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Mike
| | Posted on Sunday, September 8, 2002 - 5:00 am: |       |
G,day again guys,
I have a set of heads # 14014416. Just wanted to know if these heads are any good for performance modifications to fit onto a .030 over 350 with flat top pistons and moderate cam, single plane manifold, and 750 Holley |
Bogie
| | Posted on Monday, September 23, 2002 - 7:06 pm: | |
Mike, they're stock 80 to 86 305 with 1.9 intakes, 1.5 exhaust and 58 - 60 cc chambers. Not good on a 350 without a lot of rework of ports and larger valves. |
Mike
| | Posted on Tuesday, September 24, 2002 - 4:26 am: | |
Thanks. I also have a set of 462624 heads, would these be a better option. If so, what sort of pistons would be suitable for about 9.5:1 on a .030 block? |
Bogie
| | Posted on Tuesday, September 24, 2002 - 3:54 pm: | |
Mike, these are seventies to mid eighties smog heads for a 350 and 400s. Fairly large chamber at 76 to 80ccs. Most have 1.96 / 1.5 valves, some have 2.02 / 1.6 valves. Combustion chamber does not burn real well compared to late model heads. Casting in the deck and valvespring pockets is pretty thin and doesn't take to milling. These heads are crack prone in the combustion chamber. To get 9.5 with these you'll need pop up pistons.
I'd really try to save my money and get a set of Vortecs or aftermarket heads like World, etc. For a few dollars more, I'd look at GM Fast Burns or Trick Flow Twisted Wedge.
Neither of the heads you have, 14014416 or the 462624, are really capable of performance work. If your stuck with these choices ,I guess the 305's would be a better starting point but lots of work has to be done. The valve guides need to be moved away from each other to accommodate the valves from the 350 heads. That means valve spring pads get remachined, ports get enlarged and moved, seats get reshot to accept bigger valves. But the chambers have meat to accept reshaping and they're small enough to reap fairly high compression without pop up pistons. All-in-all a pretty serious undertaking. The 350/400 heads you have are just boat anchor material.
If your stuck with this choice, let me know and I'll data dump on you what the details of the mods you need to make are. You'll need access to a die grinder, hard seat grinder and a good drill press/vertical mill to perform the mods. |
Mike
| | Posted on Wednesday, September 25, 2002 - 3:48 am: | |
Thanks Bogie,
Your response and info have been fantastic.This is more detail than I could have hoped for! However, I think that my version of performance mods is neaderthal compared to yours! I should have properly explained my predicament before wasting your time. The 350 is going into my Toyota Landcruiser FJ40 SWB and (unfortunately) I won't be pulling any 12 sec passes, as much as I'd like to!
I was more inclined just to get the old 350 hopping a little better than mediocre. At the moment I have a single plane inlet manifold (I'm running LPG as well as gas), a mildly modified Q-jet, electronic dizzy and tri-Y headers.
So what do think: bit of a port job,some new springs and a cam (any idea on spec's ?) to get this jalopy singing through the bush? Unfortunately, I'm straddled for cash so I'm going to have to stick with the 305 heads.
Would extremely appreciate your input. |
Bogie
| | Posted on Monday, September 30, 2002 - 6:24 pm: | |
Mike, do you have access to a die grinder, a Sears store for what I think are the best grinding stones for an amature head porter to use, a hard seat grinder for shooting new valve seats?
If not let me know what you can lay your hands on and I'll try to curve a data dump around what you've got to work with.
I'm inclined toward porting the 305 heads. Following my receipe, you'll have a set of heads that have real strong mid range grunt and will be very fast to respond to throttle changes, but they'll crap out pretty fast over 5 grand when strapped to a 350. They'll let you get by with a milder cam but make the engine feel like it's pulling a much more aggressive shaft without all the poor behaviors of a long duration high overlap cam. It won't win the quarter mile but it will climb cliffs and pull stumps. |
Mike
| | Posted on Tuesday, October 8, 2002 - 6:37 pm: | |
Bogie, I do have access to a die grinder and valve grinder. What sort of cam specs do you think would suit this set up ? As you probably know we have to travel quite a few miles to get anywhere in Australia and I'd like to set the cruiser up to be fairly driveable @ 2200 rpm (that being the rev's @ 100 kph). Thanks heaps for your feedback, it's really helped focus the project. |
Bogie
| | Posted on Sunday, October 13, 2002 - 5:21 pm: | |
Mike, Neither of the heads that you have, 14014416 or the 462624, is really capable of performance work. But, if you’re stuck with these castings and have access to tools like a die grinder and a hard seat grinder, I'd attack the 14014416s (the 305 heads). As an old hotrodder, emphasis on old, I'd grind out the ports, then take the hard seat grinder and open up the seats to accept the valves from the 462624 (350/400) heads.The reason I'd go at the 305 heads, and I’m sure we’ll hear about this, and valid points will be raised as to why not, but I think since your building an off road stump puller lots of torque and sharp throttle response should be emphasized at the expense of power in the RPM range over 5000. If your carbureting this engine, you will find that a Holley of 500 to 600 CFM will be real sharp and crisp because of the relatively high mixture velocities in the engine. With a cam of 195 In/206 ex. to 205in/ 210ex, something in that neighborhood, it will deliver a solid 350 ft pounds around 2200 to 2500 RPM and a good 280 / 300 hp at 5000 rpm but because of the small ports will die pretty quickly by 5300 to 5500 revs.
