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Old 07-01-2012, 10:35 PM
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Chevy K20: Camshaft Recommendations for a Crate 350

Hi All,


I am considering upgrading from the stock camshaft in the crate 350 engine in a '77 Chevy K20 4x4.


The truck is pretty much bone stock. The engine has a Quadrajet carb and an Edlebrock Performer RPM intake. The transmission seems to have a shift kit (tends to shift a bit firm), but the torque converter is probably stock. No intake or exhaust modifications of any type, though I may possible go for a set of headers in the future. I will not be doing any head swap.


What the truck will need to do:

- pass smog

- good idle

- improved low-end and midrange torque

- good gas mileage.

- see mostly city driving and some hauling.

- will most likely not be using the 4wd, but never know



According to what I've been able to find online, I believe the following are the specs for the stock camshaft:

- Hydraulic flat tappet

- 0.390in. / 0.410in. lift, Hydraulic Camshaft

- 195 / 202 Duration @ 0.050in. Lift

- More info GM Goodwrench 350 Crate Engine and Engine Kits



What would be some ideal specs for a good, smog-legal camshaft? With my very limited understanding of camshafts, I thought this one looked ideal: Summit Racing SUM-1102 - Summit Racing® Camshafts - Overview - SummitRacing.com



Sound like a worthwhile swap and a good learning experience? Or save the money for something else?


Thanks in advance?

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Old 07-02-2012, 01:07 PM
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There's all kind s of different cams, the old Comp 252H would work.....would it be worth it? Maybe...probably....probably not, who knows. If you have the money and the time it's worth a try though for the learning experience.
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Old 07-02-2012, 03:44 PM
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Hey Dave,


Thanks for the recommendation. I did look it up on the Comp Cam's website (COMP Cams: High Energy™, 252H Strong Torque, Smooth Idle) and it definitely looks like it fits the bill. And its not terribly expensive either. But you nailed it on the main thing which is that it would worth learning how to do.


Now lets see if I've got the guts to do it lol!


Thanks again!
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Old 07-02-2012, 06:58 PM
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It's really not that hard, take some pics first where everything goes in the engine bay, set the engine at #1 TDC and make a mark on the int. manifold where the rotor points to so you can stick it back in the same place for easier start up. Take out the radiator for clearance and the rest is just taking things apart and putting them back together.

Since you sound like this might be a first for you get a KNOWLEDGEABLE buddy to give you a hand.....and take your time, do it right the first time. Clean all the gasket surfaces, use plenty of good cam lube on the lobes and lifters, 1/4" bead of RTV on the china walls. Start in the morning, have everything ready so you don't have to run to the parts house in the middle of it. Finish by evening, hate to leave stuff over night, seems like parts walk away and get lost when no one is watching. Once you get it back together have a beer and let it sit over night to cure. Next morning follow the proper breakin procedure that is housed by the millions in the search function.....and enjoy, but don't expect miracles with just a mild cam change. P.S. since it's a 350 you might want to step a notch to the 260H if that falls within your parameters of passing smog.
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Old 07-02-2012, 10:46 PM
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Thank you for the detailed breakdown in steps. That'll help me plan out the project well in advance. I do have a friend who has worked on more extensive work on engines than me and is quite excited about helping out. Not sure if he's done any cam swaps but I figure between the two of us, we can quadruple-check everything as we go along.


Yeah, I have no big expectations from this swap. If it gets me a bit more power off the line and going up hill, I'd be quite happy. But the learning experience will be huge because I'll have confidence in being able to do it again.


I did look at the 260H and according to Jeg's, it is C.A.R.B.-approved. I sent Comp Cams a request for a cam recommendation. Let's see what they say.


Thanks again for the continued help!
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Old 07-03-2012, 12:18 AM
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Good deal on the buddy....I have found that you really have to take the cam company's recommendations with a grain of salt. The last one was also Comp Cam, I told the "tech" in DETAIL exactly what I was doing and due to the fact that it was a 331" sbc I didn't want a big cam with a lot of lope. He recommends a 238/242 degree cam, says it will be perfect. I told him that he hadn't heard a word I had said. Anywho, I think the 260H will fit your needs.
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Old 07-03-2012, 10:03 AM
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Wow, that's a little disappointing as I always assumed their techs would be the ones who know what they are talking about. Glad you brought it up though because I newb like me would've gone with whatever they say. I will definitely look at the 260H as well. Thank you!
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Old 07-03-2012, 11:52 AM
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Over the years here's what I've learned about various techies.
Isky - Spot on. Quick to answer the phone. Takes the time to LISTEN to your question. Then goes over the answer in any given detail needed, he makes sure you understand before the conversation is over. Best techies I ever delt with hands down.

