Author Topic: cam selection  (Read 11844 times)

Offline Cliff Ruggles

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Re: cam selection
« Reply #15 on: February 07, 2019, 02:55:56 AM »
Tight quench improves combustion efficiency.  The engine will need less timing and fuel to make best power, plus it will run cooler. 

The higher compression makes more power at every RPM as well.

There should be lower cost shim type gaskets available.  GM used .020" steel shim gaskets for decades, I've even seem them already coated......Cliff

Offline tayto

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Re: cam selection
« Reply #16 on: February 07, 2019, 07:51:45 AM »
I can only find a steel shim .020" headgasket made by Mr. gasket p/n 1130G. I thought running under .035 put me in the danger zone of piston to head contact?
« Last Edit: February 07, 2019, 08:01:13 AM by tayto »

Offline Cliff Ruggles

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Re: cam selection
« Reply #17 on: February 08, 2019, 02:33:03 AM »
Some engine builders shoot for .025" with steel rods.  I shoot for .035" with my engines so I sleep better at night!....

Offline tayto

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Re: cam selection
« Reply #18 on: February 08, 2019, 07:29:48 AM »
You think the Mr. gasket .020" will work ok? I have not been able to find a GM part number, they might not even make them anymore? The Cometic gaskets are pricey but i lile thay they are multilayered abd reusable.

Offline tayto

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Re: cam selection
« Reply #19 on: February 08, 2019, 07:58:58 PM »
The Mr. Gasket 1130G will not work with my heads as they are the "lightweight" heads with extra exhaust bolt... I found some copper shim gaskets that are .021" https://www.summitracing.com/int/parts/sce-511152/applications/year/1987/engine-size/5-7l-350


Offline tayto

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Re: cam selection
« Reply #20 on: February 12, 2019, 04:07:34 PM »
Cliff one more question concerning the HD timing chain, do you find they stretch much after "break in" like the bicycle chains do? should i advance my cam with an offset key? think you can get them in 2 and 4 degree offsets.

I degreed the cam, even without a cam card. I found the ICL @ 120* and LSA @ 115* if i'm understanding correctly the cam is already 5* retarded? i installed dot to dot with #6 @ TDC.
« Last Edit: February 12, 2019, 04:14:14 PM by tayto »

Offline Cliff Ruggles

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Re: cam selection
« Reply #21 on: February 13, 2019, 02:37:56 AM »
Those chains don't require additional advance to account for chain stretch.

120 ICL?  I would think it would be a lot further ahead than that.  What are the cam specs?

Offline tayto

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Re: cam selection
« Reply #22 on: February 13, 2019, 05:39:52 PM »
Internet says 202/207 @ .050" duration.  .269"/.277" lobe lift. 114.5* LSA.

This is what I found

Intake
Lobe Lift: 0.262"
Open @ .050" 18* ATDC
Close @ .050" 42* ABDC
Duration 204*
ICL 120*

Exhaust
Lobe Lift 0.265"
Open @ .050" 34* BBDC
Close @ .050" 8* BTDC
Duration 206*
ECL 111*

LSA 115.5*

I plugged numbers into an online cam calculator and it's almost like my Intake and Exhaust are backwards? I did all measurements on cylinder #1, intake lifter furthest away from the front of the engine and exhaust closest. This was my first time degreeing a cam, I think I made some errors along the way...

Offline Cliff Ruggles

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Re: cam selection
« Reply #23 on: February 14, 2019, 02:47:16 AM »
Try checking the intake open point at .050" and see if it's close to 18 ATDC......

Offline tayto

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Re: cam selection
« Reply #24 on: February 14, 2019, 08:19:24 AM »
when i checked the intake @ .050 it was 18* ATDC

Offline 77cruiser

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Re: cam selection
« Reply #25 on: February 14, 2019, 08:47:13 AM »
How far are your pistons down in the hole? If it hasn't been decked they are usually .02-.025 down. Felpro makes a .015 gasket I think the part number is 1094.
Jim

Offline Cliff Ruggles

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Re: cam selection
« Reply #26 on: February 15, 2019, 02:33:47 AM »
If the intake open point checked right on the money then the cam is installed correctly.....Cliff

Offline tayto

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Re: cam selection
« Reply #27 on: February 15, 2019, 08:46:25 AM »
How far are your pistons down in the hole? If it hasn't been decked they are usually .02-.025 down. Felpro makes a .015 gasket I think the part number is 1094.
block has been decked. pistons are .0125" to .0165" in the hole. i am going to bite the bullet and buy the Cometic gaskets as I don't want to tear down the block again. with .023" thick gaskets that will put my quench in the .035 to .040". i am not comfortable going under .030" quench with .015" gaskets.

If the intake open point checked right on the money then the cam is installed correctly.....Cliff
I guess it's right on the money then, thanks Cliff!

Offline Cliff Ruggles

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Re: cam selection
« Reply #28 on: February 16, 2019, 02:14:24 AM »
The ICL method can be confusing and difficult to obtain good results especially if you are going back and forth with the crank instead of in one direction only.

As many engines as I've done over the years I just check the intake open point of the #1 intake lobe and leave it alone if it's at or close to where it needs to be.

I do NOT use double roller or multiple keyway timing sets, only factory link belt type and source out the 3/4" wide sets for my engine builds.  This makes moving the cam around a little more difficult, but well worth the effort, IMHO.

EVERYONE out there since WAY back in the 1970's when I got into this hobby runs right out and buys a "double roller" timing set like it's some sort of upgrade.  Most are just OK some are a little better and some are just plain JUNK.  The ones that fall into the decent category will have billet sprockets, seamless full roller chains and multiple keyways to move the cam around.  I still woln't use them here in my own engines.

One of my mentors ran a very successful Stock Eliminator Camaro and told me decades ago that the factory timing sets and much stronger than the roller variety, and they have constant tooth contact, absorb some harmonics, and will last the life of the engine.

So jump ahead to 2000 when I built my first 455.  The company I sourced all the parts from highly recommended that I purchase a 9 keyway Rollmaster timing set, so I went off course from what I typically do and bought one.  It did fine for a few years but I was driving the car almost every day and racing it as often as I could get it to the track. 

I was racing in Northern Ohio one evening and the car started to slow down, WAY down, but oil pressure was fine, fuel pressure was fine, no internal noises, etc.  I put the car on the trailer and pulled the engine over the weekend.  Figured I freshen it up and restore power.  Turns out the ONLY thing wrong with it was that the very expensive double roller seamless timing chain had failed.  It was so loose you could just about walk it right off the gears!

I replaced it with a Melling 3/4" wide set and the engine was fine till I replaced it in 2009.  The new engine has a Melling timing set in it and just happened to have the water pump/timing cover off recently to repair a coolant leak and the timing set looked perfect........FWIW......Cliff

Offline tayto

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Re: cam selection
« Reply #29 on: October 06, 2019, 09:01:24 AM »
Cliff, ended up selling TPI cam/rockers to a friend that needed them for his TBI truck. I found a replacement cam from Howards Cams, it has 10* more duration than the TPI cam (202/207) as you recommended previously... It also has a fuel pump lobe because I am not running a e-pump.

Specs:
266/270 @ .006"
213/217 @ .050"
.485"/.495" lift w/ 1.5 rocker

I can get the cam either 112* or 114* LSA? What would be best for me? My truck will be used for hauling/towing. believe my transmission guy recommended/sold me a 1800 stall converter for what I was doing.