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Hotrodders.com Moderator
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Discussion Starter #1 (Edited)
I already have my choice of which cam I am going to use.It is for a customer.

How about a few suggestions from youse guys.

79 Camaro Z28
4 Speed Muncie
3.73 rear
350 4 barrel Q jet
8.2 to one compression ratio (stock).

She is a real pooch right now.The owner just wants good street power and decent mileage , stop light to stop light ya know? Nothing radical

I will be overhauling the carb and tuning /servicing the distributor.

It also has headers ( hooker headers I just installed.

It also has to be a flat tappet Hydraulic
Which cam would you run, and why? LOL


GO.
 

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True Hotrodder
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Isky #201271

.465 Lift
270/270
LSA 108
2000-6200

That 108 LSA will work really well with the Muncie.
 

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That is some low compression, like a tow truck.
I would stay with 0.050 duration of no more than 210, with 108 Lobe separation.
 

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My first thought was Crane 274H06...but that might be too much vacuum loss for power brakes with a 106° lobe seperation.
274/274° Advertised, 218/218° @.050" duration, .450"/.450" lift, 106° LSA....also available as the Summit Cam #1785.

Summit #1065 would be step back from that 274H06
284/284° advertised, 218/218° @.050", .458/.458" lift, 110 LSA

I tend to be too aggressive for a lot of people, so maybe this as a step back from above:
Howards 110931-11 - 267/267° advertised, 213/213° @.050", .450/.459" lift, 111° LSA
 

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Hates: Liver. Loves: Diesel
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Hate to say it, but at 8.2:1, it will always be a pooch.

Keep it MILD. I personally wouldn't go over 205-210 @50. You can tighten up the LSA a bit. I'd shoot for 110 or so.
 

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My favorite low compression 350 camshaft is the Summit K1102, Edlebrock Performer 2101, Elgin ELGE923P, and etc. All these cams are 270/280 204/214 at .050 and .420/.443 lift. They work great in low compression 350s. I've used them in heavy pickups and they work great. With the 4 speed and 3.73 gears it should work great. It has a very slight lope at idle and still makes enough vacuum for power brakes. Get your distributor dailed in right. Get an advance kit and have all the advance in by 2000 rpm. Set the total timing at 38 degrees with the vacuum advance plugged. Then unplug the vacuum advance. Rebuild the Qjet and get it working proper and it should be a pretty snappy combination.
 

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Discussion Starter #8
I have these 2 as a toss up for this camaro.


The second cam is actually my first choice.

The wider LSA is needed for power brakes and I want a wider power band than a shorter LSA would give.
Cant get too long on the duration or it will still be a pooch at low rpms


It has to run better than the factory cam for gods sake.

Thanks to all for your contribution
 

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Discussion Starter #9
I have a hunch that the distributor flyweights are frozen into place.The car has been setting for a long time. Also it has an assortment of vacuum hoses and Thermal vacuum switches involved as well, so I doubt there is any throttle tip in action going on from the vacuum advance either. Combine that with slow base timing (probably) and the carb is probably full of dirt, and the secondarys havent been heard from at all when I drove it........yeah its a real dog.
cylinder 4 has oil on the plug (carbon like deposits -gray) so when the cam goes in(if owner goes for it) I will also replace the valve guide seals.
Should be a decent straightforward upgrade that will put a smile on the owners face, without a ton of cash.
 

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What does testing tell you about ring condition ? If the plug looks like it does , imagine what the valves & tops of pistons look like !
 

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Discussion Starter #11
It Idles smooth. No lumpiness. I hear what you are saying about crud in the cylinders. Seafoam should clear that up.
.If not, a few times rowing through the gears with the secondaries in action will...LOL

The car only has 37,000 miles on it
 

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With headers and a stock intake, I don't feel you need the duration split like the Crane choice you've made. 12° of split is a lot on that mild of a combination that doesn't have manifolds and near stock exhaust.

Your headered exauhst side doesn't need any help from adding duration but the mild intake side could use help....that was why I leaned toward straight pattern to no more than 6° split.

Isky Cams Tech Tip 2003 "Longer exhaust duration - is it really necessary?" might be of interest to you.
 

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I have these 2 as a toss up for this camaro.


The second cam is actually my first choice.

The wider LSA is needed for power brakes and I want a wider power band than a shorter LSA would give.
Cant get too long on the duration or it will still be a pooch at low rpms


It has to run better than the factory cam for gods sake.

Thanks to all for your contribution

Both of these cams are so close to each other and very close to the Summit K1102 that I doubt you'd feel any seat of the pants difference. Unless I missed something aren't both cams 112 LSA? In your case where your installing this cam into a used motor and its not a new motor build, I'd stay with a cheaper Elgin or Summit cam. I've used dozens of them and never had a problem.
 

