c3_dk

Hi,

Engine/car today:
350 0.030"
STD L46 11:1 (186 heads, 2.02/1.6 valves)
4 speed
3.70 rear
2½" exhaust
EZ-EFI 1.0
Edelbrock 2701
1.6 rockers arms

Needed:
A set with cam, hydr. lifter, chain set.
More power from 2000 - 5000RPM, maybe a bit higher.
Not rough idle.
Street car.

Please comment/recommend.
Thx,
c3_dk

marz

Comp cams you just can't beat. Call their tech line and give them the specs and they will advise you on what cam kit to get.

A great start!

scottyp99

The L46 already has a pretty good cam, I wouldn't bother to upgrade without going roller.

Scott

bluedawg

I agree 100%. These days the track record if you go to wild with the cam shaft isn't that great due to oil quality and wiped/flat lobes. Roller cams not only offer better performance, but piece of mind. If I read correctly you've got 11 to 1 compression with iron heads that might be limited on the amount lift you can run. So something different or custom even might be in order to keep the engine from pinging with out running into lift clearances. So you didn't state why you were upgrading camshafts this might help toward selecting a cam.

c3_dk

Is is for a extra L46 engine I am building.
My point was, if the cam shaft could give some extra power/bennefits, why not change it. If there are no bennefits, then I will just put the old back in the engine again.

63mako

Do not reuse the old one if your building a spare engine. You can buy it here.
http://www.gmpartsdirect.com/results...number=3896962
That cam has an advertised duration of 312 with a 114 LSA. That is the only way it can run a 11 to 1, iron headed motor. I would drop compression a little and go with a more modern cam to make better power in a better range.

c3_dk

I would really like to go 10:1 or 10,5:1 I do have a lot of problems with 11:1 and iron heads with 99octane Shell fuel here in DK. (this is with my L46 in my car)

And this is leading me to the next question, why is that??
I am getting the high octane fuel, I've set my ignition to 10 degrees, I have huge amount of cooling (Be Cool), what else can I do? (head gasket 0,040, clean heads inside)

boat196

[QUOTE=c3_dk;1586491776]I would really like to go 10:1 or 10,5:1 I do have a lot of problems with 11:1 and iron heads with 99octane Shell fuel here in DK. (this is with my L46 in my car)

And this is leading me to the next question, why is that??
I am getting the high octane fuel, I've set my ignition to 10 degrees, I have huge amount of cooling (Be Cool), what else can I do? (head gasket 0,040, clean heads inside)[/QUOTE

John
I don't think you have 11:1 compression with a .040 gasket. From my research I found that a stock L-46 had a .026 gasket. Their is a Fourm member that runs 10.4:1 with out issues. If you don't measure for compression, it's hard tell the true compression.
Do you have full time vacuum. Where is your mechanical advance all in at. Did you get your heads back from Headbytes. If I ever get my heads back I plan to run 10.3:1 in my 1970 L-46. The L-46 cam has a late closing intake valve which bleeds off compression.



Bob

gofastvette

the GM 151 hydraulic cam is hard to beat

c3_dk

Hi Bob,

Nice to hear from you Again :- )
I've disconnected the vaccum, I have "hard" springs in the mechanical advance, and I've set it @ 10 degrees. I don't know what all in is now, I will find out. (my guess is approx 30)

BR,
John

boat196

You need vacuum advance. If you get the distributor dailed in, this will help with your detonation problem. Look up the distributor articles written by Lars or email him direct.

