Need cam guru thoughts/advice

[Les Gibson]

I've changed cams in the 422 stroker small block in my Arrow. The cam that was previously in the car was a Bullet grind with the following specs:
Gross lift: Intake .685 Exhaust .682
Duration @ .050 Intake 276 Exhaust 285
LSA 106 Installed 4 degree retard
valve lash hot .026 / .026, set .018 / .020 cold

Current cam is a Comp Cam with the following specs:
Gross valve lift: Intake .659 Exhaust .662
Duration @ .050 Intake 275 Exhaust 284
LSA 108 Installed straight up on the advice of Comp Cams Tech Department.
Valve lash listed on cam card .026 / .028 which I assume is hot, card doesn't specify, set .019 / .021 cold

engine specs are 340 X block 4.10 bore, 4.00 stroke, 13.0 - 1 compression, W5 CNC ported heads, Holley Pro Dominator tunnel ram with dual 850 Venom carbs massaged by Dominic Thumper. Powerglide with 5500 converter, 4.30 rear gear.

The engine builder and previous owner of the car told me he never liked the Bullet cam and has told me this Comp Cam should perform better. My best ET/MPH with the Bullet was 9.12 @ 146 in the 1/4.

My question is what performance can I expect with this cam change. I know there are other variables that will affect performance so I'm asking in general terms what I might expect. I'm worried that I've shot myself in the foot with this change.

Also, with these aluminum W5 heads what would be a good cold lash setting for the Comp Cam?

Should also add that these are both mechanical roller cams with Harlan Sharp 1.5 roller rockers.

 

[Garrett Ellison]

Just my $.02, but I would check P/V clearance with the Bullet cam at “straight up “ and four degrees of advance and try that before going with a smaller camshaft.

 

[Demonx2]

Along the lines of Garrett above, do you know why the PO "didn't like" the Bullet cam? Or why it was installed 4 deg retarded?

Also, depending on TC flash stall, are you truly lacking any low speed torque?

Edit: I should have mentioned I'm no cam guru! But I do know a little bit from all my OEM engine years.

 

[NC Engine Builder]

I'm no cam guru, but all you have done for the most part is remove lift, that seems like the wrong thing to do. Your @.050 numbers are pretty close to the same, so doubt the powerband will move much if any. And why would you have had the bullet in at 4 degrees retard?

 

[TT5.9mag]

I dont think you’re going to see any “improvement” with that cam change. The change will likely be backwards and probably so small you won’t see it on the time slip. Have the heads been flowed? Also, I would not try to guess at a cold lash setting. Just lash em hot so it’s always right.

 

[NC Engine Builder]

Let's ask a question from another angle. What was the reason you or the builder, didn't like the bullet? Where are you wanting improvement, and like @TT5.9mag mentioned, what do the head flow numbers look like?

 

[Garrett Ellison]

Also curious as to what the car weighs and what size of rear tire you’re running. Great looking car in the avatar picture, would love to see more of it!

 

[PRH]

Hard to know how the two cams really compare, ramp speed wise, without more data.
By what is posted, it certainly seems like the Bullet has faster lobes.
That isn’t always what the engine wants, but the better the heads are, the more likely it is that the engine can use it.

I’d also be curious as to why the Bullet cam was installed 4* retarded.
And, 4* retarded from where? The lsa or the recommended c/l(which might have been 100)?
It’s always best to specify exactly where the cam is(102, 104, 108, etc) instead of saying it’s “advanced” or “retarded” from some unspecified point.

Ultimately though, the only real way to know how they compare in that particular engine/car combo is……… to try it.

If the OP has the info, I’d be interested in knowing what springs and pressures the heads are set up with.

Not that this is good or bad, but the specs for the Comp look like it’s a 20-717-9.

 

[Les Gibson]

Along the lines of Garrett above, do you know why the PO "didn't like" the Bullet cam? Or why it was installed 4 deg retarded?

Also, depending on TC flash stall, are you truly lacking any low speed torque?

I don't know why he didn't like it, he didn't give me any details. I also don't know why the Bullet cam was installed at 4 degrees retard, I asked him and he couldn't remember why he did so. I just looked at the Bullet cam card again and it said to install the cam at 102 intake centerline so with an LSA of 106 perhaps that's why it was in 4 degrees retard? Also, I changed cams because I had a roller lifter tie bar break late last season, which allowed the lifters to rotate in their bores with did some minor scoring on the cam lobes for that cylinder. I thought it best to change the cam.

 

[Les Gibson]

I'm no cam guru, but all you have done for the most part is remove lift, that seems like the wrong thing to do. Your @.050 numbers are pretty close to the same, so doubt the powerband will move much if any. And why would you have had the bullet in at 4 degrees retard?