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Discussion Starter #14
They are close.

Going on Erics advice I have decided this cam would be Ideal.


I thought about what he said about the split duration.While it is Ideal on a Pontiac engine, The SBC is not as flow challenged at the exhaust side Like a Poncho motor.
Then add the headers on the SBC as I did.......
I got to thinking it might provide some scavenging effect, but then I realized it may dilute the incoming charge (Like an EGR valve does when open) and cost some HP.
Diluting the air charge coming in is OK at cruise , but not when you want all out performance
 

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With a four speed you can drive the cam instead of the cam driving you with the typical practical limits of an automatic.

At 8.2 to 1 the compression is kinda low for a cam any larger than let’s say an RV cam. A bigger cam with that low compression will steadily surrender lower end torque which is typically why higher compression is added to regain that loss. If this was an automatic, especially an automatic not beefed up and modified to allow driver selected shifting this combination would be rather doggy in typical street driving regimes.

However, with a four speed the driver can usually find a suitable ratio that for the road speed allows the engine to be operated in an RPM band where the power available is more favorable.

Bogie
 

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I thought I taught you guys better than this LOL
Find out if he has a M20 or M21, pop the sidecover off and count the teeth on the input. If your guy has an M21/M22? He's way short, and the best thing he could do is change the input and cluster to make an M20 out of it.
M21/22 2.20 1st x 3.73 rear? only 8.26
M20 2.56 x 3.73? 9.56
9.56 would feel like you had a close ratio with a set of 4.34 rear gears in the car, for 1st gear take off.

But, to answer your question? I love the Crane 274H06 idea; knew a lot of guys with it in mild 350s and 327s. Its a fun cam. The 1102 from Summit is venerable and reliable as well.
 

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About that 4-speed, if it is original 1979 Z28 trans, it will be a Borg Warner Super T-10....last factory Muncie was 1974.

It'll be the 2.64:1 first gear version.
 

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That is some low compression, like a tow truck.
I would stay with 0.050 duration of no more than 210, with 108 Lobe separation.
I definitely agree. Your suggestion of a tighter LSA will get the intake valve closed early on the compression stroke, thus preserving cylinder pressure, maybe even raising it because the OE cams have very long seat-to-seat duration.

Don't have the part number handy, but Isky makes a 208/208 cam with 108 duration that I think would work well. And I've always thought this cam would be good in the basic GM crate engine with around 8:1 compression: Crane Hydraulic Flat Tappet Camshafts 10003 Used to be called 260H10. Looks like Crane private labels this Energizer series of cam for Summit, and they cost less.
 

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You need to think about why the OEMs use wide LSA’s and racing cams use tight LSAs.
This seems to fly in the face of hotrodder logic.

To really understand where the effect of whether a tight LSA closes the intake sooner than a wide LSA, you need to abandon the concept of LSA completely and go to where the in lobe center is in crank degrees then start looking at the lobe duration, this will tell you where the intake is actually closing. If you don’t have the degrees for the center of the exhaust lobe as these are often not published; you can take the intake center angle and add the LSA to get the exhaust lobe center. Talking the duration of each lobe you can figure the overlap.

Typical race cams use a lot of overlap as this is extremely beneficial to high rpm operation, as Mr. Vizard says, ‘this is the 5th cycle of a 4 cycle engine‘. To get this, the lobe centers are tightened up. The OEM’s go in the opposite direction of widening the angle between lobe centers, this reduces overlap which improves idle vacuum and bottom end torque at the cost of top end horsepower. There are many OEM cams that have gone as far as 117 degrees of LSA, but for the most part they hang around 112 to 114. Getting under 110 starts to get into competition cam timing.

The intake closing point and it’s affect on DCR is only one consideration of a very complex set of considerations.

Bogie
 

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My current pickup's 350 uses a relatively mild GMPP Ramjet roller cam with a 109 LSA. I was always kinda surprised at that. Also, I once ran a Crane cam that was 194/204 with a 104 LSA (yes 104) in a base Goodwrench 350 that lived at 9600 ft elevation and went as "low" as 5200 ft. It was recommended by a Crane guy back in the mid-90s as a way to build cylinder pressure and more power in the thin air. And man, did it work! That pickup would fly up mountain passes at 2500 RPM (around 65-70 mph). I mean, it was like adding 50 or more cubic inches. However, it ran out of steam somewhere between 4000-4500 RPM. Keep in mind that with 194/204 duration, overlap with even a 104 LSA isn't anything radical. Idle was smooth and vacuum was around 20", as I recall. Funny, but I had forgotten all about that cam, but would certainly recommend it to the OP if his customer could live with the RPM limitations.

I've always thought that GM used (and still uses) wide LSAs in production engines simply to get a smooth idle and wide powerband. And would I be right in saying more vacuum for accessories?
 
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