Ok Im not a big tech on engines I mean I know how they work but matching ratio's gears, compresion, and all of that is where I fall short so correct me if Im wrong.

These heads are sopose to be 205 65s.
They have the tripple valve springs and the last motor they were bolted on broke its trans pulling a wheelie down the drag strip.

I have two options
>keep them and crank out massive power
>sell them and get some steet heads

What do you think?

------------------
89 Formula Firebird
Red with T-tops
5.0 305 FI
Soon to be a 400sb.

 

Who made them? GM, Brodix, World, etc.? What model? What do you mean by the #s?

400s need more flow than 350s. Think about how an engine works for a minute: you get power from burning gasoline molecules, right? The more gasoline molecules you burn, the more power you get. More specifically, for any given motor, the more gasoline molecules you burn in each cylinder fill, the higher the torque output. The more gasoline molecules you can burn per unit of time, the more horsepower. To burn gasoline molecules you need oxygen. So, horsepower is directly proportional to gasoline molecules per minute; gasoline molecules require air, so horsepower is also directly proportional to oxygen molecules per minute; oxygen molecules at atmospheric pressure can be counted in cubic feet; so therefore horsepower = cubic feet per minute. This facr is so fundamental to engine design, so simple, so trivial, so obvious, yet it's easy to outsmart yourself trying to reason your way around it.

If you have an engine whose horsepower is limited by flow, then it won't matter whether you put a 265 cu in short block under the "flow" part of the system, or a 500 cu in one. It still flows the same, so you won't get any more horsepower out of the larger motor. It will merely occur at a lower RPM. That's oversimplifying the situation a little, but the principle is absolutely valid.

If you want to have a 400 that puts out 400/350 times as much horsepower as a 350, then it has to flow 400/350 times as much.

Get the biggest heads you can afford. You won't regret it. As far as breaking parts or otherwise being too much motor, that's what throttles and drivers are made for.

------------------
"So many Mustangs, so little time..."
ICON Motorsports

 

triple spings forsure means it had a BIG roller cam and 205 you *could* drive it on the street, but low end toruqe would be pretty poor, you can really do 2 things basically like you've said, 1) keep them and use them but you must swap out the springs unless your going to run a huge roller cam also, 2) sell them and get some more usable street heads.

if your looking to sell i would be interested, my mail is tempest68@hotmail.com email me with the specs and a price if you want to sell.

 

also to reply to redbird, just getting the biggest flowing heads you can is really a bad idea, thats why the 400's in the truck and big boats they came in only got 1.74/1.50 valves, becuase they cause more turbulance which makes the mixture more dence and lower r's and makes more torque, if you have some crazy flowing heads on the street, they will make the engine have poor low and low/mid range, but then start to catch up in the high r's, the engine is like a big team, if it has too much flow, thats just as bad as too little. theres really no need on a SBC to have 200 CFM or more on the street, that much flow is really for mostly race use.

 

400s came with 1.94" intake valves. Most of them had 882 castings.

I have "triple" valve springs (actually there is no such thing, they're double springs with a damper) in my 400 and my 305; both of them have hydraulic roller cams. Unless the springs put more than 400 lbs or so on the valve when it's open at the lift you intend to use, they'll be fine; better than lesser springs would be.

205 cc ports on a 400 is about the same flow-to-CID ratio as 173 cc ports on a 350. For a comparison, stock L98 heads are in the 165-170 cc range. In other words, those 2 combinations will produce the same torque vs. RPM curve. With a 400, everything has to be bigger in proportion to the inches; it's very easy to forget that and end up choking the motor, which will reduce horsepower. Of course there's no guarantee that the "205" in your post has anything to do with port volume; it could be that somebody has stuck 2.05" intake valves in a set of otherwise stock heads even something as poor as 882s (yuck), or it could be a part number, or any number of other things. "205 65" could even be a tire size. That's not enough information.

Before jumping to conclusions it would be wise to figure out what you've got and make an intelligent decision based on real-world experience if you can get it, rather than magazine articles and hearsay. Post any identifying marks you can find on the heads and no doubt someone here will be able to help.

------------------
"So many Mustangs, so little time..."
ICON Motorsports

 

The "s" that I most likly should not have put, I just type the way I talk. I was indicateing a pair of heads. So what do you guys think maybe I should go with selling them for maybe some vortech's??.. and useing a 350 instead of a 400? Which would be more expencive to build 400 or 350?

What do you thing some heads like that may be worth? I mean they have had some work done to them they are ported and polished. If Im not mistaken they came from a 73 Chevy.

------------------
89 Formula Firebird
Red with T-tops
5.0 305 FI
Soon to be a 400sb.

 

You tell me where to measure them and I'll do it. That will most likly give you a full pic. of what Im talking about. Im headed home right now so in about 15-20 minutes from this post I'll find out what they are.

>BRB

------------------
89 Formula Firebird
Red with T-tops
5.0 305 FI
Soon to be a 400sb.

 

Measure the diameter of the intake valves and exhaust valves, at their biggest part.

If they're GM heads they'll have a casting number in the valve cover area and they'll have "GM" on them somewhere. Other mfrs have a wide variety of ways they mark them; if you find any markings, post them and we'll see what we can do.

Make a note of whether the spark plugs are straight or angled.

If you have any intake gaskets, lay them on there and see if they fit the ports; tell what gaskets they are and how they fit, and that's another clue to what they are or have had done to them.

------------------
"So many Mustangs, so little time..."
ICON Motorsports

 

My pc crashed at home so this is what I got here at work. (not at the heads)

>spark plugs= angled
>intake valve=2".05
>about 2 inches
>Exhaust valve=1"9\16
>about 1 and a half inch

I dont have the right tools to measure to the exact diameter so that what I got on it today.

------------------
89 Formula Firebird
Red with T-tops
5.0 305 FI
Soon to be a 400sb.

 

forsure a racehead, with 205 heads. agian if you want to sell i have cash in hand and a set of 400 street heads on my 400 now if you wanted a cash and trade(i got a drag car im building)

 

its all about VELOCITY my friend

if you have all that flowing air in a motor and enough exhaust to get it out FAST...you will make horsepower and have useable torque range because the big inches make up for the larger valves

an engine is just one big AIR PUMP

as much in and as much out....ASAP

that in a nutshell is what makes horsepower