Give this 502/509 Combo Some Thought
09-29-2016, 11:13 PM
#12
Registered
iTrader: (3)
Txhawk, whats this heat you speak of with the small chamber? I ran 107cc chambers, with a blower for years, never had an issue.
Thats a huge chamber compared to a big chief head, no issues there at some extreme power levels. I wouldnt worry about that .
Those heads can be improved, if you wanted to sink some money into them. One of the best areas to focus on , for the low lifts we run in marine, is the chamber, throat/bowl and valve job. Im sure those heads could benefit from a little unshrouding in the chamber. Typically, doing that, will knock out 4-5cc of material. You'll lose a bit of compression, but done right, the airflow gains and burn quality will more than offset that.
The 741 cam wouldnt do much for you over your current cam. Theres better options for an off the shelf cam, that will be easy on parts and last a long time.
Id lose the dual plane intake, and go to a single plane like you said.
As far as a 100hp gain from just a cam swap in a combo like that, is well, a pretty tall order. Ive heard before how swapping out a crane 651 cam with a "custom" modern hyd roller, will net 100hp gain in a 540. If that was true, the 675hp 540s with a set of 290 afrs , and 651 crane cams, would have made 775hp with a "custom" hyd roller? Where those builds at lol. Seems like the 651 crane did just fine when compared to some of the recent 540 builds around here. Even if its an old grind. And it does it without hammering the pushrod tips , breaking rockers , or pounding out the valve seats.
Have you considered some 55mm cams, 903 lifters, 600lb spring pressures, 1/2" pushrods, and steel shaft rockers for a 5800rpm combo?
Thats a huge chamber compared to a big chief head, no issues there at some extreme power levels. I wouldnt worry about that .
Those heads can be improved, if you wanted to sink some money into them. One of the best areas to focus on , for the low lifts we run in marine, is the chamber, throat/bowl and valve job. Im sure those heads could benefit from a little unshrouding in the chamber. Typically, doing that, will knock out 4-5cc of material. You'll lose a bit of compression, but done right, the airflow gains and burn quality will more than offset that.
The 741 cam wouldnt do much for you over your current cam. Theres better options for an off the shelf cam, that will be easy on parts and last a long time.
Id lose the dual plane intake, and go to a single plane like you said.
As far as a 100hp gain from just a cam swap in a combo like that, is well, a pretty tall order. Ive heard before how swapping out a crane 651 cam with a "custom" modern hyd roller, will net 100hp gain in a 540. If that was true, the 675hp 540s with a set of 290 afrs , and 651 crane cams, would have made 775hp with a "custom" hyd roller? Where those builds at lol. Seems like the 651 crane did just fine when compared to some of the recent 540 builds around here. Even if its an old grind. And it does it without hammering the pushrod tips , breaking rockers , or pounding out the valve seats.
Have you considered some 55mm cams, 903 lifters, 600lb spring pressures, 1/2" pushrods, and steel shaft rockers for a 5800rpm combo?
09-30-2016, 06:50 AM
#13
Platinum Member
Platinum Member
iTrader: (6)
{ Have you considered some 55mm cams, 903 lifters, 600lb spring pressures, 1/2" pushrods, and steel shaft rockers for a 5800rpm combo? }
Calm down, deep breath, its Friday
Calm down, deep breath, its Friday
Gold Member
09-30-2016, 08:45 AM
#15
Txhawk, whats this heat you speak of with the small chamber? I ran 107cc chambers, with a blower for years, never had an issue.
Thats a huge chamber compared to a big chief head, no issues there at some extreme power levels. I wouldnt worry about that .
Those heads can be improved, if you wanted to sink some money into them. One of the best areas to focus on , for the low lifts we run in marine, is the chamber, throat/bowl and valve job. Im sure those heads could benefit from a little unshrouding in the chamber. Typically, doing that, will knock out 4-5cc of material. You'll lose a bit of compression, but done right, the airflow gains and burn quality will more than offset that.
The 741 cam wouldnt do much for you over your current cam. Theres better options for an off the shelf cam, that will be easy on parts and last a long time.
Id lose the dual plane intake, and go to a single plane like you said.
As far as a 100hp gain from just a cam swap in a combo like that, is well, a pretty tall order. Ive heard before how swapping out a crane 651 cam with a "custom" modern hyd roller, will net 100hp gain in a 540. If that was true, the 675hp 540s with a set of 290 afrs , and 651 crane cams, would have made 775hp with a "custom" hyd roller? Where those builds at lol. Seems like the 651 crane did just fine when compared to some of the recent 540 builds around here. Even if its an old grind. And it does it without hammering the pushrod tips , breaking rockers , or pounding out the valve seats.
Have you considered some 55mm cams, 903 lifters, 600lb spring pressures, 1/2" pushrods, and steel shaft rockers for a 5800rpm combo?
Thats a huge chamber compared to a big chief head, no issues there at some extreme power levels. I wouldnt worry about that .
Those heads can be improved, if you wanted to sink some money into them. One of the best areas to focus on , for the low lifts we run in marine, is the chamber, throat/bowl and valve job. Im sure those heads could benefit from a little unshrouding in the chamber. Typically, doing that, will knock out 4-5cc of material. You'll lose a bit of compression, but done right, the airflow gains and burn quality will more than offset that.
The 741 cam wouldnt do much for you over your current cam. Theres better options for an off the shelf cam, that will be easy on parts and last a long time.
Id lose the dual plane intake, and go to a single plane like you said.
As far as a 100hp gain from just a cam swap in a combo like that, is well, a pretty tall order. Ive heard before how swapping out a crane 651 cam with a "custom" modern hyd roller, will net 100hp gain in a 540. If that was true, the 675hp 540s with a set of 290 afrs , and 651 crane cams, would have made 775hp with a "custom" hyd roller? Where those builds at lol. Seems like the 651 crane did just fine when compared to some of the recent 540 builds around here. Even if its an old grind. And it does it without hammering the pushrod tips , breaking rockers , or pounding out the valve seats.
Have you considered some 55mm cams, 903 lifters, 600lb spring pressures, 1/2" pushrods, and steel shaft rockers for a 5800rpm combo?
No, I haven't considered getting deep into this shortblock, it only has 15 hours on it. I freshened it up to basically get the boat on the water after major restoration. I haven't changed a thing other than up 2 jet sizes since this boat came off the trailer. 28P LH at 5000 is 79-80 MPH and 9-10% Slip. If I can turn it another 200-300 RPM's I would be thrilled for the current money invested in power and would likely see 5 MPH based on slip.
85 in this boat will be a handful. Its entertaining at 75.
09-30-2016, 08:48 AM
#16
I was looking at Dart BBC Oval Port Single Planes and noticed they state to mill .060" to fit GM heads. Is this a Dart thing or something I should expect in general.
Is the consensus to run a Dominator flange and step back to 4150 with spacer to run my 850?
Is the consensus to run a Dominator flange and step back to 4150 with spacer to run my 850?
