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Unread 03-01-2012, 06:35 PM   #16
danturner266
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Dang Shawn, just when I thought I was about to have to live with it, you remind me of a technique I haven't thought about at all! I think it's obvious that you "live engines", which is the biggest reason why I'm grateful for your guidance. I think the 4/7 swap is in order! I've also looked at the Air-Gap intakes and kinda shy'd away because they usually show their power band from 1500 to 6500 and I feel like trying to keep mine in the idle to 5500 range. When I said "Ryan at Comp" recommended I mis-spoke his name, it's actually Chris Ryan. He quoted me the 3301 Lobe 266/.463 cam this afternoon at $297.78! Is the 4/7 swap no charge? If so, I'll probably order next week. I asked him if he could give me a cam card prior to milling, is that possible? If so, I'll post it here.

Is the 4/7 swap something I need to mention to my machinist doing the balancing? Will that make any difference in the way the crank is balanced? I plan to run those parts over to him next week as well, so I need to tell him, then I will.

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Unread 03-01-2012, 07:10 PM   #17
swatson454
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I appreciate the kind words!

There shouldn't be an additional charge for a 4/7 swap. At least I don't remember there being one before. Custom is custom, ya know. Gotta love it! That's the best $100 bucks you'll spend on the engine.


Shawn

Edit: The 4/7 swap changes nothing but the firing order. You don't need to worry about anything else.

Edit 2: I wouldn't sweat an air-gap manifold. While it might make 5 to 7 more hp on the dyno, it'll be more difficult to get the carb right and the whole thing will be more sensitive to ambient temperature. I don't know if your heads have the exhaust crossover passages or not. If they do, I'd use the reducer that should come with your gasket kit and choke them down a little. If they don't, make sure you get a manifold that has ports for running hot water under the carb or you might have to drill and tap them yourself.
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Unread 03-01-2012, 08:09 PM   #18
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We need to talk about your distributor as well. Being that the engine started out as fuel-injected and you're switching to a carb, you'll need an aftermarket distributor.

That being the case, you'll have to discuss with Comp the proper distributor gear for your cam core. Then we'll have to address the advance curve. I'm guessing you'll need a good 12* of initial advance but those Vortec chambers seem to only need around 32* of total advance. Since a lot of aftermarket distributors have a 24* curve, you just might end up with too much if you don't do some research.

Tell me what your plans are and we'll go from there.
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Unread 03-02-2012, 07:41 AM   #19
danturner266
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I don't recall the specific model number of my Accel dizzy, so, until I can check it, I'm going to assume I have this: http://store.prestoliteperformance.c...chevy-rtr.html
59107c.jpg  
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Unread 03-02-2012, 08:23 PM   #20
danturner266
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OK Shawn, I heard back from Chris Ryan at Comp Cams.. He didn't give me a "cam card" but gave me these specs....

Here is the spec card.
PART # 08-000-8 CAMSHAFT, CS 1987-1998 SR/HR ROLLER
CORE C99 CAMSHAFT BLANK, DUMMY OVERRIDE CORE
GRIND # CS 3301 /3301 HR107.0
DURATION @ .050 INTAKE 214 ROCKER ARM RATIO
VALVE ADJ INTAKE .000 DURATION @ .050 EXHAUST 214 INTAKE 1.50
VALVE ADJ EXHAUST .000 LOBE LIFT INTAKE .3050 EXHAUST 1.50
VALVE LIFT INTAKE .457 LOBE LIFT EXHAUST .3050
VALVE LIFT EXHAUST .457 LOBE SEPARATION 107.0
DURATION .006 INTAKE C/L 103.0
TAPPET LIFT INTAKE 266 ADVANCE 5
TAPPET LIFT EXHAUST 266 HYDRAULIC Y
VALVE TIMING .050 OVERHEAD CAM N
VALVE OPEN INTAKE 4 JOURNAL DIAMETER STD .000
VALVE OPEN EXHAUST 38 RECOMMEND VALVE SPRINGS
VALVE CLOSED INTAKE 30 DEPARTMENT P
VALVE CLOSED EXHAUST 4- SPC INSTR FOR CUSTOMER
INTAKE LOBE ID 3301 GRIND INSTR FOR CAM SHOP
EXHAUST LOBE ID 3301 CUSTOMER REQUESTED SPECS
DATE SETUP 03/02/2012

Does everthing look ok with this? I didn't ask for the 4/7 swap yet, but will before I order....
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Unread 03-03-2012, 07:08 AM   #21
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The only thing wrong is the 107.

My poor little brain always defaults to .030 over so I started my math with a 355 instead of a 350. At the time, I thought we were lift-limited and had to use 1.5 rocker arms so the calculation ended up with a 107 LSA. My bad so I'm glad you caught it.

With the 5 fewer cubes and the 1.6 rockers, a 108 LSA would be mathematically 'correct', although I'm not sure if you'd even notice the difference.

Anyways, the Vortec heads flow enough at low lifts to warrant the change so I'd just change it to a 108 +4, 4/7 swap and make sure you get the right distributor gear.

I thought about your combo all night and I really believe it will hit all of your targets. Strong, usable torque, good mileage, stock convertor and not be too hard on your drivetrain.

I'm anxious to see the results!