Crane - Kinda in the middle. Took him a while to answer. Then when I explained the problem he told me that I needed to adjust the valves with the engine shut off and do the top dead center 1 by 1 method. No thanks. I adjust them with it running unless I have no other choice. Even so that time I did it as he suggested it didn't solve the problem.

Comp Cams - Took them forever to answer the phone. The question was simple "I need to know the recommended valve seals on RHS Vortec heads running such and such spring" and I got a firm "I don't know" which tells me they don't even know the're own product line. So he says "I'll send you to such and such,, he knows all about our RHS line" so he transfers me over and again, I had to wait. Finally he answers, I repeat the question and get
"Uhhhh, I don't know"

Summit Racing - Completely a joke. absolutely worst techies I ever delt with. I don't think Summit's techies have ever even picked up a wrench in their lives. Whenever I get a new Summit catalog the first thing I do is go to "Ask Professor overdrive" just so I can laugh at the wrong advice they give.
In the APO section I'd say about 85 percent of the info they give is wrong.
One guy wrote them and his problem was he couldn't figure out why his car kept cracking bellhousings. The car had never been wrecked. Everything was straight. Professor Overdrive gave him a list of things to check but never once mentioned the first thing to check when trans cases start cracking and that's the dowel pins in the block. Is they are pushed in too far or not present at all the case will crack. This is why shops make extra long dowel pins for race car applications to give the trans all the support it needs.
I order alot of parts from Summit, and their ordering service is very professional and everytime I've gotten my parts quickly and the orders been right so I continue to do business with them but learned quickly bypass their techies at all costs.
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Old 07-03-2012, 12:09 PM
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Crap. Comp Cams and Summit were the two places I submitted my request yesterday. No wonder I haven't received a response yet. If I were a bit more gun-ho, I'd drive down and see Isky myself since he is just a jaunt down the freeway. I'll be sticking with 327's recommendations for sure now.
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Old 07-03-2012, 04:09 PM
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Just a got a response from Comp Cams tech support. The tech suggests X4254H (12-235-2), along with "a set of appropriate valve springs to go along with this cam.". For comparison, the 260H specs: 12-206-2 - HIGH Energy. They are both the same price. The valve lift on the X4254H is 0.447"/0.462", while on the 260H it is 0.44"/0.44". Is that why the X4254H needs new springs?
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Old 07-04-2012, 12:50 PM
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Got another swap-related question.


I've been reading the wiki "Camshaft install tips and tricks", the article recommends using weaker or stock springs for break-in:
Quote:
"You can't use 350 lb. over-the-nose springs and expect the cam to live through break-in. Assemble the heads with stock or weak single springs (only if those springs will accept the amount of valve lift and the retainers will clear the valve seals/valve guides) to break in the cam, then use one of the many tools available to change the springs with the heads on the motor."

Would this be something I would need to be concerned about?
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Old 07-04-2012, 06:50 PM
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Either will work, the 12-235-2 is a 'dual pattern" or "split duration" cam which basically means the duration has different numbers ...210/218. The 12-206-2 High energy is a single pattern cam...260/260, it's a pretty old grind and will give you very little lope but it's still a good cam. If you want to talk to a guy that REALLY knows his cams and everything else from top to bottom go by Orange Engine in Anaheim. They are located on Ball Rd. just west of State College Blvd, see the owner Jim Larr. He's an old friend and honest as the day is long. He will give you the straight scoop om what you desire....tell him Dave the retired Cop sent you.
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Old 07-04-2012, 07:55 PM
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When you get recommendations for which cam to use, make sure they understand the vehicle and how you plan to use it. A Chevy k20 is a fairly heavy vehicle already, and many folks put 33's or 35's on them, which makes it even harder to get the truck moving. This is not a lightweight Camaro with 4.10 gears and 27" tires.

I had a 222/222 @.050 cam in my GMC K25 and it worked fine, but you had to get some RPM up to get into the power band. Since my TH350 seemed to like to shift at about 3800 RPM under nearly full throttle, I could never really keep the cam in the right power band. It was also weak off the line, but this may have been more due to the lean carb than the cam.

I have now switched to a Summit 1101 cam that is 194/204 @ .050, and I've also rebuilt a newer Quadrajet (I had an Edelbrock) and set it up for my truck. This combo has lower max horsepower, but in normal driving it feels much stronger than the previous setup. I have great torque off the line, and I can merge into traffic very smoothly as long as I give it enough throttle to downshift to 2nd. It takes very light throttle to cruise at 60-65 MPH. I am also considering buying an adjustable trans governor so that I can raise full throttle shift points up a little, since it still shifts up at too low an RPM.

