Anyone using Big Chiefs?
 

Anyone using Dart Big Chief heads naturally aspirated. Pros and Cons? Thanks, Eric

I have used both Pontiac and Olds versions of the Big Chief heads in various drag racing applications over the years, but, never on a boat, the Pro's are they make alot more HP and flow A LOT more air than a conventional port head, espcially the 14 degree and later style. The Cons are mainly cost related, they wont use a traditional rocker system [you must use pedestal rockers, such as Jesel or T&D] and they are somewhat limited in the intake department, especially if you wish to run a "cast" intake, they are available now, but, aren't cheap, in other words not much, if anything, from a "regular" BB head will bolt on a Spread Port head. In a naturally aspirated configuration you would either need to have some serious cubic inches underneath them, or be running the engine at an RPM level that would warrant using them.

If price isn't an object then you can also run a "Chemi" cylinder head, designed and sold by Sonny Leonard, they use a Chevy/Hemi design that makes well over 100HP more than a Big Chief, I have seen these heads on a Naturally Aspirated BB make OVER 2000HP, but, again, they AIN'T cheap, expect to shell out around 20K for the heads, and NOBODY makes a cast intake for them.

Michael

Thanks for the reply, I've already got the heads, intakes etc...on some of Kurt's marine motors that I bought. They have T&D shaft rockers and a solid cam. I am trying to decide which way to go. If I stay with them I am going to have to redo my Stellings tails. Recommend new springs at 75 hrs. More maintainence than I really care for. If I put some AFR's or Darts with hyd. roller, they might be better for my purpose. Any one want some Big Chiefs?

Bill just had his power redone and made 1300+ with big chiefs. 598s 1471s and meth injected. I personally dont like all the extra weight and length of the push rods,valves,and custom everything.

I would go with a set of Dart 320's or 360 depending on how big the motor is, good shaft rockers, and a hyraulic roller shaft, tons of power, low maintainance, and should you ever need to change anything most of the parts are "off the shelf", I agree with Hot Pursuit, they really aren't worth the hassle for the majority of applications

Or I could go big and put a milder hydraulic cam and use some blowers to increase intake velocity. This would probably set the OSO record for fastest junked bravo.

I think the ports would way to big for most all marine apps, they make tons power, but at much higher rpm than most boat engines wil never see..and in the mid range it would be a dog... also not sure how many people even make exhaust for them for marine use as they are different...Rob

I run the Big Dukes with a Procharger, 2.375 CMI's, the Big Cheif has a bigger intake runner, on a N/A motor I doubt you would have much bottom end.

[ This would probably set the OSO record for fastest junked bravo.[/QUOTE]

:eek: :eek: Spend the $$$$ on some 6s first.. :drink:

Eric,
I was good to talk to you the other day. Everyone else seems to have the same opinion that I have.....that are not very practical for what you are trying to do. Like I told you, they are WAY to much head for 700-750 hp engines. Let me know if I can help you in any way or if you have any more questions. Thanks, Eddie.

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 (;

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.

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.

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

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 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.

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....

Pistons are BRC 4.520 bore. Here's a photo of the design.

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.

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

They were pretty stout engines. Pretty sure they idled between 1000-1200 rpms. They pushed the boat, 87' Flat-Deck Top Gun, to 80+ mph. If memory serves me correctly they were turning 6000-6500 rpms WOT.

With your size motor I've seen a lot of guys running the Crane 139651 which is fairly mild. As I stated earlier, I'm running a solid roller cam in my 580" blower motors. I'd have to double check my cam card but I think I'm running the Crane 138641. I adjust the lash once a year and I'm also running .016 lash instead of the .020 lash they call for. They Idle about 950-1000 rpms, never stall even if it's a quick shift.

I'm not sure if those cams will work with your heads but they're cams that have decent ramp speeds without crazy lift.

Frank

idanc1,
I would be interested in more info on the the combination where the 520 CI NA motors made 1100+ HP.
Ben

Is this how you make BC's last.

Jesel


http://www.hotrod.com/techarticles/e.../photo_11.html

Hmmmmm, very nice. Ti valves-check, Bryant Billet-check, Jesel valve train-check............:drink:

I hear the way to make them last is to change the valve springs every 50 hrs. if your cam is in the .700 lift area. More often if the lift is higher. Much more often. Also the offset rockers have to be inspected regularly. The geometry puts a lot of stress on them. Not worth the trouble to most people.

So how much power do you lose going from a solid roller to a hydraulic roller keeping the same duration at .050 . What's the RPM range of a hydraulic roller?

[QUOTE=PatriYacht;2815515]I hear the way to make them last is to change the valve springs every 50 hrs. if your cam is in the .700 lift area. More often if the lift is higher. Much more often. Also the offset rockers have to be inspected regularly. The geometry puts a lot of stress on them.

So ya think so ???? mmmmmmmmmmmmm:eek:

Bill,
What kind of set up are you doing with your Chiefs?????


GPM,
Jim Valako told me that the weight of the valve train is heavy and one hydraulic motor that he did started to float the valves at 6000 rpm. which would be right when the large ports start to become the most efficient.

Titanium valves, Beryliun seats, Jesel valve train :ernaehrung004::ernaehrung004:

titanium keepers and retainers............

**

I can't tell you that much about it other than what already did. It's some sort of "class" motor. Ask him the power to be sure, I'm working from memory and was busy with dyno and my 2 motors. :drink: Here is the builder link. http://www.besracing.com/

Eric,

What did you decide on for heads? How's the project coming and/or the boat running?

Frank

Jim V is working on the heads and I am building the short blocks. Should be ready soon.
Eddie

Awesome, cool!

Jimmy V is a great guy and really knows his heads .......:drink:

How do the titanium valves hold up in the marine application? Are you using them for both intake and exhaust?

My 1.90" Inconel exhaust valves are as heavy as my 2.4" SS intakes. Would love to lighten the weight but I always thought Titanium is for drag motors.

I have used Ti. valves in a pile of drag motors back in my drag racing days, they where incredibly light, but, tended to be hard on valve seats, they take INCREDIBLE amounts of heat and are lighter than Inconel, but, unless you are spinning the motor to insane rpm levels I wouldn't recommend them in a boat, unless its a drag boat and/or you have a bottomless bank account and alot of free time for maintainance.

Something else I have found out [first hand] is you DONT want to ever "backfire" the motor, as strong and light as those valves are you would be shocked at how fast they "tulip" if you burp the motor.

I guess what it comes down to is that [99% of the time] there are better ways to waste your money.

Just my Thoughts!
Michael

If I had the money I would buy a pair of these, with a 10:1 flat piston, hydraulic roller and fuel injection, OH YEAH!!!!!


http://www.sonnysracingengines.com/e...-racing-engine

You should be using a alloy valve seats on Ti valves, I use alloy on all my heads, if not the intake always on the exhaust.