Camshaft Guru needed

[geoffinbc]

I have to agree with everyone's opinions. That cam is shit. Period. Low lift, low duration, very narrow lobe centers and a ground in retarded valve timing. I am guessing it is a regrind of some sort. Then best you could do without tossing it in the garbage is advancing the cam. Otherwise change it out for a COMP 260 cam and enjoy your car.

[trotterlg]

Well, don't hold back just tell me how you really feel about it. We will see how it works I guess, it just runs and sounds so good right now, and it does have 20 degrees more duration than a comp cams 260. Larry

http://www.youtube.com/watch?v=ES4mJ...ature=youtu.be

[Superdave]

We just don't like to see people waste money, we've all done it and it sucks.. lol

[geoffinbc]

Duration at .050" is what really makes the difference. Comparing it to advertised duration is an indicator of how aggressive the ramp is. The closer the numbers are the more aggressive the ramp is.

The COMP 260 cam has 212* @.050 and yours has just 7* more. Not a huge difference. But the COMP has more lift and more lobe separation and a 4* advance. All of which mean more power and response. The signal to your carb will also be much stronger at low RPM so your engine will idle and respond much better to low speed throttle inputs. If you want a hot cam while still be drivable I would look at the Crane 272 cam.

[trotterlg]

I talked at length to the People at Delta Cam, I told them the coil bind height of the springs I had and that I wanted it to pull from about 3,500 or 4,000 to 7,000, also that is has a 12 to one CR. I know that advancing the cam will give you better low end, but that is not what I want, seems to me a Fiero needs a high turning engine to be any fun at all, now these things fall on their face at 4,500 which is just no fun at all. The narrow LSA is generally considered a patch to an engine with pour cylinder fill which any two valve engine has no matter what the piping looks like. Too bad people just keep building the same things over and over again. This one is as different as I can get it, we will see how it runs in a car, if it is as bad as you say I will just send it to the crusher and start over. Larry

[geoffinbc]

Yes a narrow LSA is good for power when cylinder volume out paces head flow. But the cam you have takes to the extreme and I don't know why they would have narrowed it up so much. Its not going to give you big power up top by doing that. I guess they just tried to give you power up high while working with your spring restrictions and compression ratio. Maybe they are trying to bleed off cylinder pressure to prevent detonation. But the thing is the aluminum heads for the 660 are not prone to detonation because they have a small well designed chamber and lots of quench. Its an odd cam and I have seen Delta do a similar job with a 4ZE1 Cam over on Planetisuzoo and I believe the owner found a used Calmini cam to replace it and he was much happier.

I think if you really want the best power at the RPM you are talking you should look at the solid lifter option from Crane and Crower.

[trotterlg]

Just from the LSA it is clear it is fairly radical, it will be interesting to see how it acts, especially with the carb on it. How and where an engine makes power has as much to do with how it performs in a car as how much horse power it makes (at least to me). The stock engine in a Fiero seems more suited to a tractor than a sports car. I think sporty cars need high winding engines with lots of gear shifting, this one is not a daily driver, it is for pure fun and something different than what I mostly see with the cookie cutter 3800 swaps and the anemic Comp cams 260 or 270's in a 2.8 iron head. If I wanted a boring engine I could have read about how to build one here for sure. I may have gone too far with this one but, the Damn thing sure sounds good! Larry

[geoffinbc]

LSA has little to do with a cam being radical or not. Optimal LCA varies only a tiny bit weather the cam is for a daily driver or a race engine. 1 or 2 degrees is not detrimental but 5 to 10 sure is. Compression, low lift flow and CID are the main determining factors when finding the optimal LSA. High compression, good low lift flow and small cubes meas a wider LSA. The opposite means a tight LSA. You would fall slightly on the wide side since you have a splayed valve head with good flow compared to the CID of the engine and high compression. If you had an optimal LSA of 110* on a 2.8L iron head and then changed to a 3.4L then you would narrow the LSA by 1* or so in order to get back optimal.

After looking over the card I realized it is laid out in a strange way. The overlap is actually 87.9* when calculated with the right events. The amount expressed on the card is at .050" which is not the traditional way to express overlap. So your overlap is where you would see an endurance racing engine designed to operate at high RPM. Your LSA is 100* (very very narrow) with a intake center of 108* (fairly normal) which is where you get the 8* of cam retard from. An optimal cam four your CID, compression and valve size would be 112* to 114*. With your compression you would want to be on the wider end of the spectrum to optimize power. If you had a wider LSA your engine would improve everywhere.

So after a second look the cam is not as bad as I first though when I glanced at the card. But it is still far from optimal. LSA should be much wider and the lift could easily be in the .550+" range and a solid lifter cam would trump the hydraulic lifters on this application any day of the week.

[trotterlg]

Thankyou for your analisis of the cam, I have had many many comments on it, and yours by far makes the most sence to me. Not saying the others are wrong, but yours seems to be based in some reality and knowledge. I an sure the Delta Cam people had some reason for setting it up the way they did, and some of it could have been just how it turned out, not really on purpose, we all know how those things go with a science experment. This chart was generated by running the cam on a machine that measures it after it was ground, not what it was intended to be. Looking at LSA for other engines, it seems to me that 60* V6 cams seem to run larger LSA's than say a Small block Chevy does, or is this because the V6 cams I am lookng at are intended for iron head engines?. In general what direction will this small LSA shift the curves?

[SappySE107]

That cam in a stock 3400 drops power after 6k.

[geoffinbc]

That cam in a stock 3400 drops power after 6k.

Yea I agree it will probably lose power everywhere versus the same cam with a wider LSA.

Even an iron head 660 has descent flow compared to a 350 or 400 small block with stock iron heads. This is why you would see most 660 cams with a couple more degrees of LSA compared to the same SBC cam. So lets say the small block cam is best with 108*LSA the same 660 cam might be best at 110*LSA now you put splayed valve aluminum heads on to bump up compression and low lift flow now 112* is the most optimal.

You will notice most LS and Gen III HEMI engines now a used wider LSA's than previous small blocks. Many old hot rodders will tell you this is to preserve vacuum and pass emissions. This is simply not the case. The engines just perform the best with the wide LSA because the flow is so much better compared to the displacement and the compression is higher. In the Pro Stock world you will see LSA's of 114* to 118* and they make no attempt to pass emissions or even idle.

[trotterlg]

At the idle in the video it is pulling a fairly steady 10 inches of vacuum, I don't have a tach on it, but I would say it is about 800 to 1.000? It will be interesting to see how the power range goes, guess it will favor a little higher RPM? Larry