Need help on 400sbc

[HAceT]

Ok it seems that I will be getting a good 400 on Monday that was running. I plan to do a compression check and see if it is still ok or if it may need boring. If it is ok I'd like to step up the cam a little but don't know what I need to go to. Maybe a RV type. I have the Airgap intake with the 750 edlebrock sitting in the back just waiting to be used. If I do use it is there some concerns I need to be aware of. The 400 is a new beast to me and all the reading and research I've been doing is making me have alot of questions about my build. I read about cam clearance issues and other stuff. I'd just like to have a good running motor with lots of tq. I have not removed the 327 yet and don't plan on getting into it till some time later if the 400 works out.

 

[one finger john]

I think that if you say "and the engine is a 400 in. sbc" every time you order anything for it you will be o.k. Also, "are you sure this is for a 400 in. small block chevy?" And "you know this is not a 350 sbc but a 400 sbc, there is a difference" will keep things clear. Also knowing what the 400 came out of will help. Get reduced base circle cams (you can run a larger cam because of the increase in cubic inches), you don't have to notch the block for rod nut clearance(but watch out for rod nut to cam clearance), run 400 balancer & flywheel, use 400 head gaskets w/steam holes, make sure the heads are drilled for steam holes, mix well, shaken, not stirred and run it like a big block. You'll be fine. Oh, also flat tappet cams require extra zinc, always. ( I think thats right, temporary CRS set in )

John

 

[Northstar T]

You can run just about any streetable cam profile you want in the 400 without any "clearance issues". keep in mind however that the cam that was just right in a 283 or 327 may be a bit of a dog in the 400. the more CI you have, the bigger the cam profile you'll need to keep it fed. I have a 377 (400 block and 350 crank) in another car, and have run the Edelbrock preformer RPM cam as well as the Comp Cams HE272. neither one was overly lumpy in it, but the next cam I use will be a roller lifter unit as the HE is starting to go soft on me even with the Z additive.
also bear in mind that the 400 crank has odd balance needs and will require the correct ballincer and flywheel to keep it (and you) happily humming along.

Cheers,
Russ

 

[Hotrod46]

The short 400 rods have recessed rod bolt heads and are not as likely to have cam clearance issues. This usually happens when using regular 5.7" small block rods in a 383 or 400.

+1 on the roller cam. The extra money up front could save you big down he road.

As I mentioned on your original post, watch the compression ratio if you swap heads. It can get pretty high with most SBC heads on a 400. You will normally need "dished" pistons to keep it down to streetable numbers.

Mike

 

[stroker]

I ran a Comp Cam 280H in a 406 SBC in a 35 Ford some years ago. Had a great idle and gobs of low end.

 

[Wild Mango]

I ran a Comp Cam 280H in a 406 SBC in a 35 Ford some years ago. Had a great idle and gobs of low end.

The 4 1/8" SBC 400CI is one very fine splendid engine. And the Comp 280 is a great cam. As One Finger says, big engine will carry a lot of cam and still be docile enough down low. Use the recommended valve springs and put serious, serious thought into running a stud girdle and roller tips, I will go for a stud girdle ahead of screw in studs every time with springs moderate like for the 280 Magnum cam. The roller tips are great but they allow the studs to flex which plays merry hell with the valve timing.If you do have to bore your engine put a lot of thought into fitting 6" rods and appropriate pistons (I use the KB Hypers)which frees up HP through easing piston/wall friction. Getting the rotating assembly dynamic balanced with these engines is a MUST. Big engine means big breathing and you really need big valve heads with big 200CC and more intake runners. 400HP with the same amount of torque (and more)is easy peasey with a 400 and still have a decent idle and low down sheer rubber burning grunt. ENJOY, ENJOY !!!!!!!

 

[Screaming Metal]

I'm with Mango, the 400 is a good motor. I wish a had a 10$ bill for everyone I setup.

On the cam clearence issues, you shouldn't have any UNLESS your running a BIG stroker setup, OR unless yur running BME alum. rods or Carillo's. If you do run those....I usually check everything with a 'Stroker Mimic', a setup where you check clearence, to make sure things are clearenced enough. If you gotta notch your oilpan rails and bottom of the cylinder webbing, you then might have to run a small base circle cam.

On the Outlaw dirt motors, the alum. rods run in those you gotta watch your cam clearence. Whoever is doing your motor, if they're a experienced shop, tell them of your concern and should be able to set you at ease.

There are so many crank/rod/block combos out there these days, unless we know exactly what your gonna run and the part #'s, its hard to tell without checking. As with cams, everything over a certain lift needs to have the spring checked for coil bind and valve guide issues.

Stroke beyond a certain range and a big aftermarket rod or a rod of non-stock dimensions for a given motor, clearences are of major concern. I have seen many a motor wrecked because of this not being checked. I always doublecheck everything....

 

[Screaming Metal]

Let me also say that I like running the smaller basecircles on the cams, I also go for smaller journals on the cranl also. I do this to lower the surface speed on the bearings, the crank and on the lifters. Slower speed means less heat, less heat means oils stay thicker provodong better cushoning on the crank/bearings/lifters. And all that adds up to less wear and less metal being shed off into the motors oiling system.

I an so anal that anytime I can get away with it, I run a oil accumulator setup. Whena motor is shut dow/turned off, the slick surface of the crank is sitting static in your bearings, with a accum.setup, you store s few quarts of your pressurized motor oil into a tank, so all you gotta do is flip the valve open to prelube your motor before starting. This extends your bearings life.

 

[Screaming Metal]

The Extra cubic inches will help ya. More power before you start to hop it up. Be doubly sure that your balancing is correct with the 400.

