Bipolar

I'm wanting to know if I should get a "nitrous" cam seeing how thats what my major power adder will be. And what is different about the grind of a nitrous cam? My heads are being fully ported and polished by Indy Cylinder Heads, I have no flow numbers yet, Will also be running 58mm TB, a LT1 Edelbrock air gap intake,(when they get them in), 3200 stall, 3.73 or 4.10 gears, Long tube headers, heads milled .20 and a thin head gasket, not sure what the compression will be yet. Was told about 11.3 to 1.. custom tune pcm, & I will be running 150-200 hp shot of nitrous. What cam should I use? And tell me if this combo has flaws please. Thanks guys..

OutlawZ

iTrader: (4)

depends on what you want OFF nitrous..... also do you have emission testing in your state???? I Like the xtreme energy line of cams personally from Comp.... a 230/236 is a good cam and if you want a more serious NA cam the 236/242 comes to mind... but the 236/242 is a big hydraulic roller and can be a PITA..... if your heads flow well and it's a daily driven car i'd keep it to the 230/236...... when i do a cam for my car I hate to do a NITROUS specific cam cuz it usually raises the lobe sep to a more nitrous friendly 114 or higher.... it cleans up the idle but when i have a cam i like people to know i have a cam so i'm a fan of the 112lsa or even 110.... and besides think about how much your car is going to actually be ON the squeeze????? Maybe 1/100th of the time you drive it right????? Setup a cam for the engine and your combo and forget about specifically setting it up for nitrous.... Either way that 150 or 200 shot is going to wake it up immensely even without a specific nitrous cam...... my car (with the 236/242 in a 355 11.75:1 motor with heads and all the bolt ons) ran like a friggin animal naturally aspirated and was uncontrollable on the 150 shot with anything less than full slicks.... it was a fun ride and I spec'd the cam out JUST for my motor and my combination..... the nitrous was an afterthought....

1997bird

iTrader: (2)

I had a custom cam made for my LT1 with a 112* LSA and 108* int centerline that would handle up to a 400 shot. It was 296*/310* advertized dur. and 234/242 @ .050" with .578" int and .568" exh. It ran strong on motor as well as n2o. It was designed for a 4L60E with a 3500 stall, 3.42 gears,headers, dual 3" to single 4" exh, 3420 lbs race weight on a 250 shot single stage n2o kit. I can get you a custom grind for $265 + $10 freight. PM me if you are interested.

seawolf06

iTrader: (8)

You can get a better cam than that one. That's just the GM847 cam with less lift and less agressive ramps. I don't know who designed that "custom cam" for you, but you got had.

For more than a 150-200 shot, you want a wider LSA especially with an A4. I'd say talk to bret bauer or joe overton about it. You can also call thunder racing or futral motorsports and they'll definitely be able to help you out. I know nothing about NOS cams, but this might be a good cam:

http://web.camaross.com/forums/showthread.php?t=483989

Do a search for good nitrous cams and then you can pick one out yourself for not much more than a shelf grind from Comp or Cam Motion. I'd recommend the comp xfi lobes since they are the most recent designs and made for EFI engines and the popular 918 beehive springs.

1997bird

iTrader: (2)

This is not a GM847 cam!! It is a custom grind from Erson camshaft. Just because it doesn't say "Comp Cams" doesn't mean that it is not a good cam. I get tired of hearing "Comp Cams" this and "Comp Cams" that. Yes they make some great products and I use them for my business, but come on they are not the only on out there that has knowledge. In fact the head cam grinder that I talk to probably knows more about cams than most of the "tech" guy's at Comp Cams. The car ran 11.75 in the 1/4 at Bandemere Speedway in Denver,CO. The corrected elevation that day was between 8000 to 9500 ft. The fact that the ECM was untuned at the time was also a limiting factor(hit fuel cut at 5800 rpm). That pass was launched off of motor and the n2o was not activated until at the 1/8 mile. The Pro Fogger n2o system was only set up for a 250 shot that day.

seawolf06

iTrader: (8)

Not trying to deviate from the thread, but:

GM847: 296/304, 234/242, .574/.595 112+5LSA
Yours: 296/310, 234/242, .578/.568 112+4LSA

I did say basically didn't I? So don't get so offended. The new GM847 is made by Crane anyway. Unless Erson has a cam grinder, they might just design a cam and have it ground elsewhere like most custom cam "manufacturers".

Let us know what you find out about nitrous cams. I think I read that you really don't need a cam made for nitrous until you get over a 200 shot.