The trick to mid range torque is both high velocity mixture and good swirl on the intake with efficient disposal on the exhaust causing a high negative pressure in the cylinder during overlap. The larger 350/400 intake valves, adapted to the 305 heads, allow the high-speed inlet airflow to slow a bit and recover pressure. This will ease the mixture around the valve seat and into the cylinder. On the exhaust side, it will cause a similar event of the gas flow over the seat and into the port. The high exhaust gas flow velocity will tend to over scavenge cylinder in the moderate RPM range, pulling harder on the intake during the overlap period which will help put more intake charge into the cylinder without having to go to a long duration, long overlap, high rpm, rough idle cam, to get this effect. This engine might be a little peaky here and there in its RPM range so a set of reversion cones in the exhaust manifold or headers would be a good idea to dampen this effect. If you want a high rpm motor with power over 5200 RPM, then follow this recipe on the 350 heads. You’ll end up with an engine that is weaker in midrange torque and stronger in top end power, with rev capability into 6 grand.
So appriciate how you’re going to use this thing, what kind of gear ratios and transmission you have, and what kind of life you want from everything. Basically, more revs equal shorter life, and trading horsepower for torque nets more shifting with an off road vehicle.
Neither of these heads will provide good fuel economy with power and torque the way a set of ZZ3s or Vortecs would. That’s life with the combustion chambers you have. A bit more compression would help reduce fuel burn, but that’s going to dictated by fuel available where you live. 87 octane is good to about 8.5, 89 is good to about 9 and 92 is good to about 9.5, maybe 10. Fast burn chambers like the ZZ3 or LS1 let you push the comp ratio a little bit harder if the head material is aluminum, cause the Al. pulls heat out faster. But then you need to run coolant pressure up, etc. to really take advantage of this.
What you want to do is move the intake flow centerline toward the long wall (common wall) looking at the intake manifold mounting surface of the head. This will provide better flow across the valve and put a strong mixture swirl into the cylinder. The trick on the intakes is to raise & lower and widen the intake port on and toward the cylinder wall side, that's where the intakes share a common wall at the manifold interface (sometimes referred to as the long wall). Run a 1/2-inch dia. stone down the port from the upper and lower corners of the cylinder wall side to give a 1/4-inch radius. Flip the heads over; get into the port through the valve opening. Streamline the guide and open up the distance between the cylinder side port wall and the guide to at least 1/2 inch. Less so between the guide and the short wall. The leading edge of the guide should be shaped, as much as possible, like a wing’s leading edge. Make the leading edge slightly off center (that's toward the short wall) to emphasize flow toward the long (common) wall. On the valve pocket side of the guide continue pull a radius around the top of the guide from the long wall side toward the short wall side, this allows the mixture to begin to flow toward the center of the cylinder as it passes the valve. The finished product should look a lot like the valve pocket of a Vortec head. Go back and blend the long (cylinder/common) sidewall into the radius cuts. If you break thru the pushrod bore, just press a piece of thin wall brass tube into the bore. Just before “homing” it, apply, a little Lock-tite at both ends to make sure the port vacuum doesn’t pull oil in. Same for the bottom and top walls, blend them into the radius cuts of the sidewall. For the opposite sidewall, just grind off the as cast surface. The finished port at the manifold interface will look like a trapezoid with the long (tall) wall being the two walls adjacent to each other when looking from the intake manifold side. Blend gaskets and manifold (go as far up the intake as possible to encourage the flow centerline to move toward the adjacent port walls at the head) to match the head port.
