sbc 400 heads

[kress1500]

I just pulled apart my 400 and am wondering if the heads are worth using. they are #3998997. I cant find any info on what kind of power they can support. thanks

[MrPbody]

997s are a decent large-chambered head. They're on the "popular" list for circle track engines where stock heads with 75 CC chambers are "legal".

To make "power" with a 400, though, no factory iron head is capable of flowing enough without massive port work and larger valves. Very little difference between 350 heads and 400 heads... That being said, adding 2.02" (or 2.05s, considering the larger bore of the 400) intakes, 1.6" exhausts and a bunch of porting, they CAN make good power.

If you want iron heads AND power, but don't want massive porting, either the ProLine or Dart Iron Eagle are called for. the ProLine has a small chamber and may not be suited to street use without major changes, either to fuel or pistons. Iron eagles come in a 72 CC chambered version.

Jim

[kress1500]

ok, thanks for the info. I don't think I am interested in a bunch of porting. I got burned out on that stuff the first and last time I did it, plus I don't have access to a flow bench anymore. Actually, what do you think of this package from Summit? What kind of power do you think it would make? Also, I was going to switch to 5.7 inch rods, do I need special pistons, or will standard 400 pistons do the trick? Thanks for your input, I'm sure I will have lots more questions. I'm not an idiot(i hope) but I am inexperienced. All i have built are a 350 and a 305, and so far this 400 is more different than I expected.

[MrPbody]

No, 400 pistons won't work with 5.7" rods. The pin is too low in the piston, and it will stick "out". Speed Pro makes a nice hyper-eutectic casting for this application. If you want nitrous "capability", you need forged pistons.

I know nothing of any Summit "kit". Our experience has been they sell cheap kits and use inferior parts in them. A good machinist can do a much better job of designing a "package" than a marketing rep.

We've built many 400SB engines over the years. They have their good and bad points. The block is the weak "link". If you have a 2-bolt main, that's more desirable than the 4-bolt (I know..., but it's true). Unlike the 350, the 400 removes too much material from the bulkheads, in the area where they need the material the most. The 2-bolt is stronger, and a good place to start if you were inclined to install "splayed" main caps (bolts at an angle, not straight into the bulkhead).

Jim

['97ventureowner]

Also keep in mind you need to have a good cooling system to support the 400. I have a 400 engine which I rebuilt back in the late '80s into a 406 cu.in. The machinist who helped me at that time had a lot of experience with these engine and mentioned I should beef up my radiator, which at the time was only a 2 core. I ended up going with a 4 core, but I think you can get away with a 3 core if there are space limitations. I also installed a high performance mechanical fan and got good results from that as well.

[kress1500]

oops, I forgot the link to the summit kit, sorry

http://store.summitracing.com/partde...2&autoview=sku

it says it is edelbrock parts, but its all put together into one kit
I want to make 400 HP if I can, and I am ready to spend time piecing together the components, but if they sell a good kit, i figure why not use it. I have some work ahead of me yet before I buy this stuff anyways, I just like to know what I am getting into. The cylinders don't look like they will need to be bored, no noticeable lip at the top to indicate wear, but I have not had a chance to mic it all out to check O.O.R. or taper or anything. If it is all good, is there any benefit to boring it to 406? I know displacement is fun, but for a hot street engine, is it worth it?

[MrPbody]

We tend to treat 400SB blocks like Fords. No bore past .040". We've seen them at .060" and "live", but as ventureowner says, cooling is an issue.

The purpose of boring a block to a "standard" oversize is to provide a fresh bore for new pistons and rings to do their job. The minute increase in displacement is negligible regarding power output. If your local machinist can "hone" the block to .040", that's what I would recommend. Be sure to do final hone with a deck plate! Chances of a boring machine being able to "clean" the bore at an additional .010" are very poor.

I looked at the Summit "kit". Conspicuous by its' absence, is the brand name of the cylinder heads. The valve springs are useless. The 3/8" studs, combined with 3/8" pushrods indicates a marketeer, not an engine builder, designed the "kit". 7/16" studs are MCUCH stronger. 5/16" pushrods are more than adequate for all but SERIOUS roller springs.

Aside from the Edelbrock Performer RPM, I see nothing "first rate" about the parts. No doubt, port work is needed to feed a larger cubed engine like the 400. The 170 CC intake runners indicate a "small" head. It would produce good power to about 5,000. Lots of torque at lower engine speed, if that's what you want.