I didn't build this engine, it was what was in the car when I bought it. I asked the previous owner why the Bullet cam was installed at 4 degrees retard and he couldn't remember why he did that, so no help there. The Bullet cam card said to install the cam at 102 intake centerline, and with an LSA of 106 maybe that's why it was in at 4 degrees retard?

 

[Les Gibson]

Also curious as to what the car weighs and what size of rear tire you’re running. Great looking car in the avatar picture, would love to see more of it!

Car weighs 2240, and rear tire is a 31X13X15

 

[Les Gibson]

Hard to know how the two cams really compare, ramp speed wise, without more data.
By what is posted, it certainly seems like the Bullet has faster lobes.
That isn’t always what the engine wants, but the better the heads are, the more likely it is that the engine can use it.

I’d also be curious as to why the Bullet cam was installed 4* retarded.
And, 4* retarded from where? The lsa or the recommended c/l(which might have been 100)?
It’s always best to specify exactly where the cam is(102, 104, 108, etc) instead of saying it’s “advanced” or “retarded” from some unspecified point.

Ultimately though, the only real way to know how they compare in that particular engine/car combo is……… to try it.

If the OP has the info, I’d be interested in knowing what springs and pressures the heads are set up with.

Not that this is good or bad, but the specs for the Comp look like it’s a 20-717-9.

it is a 20-717-9 and the cam card specifies the specs are for cam installed at 108 intake centerline. I don't know why the Bullet cam was installed at 4 degrees retard. The previous owner couldn't remember why. The Bullet cam card says to 'degree intake lobe to 102' so I'm guessing with a LSA of 106 that's why it was installed 4 degrees retard? The only info I have on the springs are 2" @ 230, 1.30" @ 655.

I will also add that the reason I changed cams was I had a lifter tie bar break on me late last season which allowed the lifter to rotate in its bore and in did some minor scoring on the intake and exhaust lobes for that particular cylinder. While I could barely catch the scoring with my fingernail, I thought it would be best to replace the cam.

 

[Les Gibson]

I dont think you’re going to see any “improvement” with that cam change. The change will likely be backwards and probably so small you won’t see it on the time slip. Have the heads been flowed? Also, I would not try to guess at a cold lash setting. Just lash em hot so it’s always right.

I have no idea if the head have ever been flowed and I wasn't provided any flow information from the previous owner. I'll ask him. How do you do a hot valve lash without having inconsistencies in the settings as the valve train cools down?

 

[TT5.9mag]

I have no idea if the head have ever been flowed and I wasn't provided any flow information from the previous owner. I'll ask him. How do you do a hot valve lash without having inconsistencies in the settings as the valve train cools down?

You lash em fast. When you do it over and over you’ll get to the point where you can do it in no time at all. The engine will retain heat for a long enough time to do one side without it being too far off.

 

[PRH]

In addition to above, drag engines aren’t typically run at real high temps anyway.
If you’re not very quick at it, warm the engine to an easily achievable temp, like 130-140…….and just do one side.
Warm it back up if necessary, do the other side.

For a fresh build “first start” cold setting, I’d just put them at .020”.

 

[71Demon540]

If the cam was cut on a 106 LSA and installed at 102 centerline, that is 4 degrees advanced, not 4 degrees retarded. Just for clarification.

 

[PRH]

The only info I have on the springs are 2" @ 230, 1.30" @ 655.

The 20-717-9 uses lobes that are pretty easy on parts, so those spring loads should be fine(depending on how high you plan to turn it).

 

[PRH]

If the cam was cut on a 106 LSA and installed at 102 centerline, that is 4 degrees advanced, not 4 degrees retarded. Just for clarification.

I don’t think anyone was saying the old cam was in at 102.
The cam was on a 106, and the card called for a 102 c/l, but it was supposedly installed “4* retarded”.
It’s a bit of a moot point now, since that cam is no longer in the engine, and it doesn’t seem like anyone checked the installed position before removing it.

 

[71Demon540]

I don’t think anyone was saying the old cam was in at 102.
The cam was on a 106, and the card called for a 102 c/l, but it was supposedly installed “4* retarded”.
It’s a bit of a moot point now, since that cam is no longer in the engine, and it doesn’t seem like anyone checked the installed position before removing it.

Agreed. I just wanted to try to help avoid confusion for the OP.

