Sbc 400

[kress1500]

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

[maxwedge]

Originally Posted by kress1500

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.

[kress1500]

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.

[maxwedge]

Originally Posted by kress1500

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.

['97ventureowner]

Originally Posted by maxwedge

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.

[TEXAS-HOTROD]

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?

[406Elcamino]

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.

[TEXAS-HOTROD]

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.

[kress1500]

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

[TEXAS-HOTROD]

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.

[kress1500]

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.

[silicon212]

Originally Posted by kress1500

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.

[TEXAS-HOTROD]

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?

[kress1500]

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.

[MrPbody]

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