I’m calling it good on the engine bay. Might as well kicks in, and I’ll have the body pulled off if I don’t watch it.
CK5
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‘75 Fullvert Blazer- K5 Cody’s build- 8.1 swap***C10’s in the park*** Back to assembly.
- Thread starter GWeakland620
- Start date
Restomod build for a late friend
This build is cool, I always enjoy the updates.
What trans is that?
If its still a TH350 you might want to find a stronger donor, like a TH400/4L80E or an SM465/NV4500 behind the 8100.
What trans is that?
If its still a TH350 you might want to find a stronger donor, like a TH400/4L80E or an SM465/NV4500 behind the 8100.
It currently has a built Th350 in it. This is temporary.
Finally took the time at my brother’s place to separate the Allison 2000 from the donor 8.1 engine. We also pulled the harness and exhaust since I won’t be using those. Tossed in the bed of Penny the C-Twenty and snuck it in the shop before the rain hit tonight.
Once I pluck it out of the back, I’ll start tearing it down and cleaning everything and prepping for paint.
Once I pluck it out of the back, I’ll start tearing it down and cleaning everything and prepping for paint.
I fixed it for you.
BTW, can you adapt that Allison to a passenger drop transfer case?
I am pretty sure that was done, the dually truck that burned down, can't remember his username nowI fixed it for you.
BTW, can you adapt that Allison to a passenger drop transfer case?
Actually, you got me thinking. Are these the same as LS motors where you don’t have to pull the heads?I fixed it for you.
BTW, can you adapt that Allison to a passenger drop transfer case?
You don't have to pull the heads to change the cam on either.
You do have to pull the intake to change the cam and/or lifters on the BBC and SBC.
For an LS you have to pull the heads to change the lifters, but not the cam if you have the stock lifter trays that hold the lifters up.
If you change the cam it will need new tune, so it depends on if you are going to do that, and/or what EFI you will use, stock or aftermarket.
You do have to pull the intake to change the cam and/or lifters on the BBC and SBC.
For an LS you have to pull the heads to change the lifters, but not the cam if you have the stock lifter trays that hold the lifters up.
If you change the cam it will need new tune, so it depends on if you are going to do that, and/or what EFI you will use, stock or aftermarket.
So I guess I am looking for a cam…
I can suggest some options if you tell me your plans...I'll send you a PM with some questions unless you prefer to do it here...?
Let’s do it here! I like to share knowledge of/when I can.
I am pasting my form here so you can see the whole thing, obviously not all questions are applicable so answer what you can and leave the rest blank, I already started some of them...
Vehicle Year, Make, Model: 1975 K5 blazer
Vehicle Weight:
Engine Model: GenVII 8100 BBC
Engine Bore: 4.25 Stroke: 4.375
Compression:
Cylinder Heads:
Cylinder Heads ported or Stock?
Combustion chamber size:
Runner Volume
Valve Sizes:
Head Flow Numbers:
EFI or Carb
Throttle/Carb Size:
Intake Manifold Model:
Intake Manifold Type:
Induction: NA Nitrous Supercharger Turbo
Stages of Nitrous:
Suprcharger Type : Roots Screw Centrifugal
Transmission:
Torque Converter Size/Stall(if applicable):
Drive Axle Gears:
Tire Size:
Intended Use:
How do you want it to idle? (smooth, fair, moderate, lopey, etc.)
What RPM range do you like to use it/drive in?
Is your priority: low end torque midrange high end power (select 1 or 2)
Can you upgrade valve springs?
Can you upgrade rocker arms?
Exhaust: Manifolds Shorty Headers Mid Length Long Tubes
Primary Diameter:
Collector Diameter:
Exhaust Diameter: Single Dual
Vehicle Year, Make, Model: 1975 K5 blazer
Vehicle Weight:
Engine Model: GenVII 8100 BBC
Engine Bore: 4.25 Stroke: 4.375
Compression:
Cylinder Heads:
Cylinder Heads ported or Stock?
Combustion chamber size:
Runner Volume
Valve Sizes:
Head Flow Numbers:
EFI or Carb
Throttle/Carb Size:
Intake Manifold Model:
Intake Manifold Type:
Induction: NA Nitrous Supercharger Turbo
Stages of Nitrous:
Suprcharger Type : Roots Screw Centrifugal
Transmission:
Torque Converter Size/Stall(if applicable):
Drive Axle Gears:
Tire Size:
Intended Use:
How do you want it to idle? (smooth, fair, moderate, lopey, etc.)
What RPM range do you like to use it/drive in?
