I'm going to replace the cam. Need lots of guidance

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hertfordnc

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Apr 1, 2012
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The 76 Birch is still for sale at the moment. I've had a lot of genuine interest and a few people have come to see it. Mostly old car guys who know a lot more than me.

It has a stuck lifter and a wiped cam. At first i wanted no part of repairing it but now i'm warming to the idea.

It's a 455. First question, what cam kit do i want? Cam, lifters, valve springs etc?
 
I think that's a good choice, Dave. It'll be a good amount of work you probably prefer to avoid, but it'll sure make that coach a lot more sellable! I know that's been a challenge. It's such a great coach--it'd be nice to see it sell well.

I'm sure @tmsnyder will have some cam recommendations for you.
 
You probably only need a cam and lifters. No need to replace the valve springs unless you are building a high performance engine with a high lift cam. You want a low end to mid-range power cam. Maybe contact Jim Bounds and get the spec for his "Kryptonite" cam from Comp cams.
 
Carl Stouffer said:
You probably only need a cam and lifters. No need to replace the valve springs unless you are building a high performance engine with a high lift cam. You want a low end to mid-range power cam. Maybe contact Jim Bounds and get the spec for his "Kryptonite" cam from Comp cams.
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I just thought valve springs was one of the things you do after 50 years. I have no interest in changing anything from stock.
 
Valve springs are part of head repair/service. Valve springs must be changed if you install a "radical" cam that would open the valves further and possibly longer than stock heights and durations.
Realize you will have to remove the intake manifold, everything on the front of the motor and the waterpump to access the camshaft. You will want to replace the timing chain and gears with double roller chain. Probably consider a full engine gasket set. The intake will possibly be separate. Note that it is best to use RTV sealant instead of the supplied rubber pieces where the intake meets the block.
One point of note: You probably not be able to replace the cam bearings. Ensure they are serviceable upon disassembly!
Best of luck!
 
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mech0001 said:
Valve springs are part of head repair/service. Valve springs must be changed if you install a "radical" cam that would open the valves further and possibly longer than stock heights and durations.
Realize you will have to remove the intake manifold, everything on the front of the motor and the waterpump to access the camshaft. You will want to replace the timing chain and gears with double roller chain. Probably consider a full engine gasket set. The intake will possibly be separate. Note that it is best to use RTV sealant instead of the supplied rubber pieces where the intake meets the block.
One point of note: You probably not be able to replace the cam bearings. Ensure they are serviceable upon disassembly!
Best of luck!
Click to expand...
I'm halfway there. I pulled the intake to confirm the damage. I've been this far into these engines before. But i don't love it.
 
hertfordnc said:
The 76 Birch is still for sale at the moment. I've had a lot of genuine interest and a few people have come to see it. Mostly old car guys who know a lot more than me.

It has a stuck lifter and a wiped cam. At first i wanted no part of repairing it but now i'm warming to the idea.

It's a 455. First question, what cam kit do i want? Cam, lifters, valve springs etc?
Click to expand...
Comp Cams Xtreme Energy Camshafts 42-413-11.

This is Jim Bound's COOP 455 Cam + roller rocker. See Post #19 on Engine Rebuild Wish List.
 
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sailor man said:
Do you have any dyno testing results for the Melling MTO-1 cam on an Olds Rocket 455 with carb or fuel injection?
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I don't think he's looking to go with a roller cam setup or dyno results, just trying to get it running again.

Comp does have their 'smallest' flat tappet cam for the 455, lowest rpm range, 42-220-4 which is 206/212 at 0.050, 600-4800 RPM "Xtreme Energy 206/212 Hydraulic Flat for Oldsmobile 260-455. Very strong torque with excellent mileage and a smooth idle." I _suspect_ this is the flat tappet cam that Jim Bounds developed with Comp, which they than put in their regular lineup. According to Jim they developed both roller and flat tappet. Speedway and Jegs has the flat tappet cam and lifter set in stock for $417

RockAuto has the MTO-1 cam and lifter in stock for $313, it's 204/214 duration at 0.050: "
MELLING CLMTO1 High Performance; Class 1, Excellent Low End Torque and Horsepower; Good Idle and Daily Usage; No Warranty Info
Use w/ VS-720 Valve Spring. Installed Height 1.67 Inches; Not California Compliant"

Howard cams has this small one, 800-4800 rpm: CL510011-12 Lift: .448 / .475, Duration @ .050: 205 / 215, Centerline: 108, Street Force 1, Good idle, Mild street performance, Strong low end torque. Summit has the cam and lifter set for $395

Howard also has some duplicates of original GM cams, such as this one: CL517771-09 " Lift: .400 / .400, Duration @ .050: 187 / 200, Centerline: 106, American Muscle, Near duplicate of the Olds 310HP/350 cam (GM #400084)." GM is known for their cam design which lifts up and sets down the valve very gently. This also puts less stress on the lifters, and in these days of low ZDPP oil and questionable cams and lifters from off shore sources, who doesn't want less chances of wiping a cam lobe?
 