On the exhaust side, run a 1/2-inch stone down both sides of the top of the port giving a nice 1/4-inch radius into each sidewall. OK we're using up stone diameter here. Use the shrinking stone to streamline the guide, leave more meat here compared to the intake, because the higher temps stress this more. The exhaust guide should be centered in the port. The top of the guide boss back to the port wall should look like the leading edge of a wing. The down stream edge should taper like an airfoil as much as is practical to achieve with the material available. Blend all walls into the corner radius. The bottom wall (installed position) should only be smoothed to eliminate the as cast surface. This should look like a trapezoid with the top wall (installed position) being the widest. Modify the gasket and exhaust manifold/header flange to match port shape. If this head has round ports, use the same porting plan and stay with the round shape the finished gasket edge will look egg shaped with the widest part on top, when the head is in the mounted on the engine position.
OK, you now have a real decent set of torquer ported heads. Polishing is unnecessary as in many locations it's undesirable; a little boundary layer instability is good as it helps the airflow disconnect itself in divergent (expanding sections). If you ever have a chance to get close to a jet airliner, you will see that aft part of the fuselage, under the tail, is all riveted with headed rivets that project above the skin, not smooth like the rest of the airplane. This is done to put a little turbulent energy back into the air stream, which helps it let go of the airplane. Otherwise the airplane would drag tons of dead air along with it. Same principle applies in your ports. A little turbulence is a good and the grinding stone leaves the perfect finish for this purpose. The as cast surface is too rough and the excessive turbulence from that surface effectively reduces the "apparent" port size, as seen by the airflow. You should plan a new stone for each port. If you follow the sequence I outlined, you'll find the stone wastes at about the right rate to move from roughing the wall or wide side radiuses to streamlining the guide and then smoothing and blending the walls. Sears is a good source if 1/2 x 2 inch long stones that are perfect for porting.
Go slow, if you've never done this before expect to take an entire evening with the first port. Once you get a rhythm and a visual of what your doing, the time will go way down on subsequent ports. I suggest a full face shield and good ear protectors as being comfortable greatly reduces errors and fatigue. Take frequent breaks to get blood back in your hand and forearm. A mask is helpfull to keep your lungs and breathing passages clean.
Now the 58cc chambers on a 350 will want to push compression toward 11 to 1, which is pretty stiff. You can ease the radius between inlet valve and spark plug a bit which will help flow and increase chamber size. You can do the same on the exhaust side from the spark plug toward the far wall on the exhaust side. I'm not to keen on too much of this as it encourages exhaust gas flow on the bottom of the port, which usually comes at the expense of total flow if you don’t have a flow bench to check what your doing. But you need to get at a chamber size around 65 to 70 ccs and do any cleanup milling of the deck before selecting pistons. When finished the deep (spark plug) side of the chamber will look like the top of a heart diagram, with a spark plug in the middle. Once again if you have a picture of a Vortec chamber, you will see the similarity. You can lay the wall back a 1/16 to 3/32 inch or so by the plug. Roll the shape over to put a chamfer on the chamber wall to gasket deck emphasizing the radius as you approach the plug. Do not open the chamber wall more than 1/16 where it begins to turn around the valve on the cylinder wall sides, it’s thin here and will crack if you get carried away. Do not open the chamber wall between the valve and the cylinder wall side of the chamber more than is necessary to clear the valve. It’s real thin here and cracks are a risk. Well, actually it’s thin everywhere and might crack anywhere. Welcome to porting. I’ve ground the daylights out of some heads with no problems and others cracked with little more than kissing ‘em. You puts down your money and takes your chances.
Most likely, you'll need pistons with about a 15 to 20 cc dish to get compression around 9 to 1. Check out different head gaskets to get a thickness that dials in the compression at 8.5 to 9 to 1.
Now come the seats, with a hard seat grinder, open up the seats to accept the 350 size valves. Carefully blend any rough edges into your porting and your done.
Now we’re likely to hear from lot of folks who want to and have ground out the entire port, and that’s OK if you’re going for higher RPMs and horsepower. What I’ve outlined will give you a pretty conservative engine that generates lots of low and midrange torque, has sharp throttle response and doesn’t require gobs of RPM, lots of compression and a nasty cam to get it. As I said earlier, this engine will be a stump puller; it will want to twist the flywheel bolts off. From idle to 4500/5000 RPMs this thing will eat any competition, but around 5.5 grand it will hit the wall, but damn son, you’ll get there quick. |
Mike
| | Posted on Monday, October 14, 2002 - 2:23 am: | |
Thanks Bogie,
I'm going to start tackling these heads next week so I'll keep you updated as to how it's all going. Thanks again. |
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