Which Head?- 598 NA

fastashley wrote:Want to do a NA 598 for the Sand Truck
'77 F150 4x4
4000 lb
33" scoops, 5.40 gear, hi-range
Track varies between 300'-600'
Want to build a 'reliable' BBF. I don't want to change valve springs every weekend. Max rpm, probably 7500.
A460 or Eliminator block
4.600 bore or larger
Scat steel crank
Oliver or Crower steel rod
14:1
HEADS?- Are CNC A460 enough? Is it worth considering C460 or Thor? If I went with a big bore/short stroke combo, would that change the head decision? (4.700 bore) I want to be less than 600". There are no 'class' rules, just line up with guys also runnin full size trucks. Cost is not an option...mostly

4.600" X 4.500" works well with either the "A" or "C" head.

I'd come down to your budget. If you are going to use Ti valves and a shaft rocker system you may as well jump to the C460 program.

fastashley wrote:Lem, are the valves poor quality or just the wrong size?

Scott Foxwell wrote:To get the most out of that cubic inch at 7500 you're going to need something you can put a 2.450+ intake valve in. Good luck finding a set of Thor's. Keep the stroke on the short side if you can and it won't put such a demand on the induction. 4.63 x 4.375 keeps you under 600ci and with a 6.8 rod is only a 1.31 piston. Not a bad combination and 7500-8000 would be a walk in the park.

Lem Evans wrote:I see where you are coming from but, I've been involved with several dozen 588/598/604 engines with the "A" or "C" heads and haven't seen the 4.5" stroke to be an issue at that kind of RPM.

It may be one of those deals where something isn't as bad as it looks like it is.    

Lem Evans wrote:I didn't say you were talking ring seal.....Randy was.

Most of the time there is a practical & a financial factor to my view of an engine package. Both are very kin.

The practical aspect of the crankshaft is: OP said he is gonna use a Scat crankshaft...the readily available shafts from Scat and most others are 4.300" not 4.375".
The financial aspect of the crankshaft is: strokes other than 4.150/4.300/4.500" really effect the price point.

Another aspect of the practical side of a package for this truck is: The thing weighs TWO TONS and the track can be as short as 300'. I'll take some 'peak' or any other way I can get it piston acceleration.

rmcomprandy wrote:

Lem Evans wrote:I didn't say you were talking ring seal.....Randy was.

Most of the time there is a practical & a financial factor to my view of an engine package. Both are very kin.

The practical aspect of the crankshaft is: OP said he is gonna use a Scat crankshaft...the readily available shafts from Scat and most others are 4.300" not 4.375".
The financial aspect of the crankshaft is: strokes other than 4.150/4.300/4.500" really effect the price point.

Another aspect of the practical side of a package for this truck is: The thing weighs TWO TONS and the track can be as short as 300'. I'll take some 'peak' or any other way I can get it piston acceleration.

I have often witnessed "blow-by" meter testing when reaching over 90 feet per second average piston speed, that a normal big bore .043" thick ring weighs enough that it WILL flutter and not seal against the piston ring land when changing directions at TDC unless it is assisted by some kind of gas port or crankcase vacuum or preferably both.

Believe whatever you wish to believe and I will, too.

rmcomprandy wrote:

Lem Evans wrote:I didn't say you were talking ring seal.....Randy was.

Most of the time there is a practical & a financial factor to my view of an engine package. Both are very kin.

The practical aspect of the crankshaft is: OP said he is gonna use a Scat crankshaft...the readily available shafts from Scat and most others are 4.300" not 4.375".
The financial aspect of the crankshaft is: strokes other than 4.150/4.300/4.500" really effect the price point.

Another aspect of the practical side of a package for this truck is: The thing weighs TWO TONS and the track can be as short as 300'. I'll take some 'peak' or any other way I can get it piston acceleration.

I have often witnessed "blow-by" meter testing when reaching over 90 feet per second average piston speed, that a normal big bore .043" thick ring weighs enough that it WILL flutter and not seal against the piston ring land when changing directions at TDC unless it is assisted by some kind of gas port or crankcase vacuum or preferably both.

Believe whatever you wish to believe and I will, too.

rmcomprandy wrote:

Lem Evans wrote:I didn't say you were talking ring seal.....Randy was.

Most of the time there is a practical & a financial factor to my view of an engine package. Both are very kin.

The practical aspect of the crankshaft is: OP said he is gonna use a Scat crankshaft...the readily available shafts from Scat and most others are 4.300" not 4.375".
The financial aspect of the crankshaft is: strokes other than 4.150/4.300/4.500" really effect the price point.