Is your priority: low end torque midrange high end power (select 1 or 2)
Can you upgrade valve springs?
Can you upgrade rocker arms?
Exhaust: Manifolds Shorty Headers Mid Length Long Tubes
Primary Diameter:
Collector Diameter:
Exhaust Diameter: Single Dual
Ok @folkenheath let’s try this. I can measure the exhaust manifolds if I need to, but something is telling me you’d recommend headers.
Vehicle Year, Make, Model: 1975 K5 blazer
Vehicle Weight:
Engine Model: GenVII 8100 BBC
Engine Bore: 4.25 Stroke: 4.375
Compression: 9.1:1
Cylinder Heads: Stock
Cylinder Heads ported or Stock? Stock
Combustion chamber size: 107cc-108cc
Runner Volume: 320cc intake ports
Valve Sizes: 2.190 intake 1.725 exhaust
Head Flow Numbers: 235-270cfm intake 205cfm exhaust
EFI or Carb: Stock EFI
Throttle/Carb Size: 75mm
Intake Manifold Model: Stock
Intake Manifold Type: Removed intake baffle for more flow and cooler air intake
Induction: NA
Stages of Nitrous: N/A
Suprcharger Type : N/A
Transmission: Mild built th350
Torque Converter Size/Stall(if applicable): 1800rpm stall
Drive Axle Gears: 3.73
Tire Size: 33”
Intended Use: Street/Cruise + very mild trail
How do you want it to idle? (smooth, fair, moderate, lopey, etc.)
Would like moderate to lopey.
What RPM range do you like to use it/drive in?
2,000-2,500 highway
Is your priority: low end torque midrange high end power (select 1 or 2)
High end power
Can you upgrade valve springs?
Yes
Can you upgrade rocker arms? Yes
Exhaust: Manifolds Shorty Headers Mid Length Long Tubes: Stock BBC Squarebody Manifolds
Primary Diameter: Unknown
Collector Diameter: Unknown
Exhaust Diameter: Single Dual
Dual 3”
Vehicle Year, Make, Model: 1975 K5 blazer
Vehicle Weight:
Engine Model: GenVII 8100 BBC
Engine Bore: 4.25 Stroke: 4.375
Compression: 9.1:1
Cylinder Heads: Stock
Cylinder Heads ported or Stock? Stock
Combustion chamber size: 107cc-108cc
Runner Volume: 320cc intake ports
Valve Sizes: 2.190 intake 1.725 exhaust
Head Flow Numbers: 235-270cfm intake 205cfm exhaust
EFI or Carb: Stock EFI
Throttle/Carb Size: 75mm
Intake Manifold Model: Stock
Intake Manifold Type: Removed intake baffle for more flow and cooler air intake
Induction: NA
Stages of Nitrous: N/A
Suprcharger Type : N/A
Transmission: Mild built th350
Torque Converter Size/Stall(if applicable): 1800rpm stall
Drive Axle Gears: 3.73
Tire Size: 33”
Intended Use: Street/Cruise + very mild trail
How do you want it to idle? (smooth, fair, moderate, lopey, etc.)
Would like moderate to lopey.
What RPM range do you like to use it/drive in?
2,000-2,500 highway
Is your priority: low end torque midrange high end power (select 1 or 2)
High end power
Can you upgrade valve springs?
Yes
Can you upgrade rocker arms? Yes
Exhaust: Manifolds Shorty Headers Mid Length Long Tubes: Stock BBC Squarebody Manifolds
Primary Diameter: Unknown
Collector Diameter: Unknown
Exhaust Diameter: Single Dual
Dual 3”
Ok, this is why I ask, often answers are not as I expect. So I can offer some advice and let you fine tune the direction you want to go and then we can select the cam options.
Yes you are correct on the headers. Stock manifolds can be used, but they will significantly reduce HP.
The Gen VII BBC uses a decent factory head, and the cam is nearly the same as a Gen VI BBC cam, but the firing order has a double swap and matches the LS firing order.
There first two restrictions on that engine for upper RPM HP, are the stock intake/throttle body, and the stock exhaust manifolds.
So, we can get you a cam for midrange, but your top end likely will be bottlenecked by the stock intake and throttle body.
Although you can always upgrade or modify those things later.
When you do upgrade your trans, you keeping an auto?
Are you going to have the stock ECU tuned?
What do you consider upper RPM?
Yes, staying with Auto trans.
Stock ECU tuning.
As for upper rpm, I don’t really know. This is newer territory for me and this truck.
