AFR 165 + b-31 cam = NO POWER???

[RacEoHolic330]

I just put on a set of AFR 61cc heads with an AFM b-31 cam (.542 max lift) on my stock shortblock. Set the fuel pressure to 38 psi no vac and the base timing to 18* . My problem is that the car feels like such a dog. It is faster than the stock heads but not a lot. It just isn't pulling the way it should anywhere in the powerband.

I don't understand what it could be. My only thoughts are that the cam is too much for the stock afr springs and I might need to upgrade them. Also, maybe my 6.300" pushrods are the wrong length. Maybe I possibly have valve float?? All the geomentry looked good when I set the rockers. I have no idea what the problem could be. I really need some help on this issue

-scott

 

[RacEoHolic330]

just a few more details:

it's got a stock ported intake, 24lb injectors, 75mm pro-m mass air meter, 70mm tb, 1 3/4 shorty headers, scorpion 1.6 roller rockers, a 255lph in-tank pump, and a double roller crane timing chain.

 

[795.0pacecar]

Stock intake is realy killin you.

 

[shorty1993]

Stock intake is realy killin you.

that sounds like a good thought. did the timing chain go on at the same time? any chance your valve timing is out.

 

[88POSLX]

Is 18 degrees base timing a typo?

 

[RacEoHolic330]

the stock intake shouldn't be hurting me THAT much. The car should still be pulling better. When I installed the cam and the timing chain I put it in straight up. I lined up the dot on the timing gear with the dot that was on the other gear on the crankshaft. As for the timing, i set it at 18* with the spout out and then put the spout back in, I have no pinging.

 

[thumper460]

If you need more low end... pull the cam up to 106 or 105 intake center line.. this will increase the low end velocity and make things rock!! the intake is restrictive, but as you said it should still get a lot of power from it!! Ign timing at 18* and no ping... what were the CC's on the heads?? you could have lost a lot of power by dropping compression ( 62 CC's are the stock e7's).. now all that flow is stumbling around cause there is NO velocity!! cool>>?

Just me............................

Thumper

 

[RacEoHolic330]

thumper, what do you mean by 106 or 105 intake center line?

 

[thumper460]

to increase Veloicity and low end power ( Compression) you need to close the intake valve sooner... thus ADVANCE the cam !! what is the intake centerline on the cam?? and what are the CC's on the heads?? both could be killing all your low to mid range rpm!! and by the time the velocity is building in the heads... the race is over!! Just need to tune what you have a bit!! Yes an intake will help...but correct the power loss thru tune and the bennifits with a new intake will be that much more...cool??

Just me..............................

Thumper

 

[ironmedic]

hey its mr. thumper! YAY! he is a cylinder head god LOL!
he has cheap prices on his kits too. i once bought him burger king and traded it for some cylinder heads! (joke)

 

[RacEoHolic330]

I just installed the cam straight up. No advance, no retard. The heads are 61cc because I'm going to be adding a supercharger in a few months. My timing chain allows me to advance or retard the cam 4* but that seems like a lot.

 

[SmockDoiley]

Honestly, you need to get some numbers for us to really tell you if something is wrong. Maybe it really is moving pretty good but you expected more. By just telling me its not fast enough, really doesnt say much. Get some track numbers or a before and after dyno run. With that we can go somewhere. Also, what is the duration on the cam, and does the car seem sluggish off the line and then it starts to pull hard. Get a little more specific. Also, have you allowed the computer time to adjust to everything, and what is your A/F ratio at right now?

 

[RacEoHolic330]

i ran the car last night and it ran a 13.88 at 99.14 mph with a 2.02 60'. I did spin off the line but those times should be a second faster. If the car was just getting a really bad launch, my mph would be a lot higher. The cam duration is 218/228. I've been driving the car around for a few days so the computer has had plenty of time. I don't know the exact a/f ratio. The plugs are clean and there is no smoke between shifts.

 

[Rick 91GT]

I know Ed has said many, many times that the AFM cams just do not go well with a AFR head flow characteristics. The AFM B series cam is made for a blower so you will not have that super crisp NA cam feel or power.

What was your piston to valve clearance? I ran a AFM N-61 series cam and needed to the flycut for clearance .544/.563 228/232 110 center Stock shortblock, Holley heads.

What are the 330' and 1/8' mile numbers (time and MPH) this tell you more then the 1/4mile time as far as power.

That intake is hurting you....

 

[RacEoHolic330]

330- 5.794
1/8th- 8.927 @ 79.63

The valves are not hitting the pistons as I checked when I installed everything. I do have a holley lower intake sitting in my room. I could buy an upper and see how that does over the stock intake. I think it would be too big though without the blower.

 

[Rick 91GT]

The Holley would not hurt that combo with the proper cam. I ran the entire Holley kit and went high 11.80's @ 116mph, 8.8:1 comp 302, AFM N-61 cam, would have been quicker with more gear. If memory serve me correct my 1/8th were around 7.7's @ 91mph.

Your 1/8mile times show the car is down on power, there is something wrong for sure. I think the 1.75" headers are also slightly large for your current combo if you are not reving it to the moon. Pushrod length is very important, did you check to make sure the rockers were centered in the valve, etc even when rotated.

 

[RacEoHolic330]

I did not check that placement of the rockers on the valve stems. If it isn't lined up does it mean that the pushrods are too long? I've heard people say that when you lock down the rocker nut there should be about three threads showing at the top of the nut. I think I had more than three threads showing. My pushrods might be too long. I think I'm going to go to Ed and get some upgraded valve springs and stock length pushrods and give that a shot. Maybe the .05" extra is killing me. I know the headers are a bit large but I got them in preparation for the supercharger.

 

[Rick 91GT]

Go to www.cranecams.com click on tech and go to installation instructions, follow the instructions for the extruded alum arms the rockers up it may be you have the valves too tight and they are staying open letting the power go right out the exhaust, adjustment is very important.

You want to mkae sure the rocker tip stays on the center of the valve when the motor is rotated, if the pushrod is to short it will ride on the backside of the tip, if they are to long it rides on the front of the tip. You can take a Black marker and mark the tip on the valve, bolt the rocker on, adjust it, then rotate the motor and take the rocker off, ot should leave a nice thin line in the middle of the valve tip.

You can't go by threads sticking out the top.....

 

[RacEoHolic330]

Thanks a lot for the info Rick. I really think that my pushrods are the wrong length. I'll check the rocker position and let you know what things look like.

 

[90Notch]

"I just installed the cam straight up. No advance, no retard. "

Almost all AFM cams have advance built into them, you need to degree it to see where it's installed. I.e. if this cam has a 112LSA then I willing to bet that the cam installed dot to dot is on (or should be) a 108ICL. Thumper is telling you to advance it 2 more degrees.

My vote goes to wrong cam and too small intake.