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‘75 Fullvert Blazer- K5 Cody’s build- 8.1 swap***C10’s in the park*** Back to assembly.

Restomod build for a late friend
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It sounds to me like he had a completely wrong camshaft for the application. I've said for a long time, I don't like "stage " camshafts, especially the wrong one.

It also sounds like the tuners didn't know what they were doing. The timing on a rowdy cam would make a bigger difference on the idle smoothness than a DBW throttle. I have a 632 cubic inch BBC with a custom solid roller racing camshaft and it idles consistent with just an IAC valve and no DBW. However, if he is expecting it to idle smooth with a large cam, that just won't happen. But that goes back to the wrong cam for the application, they should of known Larry would not be happy with that, if they just asked a few questions.

However, in this particular case, I don't recommend a camshaft swap without a tune change.

And I would not recommend a camshaft with a lopey idle with a stock converter anyway, just like I wouldn't recommend it with a manual in a towing application.

Larry more than likely would of been even happier with the correct camshaft for the application, that wasn't stock, but wasn't a "stage 2" either. But had the proper specs for duration, lift, lobe seperation, etc to work with his application and what he personally wants to get out of it.

I don't use Raylar cams, nothing against them I just won't pick a cam by the "stage number" or other name, I need to know the specs, and they still don't list them.

Also the descriptions they give are full of contradictions....

All of our billet steel camshafts are designed to idle at or near stock idle RPMs with broad torque curves....

.........Extreme / race camshaft. Very choppy idle. 3000rpm stall recommended.
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These are two vastly different applications in one sentence.

The BP-201 camshaft is designed to make maximum torque for truck pulling competitions or very heavy towing applications over 8000lbs.
Click to expand...

The ZZ502 cam is not this at all, it has a tight LSA and a somewhat lopey idle...

The BP-202 camshaft sometimes called the "ZZ496" because of its similarity to the "ZZ502" but with GEN7 firing order, is designed for truck and workhorse RV use with emissions compliance, stock-like idle, fuel economy and peak towing power of primary importance.
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Because of this I have no idea what the camshaft is they are selling, might be great, might not.

But I am glad they are offering products for the 8100, it's a great engine that deserves the support, and no one else has stepped up with cylinder heads.
 
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folkenheath said:
It sounds to me like he had a completely wrong camshaft for the application. I've said for a long time, I don't like "stage " camshafts, especially the wrong one.

It also sounds like the tuners didn't know what they were doing. The timing on a rowdy cam would make a bigger difference on the idle smoothness than a DBW throttle. I have a 632 cubic inch BBC with a custom solid roller racing camshaft and it idles consistent with just an IAC valve and no DBW. However, if he is expecting it to idle smooth with a large cam, that just won't happen. But that goes back to the wrong cam for the application, they should of known Larry would not be happy with that, if they just asked a few questions.

However, in this particular case, I don't recommend a camshaft swap without a tune change.

And I would not recommend a camshaft with a lopey idle with a stock converter anyway, just like I wouldn't recommend it with a manual in a towing application.

Larry more than likely would of been even happier with the correct camshaft for the application, that wasn't stock, but wasn't a "stage 2" either. But had the proper specs for duration, lift, lobe seperation, etc to work with his application and what he personally wants to get out of it.

I don't use Raylar cams, nothing against them I just won't pick a cam by the "stage number" or other name, I need to know the specs, and they still don't list them.

Also the descriptions they give are full of contradictions....



These are two vastly different applications in one sentence.



The ZZ502 cam is not this at all, it has a tight LSA and a somewhat lopey idle...



Because of this I have no idea what the camshaft is they are selling, might be great, might not.

But I am glad they are offering products for the 8100, it's a great engine that deserves the support, and no one else has stepped up with cylinder heads.
Click to expand...
Not to derail much, but here goes. The whole stage 2 cam choice was way out of character for our boy Larry. But through the shared interest in 8.1’s they got talking. Coincidentally, that guy is named Larry too. Raylar has the 8.1 thread here on ck5 linked on his website too. But through a few of those conversations the cam came up and if I remember right, just sent him the cam to try. Larry was interested but skeptical too. He’s a stickler for OEM like drive qualities, but not against a little more performance and a little choppy idle. But the key factor is the cam must play nice with the OEM pcm with a tune. Even going to the point of using headers over cast manifolds to take full advantage of the camshaft. He even told Raylar that.