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tmsnyder said:
I don't think he's looking to go with a roller cam setup or dyno results, just trying to get it running again.

Comp does have their 'smallest' flat tappet cam for the 455, lowest rpm range, 42-220-4 which is 206/212 at 0.050, 600-4800 RPM "Xtreme Energy 206/212 Hydraulic Flat for Oldsmobile 260-455. Very strong torque with excellent mileage and a smooth idle." I _suspect_ this is the flat tappet cam that Jim Bounds developed with Comp, which they than put in their regular lineup. According to Jim they developed both roller and flat tappet. Speedway and Jegs has the flat tappet cam and lifter set in stock for $417

RockAuto has the MTO-1 cam and lifter in stock for $313, it's 204/214 duration at 0.050: "
MELLING CLMTO1 High Performance; Class 1, Excellent Low End Torque and Horsepower; Good Idle and Daily Usage; No Warranty Info
Use w/ VS-720 Valve Spring. Installed Height 1.67 Inches; Not California Compliant"

Howard cams has this small one, 800-4800 rpm: CL510011-12 Lift: .448 / .475, Duration @ .050: 205 / 215, Centerline: 108, Street Force 1, Good idle, Mild street performance, Strong low end torque. Summit has the cam and lifter set for $395

Howard also has some duplicates of original GM cams, such as this one: CL517771-09 " Lift: .400 / .400, Duration @ .050: 187 / 200, Centerline: 106, American Muscle, Near duplicate of the Olds 310HP/350 cam (GM #400084)." GM is known for their cam design which lifts up and sets down the valve very gently. This also puts less stress on the lifters, and in these days of low ZDPP oil and questionable cams and lifters from off shore sources, who doesn't want less chances of wiping a cam lobe?
Click to expand...

I start with the presumption that the original engineer was smarter than me. I do not deviate from that unless a compelling argument is made, usually by an engineer.

The stock motor worked perfectly well. I want to replace the cam that was in there.

But, this is a GMC and we have over 50 years of design improvement so if there is a "standard upgrade" that has unanimous buy-in, then I'm open to it.
 
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hertfordnc said:
I start with the presumption that the original engineer was smarter than me. I do not deviate from that unless a compelling argument is made, usually by an engineer.

The stock motor worked perfectly well. I want to replace the cam that was in there.

But, this is a GMC and we have over 50 years of design improvement so if there is a "standard upgrade" that has unanimous buy-in, then I'm open to it.
Click to expand...
"Comp does have their 'smallest' flat tappet cam for the 455, lowest rpm range, 42-220-4 which is 206/212 at 0.050, 600-4800 RPM "Xtreme Energy 206/212 Hydraulic Flat for Oldsmobile 260-455. Very strong torque with excellent mileage and a smooth idle." I _suspect_ this is the flat tappet cam that Jim Bounds developed with Comp, which they than put in their regular lineup."

I went with the flat tappet version of this cam, sourced directly from Jim Bounds when I rebuilt my engine about 7 years ago. I am very happy with the results even now with over 65,000 miles on the rebuild.
 
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From the chart at https://classicoldsmobile.com/tech/78.shtml
It's probably cam #400117
cam # , Overlap, Duration , Lift, Applications
400117 44 258/272 .435/.435 455 ex W-30, Marine, 455 LC

From https://classicoldsmobile.com/forums/big-blocks-2/camshaft-identification-66364/ the 0.050 duration numbers are: 194 intake / 207 exhaust at 0.050"

This was apparently the common auto low compression (LC) cam of the day.

Notice how the advertised duration seems kind of large on the GM cam, 258/272, but the 0.050 is puny. 194/207. That's GM picking up and setting down the valves very gently.

Compare that to the Comp Cam flat tappet cam, advertised at 250/260 (smaller at 0.000) but is 206/212 (larger) at 0.050. Comp is popping open and closing the valves more aggressively than GM did.

Howard actually does have a copy of the 400117 cam: Advertised duration 272/294

Hydraulic Flat Tappet American Muscle Camshaft & Lifter Kit; 1967 - 1990 Oldsmobile 260-455 1000 to 4400 Howards Cams CL517441-10 | Howards Cams

www.howardscams.com www.howardscams.com

Lift: .413 / .414, Duration @ .050: 196 / 208, Centerline: 111, American Muscle, Near duplicate of the Hurst/Olds 375HP/455 cam (GM # 400117).
 
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