 

[Garrett Ellison]

According to gear ratio and rpm (but without knowing how tight or loose the converter is!), it should be trapping somewhere around 7,000 rpm. If it were a clutch car (locked up) it would be around 6700 rpm accounting for an inch or so of tire growth at speed. Do you know what the car was being shifted at before? I’m going to go out on a limb and say the PO was favoring the slightly smaller cam because the converter may have been tighter than anticipated with the other cam retarded four degrees. It's really kind of a "WAG" how it's going to react without knowing the engine's intended power peak based on head performance. Any idea who did the CNC work on the W5's and what valve size they are? Probably safe to stay on the conservative side and guess 300 to 310 cfm based on other W5 heads that aren't full of filler rod or epoxy.

 

[Les Gibson]

I don’t think anyone was saying the old cam was in at 102.
The cam was on a 106, and the card called for a 102 c/l, but it was supposedly installed “4* retarded”.
It’s a bit of a moot point now, since that cam is no longer in the engine, and it doesn’t seem like anyone checked the installed position before removing it.

Yes previous cam was installed at 4 degrees retard. I took photos of both the cam and crank sprocket before I removed the Bullet cam. Crank sprocket was definitely installed on the 4R keyway.

 

[Les Gibson]

According to gear ratio and rpm (but without knowing how tight or loose the converter is!), it should be trapping somewhere around 7,000 rpm. If it were a clutch car (locked up) it would be around 6700 rpm accounting for an inch or so of tire growth at speed. Do you know what the car was being shifted at before? I’m going to go out on a limb and say the PO was favoring the slightly smaller cam because the converter may have been tighter than anticipated with the other cam retarded four degrees. It's really kind of a "WAG" how it's going to react without knowing the engine's intended power peak based on head performance. Any idea who did the CNC work on the W5's and what valve size they are? Probably safe to stay on the conservative side and guess 300 to 310 cfm based on other W5 heads that aren't full of filler rod or epoxy.

I shift the car at 6500, which I know is a conservative shift point, but I don't like to abuse my equipment unnecessarily. In the 1/4 it does trap around 7000-7200. I have no idea who did the machine work on the W5 heads, and there is minimal epoxy in some of the intake ports.

 

[Les Gibson]

I appreciate everyone's responses and opinions on this subject. I should make clear that the only reason that I changed cams is because of the slight damage done to a couple of lobes of the Bullet cam when I had a lifter tie bar break late last season. Both lobes for that cylinder had slight scoring from the lifters rotating in their bore when the tie bar broke. By slight scoring I mean you can see it, but I can just barely feel it with my finger nail. For all I know the Bullet cam may still be perfectly serviceable but I thought it better safe than sorry. In discussing my thoughts on changing cams with the previous owner of the car ( who lives 15 minutes from me) that is when he told me he didn't really like the Bullet cam ( but didn't elaborate on specifics) and thought this Comp Cam would be a good replacement. He told me he felt the Comp Cam would give better top end performance.
Because of the crappy weather we have been experiencing up here in Maine this spring the tracks have been late opening. I was finally able to go to New Oxford Dragway ( 1/8) this past Friday night to do some test & tune runs, but it proved to be fruitless as the track was so green it had no grip. I made two runs. The first run when the brake released the rear tires spun well past the 60 foot light and gave me a 6.26 run at 112. ( normal 1/8 mile passes are in the 5.70s at 118ish.) So I drop air pressure, lowered my launch RPM and loosened the front shocks a couple of clicks and the second run wasn't must better with a 6.23 at 112. I hung it up after that run as it was pointless to do any more passes. I was also trying a Mopar Performance M1 W5 intake that I'd had sitting around as I was curious what it would do. Turns out not much. Engine felt like it was suffocating going down track once I found some traction. So off it came this past Saturday. I thought about putting the Indy single carb intake back on, coupled with Thumper 1050 dominator style carb, but decided to stop experimenting and put the original Holley Pro Dominator dual carb tunnel ram back on as this was on the car when I bought it and I know it works. Planning on running at New England Dragway this weekend as I know the track prep will be top notch and I should get better performance.

 

[Les Gibson]

In addition to above, drag engines aren’t typically run at real high temps anyway.
If you’re not very quick at it, warm the engine to an easily achievable temp, like 130-140…….and just do one side.
Warm it back up if necessary, do the other side.

For a fresh build “first start” cold setting, I’d just put them at .020”.

When discussing this Comp Cam with the previous owner of the car ( he and his wife ran it for 16 years so he knows it like the back of his hand) he recommended cold lash setting of .019 intake and .021 exhaust. I'll try this for a couple of runs this weekend and depending on results may reset them to your .020 suggestion.

 

[NC Engine Builder]

Your results are about what I would expect. The MPH tells the tale. Lost power. But now how much did the cam loose, and how much was the intake. I'm suprised it wasn't worse really, that M1 is a MASSIVE downgrade compared to a pro dominator.