I recently purchased a 1987 Iroc-z with a 400 SBC bored .030 over, it had the following mods on it: 750 Holley double pumper, street dominator intake, roller rockers, hedman hedders, wolverine blue racer mild cam, and a crane crank. I have not been able to dyno it, and had my father drive it (im deployed). Anyone have any idea how this engine should perform with said mods. Any ideas or help would be great!

 

Impossible to be sure; you don't say what heads are on it, what pistons are in it, or what cam it is.

400s were all terrible dogs, in stock trim. Obviously that's easy enough to fix, and once the factory's criplling stuff is undone, they're a great motor. Question is, how much of that "dog" crap is still there. None of the "mods" you list, except maybe the headers and possibly the cam depending on what it is (although that brand is a super generic product line of copied copies of generically copied generic copies of copied generic cam copies so there's not a whole lot of hope there), address the problems that made the motor slow in the first place.

It should have plenty of torque, regardless.

 

Thanks for the response, I havent been able to confirm what heads or internals the engine has. The owner claims a little under 400hp, I'll have to find out for myself when I return. Hopefully he was 400sbc savy, and new what to replace. If he didnt I was planning on adding 350 vortec heads. Do you know If that would be a hard swap?

 

A little under 400 HP for a 406 cid engine is pretty mild. The typical stock 400 882 heads were really lame.

To put 350 Vortec heads on it, you will need the steam holes drilled in the heads, a Vortec-specific intake manifold, and self-aligning rocker arms. Factory Vortec valve springs aren't good for much more than factory Vortec cam lift, and valve travel can be pretty limited (reports are as bad as .440"). Either installing beehive springs & retainers; or getting the tops of the valve guides cut & new springs, is in order.

Other than that, it's pretty much an unbolt/bolt on proposition.

 

Thanks for the help! I dont mean to sound like a tool when I ask this, but when you say 400 hp for a 406sbc is pretty mild; do you mean rare? And if so, is that with the stock 882 heads or even after throwing the vortec heads on? Im on a $3,000.00 budget including labor, do you think low to mid 400hp is attainable? Thanks for all the help!

 

"Mild", as in, "not much".

450 HP with Vortec heads should be a cake walk with proper exhaust, induction, and cam.

 

Thanks for all the great information everyone! Am I going to be running into any problems with the compression being to high?

 

I had a friend check out the engine today. All he can tell is that it has double hump 202's on it. And I know it has roller rockers. Should that add up to be a pretty decent engine with all the other mods I listed?

 

Those are better heads than the typical 882's. So it'll probably be fine. Pulling the valve covers and getting the specific casting #'s would still be recommended, though.

Some more specifics on the cam and pistons would be helpful. The chambers aren't all that large on double humps.

 

I guess ill just have to wait and see. Thanks for all the great advice. This sight is a life saver, definitely learning alot!!

 

That's not a casting number I'm familiar with, and I'd like to think I have run across about all of the double-hump castings at one time or another over the last 40 years or so. But maybe not, who knows.

Get him to re-check the casting # and post it here.

 

If im not mistaken, "Double Hump 202's" are just a nickname for the 492 casting. They just call it this because it has 2.02" intake valves. I should have used the correct name being 492 fuelie camel hump heads.

 

Its time to ditch those dub hump junk(as my frend calls em) heads as the vortec heads are light years ahead.. run the numbers on the heads and sell them to someone with a 327, 3/4 race cam, holley 650 dub pumper and 1 5/8 headers to recoupe some money 4 your build..
for a 400 I personaly would step waaaay past the vortecs but you are on a budget.. they should do 400hp fairly easy

 

Lol ok thanks for the advice! What aftermarket heads would you recommend that wouldn’t shoot my compression up too high? I’m assuming anything I get will have to have the steam holes machined. And would the heads work with my street dominator intake?

 

You didn't say anything about 2.02" intake valves; you just said "202's", as if that was some kind of identifying mark.

None of the sets of 492s that I've ever had, had 2.02" intake valves in them when I got them. No point in getting sucked into mythology land by false rumors, however romantic and appealing they may be on the surface.

There's no way to know what intake valves are installed in ANY of them without pulling them. Nearly all came with the usual 1.94" valves. Some of the castings could have been equipped with 2.02" valves, in some applications, 186 for example when used on the 302 rather than 1.94" in about everything else; but you can't know that from the outside. About the only ones that you can be fairly sure have the larger valves in them without measuring, are the 291 and 292, but even those, it's still possible to put 1.94" ones in them.



This is a set of 186s sitting in my garage, on a 400 ATM.... that came with 1.94" intakes in them.

Take a look at the casting # in the block those heads are bolted to, below the one head. This is how we can be sure it's a 400.

So just to be clear here, I REALLY DO know what I'm talking about.

Bottom line is, if you want to know what you've got, you're going to have to dig into it a little bit. The place to start is the CASTING NUMBER, and not with a bunch of "202" monkey-spank. That's just a shiny thing beside the path to distract people with short attention spans.

Meanwhile, while Vortec heads certainly are a FAR better starting point than older heads, people have been making WAY MORE THAN 400 HP out of 400s for AHELLUVALONG time before Vortecs were ever introduced, using double-humps mostly. It's not like, the 400 HP barrier wasn't broken until 1996, any more than it was not possible to drive cars in the winter before EFI appeared. It was just a little harder to get there.

First thing to do is to ignore all the idle speculation and hot-rodder Friday night McDonalds parking-lot monkey-spank, and concentrate on accurately and non-emotionally identifying WHAT YOU'VE ACTUALLY GOT.



Any moron can drill the steam holes. Even I can do that, and I'm about the stooopidest blob of protoplasm to ever splatter itself onto this planet. (just ask my college-age kids!!) While not necessary to drill them, it's usually a real good idea, especially if you're going to drive the motor on the street. Here's a set of Darts - intended for a 400 BTW - that I have also sitting in my garage, that I drilled.



If your 400 doesn't have the circled hole, you might want to get your machine shop to drill it. This one is a bit tougher to get right on your own though by no means impossible. This particular one, I drilled myself, so I could put this particular 400 in my third gen.

If you'd like to know about 400s, double-hump heads, and these cars, I'd be happy to answer any questions you might have TRUTHFULLY, using FACTS, without having to rely on "I've always heard" or "they say" or "I thought".

 

Thanks for all the great info! If you dont mind Im sure I will bug you with more questions the closer I get to actually being able to seeing/ working on the car. Greatly appreciated!

 

Im a huge 400sbc guy. I don't care what anyone says heads are where u make your power. Junk the stock casting, and for the love of god do not put those worthless vortec heads on that motor. Procomp makes a great pair of aluminum heads for cheap. Let that baby breath, would u wanna breath through a straw no way man. But small blocks do like velocity. So if your not drag racing, go 190 runner 2.02 in. 1.6 ex. U will be happy. Stick with a 600 to 700 cfm carb for that app. Voo doo or com cams great stuff call them. And you must have the steam holes drilled, procomp will do this for you. Steam holes don't try yourself, and you must have them.