If you do have to run your 327 or 350 flywheel, go to Goodsons and get the weight that attaches to the rear of your crank. That way you will be withen stock bal. specs.

If your gonna build it at all, get your assembly balanced, send everything, I mean everything, down to the last nut and bolt. PAW, and SCAT have some good stuff if you want or need to tweek your motor.

While its not totally necessary, it is ofter desireable to do this, I've seen the weekend enginebuilder substitute a part that needs to have itself included in the balancing scheme-of-things, only to have a rod or a crank break later.

The 400's are a good motor if you put them together right. Thers alot of rebuild info out there alot of info in the books.

 

[ellis8500]

You will find that most cams give an RPM range; idle-to-3,500, 1,500-to-4,500, etc. The factory cam will be an idle-to------. I chose a safe route for my Ford 302 and got a 1,200-to-4,500 cam that wouldn't require new springs or have clearance problems. Keep in mind that higher lift cams might require different valve springs. The engine has a nice idle, not factory smooth, but not all lopey either, just a bit on the mean sounding side. One thing you do need to know is the compression range on your valve springs. As for torque, the cam, with a given set of heads, won't actually change it that much, Rather, it moves the torque range higher or lower depending on the durations and lobe center angle. A good rule of thumb is that with standard or slightly modified heads you can expect from 1.00 to 1.10 times the displacement as a torque value. So, your 400 should easily put out 400 to 440 ft-lbs. You have to decide at which RPM range you want that to happen. Also keep in mind that any torque value over about 250 ft-lbs will just spin the tires more in these light weight cars. Go too big and you might need a higher stall torque convertor too. As you'll find, ya just can't change one thing sometimes.

Check out Summit Racing cams SUM-1102 1,200-4,800 RPM or SUM-1103 1,600-5,200 RPM. This will give you an idea of course. I'm not recommending either. Good luck in your quest and do lots of research.

 

[Northstar T]

Check out Summit Racing cams SUM-1102 1,200-4,800 RPM or SUM-1103 1,600-5,200 RPM. This will give you an idea of course. I'm not recommending either. Good luck in your quest and do lots of research.

MrBill brings up a good point here. I don't know who makes Summits "branded" cams, but if you're planning to use a flat tappet cam they are a very good bargin. I used an 1105 in a low buck 350 I built a couple years ago and was very happy with that profile.

Russ

 

[HAceT]

I like for the motor to have good torque and a good loby sound. Will the 1105 be a good one for that?

 

[Northstar T]

I like for the motor to have good torque and a good loby sound. Will the 1105 be a good one for that?

It had a really nice lope in the 350, and even though mine was backed by a 5 speed I think it would be fine for a 400 in a lightweight car with auto trans. having said that, I would still recomend you call the Summit tech guys and ask their opinion for your particular setup and needs. a lot goes into a proper cam selection: vehicle weight, rear end gearing, trans gearing and stall speed if auto, type of heads, intake, carb or injection, headers and on and on.

Russ

 

[ellis8500]

Note what it says in the cam tech info:

Basic Operating RPM Range2,400-6,000Fair idle, excellent midrange power. Requires 9.5:1 and higher compression, 2,500+ stall, and gearing. Works well with N2O and superchargers.

This would be OK if you had a 3,500 lb car and wanted more pep. You mentioned wanting good low end torque; this is not a low end torque producing cam. Here's what it says about the 1103:

Basic Operating RPM Range1,600-5,200Fair idle, low midrange torque/horsepower, works well in 327 and higher c.i.d. engines. Largest camshaft with stock converter.

Finally, the 1102

Basic Operating RPM Range1,200-4,800Smooth idle, low -midrange torque, towing in 350 c.i.d. engines. Works with stock converter and lower compression.

Unless you are ready to move up to higher flow heads and a higher stall torque convertor, it looks like the grind on the 1103 is the biggest you can go without making other changes. The camshaft is only $60. When the time comes that you want to start adding all the big buck power adders, you can get another cam shaft; the cost of which will only be a small portion of the total.

 

[HAceT]

Ok here it is.....Motor is at machine shop. I'll be picking it up I hope tomorrow. I used the stock heads but had 1.94 Intake valves cut in. The motor was out of a mid 70's 4 speed truck so the valves seemed small for any cam. The block was bored 30 and I stuck with the standard style pistons which were 8.5-1's to basically keep some cost down. I ordered everything minus the cam as a kit. The cam I ordered specs are as follows...

Intake Exhaust
Advertised Duration 272° 282°
Duration @ .050" 214° 224°
Valve Lift w/ 1.5 Rocker Arms 0.442 0.465
Valve Lift @ Cam 0.295 0.310
Max Lift Angle 107° 117°
Lobe Separation 112°
Cam Timing @ .050" - Opens 0° ATDC 49° BBDC
Cam Timing @ .050" - Closes 34° ABDC -5° BTDC

I hope all this works together pretty good with everything I got. Now I got to find a bigger Radiator....looking at a 75 Dodge Dart Sport360. Will fit the frame nicely and will be cross flow too. Should run cooler.

 

[ellis8500]

Wayne,

Looks like a good choice for a mildly modified engine. Should have a mean sounding idle with good street manners. Be a good tire spinner. Make some smoke.

 

[HAceT]

Wayne,

Looks like a good choice for a mildly modified engine. Should have a mean sounding idle with good street manners. Be a good tire spinner. Make some smoke.

I hope so. I really do hope so.

 

[409T]

I have that same cam in a 327 that is .030 over and it works very well.

Jeff

 

[rooster57]

ACE i sent you a PM about a radiator i have

 

[HAceT]

I sent one back....Thanks