Tuning it after the cam was a whole other circus to deal with. Both he and I having tried tuning an unlocked mefi IV controller( same as the ramjet crate or mercruiser). Neither of us felt comfortable or knowledgeable enough to dial it in. It needed to go to a pro. None of which are found in Pueblo, CO then. First one was a hour away. It seems like some tuners are like car painters in that as soon as they see the details they have to talk shit about the last guy that tuned it. The main target on the tune was to get the idle back and make the fuel and timing tables happy with the cam. So to confirm your thought Heath, they didn’t know what the were doing. Second tuner was 3 hours away and went identical to the first. Talk crap about the last guy and then flounder getting the idle to smooth out. Sure it ran like a scalded dog but with a manual transmission you had to time your left foot on the clutch. Let out with the rpm high and you’d chirp the tires, too low and you almost stall it. The Jeckle and Hyde nature taking off from a stop was the last straw. Frustration set in knowing right next to the burb in the garage was an almost identical copy that drove and worked just like his factory equipped 8.1 Silverado. Out the cam came.

It’s been a while since I jumped on Raylars site and do remember the crowd he was catering too. Most wouldn’t catch what you did.

I’m not saying his stuff is bad by any stretch, but if the intent for the truck to have all the low end grunt and do low speed off road things, it’s not a good fit. That cam is probably better suited to using an auto trans with a plan of hauling ass more than going slow off road.

Raylar is the source for 8.1 stuff for sure. I’m guessing the lack of heads comes down to two factors. One is the low sample size. Compared to all other big blocks of all generations the 8.1 is a sliver of the total. Second is the design itself. 8.1 heads have a right and left side for the coolant cross over. That means two dedicated castings since you can’t just use these casting flipped side to side. The head bolt layout is different too, but the right/left head need to me kills any idea of putting money up to invest in the tooling to make them.

You are right, going with a cam without optimizing the tune is not the way to go. Even when the cam is better suited to the application.
 
folkenheath said:
I think if you change the cam and don't change the ECU tune, it won't run right unless it's a very small cam change.

The cam change would have to be small enough I don't think it's worth changing the cam without changing the tune, I think it won't give you the benefit you desire, and it will likely run worse with a factory tune and an aftermarket cam.
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Sorry I said that wrong. Stock ECU with some tuning.
Truckman4life said:
I just saw a guy on YouTube do his Duramax engine with an acid wash product. It takes the corrosion off. It will turn your aluminum more of a white color. It's what they do to semis when the wheels and fuel tanks and stuff get too corroded and they don't want to polish them. https://blingchemicals.com/products/absolute-acid spray it on and let soak then wash off.
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My brother told me about the same stuff.
 
For your application I have a few recommendations. Both these are midrange cams, I don't think the stock heads are going to do much for top end (5500 RPM+)

If you are going to use some headers and eventually enlarge/port the stock intake behind the throttle body, then I would recommend this:

(Both these cams are in stock)

Comp #46-422-9
Adv Dur = 270/276
Dur .050 = 218/224
Lift = .510"/.510"
LSA = 114

If you are going to keep the intake and exhaust manifolds stock, then I would recommend this:

Comp #46-413-9
Adv Dur = 264/270
Dur .050 = 212/218
Lift = .510"/.510"
LSA = 114

I can also get nearly any cam profile ground for a Gen VII BBC from Howards, but it would take a couple months as its not a stock item. Its basically a Gen VI BBC cam but ground with the 8100 firing order. Might be a little less expensive vs the comp.

I typically like Howards BBC grinds better, they usually have a little more lift for the same duration, but I don't think it would help with the factory 8100 head, and it would decrease the PtoV clearance with the stock piston.

If you had aftermarket heads and pistons, or a Gen VI BBC, then I would recommend a Howards cam in those applications.

You would likely need new valve springs and adjustable rockers as the valvetrain is similar to the Gen VI BBC.
 
folkenheath said:
For your application I have a few recommendations. Both these are midrange cams, I don't think the stock heads are going to do much for top end (5500 RPM+)

If you are going to use some headers and eventually enlarge/port the stock intake behind the throttle body, then I would recommend this:

(Both these cams are in stock)

Comp #46-422-9
Adv Dur = 270/276
Dur .050 = 218/224
Lift = .510"/.510"
LSA = 114

If you are going to keep the intake and exhaust manifolds stock, then I would recommend this:

Comp #46-413-9
Adv Dur = 264/270
Dur .050 = 212/218
Lift = .510"/.510"
LSA = 114

I can also get nearly any cam profile ground for a Gen VII BBC from Howards, but it would take a couple months as its not a stock item. Its basically a Gen VI BBC cam but ground with the 8100 firing order. Might be a little less expensive vs the comp.

I typically like Howards BBC grinds better, they usually have a little more lift for the same duration, but I don't think it would help with the factory 8100 head, and it would decrease the PtoV clearance with the stock piston.

If you had aftermarket heads and pistons, or a Gen VI BBC, then I would recommend a Howards cam in those applications.

You would likely need new valve springs and adjustable rockers as the valvetrain is similar to the Gen VI BBC.
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I like the idea of the 114 LSA. As for company, as long as someone has had a good experience with them, I’m in.