For that kind of money, I would recommend Dart Pro-1s (200 CC intake runner, 72 CC chamber for 93 octane). For a few more dollars, you can have the best!

Jim

[kress1500]

ok, Thanks.

I will look into that. I am not ready to buy anything right now. How hard would it be to break 400 hp? Edelbrock has a kit that they claim would make ~435 on a 350. It is just their Performer RPM heads, intake, and cam with the basic bits you need to install, for about 1700.

Thanks again,

Tommy

[spurlinperformance]

400's had some damn good heads for factory.rework them and use um.

[MrPbody]

Actually, with one exception, 400 heads ARE 350 heads, with "steam holes" drilled in them. There was one casting in the '70 model year, that the head had the 1.94 intake vales, but had a 1.6" exhaust valve. Only one I know of specific to 400. The 997s mentioned are among the better flowing "stock" heads. The only large chamber "better" would be the 441. The other good-flowing heads are small chamber (64 and less).

Jim

[luxeryvic]

pot on 350 or 305 heads if they fit to raise the compression ratio

[MrPbody]

Chevyvic,

400 heads and 350 heads are identical except the "steam holes" drilled in the 400s. ALL are 76 CC chambers except the early "performance" 350 heads. 305 heads will raise the compression alright, but that may not be the best approach. While "compression is power", with the fuel situation we have today, a well-ported set of heads with a modern cam profile will outperform the higher compression setup unless race gas is used. Even then, unless they're ported to the same level, they won't make the same power. In short, "flow trumps compression". We have MANY examples of that with Chevy and Pontiac engines performing very well at less than 10:1.

FWIW

Jim

[he.v_rtft]

]
can anyone estimate how much horsepower ,torque these parts on a 350 Cheverolet can give
1-600cfm Holley manual -choke vacuum sec.
2-edelbrockTorker 2 intake single plane (2500-6500 ) pm
3-summit steel roller rockers 1.52
4-Block hugger headers15/8".
5-trick flow track heat cam [email protected]=246/254--lift=.495/.510--3500-6700rpm.
6-Crane cam valve spring 1.255 0.060 clearance 0.490 lift.
7-silvolite hyper eutectic pistons 10.3:1
8-summit racing digital ignition + blaster 2 coil.
9-the heads are stock 1.95 in valve--1.50 exhaust ported to match in manifold and headers.

what other parts might i need to get 330 hp out of this ,
Many thanks/ Moon.

[MrPbody]

Moon,

Getting 350 HP from a 350 Chevy is a no-brainer. You have a good start, but certain areas need attention.

The T/F cam would be much better suited to Trick Flow heads. I would recommend a Comp XS268S or XE274H, depending on your choice of lifters. The solid lifter cam will make more usable power. We've been steering people away from hydraulics of late, seeing a lot of failures. Same is true of rollers if your budget can stand them. Solids are the way to go. (No, not "old school", as solid rollers have only recently become a viable option for street engines)

The carb is a bit on the small side. A 650 or 700 may be a better choice. When using an open-plenum intake (like T-2), a bigger carb is called for.

Those little headers gotta go. You need long-tube headers to make real power. Shorties are more for ease of installation and bragging rights.

The valve springs will cause broken valves. Your choice of cams has over .500" lift, while the springs can only support .490. Coil bind will KILL an engine.

If those are the Kieth Black Silvolites, RUN AWAY!!! We've seen nothing but grief from them. SpeedPro offers a much better hyper-eutectic casting in the most popular sizes and dome/dish combinations, without "special" ring gapping requirements. If you intend to EVER spray nitrous to it, get forgings, not castings.

You didn't say which head you have. The casting number is located between the valve springs under the valve cover. The last three digits are all we beed here. Since they've been ported, they should also get the 2.02/1.60 valve modification to take full advantage of the porting.

Lastly, 10.3:1 is too high for current pump gas and iron heads. I would lower the ratio to under 9.5:1, eliminating detonation from a list of "worries". This can be done by enlarging the chambers (not very practical) or using a "dished" piston (much more practical). You will find, if you use the Comp XE grind, you won't be "giving up" anything to the lower compression ratio.

Helpful?

Jim

[luxeryvic]

wow mrpbody, how do you know all this?