odd ? can you have too much port volume and head flow with an S/C

[JavmanBBG]

I was looking a set of out of production race wedge heads for a 401 AMC. AMCs have the same bore spacing as BB mopar so back in the late 90s FBS made a few sets of heads to fit AMC engines but they had the same huge port volume and flow of a head designed for 500+ ci mopars. I have personally seen a set that had flow sheets of 430 intake 320 exhaust @ .750 lift but the 427 AMC it was on was too small for an N/A engine and had to he spun to the moon to work. There is a set for sale rather reasonably but I don't know if something that large would work with a 401ci engine even with a Procharger and still be able to use 91 gas and stay under 7200rpm? Anyone have any experience with this type of thing ?



Thanks

[mitch_04]

I would think that with boost you should be fine. N/A you would probably not have enough port velocity to fill the cylinders and the fuel would "fall" out of the mixture.

[mmosley]

What information I can find on the FBS heads is that they were made for Pro Stock. Exhaust bolt pattern looks like Mopar BB Wedge (AMC site said Hemi, but the picture posted looked like the wedge pattern to me - I have one, trust me...) Some of them had casting issues. They have good port velocity, especially for the size.

Unless you are going straight line down a track and trying to compete in a quick 8 type format I would definately pass on these heads.

The only reason I would put these on a "street car" would be if it was a trailer queen going to shows only and I wanted the extra bling.

These will require you to run very long titanium valves. Fabricated intake. Fabricated exhaust header. Nothing will bolt up to them. And, with a Procharger you can probably make more power than the block can handle with stock heads anyway.

If you are looking for more power or weight loss with an aluminum head look into the Edelbrock AMC heads. The FBS heads will likely just be a headache.

The Edelbrock heads have a beautiful modern 54cc chamber, 2.02 intake, 1.60 exhaust, and the heads flow reasonably well for the valve size. Run these heads with a 0.39" head gasket, zero deck height, and a forged dished blower piston with a large quench area. Shoot for 8:1 static and turn up the boost! The dish will allow you to run low static compression, the quench area will help you run more boost before the onset of detonation.

[JavmanBBG]

Biggest thing I was looking at was if it would be responsive down lower in the rpm band and if it would take too much cylinder pressure or RPM to make things work.

I have a decent set of ported stock heads and a set of the Edelbrocks but was looking for something a bit bigger like in the 340in 230ex range without spending big money porting a set of Indy heads. The FBS heads where on Racingjunk near enough to me I could check them out and had new valves, offset shaft rockers and a sheet metal tunnel ram and where advertised for $3700 but have been out there a long time as they are way big unless planing on welding them up and bolting them on an Indy alum 500ci Short block and such builds are few and far between.

Not too worried about breaking an AMC block or crank with the right mods as they as there are folks that are making over 1000hp using an offset ground stock crank and a stock block with all 5 program main caps.

Thanks

[mmosley]

One thing that was not clear to me, some of what I read was these were made for the race block, extra bolt and such, and folks implied, but did not specifically say they would not work on a factory block. Is that the case or not? Sounds like an interesting piece.

I drew the line on my 440 at about 300 cfm flow on the intake, the next step up (about 330-ish), running either Indy EZ or Eddy Victor heads moved the intake and exhaust ports up and would be better left for a race only effort. The 440 is already difficult to squeeze into this car. My current head / intake / induction set up and a seriously low profile air cleaner set-up leaves me about 1/4" from the hood and that is with a 3" six pack scoop. I also want to run a specific intake, the bigger heads have bigger ports and need a different intake than what I currently have. So all of that, and the desire for this to be a street / highway cruiser capped me around 300.

[JavmanBBG]

There comes a point where most folks will drill and tap extra bolt holes near the outside edge of the block and heads to help with gasket seal. Stock the Brewer heads will fit a stock block and I believe they already have the extra bolt holes in them. Now the Indy block has a larger bore provision and has provisions for the extra bolt holes cast in so it uses custom heads with a larger bottom ledge to allow for this. The FBS heads have a larger flow capacity than the indy's when ported to the max so people will weld up the lower rail and re drill it for the Indy block.

Now my buddy that had a set at one point had them ported for about a .750 lift nitrous cam and had flow numbers well in the 400s on the intake and 300s on the exhaust but was running a 427ci engine up near 9000rpm with 14.8:1 compression to make 900 hp n/a with a single dominator then had both a plate and fogger kit. He was using a sleved block that had previously cracked into a water jacket and it started to leach when hot and try to hydro lock not long after he put it in his car and he went a different direction. He is now making the same power with less port volume and flow but with 2 dominators and a set of very highly modified Indy street heads that have had the pushrod holes welded up and re drilled offset and sent to Adkins for massive port work using about an .860 lift cam ( witch is about max for stock cam bearings but you can go bigger if you drill for ford FE bearings). He is much happier with his low lift flow numbers and how it acts at lower RPMs although it is still built to shift @ 8700rpm and still using a modified stock block and crank.

Thing is he builds monster n/a and nitrous engines but has limited experience with FI although he has plans to build a big HP turbo AMC one day.

Personally I would be very happy to get a real 700hp with 91 gas but feel the smaller ports of the stock and Edelbrock heads would require e85 to do that. Although I would rather have 400hp across a broad rpm range than nothing with a spike of 700hp at the end.

[JavmanBBG]

Btw the FBS AMC tooling was destroyed in the early 2000's while being reworked so they are no longer available although there have been efforts to build copies out of billet.