Anyone using Big Chiefs?
#11
Registered
iTrader: (1)
A good set of 24 degree heads ( 345cc ish) will flow as much as the Big Chief heads until about .600 valve lift on the intake side. After that the BC heads really take off and will flow over 500 cfm with a big port at high lifts..(950+ lift). The exhaust ports are the same way, at higher lifts they will flow 370 cfm + @ .850 lift whereas the conventional heads poop out. If you have a big inch motor I'd run them with a lot of lift on the cam. If you decide not to I'll come pick them out of your trash (;
#12
Jim V,
Thanks for the reply. I've got 594 c.i., found out that my heads are custom chambered to my pistons. New heads would require either piston change or custom chambered heads. Not really a road I want to go down. Kurt claims good performance and longevity with new cam profiles and hyd. roller cams. There are reputable naysayers with this combo.
Thanks for the reply. I've got 594 c.i., found out that my heads are custom chambered to my pistons. New heads would require either piston change or custom chambered heads. Not really a road I want to go down. Kurt claims good performance and longevity with new cam profiles and hyd. roller cams. There are reputable naysayers with this combo.
#13
With all that talk about big power, are you going to do some in that 28ZX? For a sub 30 footer, those like some power.
#14
Geronimo36
Gold Member
Eric,
Mercury used those heads in their Class engines a while back because they made a lot of power. They have some steep valve angels and longer than a standard valves. Set-up is critical and up-keep on springs, lash and valve guide wear are imperative. If you keep up on them and maintain them accordingly they will last but if you don't you can drop valves.
If it were me and I had the cash to spring for new heads I'd probably go that route but if not I'd run them. I'm not sure what Kurt put in those engines as far as a camshaft but I know Mark/Garry needed to be able to idle around the docks so I'm not sure how aggressive Kurt was in his selection.
If you're going with a new cam some of the new solid roller profiles will go 250 hours on rollers/springs etc... I have a solid Roller profile in my blower motors that JCPERF recommended/installed and have two seasons of boating with absolutely no problems.
There's also been some advances on how they set up valve guides in those heads for marine use. I believe the valve guide runs thru the water port and they've come up with a two piece guide design to help with distortion from the heat and cold.
I see you're in contact with Eddie and I'm sure he'll set you in the right direction. Also, I'd recommend talking to JCPERF about your setup. Him and I talked in great detail about setting up the Big Chiefs last summer and he had some valuable input!
If there's anything you need please let me know.
Frank
Mercury used those heads in their Class engines a while back because they made a lot of power. They have some steep valve angels and longer than a standard valves. Set-up is critical and up-keep on springs, lash and valve guide wear are imperative. If you keep up on them and maintain them accordingly they will last but if you don't you can drop valves.
If it were me and I had the cash to spring for new heads I'd probably go that route but if not I'd run them. I'm not sure what Kurt put in those engines as far as a camshaft but I know Mark/Garry needed to be able to idle around the docks so I'm not sure how aggressive Kurt was in his selection.
If you're going with a new cam some of the new solid roller profiles will go 250 hours on rollers/springs etc... I have a solid Roller profile in my blower motors that JCPERF recommended/installed and have two seasons of boating with absolutely no problems.
There's also been some advances on how they set up valve guides in those heads for marine use. I believe the valve guide runs thru the water port and they've come up with a two piece guide design to help with distortion from the heat and cold.
I see you're in contact with Eddie and I'm sure he'll set you in the right direction. Also, I'd recommend talking to JCPERF about your setup. Him and I talked in great detail about setting up the Big Chiefs last summer and he had some valuable input!
If there's anything you need please let me know.
Frank
#15
Registered
Panther,
I agree with your post 100%. The heads can be made to live if set up and maintained correctly. The thing is......Eric has 594 ci and is only trying to make 700-750 hp. Anybody worth a damn should be able to do that with 23 deg heads and a fairly mild hyd. roller. If they can't, they need to not be building engines. Big chiefs definitely have there place, just not here for the amount of power he is looking for.
Eric, can you find out just what pistons are in the engine?
Eddie
I agree with your post 100%. The heads can be made to live if set up and maintained correctly. The thing is......Eric has 594 ci and is only trying to make 700-750 hp. Anybody worth a damn should be able to do that with 23 deg heads and a fairly mild hyd. roller. If they can't, they need to not be building engines. Big chiefs definitely have there place, just not here for the amount of power he is looking for.
Eric, can you find out just what pistons are in the engine?
Eddie
#16
Geronimo36
Gold Member
I hear ya... those engines made 780/800 hp with 9:1 compression. The engines had Kinsler injection on them for a dyno pull and made 830 hp.
Might be easier to go with a flat top piston and some AFR's or something.
Might be easier to go with a flat top piston and some AFR's or something.
Last edited by Panther; 03-04-2009 at 01:04 PM.
#17
Agreed, conventional stuff should be good into the 900hp range NA on pump gas below 6500 rpm. Chief stuff is for big inch high rpm 7500+ max effort. A cool compromise head I would try if I ever went NA again would be the 18 degree dart ovals...of course you have to go with sheet metal intake but I hear those heads are pretty sick. BES had an engine on the dyno before mine last spring that was a 520" BBC with conventional heads and single quad that made ~1165hp @9000rpm.... (I can't remember the exact power but that is close) Stupid motor, and it didn't look like anything special sitting on the floor....
Last edited by jdnca1; 03-04-2009 at 08:36 PM.
#19
Frank,
How did they run? What RPM's were they turning. Kurt says use the heads, with newer cam profiles he has had good performance and longevity. Cam was solid roller .714, 266 intake and 270 on exhaust, crane 13519-16. Not much ramping very rapid open and close.
How did they run? What RPM's were they turning. Kurt says use the heads, with newer cam profiles he has had good performance and longevity. Cam was solid roller .714, 266 intake and 270 on exhaust, crane 13519-16. Not much ramping very rapid open and close.
Last edited by SkiDoc; 03-04-2009 at 09:40 PM.
#20
Registered
Looks like a pretty standard inverted dome. The only problem I see with using a standard 23 deg head is that the compression will be kind of low. By that I mean that you will not be able to get 10:1. The big chiefs have a much smaller combustion chamber that standard BB heads. I would think that 9:1 would be attainable, which is enough to get you to 700+ hp.
Eddie
Eddie