The carburetor I am using is from an '86 Chevy truck, and its the last Quadrajet model GM used before adding any electrical connections to the carburetor. It has several improvements over the carb in your '77, and the adjustable APT provides a little more flexibility for tuning the part throttle response. I should have been able to get similar results with the Edelbrock 1406, but I was never really satisfied with how it performed. I tried using the Edelbrock tuning kit to improve its response, but it never came close to the Quadrajet I have now.

If you are going to keep everything else near stock, I would probably look at something in the 204/214 @ .050 range for this truck You won't lose much on the low end, but will pick up some power in the upper RPM range.

Bruce

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Old 07-05-2012, 03:45 PM
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Hay Dave,
Quote:
Originally Posted by 327NUT View Post
Either will work, the 12-235-2 is a 'dual pattern" or "split duration" cam which basically means the duration has different numbers ...210/218. The 12-206-2 High energy is a single pattern cam...260/260, it's a pretty old grind and will give you very little lope but it's still a good cam. If you want to talk to a guy that REALLY knows his cams and everything else from top to bottom go by Orange Engine in Anaheim. They are located on Ball Rd. just west of State College Blvd, see the owner Jim Larr. He's an old friend and honest as the day is long. He will give you the straight scoop om what you desire....tell him Dave the retired Cop sent you.
Just looked it up and that shop is pretty close. Thanks for the recommendation. I'll mention you sent me.




Hey Bruce,
Quote:
Originally Posted by 75gmck25 View Post
When you get recommendations for which cam to use, make sure they understand the vehicle and how you plan to use it. A Chevy k20 is a fairly heavy vehicle already, and many folks put 33's or 35's on them, which makes it even harder to get the truck moving. This is not a lightweight Camaro with 4.10 gears and 27" tires.
I made sure I gave them as much info as possible, as well as exactly what kind of driving the truck will see. Summit has yet to respond. The one thing I wanted to mention but never did - becasye the form forms surprisignly never asked - was the tire size. The truck presently has 33s in the back, but I will be stepping down to a more normal street tire soon.




Quote:
Originally Posted by 75gmck25 View Post
I had a 222/222 @.050 cam in my GMC K25 and it worked fine, but you had to get some RPM up to get into the power band. Since my TH350 seemed to like to shift at about 3800 RPM under nearly full throttle, I could never really keep the cam in the right power band. It was also weak off the line, but this may have been more due to the lean carb than the cam.
I never did pay attention to when the transmission shifts under light load or full throttle. I know the shifts came very early under light load. I actually never did floor it in that truck off the line. It was usually on the freeway when trying to speed up a bit. Off the line, it seems ok. But going up even the slightest hill (freeway overpass) or speeding up past 55 mph is a huge struggle. I don't think I have ever gotten it past 70.




Quote:
Originally Posted by 75gmck25 View Post
I have now switched to a Summit 1101 cam that is 194/204 @ .050, and I've also rebuilt a newer Quadrajet (I had an Edelbrock) and set it up for my truck. This combo has lower max horsepower, but in normal driving it feels much stronger than the previous setup. I have great torque off the line, and I can merge into traffic very smoothly as long as I give it enough throttle to downshift to 2nd. It takes very light throttle to cruise at 60-65 MPH. I am also considering buying an adjustable trans governor so that I can raise full throttle shift points up a little, since it still shifts up at too low an RPM.
How interesting. The cam that you have now is not much different from the cam in the engine now: 195 / 202 Duration @ 0.050in. lift. I am interested in knowing more about the adjustable trans governor.



Quote:
Originally Posted by 75gmck25 View Post
The carburetor I am using is from an '86 Chevy truck, and its the last Quadrajet model GM used before adding any electrical connections to the carburetor. It has several improvements over the carb in your '77, and the adjustable APT provides a little more flexibility for tuning the part throttle response. I should have been able to get similar results with the Edelbrock 1406, but I was never really satisfied with how it performed. I tried using the Edelbrock tuning kit to improve its response, but it never came close to the Quadrajet I have now.
Good to know. I recently stocked up on a few Qjets for rebuilding practice. I'll go through the ID numbers to see if there is anything similar to the one you have. I'm pretty sure at least one of them has an APT.



Quote:
Originally Posted by 75gmck25 View Post
If you are going to keep everything else near stock, I would probably look at something in the 204/214 @ .050 range for this truck You won't lose much on the low end, but will pick up some power in the upper RPM range.

Bruce
I do plan on keeping everything stock. The most it might see is some used headers, if I ever come across a good deal. So the cam you are suggesting is the same Summit one I posted earlier: Summit Racing SUM-1102




Regardless of what I get, I will need a new set of lifters too, right?




Thanks guys!
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Old 07-05-2012, 03:55 PM
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Quote:
Originally Posted by lt1silverhawk View Post
Regardless of what I get, I will need a new set of lifters too, right?
New flat tappet cam = new lifters, always, no matter what, no exception. Ever.
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