Another aspect of the practical side of a package for this truck is: The thing weighs TWO TONS and the track can be as short as 300'. I'll take some 'peak' or any other way I can get it piston acceleration.

I have often witnessed "blow-by" meter testing when reaching over 90 feet per second average piston speed, that a normal big bore .043" thick ring weighs enough that it WILL flutter and not seal against the piston ring land when changing directions at TDC unless it is assisted by some kind of gas port or crankcase vacuum or preferably both.

Believe whatever you wish to believe and I will, too.

Scott Foxwell wrote:

rmcomprandy wrote:

Lem Evans wrote:I didn't say you were talking ring seal.....Randy was.

Most of the time there is a practical & a financial factor to my view of an engine package. Both are very kin.

The practical aspect of the crankshaft is: OP said he is gonna use a Scat crankshaft...the readily available shafts from Scat and most others are 4.300" not 4.375".
The financial aspect of the crankshaft is: strokes other than 4.150/4.300/4.500" really effect the price point.

Another aspect of the practical side of a package for this truck is: The thing weighs TWO TONS and the track can be as short as 300'. I'll take some 'peak' or any other way I can get it piston acceleration.

I have often witnessed "blow-by" meter testing when reaching over 90 feet per second average piston speed, that a normal big bore .043" thick ring weighs enough that it WILL flutter and not seal against the piston ring land when changing directions at TDC unless it is assisted by some kind of gas port or crankcase vacuum or preferably both.

Believe whatever you wish to believe and I will, too.

I completely agree with you...but I can't imagine building an engine like this without either (gas porting, proper ring gaps and a vac pump). I guess I figure that's a given.

Scott Foxwell wrote:

rmcomprandy wrote:

Lem Evans wrote:I didn't say you were talking ring seal.....Randy was.

Most of the time there is a practical & a financial factor to my view of an engine package. Both are very kin.

The practical aspect of the crankshaft is: OP said he is gonna use a Scat crankshaft...the readily available shafts from Scat and most others are 4.300" not 4.375".
The financial aspect of the crankshaft is: strokes other than 4.150/4.300/4.500" really effect the price point.

Another aspect of the practical side of a package for this truck is: The thing weighs TWO TONS and the track can be as short as 300'. I'll take some 'peak' or any other way I can get it piston acceleration.

I have often witnessed "blow-by" meter testing when reaching over 90 feet per second average piston speed, that a normal big bore .043" thick ring weighs enough that it WILL flutter and not seal against the piston ring land when changing directions at TDC unless it is assisted by some kind of gas port or crankcase vacuum or preferably both.

Believe whatever you wish to believe and I will, too.

Yeah, I never understood the odd crank choices for Fords. In that case I'd go for the 4.5 as well. Just wouldn't be my first choice especially with an A head.

Lem Evans wrote:

What is  "normal" .043" deal look like? Is it a .210" or 170"?

Lem Evans wrote:

Scott Foxwell wrote:

rmcomprandy wrote:

Lem Evans wrote:I didn't say you were talking ring seal.....Randy was.

Most of the time there is a practical & a financial factor to my view of an engine package. Both are very kin.

The practical aspect of the crankshaft is: OP said he is gonna use a Scat crankshaft...the readily available shafts from Scat and most others are 4.300" not 4.375".
The financial aspect of the crankshaft is: strokes other than 4.150/4.300/4.500" really effect the price point.

Another aspect of the practical side of a package for this truck is: The thing weighs TWO TONS and the track can be as short as 300'. I'll take some 'peak' or any other way I can get it piston acceleration.

I have often witnessed "blow-by" meter testing when reaching over 90 feet per second average piston speed, that a normal big bore .043" thick ring weighs enough that it WILL flutter and not seal against the piston ring land when changing directions at TDC unless it is assisted by some kind of gas port or crankcase vacuum or preferably both.

Believe whatever you wish to believe and I will, too.

Yeah, I never understood the odd crank choices for Fords. In that case I'd go for the 4.5 as well. Just wouldn't be my first choice especially with an A head.

Well uh, there is nothing 'odd' about it.:

4.500" stroke with a 6.700"  or a 4.300" stroke with a 6.800" rod works with the same piston CH/CD.... grade school math.

rmcomprandy wrote:

Lem Evans wrote:

What is  "normal" .043" deal look like? Is it a .210" or 170"?

NORMAL piston ring radial dimension is spelled out in the automotive machinists handbook as "bore size divided by 22"

Anything else in the aftermarket costs more money and a lot of cheap-ass people don't believe is is necessary to spend their money on things like that.  It doesn't show and they don't know how to talk about it.