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Young Gun
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Discussion Starter · #1 · (Edited)
I've been busy with my engine lately and haven't been able to check out the site much. I just bought some AFR 195/65cc heads and a Lunati Voodoo 278 cam (RPM Range: 2,200-6,400 RPM, Dur at 050: 233/241, Adv Dur: 276/284, 504/525 lift, LSA 110.) I'm getting my pistons this week and will be around 10.5:1 with Speed Pro hyper flat tops.

My complete combo is:
-sb 400 block over 0.040 (408).
-Comp ratio around 10.5:1
-AFR Eliminator 195/65cc heads
-Lunati Voodoo 278
-Edelbrock RPM Air Gap Intake manifold.
-Long tube Flowtech headers.
-2 1/2" full exhaust with a H-pipe.
-Carter AFB competition series 750 cfm carb.
-MSD 6A box.
-MSD plug wires.
-Turbo 400 trans.
-Hughes Performance 2,500 stall.
-12 bolt posi rear, Richmond 3.55 gears (for the highway,) Eaton carrier.

What kind of numbers do you think the engine will make at the flywheel? Also, are they any week points you see in the combo, like stall, gears etc? Any advice is appreciated. Thanks, -Zach.
 

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http://teamrfc.gospelcom.net
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1,742 Posts
It looks like a good combo to me. I think overall it should do very well. If there any changes that I would consider, they would be using 1.6 rockers in the intake to take advantage of the flow of those heads, and a little more stall (maybe like 2800). The additinal stall may not be necessary, but I think it would just give it a little more snap. As for power, it is a little difficult assuming that you have the new eliminator heads. Not many tests have been done on those yet. I think you can be fairly safe saying it has 500 hp with the 1.6 rockers. Here are some dyno tests to look at.

Look at the first 406 test. It uses the old style 210cc race ready heads but the new street 195's flow as well or better than them even with the smaller runner. There is also a hydraulic roller (about the same duration of your cam) used here but it made 550 hp.
http://www.airflowresearch.com/chevy_dyno.php

Here is another comparason. It uses a 236 242 @.050 .550 lift hyd roller cam. It also uses the old comp afr 195cc heads, but the new street 195's actually flow almost exactly what the old comp 195's did.
http://airflowresearch.com/articles/article031/A-P4.htm

With either of these combos, you will probably not give up 50 hp having a flat tappet over a roller, but just to be on the safe side I will guess you will have around 500hp and between 500 and 550 ft lbs (with 1.6 rockers on the intake).

Adam
 

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3,519 Posts
Man, when I was 17 I couldn't rub two nickles together, let alone build a 5,000 dollar street/strip motor! I don't understand how some of you guys do it!

Anyway, 1.6 rockers add a bit more lift, and the make your valves move a bit faster. If it were a smaller cube motor I'd be a little concerned about hole-shots, but with this one I think you can use them if you like. Many guys think the 1.6's are better in all cases, but like anything else in a solid-state motor, they're a trade-off. You said they cost extra money? How much? From what I remember you could just order the rockers you want in either ratio and they were about the same. Maybe I'm mistake, also may depend on brand. Spend decent money on rockers (have harland sharps on mine, can't go wrong with those).

Also, with as many cubes as you have it will shift the RPM band of your cam down a bit from the 350-rated estimate. Idle quality will be noticeably better, too.

K
 

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Young Gun
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Discussion Starter · #5 ·
killerformula said:
Man, when I was 17 I couldn't rub two nickles together, let alone build a 5,000 dollar street/strip motor! I don't understand how some of you guys do it!
lol washing cars and boats all summer and a lot of saving. :D
I was mistaken the 1.5/1.6 combo is barely any more money ($30.) I'm using Summit's brand, they're really made by Comp.
 

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That's quite alot of valve lift on that cam. Even with flat tops make sure during assembly that you have enough clearance. You may need to cut some valve reliefs into the piston tops. Just a thought I had while looking at your package otherwise everything else looks pretty tough. Good luck. :cool:
 

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Young Gun
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Discussion Starter · #7 ·
rossco said:
That's quite alot of valve lift on that cam. Even with flat tops make sure during assembly that you have enough clearance. You may need to cut some valve reliefs into the piston tops. Just a thought I had while looking at your package otherwise everything else looks pretty tough. Good luck. :cool:
What does valve lift have to do with valve reliefs in pistons? The pistons I'm looking at have valve reliefs.
 