Intake, headers, rockers and springs will most likely be done before it’s stabbed in.
 
I found out the other day that the welding teacher at our high school also does powder coating. I bought the powder and he powder coated these parts for me for free today. They turned out great!

IMG_9613.jpeg

I opened up the engine for inspection today also. I’m happy with everything I see.

IMG_9617.jpeg

IMG_9619.jpeg

IMG_9618.jpeg
 
GWeakland620 said:
I like the idea of the 114 LSA. As for company, as long as someone has had a good experience with them, I’m in.

Intake, headers, rockers and springs will most likely be done before it’s stabbed in.
Click to expand...

Yeah you want the wide LSA for a broad torque curve and less overlap, which also makes it easier to tune with EFI.

I would suggest at least one more item to add to your list...one piece pushrods instead of the 3 piece factory pushrods. They are more durable than factory pieces.

And possibly a new timing set depending on miles and condition.

GWeakland620 said:
I found out the other day that the welding teacher at our high school also does powder coating. I bought the powder and he powder coated these parts for me for free today. They turned out great!

I opened up the engine for inspection today also. I’m happy with everything I see.
Click to expand...

Free power coating is a great price! :waytogo:

Engine looks good, do you know how many miles are on it?

GWeakland620 said:
So mid length headers? I don’t want to do long tube because those hang too low.
Click to expand...

Mid length are much better than shorties, because most shorties are made to work with the stock exhaust Y pipe, which is a real power killer. Mid length can work well for a larger collector and true dual exhaust. Long tubes make the most torque, but mid length are close.

Let me know when you are ready and I can get some of this stuff on the way to you. It is an awesome project, your are gonig to be very happy with the results, your TH350, maybe won't be so happy...;)
 
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folkenheath said:
Yeah you want the wide LSA for a broad torque curve and less overlap, which makes it easier to tune with EFI.

I would suggest at least one more item to add to your list...one piece pushrods instead of the 3 piece factory pushrods. They are more durable than factory pieces.

And possibly a new timing set depending on miles and condition.



Free power coating is a great price! :waytogo:

Engine looks good, do you know how many miles are on it?



Mid length are much better than shorties, because most shorties are made to work with the stock exhaust Y pipe, which is a real power killer. Mid length can work well for a larger collector and true dual exhaust. Long tubes make the most torque, but mid length are close.

Let me know when you are ready and I can get some of this stuff on the way to you. It is an awesome project, your are gonig to be very happy with the results, your TH350, maybe won't be so happy...;)
Click to expand...
It’s roughly a 70k mile Kodiak application. I’ll be pulling the timing cover to at least inspect it and put in a new crank seal.
 
folkenheath said:
Yeah you want the wide LSA for a broad torque curve and less overlap, which also makes it easier to tune with EFI.

I would suggest at least one more item to add to your list...one piece pushrods instead of the 3 piece factory pushrods. They are more durable than factory pieces.

And possibly a new timing set depending on miles and condition.



Free power coating is a great price! :waytogo:

Engine looks good, do you know how many miles are on it?



Mid length are much better than shorties, because most shorties are made to work with the stock exhaust Y pipe, which is a real power killer. Mid length can work well for a larger collector and true dual exhaust. Long tubes make the most torque, but mid length are close.

Let me know when you are ready and I can get some of this stuff on the way to you. It is an awesome project, your are gonig to be very happy with the results, your TH350, maybe won't be so happy...;)
Click to expand...
Just ordered the 1 piece pushrods. Any idea what ratio rockers and what springs?
 
Where did you order them from? I was hoping you were going to order them from me...

Did you get the pushrods with the 210 radius? The 8100 is famous for making noise without that clearance, although aftermarket rockers may not require that, it's still a safer bet.

For rockers, are you thinking full roller rocker or just roller tip? The full roller have less friction, but cost more.

You will need an adjustable stud kit as the factory studs are not adjustable.

I can get you a quote/parts list if you want?
 
folkenheath said:
Where did you order them from? I was hoping you were going to order them from me...

Did you get the pushrods with the 210 radius? The 8100 is famous for making noise without that clearance, although aftermarket rockers may not require that, it's still a safer bet.

For rockers, are you thinking full roller rocker or just roller tip? The full roller have less friction, but cost more.

You will need an adjustable stud kit as the factory studs are not adjustable.

I can get you a quote/parts list if you want?
Click to expand...
Oh! I misunderstood. I’ll PM you!
 
Wouldn't push rods be one of the last valve train components to get, after check valve geometry and length ?
 
Yes I got that. Been my experience that push rods sometimes need length changed to correct valve geometry,esp on non adjustable rockers.
If any machine work has been done things change
 
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