63mako

Retarded timing causes the engine to run hotter. Too hot increases detonation. I agree with getting your timing sorted out first. If you have a performance timing curve and a 160 thermostat and you still get ping then drop 2 degrees from your initial and recheck. Email Lars. It is V8fastcars@msn.com

c3_dk

Mail sent to Lars, and you still think I should buy the GM cam and lifters?
If yes, then I will also buy lifters, is this set ok, or is it China?
http://www.ebay.com/itm/chevy-sbc-performance-camshaft-lifter-kit-282-302-305-327-350-383-400-gm-/251486240957?pt=Motors_Car_Truck_Parts_Accessories&hash=item3a8dbf80bd&vxp=mtr
Thx 63mako.

c3_dk

Hi,

Lars told me to start by going from 11:1 to 10:1, before doing anything else.
I've calculated that my chamber volume is 71.50cc, and my cylinder volume is 716.60cc, this gives me 11.02:1
If I will go to 10.07:1, then I have to have a chamber volume @ 79cc = 10.07:1
So I have to increase by 7.5cc right???
If yes, then as I understand it, I can buy a head gasket @16.5cc (0.080")instead of the one I have that is 9cc (0.040")

Is all this right?

My 71.50cc comes from this:
Piston +2.4
Heads (186) 63cc
Head gasket 8,9cc
Deck 2cc

63mako

If your pistons are down in the hole .025 going with a .080 thick head gasket gets you .105 quench which causes more issues than it solves. Your best bet is going with a 75 CC head chamber and .015 gasket to get to .040 quench. This puts you right at 10 to 1. Or rebuild and change to a 7CC flat top piston and the same .040 quench. This gets you to 10.3 to 1 with iron heads. Your existing cam would work then.

c3_dk

http://www.summitracing.com/int/part...make/chevrolet

63mako

http://www.yellowbullet.com/forum/sh...37&postcount=2
Best off going with the 75CC heads

boat196

John
What are you saying about those pistons.
Speed Pro makes the L46 cam/lifters, I've never hear of that brand of cam from ebay. Did you talk too Lars about your distributor.
Bob

cardo0

c3 i read u are rebuilding a spare L46 out of the car not the one currently in the car correct? Or are u just re-camming the spare L46? Or are u replacing the cam in your current L46?

Well from post #5: "Is is for a extra L46 engine I am building." we will look at the spare motor cam.

With the engine out of the car u can remove the heads and measure their volume. Next u will have to identify the pistons as the stock piston were domed. Once u know what piston u have u should be able to look up the dome size in cubic centimeters. The stock piston sits 0.025" down the cyl hole so use 0.025" times 4" bore divided by 2 (2") then squared = 4 (again) and multiplied by pi (3.14) gives 0.3142 cubic inches which = 5.1482cc. Now add the 5.1482cc to the measured head chamber volume. Also add the gasket volume using the compressed height for example 0.040" times hole dia divided by 2 (4.125"/2=2.0625") then squared, then multiply by pi (3.14) = 0.5346 cubic inch = 8.76cc. The domed volume will be subtracted from the head chamber volume + 5.1482cc + 8.76cc to give you the "static volume".

U can calculate the "swept volume" using bore area times the stroke which is 4 x pi x 3.48" = 43.731cubic inches = 716.624cc.

So to nail your compression ratio take the swept vol + static vol all divided by the static vol. something like: (716.624cc + 5.1482cc + 8.76cc + chamber vol - piston dome)/716.624cc.

Once u truly know your comp ratio u can choose the correct cam. Dont buy a cam until u know this. U may want to change piston or heads or rework your heads.

For high compression ratios using pump gas u need to calculate the dynamic ratio which requires choosing an intake valve closing point to get the dynamic compression down to a usable range for your pump gas octane.

Hope this helps more than it hurts,
cardo0

c3_dk

Thx cardo0,

I do have a L46 engine in my 69, but this engine is a extra L46 that I have in "stock"
The engine is 100% factory, nothing have be done with the engine, it is factory pistons (dome), factory heads, everything is like it left the factory back in 69

You bet the above helps me a lot.
But please help me understand, why does "choosing an intake valve closing point to get the dynamic compression down to a usable range for your pump gas octane" help detonation?
Can you explain that to me?

I am assuming that it is 11:1 since it is 100% factory.

Also, must a intake valve close "before or after" to prevent detonation?

Thx.