1997bird

iTrader: (2)

This particular core was not one from Crane. However there are only three plants that manufacture cam blanks. They are then shipped out to different cam company's for them to grind into useable blanks. Crane is one of the biggest cam core general grinders out there due to the multi-million doller machine that they bought back in the early 70's. There are other cam blank grinders out there, but they have to use grinding stones which is a much slower process. The cam was built useing a 1.7 int ratio rocker and a 1.6 ratio exhaust rocker. What we were doing was trying to open the valve faster like other professional racing teams utilize. The reason that we were delaying the n2o was due to the early fuel cut and not wanting to damage the motor. The car was meant to use the n2o right off of the tree but run out of time getting the ECM out to be tuned by Fastchip before the race. I would also be hesitant to use the Comp 918 spring due to the weight of the valves. The stock lt1 valves are light and would work well with the 918 spring. If you converted to the 8 mm or 5/16" valves then it would work well with the 918 spring on a 2.02" or larger int valve/1.6 exh valve. Valve float would be a problem more than likely with a 11/32" solid stem valve.

seawolf06

iTrader: (8)

I agree, the 918's were designed for the lighter LS1 valves, so they can't be used for anything too heavy. That's why I went to a larger beehive spring.

SStrokerAce

iTrader: (2)

Only issue you will have there is the larger rocker is going to compound the valve control issues due to the increases acceleration.


Ok so the spring, valve, retainer and lock combination that moves together during operation is going to want a higher mass spring because the valve is of higher mass? Man someone better tell the BBC guys running 140g valves that they have to get back to higher mass springs to control that valve better then.... hell let's all just take the Ti retainers and copy them exactly in tungsten then.

Obviously there is some serious sarcasim in that last statement...... under almost every condition a lighter valve, lighter retainer and lighter SPRING in terms of mass, not pressure will result in better valve control and less valve bounce.

Trust me a 11/32 soild stem 2.055" valve +.100" long with a beehive can be stable to 7500rpm if you do everything right.

Bret

1997bird

iTrader: (2)

Bret I didn't know that BBC guy's were useing the 918 spring. I thought that they were using part # 26120-16, with a 1.88" installed height, instead of the 1.8" installed height on the 26918-16 spring. I know that they took a test motor with AFR heads on a BBC and took the dual springs off after getting dyno #'s. They then put a set of 26120-16 springs on there and dyno'd the motor all over again and gained close to 30 HP and 1300 rpm more than the dual spring set up with the same camshaft. I was referancing info that was given to me by Comp Cams tech line. I like the beehive style spring and the advantages that they bring to the table. I would probably use the 26120 spring over the 26918 spring with the larger valves. Honestly I am not trying to be a smart alec here, just trying to help with the info that I have been given.

Shane
Precision System's LLC

SStrokerAce

iTrader: (2)

Right the larger beehive is normally used on BBC's.

You have to take a lot of things into account.... valve and spring mass being one of them. The average 2.00" Valve is around 110g, going to a 2.055" adds about 7-10g.

Now the change from a 918 to a 120 is going to add more mass in the spring change than the valve change does, but it does add more pressure.

Bret

seawolf06

iTrader: (8)

Is that why some aftermarket heads use titanium retainers to keep the weight down on their bigger beehive springs?

SStrokerAce

iTrader: (2)

Well if you weigh them out a Ti retainer isin't worth too much mass savings on a beehive. It's VERY small and just some work to take mass out of the valve will get you there. I have gone all out and put lightweight valves, beehives and Ti retainers together and they will rev to the moon without issue.

90% of the time you don't need a Ti retainer with a beehive, in fact the steel stuff is more durable.

The trick setup would be lightweight steel retainers like Cup teams use. Problem is you guys aren't going to pay $680 retail for the retainers! I have two sets of those in the shop and they are trick ****! Now if we can take some of that and apply it to some inexpensive steel retainers for the street we will be all set!

Bret

1997bird

iTrader: (2)

I have used both the 26120 and the 26918 springs with the steel and Ti retainers. The steel retainers are more than half the weight of a Ti retainer for a 1.46" dual spring and for the $220 differance between the Ti version's are just not worth it. Thanks for the great info Bret!!

Shane

SStrokerAce

iTrader: (2)

No put the whole spring and retainer mass together and see what you get.... big difference.

Bret

1997bird

iTrader: (2)

Yeah with my 26918 springs, Ti retainers, and my hollow stem 1.6" exhaust valve, it was about the same weight as my Comp Cams 978-16 spring and Ti retainer. With my new solid roller cam I had to change my springs out to handle the lift and increase my spring pressure. Erson has a nice dual spring that is lighter than the #978-16 and has a lightweight Ti retainer to match.

SStrokerAce

iTrader: (2)

There are some dual springs out there that are only 17g more than a beehive! They aren't cheap but there is some pretty cool trick stuff out there.