Thread: using 305 heads on a 400 sbc

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can u put 305 heads onto a 400 sbc and the heads have a 58cc chamber. so will this hurt me or can it help me.

If your gonna be runnin' alcohol or racing fuel you could use those heads but a 64 cc head with flat top pistions runs over 12:1 compression. I have a 406 with flat tops and it's 10:1 compression which is borderline with 93 octane. but if your goin' preformance you will have to rework those heads to get them to breath right and that's alot of work so why not get a used 441 ? thier pretty easy to find....

well i am only 17 and don't have alot of money and i have a 400 but no heads and i only paid $20 for those heads. I was just goin to try it out because a friend of mine said u can put bigger valves in them.

so what heads do u think would work best for the best performance for the 400 small block

I'm no expert but I remember that when I rebuild a 400sbc to my 4x4 stepside, 400 c.i.d block and heads had extra water canals between the cylinders. So I couldn't use other heads that 400 sbc without warming problems. I was told that 400 c.i.d heads can be used to other sbc:s but not vice versa.

Jani

you have to drill out the steam holes for the heads to work on a 400. so if anyone out there has ever tried this combination i would like to here how it worked if it worked at all with 305 heads.

You need steam holes and be sure you have the right head gasket. FelPro sells performance gaskets for small block 400's but they are not recommended for extended use under 3000 RPM. Just use their standard gasket. Ditch the 305 heads. Sell them to somebody with a 305. Anything from a 350 or 400 with 76cc chambers and steam holes will work. If they don't have steam holes have an engine shop drill them.they're not just 'holes.'

well this weekend i talked to a guy and he had 305 heads on the 400. He had 2.02 intake and 1.6 exhaust valves and he said since the 400 in a low compression motor it works.and its pretty snappy.

I'm planning on doing the same set up with my 400 SB
using 305 heads. ( 416 casting) 58CC combustion chambers
1.84/1.5 valves. I figure the valve is a tenth of an inch small then the 400's heads, but i dont know it it'll choke the motor or not.
This Engine is going in my chevette.

It is not advisable to use 305 heads on a 400, even the 416's, if you look into the intake ports you will see the small "window" that these heads have, that along with the smaller valve is done intentionally to give the 305 some throttle response and keep the intake flow moving, you will also have a very octane sensitive engine unless you keep the quench area right at .040, pitting big valves in these heads is like putting a 36" screen door on a 30" door opening, what have you gained? also when drilling steam holes in the heads you must use a slight angle towards the center of the head. I do these every week, I try to direct customers a different way but I won't try to loose the sale.( For the money you invest in these junk heads you can get aftermkt that make 30 hp. more stock right out of the box), I gotta eat too! and the customer is always right.

yea, i tihnk u use a 3/16th bit and drill on a 30 degree angle, then i tihnk a 5/16th bit for the other, i'm not building a serious street machine, as long as it works decently, its all good,i'm thinking with the cam i have, maybe the lift will make up for the small intake valve? or else maybe the compression these heads will make up for air flow? i would use a pair of 350 heads, but there arent any around for decent prices, its always usually smog heads with 76CC chambers, would like to maybe find a pair of closed chamber camel back heads, maybe i'll slap some on later on.

The 58cc chamber sounds nice for compression, but I wouldn't use them on a 400 unless it has dish pistons and a mild cam like a CompCam 268H. I also wouldn't use them on the 400 unless they have at least the 1.84 intake valve. I have heard that a 1.94 intake valve will be shrouded in the 305 heads. But I don't know if that is on a 305 block or all blocks or what. Maybe sombody else can shead some light on that for you.

You would be better off with a set of 333881, 333882, or 333883's. But, look at it this way, I have a set of 883's on my 355, I spent $750 on them installing 2.02/1.60 stainless valves, 1.44 inch dual valve springs, new guides, hard seats, 7/16 studs, guide plates, and I had them drilled to work with 1.6 ratio rockers. And I still have a set of heads with stock ports. Granted the 883's do have a port around 165-170cc's, but for the same money I could have had a set of World Products heads. The only reason I used the 883's is becouse they came with the motor, and the motor was out of my friend's first car and I wanted to keep it whole when I dropped it into my Firebird.

This is a topic that has been talked about several times here before, you might want to check the archives about previous discussions.

Basically, if you just want to make the engine run, you can drill the steam holes in the 305 heads (use a 400 head gasget as a template) and bolt them on. As I said, the engine will run, but as far as drivability/preformance it will be marginal.

Most of the old timers/geezers here will tell you that a lot of their knowledge was gained by trying things for themselves (especially when they were young and didn't have a lot of money). If you HAVE to get the engine running by all means try the 305 heads. If you have the time, as T/A pointed out you'll be a lot better off at a minimum finding a set better heads (I would say at a minimum a set of 1.94s off a 350) than at some point trying to make the 305s perform.

One thing about "bargin" parts. If you find that the $20 heads you bought give you too much compression to be able to drive the car (or you have to pay the $.20 a gallon difference for premimum fuel to be able to drive it) your $20 for the heads plus the price of gasgets and your time has been pretty much wasted, and you don't really have that much of a bargin.

One last thing on the heads if you decide to use them. The 305 heads (as with most of the latter model heads) were a thin casting and are prone to cracking. If you decide to try these heads, have a machine shop check them for cracks prior to installing them.

chevy hi performance magazine has a good article on drilling the steam holes and it looks simple enough, as long as you get the correct angles. i was on a pit crew for a guy who threw a set of rebuilt 305 heads on his 350 with little luck, warped and cracked them in the first race he tried them. this is the only experience that i have had with them but if you would like i could find the article about drilling the holes and give you more details

hey i got that 400 running with the 305 heads. it runs pretty darn good. i have it in a 74 javelin and took it to the quarter and it ran 12.46 at 109mph not bad i thought.