Thanks a lot,
Tommy

You need to call Summit's tech department and verify 2 things.
Make sure they are compatable on a sb400. A 400 head gasket seals a bigger bore than a 350, you need to make sure that there aren't any water jackets that will interfere w/gasket sealing.
The heads will have to be drilled for steam holes. Ask if these castings will allow for them.

i bet the comp cams xtreme energy 274 cam would kick serious ass in this combo, especially if you dont want to rev it over 5500 or 6000

Summit says that the heads can be drilled for steam holes, but can anyone tell me how well the vortec design will work with the 400/409? im not lookin for much over .475 lift. thanks, Tommy

Wow. I don't think I've ever read the terms "'993 heads" and "better" in the same context. :D "Better" is a very relative term here. If we're talking about wheel chocks or mud anchors, that might apply

That being said, I've also ported and refit 2.02/1.60s in '993 castings - Screwed studs, guide plates, bowl porting and blending - The whole nine yards. They still don't flow worth a damn, but they are certainly "better" than what they were (I think I even still have those lying around somewhere, since I'd feel bad about giving them to anyone except for the aforementioned uses). They are probably "better" than some of the other possible smog-dog castings used by The General. Still, there are probably far better choices just sitting in junk yards waiting to be unbolted. '083s come to mind first, but the tighter 64cc chambers might boost the larger bore to more compression than you might be prepared to use. BTW - The 3998993s I had started out as 75cc chambers and finished up just over 73 after fitting the larger valves (a little shallow on the seat grind for better rocker geometry).

Never mind ... the heads I had were 3973493 not 993 ... I stand corrected!

It's been 18 years since i had them. They were off of a 1971 400.

I have a Comp Cams 292H in my Biscayne's 406. It has an impressive idle, yet not too rough.
Beware that most stock 400 heads (I don't know the casting #s) are prone to cracking.

Thanks for all the advice. i really appreciate it. i've got the 400 sittin in the garage, but im going to have to hold off for a while because i've got to pay for school and so on. after im done with school i'll have a lot more money to play with, and i can afford some decent stuff.
Thanks a lot, Tommy

Good luck in school.
Post an update when you get back on the wrenching.

Does anyone have any experience with the Holley systemax II kit? (heads, intake, cam, timing set, bolts, and so on) it looks like a steal and it would be a lot easier than piecing things together. thanks.

Yes, it looks like a good package. The cam specs are decent and the package is designed for good torque. It's based on a 350 engine, so on a 400 the torque would be even better. Don't go any smaller than a 750 double pumper.
I have always prefered Holley 850 and Victor Jr. combos. The dual plane intake would be good for a truck application.

okay, thanks. the stock rotating assembly looks good on first inspection. as long as it is in good shape would it be okay to reuse with the holley kit, and if so what are its limits? i found an Eagle ESP assembly that ive heard is not bad, but if i dont have to spend the money id rather not. it is not going to be a race motor, after all