As many of the members here know we got one of Bob Walla's aluminum 409 blocks earlier this summer. Here's Bob delivering it.
We are just now getting started on the actual build. I dropped the block off at the machine shop earlier this week. (A P Racing Engines, Windsor Ontario Canada) They have experience with race engines and 409's so I'm leaving it up to them to order the parts they think are best for the short block assembly.
We're shooting for about 520 ci. with a 4.25" stroke. The bore will depend on the best availability of ring sizes but it will be around 4.42 Since this will be a "race only" engine we're hoping for about 13.5 to 1 compression.
Bob Walla is supplying the cam. The specs I've asked for are 276 @.050 intake and 286 @ .050 exhaust with a lobe separation angle of 112 degrees. The lobe lift will be about .450 intake and .420 exhaust which translates to .765 - .714 lift with 1.7 rockers or .787 - .735 with 1.75 rockers. The cam company he deals with may not have those exact specs so they may change a little.
The heads we'll be using are the ones we got from Bob a few years ago. As everybody knows cylinder heads are usually the limiting factor when it comes to making horsepower so we've got some modifications planned to help feed the bigger engine.
The regular 690 style heads work great up to a point but when the air flow gets really high like at high rpm or with a big cubic inch engine the air has a tough time making it's way around sharp corners like the short side turn of the 690's
The raised port on the Z11 style heads are much better. Here's a picture of a Z11 head beside a 690
(I think I got this from one of Wrench's posts)
We've been talking about grafting a slab of aluminum onto the heads to raise the ports and today we finally bit the bullet and started milling down the heads. We're doing this on the mill at our shop.
We milled the valve cover rail down and made it parallel with the deck surface just to keep things simple. You can see the difference if you compare the untouched head in the background to the one we milled.
The piece we'll be adding will look a little like a valve cover spacer except that it will be much heavier and it will have two rails that will span across the head directly over the intake ports. It will be clamped down with four head bolts and be bolted to the head with several other bolts. It will also be epoxied into place.
We're hoping to raise the ports by about 1 1/4 inches but valve train clearance will be the limiting factor so we may not get that much.
We'll be using a T&D shaft rocker system like the one on the Sherman engine in the 55 Chevy.
The rocker pedestals will have to be milled down to the proper height to accept the T&D setup but before we can do that we'll have to get the new longer valves so that we can determine the proper height and angle.
Anyway, this engine build will probably be a winter long process but I thought I'd get a thread started.
We are just now getting started on the actual build. I dropped the block off at the machine shop earlier this week. (A P Racing Engines, Windsor Ontario Canada) They have experience with race engines and 409's so I'm leaving it up to them to order the parts they think are best for the short block assembly.
We're shooting for about 520 ci. with a 4.25" stroke. The bore will depend on the best availability of ring sizes but it will be around 4.42 Since this will be a "race only" engine we're hoping for about 13.5 to 1 compression.
Bob Walla is supplying the cam. The specs I've asked for are 276 @.050 intake and 286 @ .050 exhaust with a lobe separation angle of 112 degrees. The lobe lift will be about .450 intake and .420 exhaust which translates to .765 - .714 lift with 1.7 rockers or .787 - .735 with 1.75 rockers. The cam company he deals with may not have those exact specs so they may change a little.
The heads we'll be using are the ones we got from Bob a few years ago. As everybody knows cylinder heads are usually the limiting factor when it comes to making horsepower so we've got some modifications planned to help feed the bigger engine.
The regular 690 style heads work great up to a point but when the air flow gets really high like at high rpm or with a big cubic inch engine the air has a tough time making it's way around sharp corners like the short side turn of the 690's
The raised port on the Z11 style heads are much better. Here's a picture of a Z11 head beside a 690
(I think I got this from one of Wrench's posts)
We've been talking about grafting a slab of aluminum onto the heads to raise the ports and today we finally bit the bullet and started milling down the heads. We're doing this on the mill at our shop.
We milled the valve cover rail down and made it parallel with the deck surface just to keep things simple. You can see the difference if you compare the untouched head in the background to the one we milled.
The piece we'll be adding will look a little like a valve cover spacer except that it will be much heavier and it will have two rails that will span across the head directly over the intake ports. It will be clamped down with four head bolts and be bolted to the head with several other bolts. It will also be epoxied into place.
We're hoping to raise the ports by about 1 1/4 inches but valve train clearance will be the limiting factor so we may not get that much.
We'll be using a T&D shaft rocker system like the one on the Sherman engine in the 55 Chevy.
The rocker pedestals will have to be milled down to the proper height to accept the T&D setup but before we can do that we'll have to get the new longer valves so that we can determine the proper height and angle.
Anyway, this engine build will probably be a winter long process but I thought I'd get a thread started.