Well, You do have a 5 speed and a 4.11, 434 CI so a little bit less bottom end torque probably won't even be noticed and the power gain at mid and upper will probably more than compensate for it. Might ask if angle milling that much affects the flow numbers and how much.

 

I would mill a little off the 235cc, and change the cam as it will surely not be the right match for your new more efficient heads. Get the cam to build as much pressure as you can for the comp you come up with after milling. Really would be splitting hairs at that point.

 

Having the shaft system would be a nice addition. This kind of money for a 25 hp increase ?. How much money can you sell your old heads for ?
How much for just a sportsman shaft system.

Have you looked at the airwolf head. 23 degree, 265 runner, 64 to 72 chambers, 2.15 intake valve, 40/60 valve spacing www.j-performance.com or the all pro 23 heads in 245 to 290 runner 2.18 intake valve www.allproheads.com

 

The only heads I have for sale are AFR 210 flat milled to 64 cc Just refreshed with All new guides, manley raceflow stainless 2.08/1.60, CC 1.46 dia h-roller springs 145# seat, and new vinton seals. I'd like to get $1200. AFR heads are about $1500 then $280 to flat mill The other parts are big upgrades worth a few hundred

I've seen some of the cheaper shaft systems for $900 for only $300 more you can get the T&D

 

I was looking at your earlier post talking about $3500 to $4100.00 spent. A lot for 25hp.

 

It is the difference between heads that now top out in the mid 600 hp to heads that top out in the low- mid 700's

But I need offset shaft rockers. Both on my present heads or future heads. My springs are a couple of years old and the guides are using oil. They are $ 600 dollar springs and doing the heads are another $300 So the way I see it I would have spend over $2000 to refurbish my heads & rockers or get the new AFR at a great price for about $4000

 

Was thinking about you needing to spend money to refresh your heads why i was asking what you could sell your curent 227 heads for to recoup some of the expense.

Those airwolf heads have room to grow. 2.15 valve size 265 runner. $2500.00 bare say $ 700.00 for springs, $300 valves, $1200.00 shaft system $4700.00. $700.00 more for more potential. 265 runner is not to big for a 434 like you have.

 

gkull, I am no expert, but IMHO, you will have more options, in the long run, if you change to a piston with less dish, or even a flat-top. I am sure you are aware of this, IJSIA (I'm just sayin', is all.)


Scott

 

Some things you don't sell. Instead of selling things at a loss. It is better to keep them. I don't need a few dollars.


Pistons were about $800 a set of 10 or so. milling is only $280 When youget into 434 pistons they are for race motors. So they are made for big valve and clearance to .800 lift with altered valve angles. When you get into real chevy small block racing heads they have tiny flat chambers as small as 38 cc to get 15-17 C/R for alki motors. So 60 cc heads only gets me to 11 ish C/R

 

I'm sure they were pricey new. Just a thought on some other heads. Do you already have 40/60 valve spacing.

 

yes, It is the only way they can fit in 2.10/1.625 valves in a 4 inch bore. If you remember the 396 ci BBC actually had a machined notch in the cylinder wall for valve clearance

 

I remember that now that you mention it. I had a 396. They used as big as a 2.18 valve and had an even worse 26 degree intake angle, at least they had a 4 degree cant . I used both oval and retangle heads on mine.

Big cubic inch small blocks become under valved

 

Are you saying that you can't run a flat-top piston because of valve clearance? Or that the selection of pistons is limited to those designed to use a 38cc combustion chamber head? Wow, I am really in over my head here.

If you could run a flat-top piston, you could use a 64cc combustion chamber head. There is a large selection of heads with this combustion chamber size. You could keep SCR up and have a larger assortment of heads that wouldn't require as much modification to choose from.

I understand that with a 4" stroke, compression height of the piston would have to correspond to that measurement, and there isn't a lot of demand for pistons at that level, which means a small selection of available pistons, and you have to use whats available. Also, I don't know much about the heads available at that power level. But I enjoy learning about this sort of thing, and I appreciate you guys letting me take part in this discussion.


Scott

 

Scott, try to picture this. You have the quench side of the head and the flat quench side of the piston. It is a must to keep the quench near to .035 -.040 to blow all the A/F over towards the spark plug.

You want to keep piston weight at a minimum. So the piston top is a trade off. weight vs strength. So when you are making a race piston and the majority of your market is running 2.15 - 2.20 intake valves and .800 lift numbers you have to design deep valve clearance pockets. If you tried to machine a flat top piston to clear big diameter intake valves for .800 lift that you would go right through the top of the piston.

So when I say that my pistons are 15 or 16 cc it is not like a low compression stock dished piston. It has big valve clearance.

Because the valves are at an angle the piston cuts are very deep with bigger diameter valves.

You don't find 434, 441, or 447 ci pistons in a book. Only a few manufactures sell them and they call them custom pistons. That is why you get 10 in the box. So you have a spare when you blow a hole in one.

real racing heads are very small cc chambers with small valve angles. They figured out long ago that big chambers need a big cooling system and all that wasted energy just heating the water and poor flame travel. Look some time at a modern rice bike motor cycle chamers with 4 or 5 valvles. It is not even a chamber, it is nearly flat. Any dish is on the piston side.

As to your question 434 pistons are really made for heads with 38 - 58 cc chambers

 

Just go for it and build a motor with the 325cc Dart Little Chiefs that flow about 450cfm, 1000HP knocking at you door N/A beat all the S/C Vettes on your block with a carb, you know you will want more power 3 months after you build the new motor, just save yourself a step, $3500 each bare

My next motor BTW, a few years away yet when I am ready to open the piggy bank

 

I know its costly more parts involved, making headers. But it just seems like a shame to have a need for a shaft system and not go ahead and switch over to at least a 15 degree raised runner head.

Your going to sink $1200.00 in a shaft system for 23 degree heads.

 

Thanks for taking the time to explain all that. My brother is a motorcycle mechanic, and he has that sort of stuff laying around, I'll have to take a closer look next time I am over at his house.


Scott