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View Full Version : Bow Tie Aluminum Head Info??????



DansBlown73Nordic
10-14-2004, 04:39 PM
Can anyone give me any info on these heads? I just bought them and would love to find out intake runner CCs. Has anybody used them before? They are called W port heads.
12363425 Signature Series Racing Bow Tie Cylinder Head 1965-96

Fiat48
10-14-2004, 05:05 PM
Intake runner raise .100
Exhaust ports raised .750
W port
Conflicting info on Chamber cc's 1 chart says 115cc and the other shows 105cc.
Requires intake valves .200 longer than stock or valve spring pockets must be machined.
Pushrod guideplates must be ground for clearance. And a lot of times you have to shim them to get them right.
Most guys grind out the hump in the W.
Valve seats are too little for blown alcohol use and known to fall out.
Intake runner 380 cc.

DansBlown73Nordic
10-14-2004, 05:55 PM
So are these a decent choice for my blower motor? Its just a 468. I hope the cc's are 115...

Fiat48
10-14-2004, 06:02 PM
I really think they are 115 rather than 105. And something in my head keeps telling me these used a .400 long valve and not a .200.
I'll dig for more info.

Fiat48
10-14-2004, 06:05 PM
Here we go:12363425
BBC Signature Series Racing Bow Tie Cylinder Head 1965-96, Aluminum, Raised Port.
This aluminum Bow Tie cylinder head offers a significant performance improvement over production castings. Bow Tie heads are recommended for large displacement competition engines 1965-1996 Mark IV, Gen V and Gen VI. The Bow Tie head’s intake runners are raised .100” above the standard port location and enlarged to improve airflow. The rectangular exhaust ports are raised .750” from the standard position to reduce turbulence in the runners. Vanes in the floor of the exhaust ports reduce turbulence (these are referred to as “W” ports by some Chevrolet enthusiasts). The big-block Bow Tie head has unique 115cc open combustion chambers. Material was added between the valve seats to reduce the combustion chamber volume, and the chamber walls adjacent to the valves are not relieved. The seat inserts and bronze valve guides are semi-finished for 2.19” diameter intake valves and 1.88” exhaust valves. The rocker arm stud bosses are reinforced and heli-coiled to improve reliability with racing valve springs. The rocker cover rails are raised .250”; standard valve covers can be installed. Two additional head bolt holes are drilled in valley area.
Technical Notes: The Bow Tie cylinder head’s raised intake runners require valves which are .400” longer then the stock. The valve spring seats can be machined .200”; check the valve spring installed height after machining the spring pads. Pushrod guideplates (P/N 3860038) must be ground for clearance before installation. The upper intake manifold bolt holes are not drilled in Bow Tie cylinder heads. Ports in production and after market intake manifolds must be modified to match the intake runner entrances. This head’s exhaust flange bolt holes are in the standard big-block location; drill and tap new bolt holes in the exhaust manifold flange or modify the header flanges to center the exhaust pipes over the port exits the deck thickness is 9/16” for maximum strength. The four head bolt bosses adjacent to the exhaust ports are taller than production heads: for 3.38” use 4.19” bolt(6)or 4.50” bolt(2); for 4.69” use 5.50” bolt(4); for 1.38” use 2.19” bolt(4). The heads are cast from A356-T6 material and the casting P/N is 14044861, same as the first design heads.

Fiat48
10-14-2004, 06:18 PM
So the performance catalog left out some things. Must have wanted to save ink. :)
I did a couple sets of these way back. We chose to take .150 out of the valve seat pocket and use a .250 long intake valve. Or you could take the .200 out and use a .200 long valve. I wouldn't use a .400 long valve...no sense to pack the weight. You'd be wise to use .100 long exhaust valve also in these. You'll be using custom length pushrods anyway.
On the valve seats....I say mild blown gas use. The thin little seats scare me and can be replaced with larger seats. Keep your seat pressure 240lbs or more...you don't want to beat on these little seats. They won't take it. And seems to me we had to do some intake manifold work to get a port match decent. Other than that, the heads work well. All the known head porters took out the hump in the W exhaust. They all cussed it but I have no flow numbers one way or another.

DansBlown73Nordic
10-14-2004, 10:26 PM
I will have some flow numbers next week.

Fiat48
10-14-2004, 10:45 PM
Take picture of heads (seats) if you can. Maybe Chevrolet started putting heavier seats in. They did on some models of later aluminum heads.

DansBlown73Nordic
10-17-2004, 03:51 AM
Fiat, I just thought Id ad that im only running a flat tappet cam. I think I have #120 spring pressure. I am planning to ad roller cam in the future.

Fiat48
10-17-2004, 09:37 AM
These heads were sold bare. Are they bare or did someone already set them up?

steelcomp
10-17-2004, 10:08 AM
one thing I've found that helps valve springs on these heads, specially after cutting spring pockets deeper, is to grind a small groove in the lower side of the spring pocket to let oil escape from under the spring. Otherwise the oil will sit in the pocket and cook the bottom of the spring. By allowing the oil to flow, you help keep the spring cooler. Fiat's right...SOP on these heads is to remove the ex. vane. Big port volume, not real good velocity...need a lot of RPM for NA smaller motors (under 500 ci) but will work on blower app. After clean up, ex port is good for blower motor. Chambers need a lot of attention.
Depending on boost, there's a kit that someone makes that allows you to attach a boss on the inside of a standard block so you can use the extra two head bolt holes.