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Topic Review (Newest First)
07-14-2008 06:57 PM
Originally Posted by DoubleVision
200cc heads are too big, it'll be rather soggy in the lower RPM ranges. 180 would have been far better. the smaller 600cfm carb will make up for some of it, but not much. Since you dont know for sure your rear gear I'd find out, as it will be a big influence on how it performs. I always use GM head gaskets that are .028 in thickness, the 64cc chambers will give you a ratio somewhere in the 9:1 area even with the thin head gaskets depending on how far down in the bore the pistons are. rest of the combo looks good, but I think you have a bit too much head for it.
If he shaved the heads and uped the compression would that not help for the large runners?
03-23-2008 07:46 AM
Stroke Probably up and running, but do you have a pic of the guide boss more visible than in the above pic?
03-22-2008 07:41 PM
New Engine Combo - Your Opinions

01-13-2008 02:39 AM
300Deluxe For those interesed, here are a few pics of the heads.

01-12-2008 07:01 PM

First I would Like to thank you 300Deluxe for posting this thread. Next I would Like to thank Double Vision, F-Bird'88 and 454C10. I am very very new at this and you guys have answered a lot of questions that I have been asking my self. The four of you have also given me so much to look and thank about. If not for people like you guys my '73 Malibu would be half of what I would like to thank it is going to be. Again THANK YOU so much all of you. RAH!
01-12-2008 05:08 PM

Found out about the site a day or two ago. Apparantly it's not 100% functional, but there is a pdf catalog.
01-12-2008 08:34 AM
300Deluxe One more thing: With this combo, is there a ballpark horsepower/torque figure? Just curious.

01-12-2008 08:14 AM
300Deluxe The specs for the 1.47" springs are on a card attached to a spring on each head.

F-Bird, I appreciate your help.
01-11-2008 06:27 PM
300Deluxe Bump. I'm getting lost in the shuffle, lol.
01-10-2008 11:31 PM
300Deluxe F-Bird,

I got the spring specs from both Jegs and Summit's product description on their websites. I want to say that I looked them up at one time on Holley's website as well. I'm guessing that they can't be found there anymore.

It's a relief knowing I won't have to purchase new valvesprings. I just wanted to be certain.

What about pushrods? I plan on purchasing a length gauge. I was told that the stock pushrods wouldn't work. I've read that with the proper length, that the tip of the rocker arm should be centered over the pushrod. I *think* this came from article on Comp's website. I may have to dig up the link. Is this something you eyeball to see that it "looks" centered? Or is there a more precise way of measuring?

Also, I'll pose this question again: With such a thin head gasket, do I need to be concerned with valve-to-piston clearance?
01-10-2008 05:30 PM
300Deluxe Guys I certainly appreciate your input.

I've read horror stories on various forums of cams failing prematurely. This is why I'm trying to go about this build as meticulous as I can. I've read about cam break-in procedures at-length and hope to follow the guidelines provided here and elsewhere.

There seems to be differing opinions on the valvespring issue here. Here are the specs of the springs provided with the heads:

1.47 Dia

Intalled Height (Intake): 1.88 (Exhaust): 1.88

Seat Pressure: 130

Open Pressure: 320

There are various check boxes with the different types of cams on the spring card with "Hyd Roller" checked.

Lunati's recommended valvespring specs:

1.266 Dia - single spring

Installed Height: 1.75

Installed Pressure: 108

Open Height: 1.25

Open Pressure: 339

Coil bind height: 1.060

Spring rate: 462 lbs/in

I realize we need to compare apples to apples here, but the above info is what I found on both springs.

Judging by the numbers, the provided springs are obviously heavier. So F-bird, do you think that these will be OK for my cam? My line of thinking is the fear of having too much pressure on the lobes. You suggested removing the inner springs. What are the specs of just the outers? Are they similar to Lunati's recommended specs?

454C10, you recomment NOT removing the inner spring, right? What would your alternative be?

I apologize for the redundancy. I just want to be confident before I start assembling anything.

You all have already been a big help.

01-10-2008 12:12 PM
454C10 Yes, it will make a good mild cam. However, it has very aggressive lift rates which often can cause lobes to go flat.

When selecting the cam, the intake/exhaust flow ratio should be considered. A stock GM cylinder head typically has a poor I/E ratio (65 to 75%) so it does well with a cam with more exhaust duration, like the one you have. However, after market heads tend to have good I/E ratios (>80%) so a cam with the same intake and exhaust duration should be used.

Do a search on this site for "flat lobes" or "bad cam" or the like and see how many are voodoo or xtreme cam grinds.
01-10-2008 11:52 AM
300Deluxe The cam was suggested to me form another member on another forum. Being as the bottom end of the engine is basically stock with dished pistons, I didn't want to get too radical of a cam. I'm not knowledgable enough with valvetrain geometry to specify a particular duration for the intake/exhaust; hence I didn't get a custom grind. I was under the assumption that this would be a decent cam for a mild build. Was I wrong? I'm beginning to doubt the cam selection now.....
01-10-2008 11:46 AM
454C10 Just running the outer springs will cause harmonic issues. The inner and out springs have different natural frequencies so they dampen each other. Therefore, I would recommend you buy the correct single spring with dampener for your new cam. check with Lunati.

I think a 2000rpm stall should do it. I would think you could even run the stock converter. Again, check with Lunati.

Why did you select a cam with so much more exhaust duration? Do your new heads have poor flowing exhaust ports?

Good luck keeping that cam from going flat. Those voodoo (lunati) and xtreme (compcams) cams have very aggressive lobes tend to go flat quickly. Sure, they make more power but not worth the damage that a flat lobe can cause.
01-10-2008 07:47 AM
DoubleVision I wouldnt even consider roller cam springs on a flat tappet cam. But then again, my belief is always run the springs that are matched to the cam.
The cam companys say do not use flat tappet springs on a roller cam, machinists will tell you the same, same thing applies to vice versa. With todays crappy oils that are killing flat tappet cams and a roller springs pressure, it wouldnt take long to eat the lobe off.
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