Intake Runner volumes
04-02-2016, 10:32 AM
#41
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i,m also going to say that if the op went with eq heads out of the box and a 525 efi cam he would see a decent increase in power for not a lot of money,jmo.in most cases the eq heads would be cheeper than freshening up the stock gm heads and make more power from start to finish,a win win in my book.
Last edited by mike tkach; 04-02-2016 at 10:34 AM.
04-02-2016, 10:32 AM
#42
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could be the cam was retarded 4° from the get go over the spec,and advancing it put it back to straight up.
04-02-2016, 10:33 AM
#43
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04-02-2016, 10:52 AM
#44
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Thread Starter
i guess to see the 16 hp gain you would actuially need to do back to back dyno pulls with the cam straight up and then retarted.i know that sounds simple enough but even with a cloyes 2 peice timing chain cover and a cloyes hex a just timing set it still requires some work.all the rocker arms need to be backed off before making the cam adjustment and even if you think you moved the cam 4 deg without checking with a deg wheel you really don,t know exactly where the cam timing is at.imo the hex a just is great for helping the builder degree the cam but i would not trust the marks on it without redegreeing the cam after the move.
Imo, most camshafts, are not 100 percent optimal out of the box. Theres just too many variables that effect what the cam timing the engine will like. Simply doing a nice trick valve job, increasing low lift airflow, can change what the engine wants for cam timing. In other words, just doing the valve job, and no other changes, you might not notice a lot. Change the cam timing to work with the fact the cylinder fill is better within that timeframe of the valve opening and closing, and you might see the benefits of a cam timing change/valve job work. Maybe its 5hp, maybe its 30hp. Nobody can answer that on paper.
Its all time based. You have X amount of time at 2,000RPM, to fill a cylinder the best you can, and you have x amount of time, at 6000RPM to fill a cylinder the best you can. Low rpm, close the valve too late, you lose power. High rpm, close the valve too soon, you lose power. Unfortunately, the BBC , doesn't have variable cam timing like some modern engines, and its a fine line of balancing things out. If you want big power at 6000rpm, you may have to give something up at 2000rpm. Most off the shelf, and even custom cams, have a certain amount of advance built into them, how much usually depends on the LSA. Wider lobe sep's, 4-5 deg of advance is common.
i think generally speaking, if you advance the cam and gain power everywhere, the cam was too big. If you retard the cam, and gain power everywhere, the cam was too small. Then of course theres LSA's, lift values, ramp profiles, and so on.
I think if you really wanna validate your cam choice, to find out if in fact it is the best, it must be compared against other cams, or cam timing changes. Same goes for cylinder heads. But, thats impossible for the average guy, so we pretty much are either happy, or not happy with the power output. I've seen a few builds at the 1000hp mark, pick up close to peak 50hp with just a cam timing change, with a slight loss of torque in the 2500-3000 range. Which can make sense. You are now opening, and closing, the valves later in the combustion cycle. just like going to a longer duration cam may net a little more peak power, and little less low rpm power, and then you get to the point where the cam has too much duration, and simply loses everywhere in the power band.
04-02-2016, 11:40 AM
#45
Registered
Well, it's new news to me. I'm still a student, so....I try to learn something new every day. 
As far as heads go on the same sized cubic inch engines, I was impressed with the 20cc smaller Intake runner size and how well it performed on the Whipple engine at a lower 300rpm range with less boost compared to the larger head sizes of the Roots and the Pro-Charger engines all making the same HP/TQ within 10hp.
Also, I just thought the Pro-Charger was really going to be more dominate....maybe in more of a higher RPM category...like a racing application. Of course, this is my initial observation and opinion. I'm just a weekend warrior, so it's just very interesting for me to learn about it.
As far as heads go on the same sized cubic inch engines, I was impressed with the 20cc smaller Intake runner size and how well it performed on the Whipple engine at a lower 300rpm range with less boost compared to the larger head sizes of the Roots and the Pro-Charger engines all making the same HP/TQ within 10hp.
Also, I just thought the Pro-Charger was really going to be more dominate....maybe in more of a higher RPM category...like a racing application. Of course, this is my initial observation and opinion. I'm just a weekend warrior, so it's just very interesting for me to learn about it.
Last edited by KAAMA; 04-02-2016 at 11:42 AM.
04-02-2016, 11:42 AM
#46
Registered
Thread Starter
Well, it's new news to me. I'm still a student, so....I try to learn something new every day.
As far as heads go on the same sized cubic inch engines, I was impressed with the 20cc smaller Intake runner size and how well it performed on the Whipple engine at a lower 300rpm range with less boost compared to the larger head sizes of the Roots and the Pro-Charger engines all making the same HP/TQ within 10hp.
Also, I just thought the Pro-Charger was really going to be more dominate....maybe in more of a higher RPM category...like a racing application. Of course, this is my opinion and initial observation. It's just very interesting.
As far as heads go on the same sized cubic inch engines, I was impressed with the 20cc smaller Intake runner size and how well it performed on the Whipple engine at a lower 300rpm range with less boost compared to the larger head sizes of the Roots and the Pro-Charger engines all making the same HP/TQ within 10hp.
Also, I just thought the Pro-Charger was really going to be more dominate....maybe in more of a higher RPM category...like a racing application. Of course, this is my opinion and initial observation. It's just very interesting.
04-02-2016, 01:37 PM
#48
Platinum Member
Platinum Member
i guess to see the 16 hp gain you would actuially need to do back to back dyno pulls with the cam straight up and then retarted.i know that sounds simple enough but even with a cloyes 2 peice timing chain cover and a cloyes hex a just timing set it still requires some work.all the rocker arms need to be backed off before making the cam adjustment and even if you think you moved the cam 4 deg without checking with a deg wheel you really don,t know exactly where the cam timing is at.imo the hex a just is great for helping the builder degree the cam but i would not trust the marks on it without redegreeing the cam after the move.
04-02-2016, 02:12 PM
#50
Registered
I bet valakos NA 565 has no more than 310/320 max intake runner and he's well over 900 hp on pump gas. That certainly wasn't achieved with just out of the box anything. He prefers darts cause there's enough casting to port where necessary so he can achieve flow numbers like non others.