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. . . and as the motor is going together, you use modeling clay to check the clearance as you rotate the motor. Put it together (one cylinder's worth, at least) with clay on the valve reliefs. Rotate two revolutions of the crankshaft. Remove the cylinder head and measure the thickness of the clay. My recollection is that 0.100 minimum clay thickness is the goal on both valves, but perhaps I'm off that. Someone will chime in if I'm giving you a wrong dimension. If the clay is too thin, you could go back to the 1.5 rockers, and try again.

Pat
 

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http://teamrfc.gospelcom.net
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The main reason I recommend the 1.6's on the intake is that the AFR heads gain in flow from .500 to .530 lift. Those heads cost a lot, and I would want to get as much flow as possible out of them. Being that there is not much price difference I would think as far as performance goes, you would have nothing to loose. As far as how much power gain, on a motor like this, I think you can expect around 1.8 hp per cfm of max flow. from .500 to .550 lift there is a 6 cfm improvement. If you assume you are gaining 4 to 5 cfm from .500 to .530, that would theoretically be a gain of ~7 hp. Beyond that, I think on average, at any given time during the cycle, your valve will be seeing more lift, not just at peak lift. That translates into more flow through the entire lift range. At lower lift, the gain of flow given a gain if lift is more. For example, whereas the flow difference between .500 and .550 lift is only 6 cfm, from .300 to .400 is 47 cfm. If you divide that by two to get an idea of the flow gain between .300 and .350, it is 23.5 cfm. You may only be gaining .02" of lift with 1.6 rockers over 1.5's at .300 lift, but you could actually be gaining a greater amount of flow there than at .500 to .530 lift. I hope that makes sense. The main point is that you gain flow throughout the entire lift range not just at max lift with the 1.6 rockers so it is a little hard to say exactly how much power you would gain, but I bet it would be more than 7 hp.

Adam
 

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It is not necessarily that the valve is open longer (although slightly it is). It has more to do with the fact that it opens faster so that in the same time of being open, the average valve lift seen is greater. More lift means more flow in the case of your heads. As far as the exhaust goes, I dont think it will gain you anything and it may actually hurt you. This is where the intake to exhaust flow ratio comes into play. If your heads flow well on the exhaust with respect to the intake, you dont need as much or any more lift and duration on the exhaust. The reason dual pattern cams were invented was for heads that had weak exhaust ports compared to the intake ports. That is not the case with the AFR heads. I have heard that if you have ~80% intake to exhaust, you should use a single patter cam, 75% is kind of in between and below that needs a dual pattern. The AFR 195cc heads range from 75% to 80% depending where you look in the lift range. Because of that, I think a little help may be beneficial on the exhaust, but not a whole lot. 1.6 rockers add around 1-2 degrees of duration at .050. With the 1.6 rockers, you will have around 235 241 @.050 duration and .534 .525 lift. I think that will work well. More on the exhaust may be too much.

The reason has to do with how the exhaust leaves the motor. You want to get as much of the spent gasses out of the motor as possible, but you dont want to leave the valve open too long. As I understand it, you can imagine that there exhists a point where all of the gasses have left the cylinder and the momentum of the exiting gas is still trying to pull more gasses out. If you can catch this point and open the intake valve/close the exhaust valve here, it will have the effect of creating a little bit of low pressure in the cylinder which will act on the incomming charge and help to pull it into the cylinder better. On the other hand, if you just leave the exhaust valve open, this low pressure time period will happen and then balance out. At that time, you loose the effect you had before. It is a balancing act and a little bit of hand wavy guess work, but the intake to exhaust ratio calulations seem to give a reasonable way to work it out. Someone else may be able to explain this better or point out places where I dont have a 100% grasp on the concept.

Beyond that, I reciently read an article (I think buy Joe Sherman who is a very highly regarded engine builder) that he often uses 1.6 rockers on the inake, but never never uses 1.6 rockers on the exhaust and that in his tests, it has not improved performance to have them on the exhaust. I will try to find that article to make sure it was him that said it.

Adam
 
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