Shawn
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Unread 03-04-2012, 05:26 PM   #22
danturner266
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Shawn, before I ask for the cam re-spec, is there anything else you can think of? And, should I up the lift if I stick with 1.5 lifters and not 1.6's? Thinking to drop this order this week after you and I finalize the spec....
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Unread 03-04-2012, 08:06 PM   #23
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With the 3301 lobes, I'd most-definitely run the 1.6 rockers. To be honest, I'm even on the fence about using 1.65 rockers on that lobe. Lunati has some really nice 1.65, self-aligning roller rockers but they're in the $350 range.

I just spoke with Brad at Comp not two weeks ago about their 3190 lobe; which is 266, 214 at .050 but it has 12* more duration at .200 than the 3301 lobe and .353 lobe lift vs the 3301's .305. That will put your valve lift at .530 with 1.5 rockers vs .488 with 1.6 rockers on the 3301 lobe.

Although I had my reservations, Brad told me not to worry about the pressure angle at the lifter and that there are no problems with that lobe on the street. I've never run a hydraulic roller that aggressive so I didn't want to recommend it to you. What I don't want to do is recommend a lobe that's going to potentially cause problems with lifter body distortion. This is especially important if you're planning on running stock GM lifters.

I don't want to vag out and spec a cam that falls short of your expectations but I surely don't want to be a moron and cause problems with your valvetrain.

Tell you what, call your guy when you get a chance and tell him what we're talking about here with the 3190 lobe and a 1.5 rocker vs. a 3301 lobe with a 1.6 or even a 1.65 rocker (GM lifters?) and see what he has to say. If he makes you warm and fuzzy then go for the 3190 lobes and a 1.5 rocker arm. He may want more expensive push rods and rocker arms than you're planning on so discuss that as well. Screw-in studs?

Everything else will stay the same: 108 +4, 4/7 swap, correct distributor gear. That 3190 lobe just really gets with the program of getting the valve off the seat. As long as the lifter isn't compromised, the idle quality should stay the same as the other lobe but you'll see some more power. Again, I don't want to vag out but I sure don't want to cause you any problems. I don't want to scare you either so I'll let you and Chris hash that out.

But yes, 1.6 rockers with the 3301 lobes.

Clear as mud... again? Lol


Shawn
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Unread 03-05-2012, 08:24 AM   #24
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I just read your first again and saw where you want to run roller-tipped rockers. If you're talking about something like the Magnum rockers http://www.summitracing.com/parts/CCA-1418-16/ I've run them before and I like them. I haven't run them on a roller though. There's no way I'd stick them on that 3190 lobe!

Those rockers in a 1.6 ratio on the 3301 lobe is a good question for Chris. Unless you're planning on running Pro-Magnum rockers, Comp lifters and Pro-Magnum pushrods, disregard everything I said about that other lobe and we'll stick with the original 3301 game plan, assuming Chris is ok with Magnum rockers on it.

If he has reservations, we'll just have to move to a less-aggressive lobe. Not a problem, just let me know what he says and we'll go from there.
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Unread 03-05-2012, 08:43 AM   #25
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PM sent
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Unread 03-05-2012, 10:53 AM   #26
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FWIW I have never had good luck with roller tip rockers and never known anyone personally who did. If you need the roller tip the fulcrum pressures are so high you need a roller body.

I used to be a manufacturing engineer at a foundry that made the rocker bodies (and some complete rockers) for several aftermarket manufacturers, a couple of OEMs, some american, some german, including a few OEM in house racing programs. Got very familiar with their materials and quality requirements.

When I need anything beyond a stock rocker, my money gets spent on comp cams pro magnum full rollers. Nuff said.
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Unread 03-06-2012, 08:36 PM   #27
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Quote:
Originally Posted by Foundrydude View Post
When I need anything beyond a stock rocker, my money gets spent on comp cams pro magnum full rollers. Nuff said.
I definitely hear what you're saying, foundrydude, and I agree.

Pro-Magnums are awesome and work extremely well in all but balls-out kind of deals.



I respect your reservations about roller-tipped rockers but I really think he'll be good to go with the Magnums on the 3301 lobe. The only beef I have with them is the damn adjustment nuts. They tend to back out every few months (at least mine did) and I finally got sick of it and ponied up for some nice lock nuts http://www.summitracing.com/parts/CRO-86051S-16/

Comp has them too but the picture didn't look right.


Shawn
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Unread 03-09-2012, 03:16 PM   #28
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So did you pull the trigger? Talk to me, I'm anxious
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Unread 03-13-2012, 06:54 PM   #29
danturner266
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Hey Shawn!, I haven't "pulled-the-trigger" yet, but have pretty much settled on the spec you gave me. I forgot to mention that Comp won't do the 4/7 swap with a hydro/roller, all the others, but not that one. Any thoughts on that, and why that might be? I've been pretty busy these last two weeks at work and didn't get my parts over to the balancing shop yet either, but since I can re-use my pistons, I have everything ready to go. I'll order the cam just as soon as I drop them off.
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Unread 03-13-2012, 07:14 PM   #30
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Ahhh, they might not have enough demand for a 4/7 swap in a hyd/roller to justify another run of cam cores. It's not a huge deal. I was just trying to help with heat management.

I was shooting the breeze with Steve at Lunati last week about another project and I firmly believe that this is the right cam.


Shawn
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