Started removing accessories and running the wire wheel. This motor is peeling pretty good. Definitely going to have to coat it good before it gets dropped in.
Cam shafts are cool, just saying
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.
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.
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.
Just a little second hand experience with Larry’s 8.1 swapped burb. He originally went with a Raylar “stage 2” cam. I don’t remember the specs but it was a lot more rowdy across the board. Raylar is about the only game in town when it comes to pushing the performance of an 8.1. Not saying Heath can’t come up with something that is probably better suited, but options are pretty minimal otherwise.
Here’s the thing about the “stage 2” cam. (I hate the name btw but that’s a whole other deal). The entire torque curve jumped about 1000 rpms up the scale. Point of note, he did get the tune tweaked by a couple of shops to try and dial it in. However two things were evident. One if you want to go with any more aggressive cam you’ll need to stick with a drive by wire throttle body. A mechanical throttle body could not react to the surge caused by the big cam and the IAC had the idle rpm constantly swinging up/down to try to react. If you are a picky sob for idle quality like Larry is, it was a constant source of frustration. Each tuner talked crap about the last guy but nobody he went to could fix it. They both tried to get him to switch to a dbw throttle so they could smooth out the idle by letting the throttle body crack open slightly since the IAC didn’t have enough range to smooth it out. That’s no bueno.
The second issue was the fat torque curve that is known to be right off of idle for an 8.1 was gone. Torque didn’t come in until 2500 rpm. I never thought I’d ever feel a 8.1 with that sort of a low end but he was right. You had to wind it out to start feeling the oats. Gone was the tractor like torque you could lug down in any gear.
I drove it a couple of times. If you wanted to go lay waste to some coal puking diesel bro, that burb was the ticket. The speed that thing had for being a lifted burb defied logic. But you had to dump the clutch and let it eat by getting it spinning right now. As fun as it was, that wasn’t the intent Larry was going for with the truck.
Larry had been talking directly to the main guy at Raylar that told him this was the way to go. Went in knowing the specs and what it could do. Ultimately, I helped him swap a stock GM cam back into it and he put the same tune he originally had from Howell. It’s not near as rowdy, but the low end torque was back and the mechanical throttle body had the idle smooth again.
I tell the story to give some idea what a cammed up 8.1 can do. If you wanted a hot rod 8.1 it will wake it up. Larry did go with Sanderson headers on the idea of the bigger cam needed the better flow. I’m certain Heath can do a much better job dialing in a cam that can keep the low end and build from there vs Raylar’s go big or go home spec. Might be worth the research to see what his specs are just to know what that had and where to go from there.
Here’s the thing about the “stage 2” cam. (I hate the name btw but that’s a whole other deal). The entire torque curve jumped about 1000 rpms up the scale. Point of note, he did get the tune tweaked by a couple of shops to try and dial it in. However two things were evident. One if you want to go with any more aggressive cam you’ll need to stick with a drive by wire throttle body. A mechanical throttle body could not react to the surge caused by the big cam and the IAC had the idle rpm constantly swinging up/down to try to react. If you are a picky sob for idle quality like Larry is, it was a constant source of frustration. Each tuner talked crap about the last guy but nobody he went to could fix it. They both tried to get him to switch to a dbw throttle so they could smooth out the idle by letting the throttle body crack open slightly since the IAC didn’t have enough range to smooth it out. That’s no bueno.
The second issue was the fat torque curve that is known to be right off of idle for an 8.1 was gone. Torque didn’t come in until 2500 rpm. I never thought I’d ever feel a 8.1 with that sort of a low end but he was right. You had to wind it out to start feeling the oats. Gone was the tractor like torque you could lug down in any gear.
I drove it a couple of times. If you wanted to go lay waste to some coal puking diesel bro, that burb was the ticket. The speed that thing had for being a lifted burb defied logic. But you had to dump the clutch and let it eat by getting it spinning right now. As fun as it was, that wasn’t the intent Larry was going for with the truck.
Larry had been talking directly to the main guy at Raylar that told him this was the way to go. Went in knowing the specs and what it could do. Ultimately, I helped him swap a stock GM cam back into it and he put the same tune he originally had from Howell. It’s not near as rowdy, but the low end torque was back and the mechanical throttle body had the idle smooth again.
I tell the story to give some idea what a cammed up 8.1 can do. If you wanted a hot rod 8.1 it will wake it up. Larry did go with Sanderson headers on the idea of the bigger cam needed the better flow. I’m certain Heath can do a much better job dialing in a cam that can keep the low end and build from there vs Raylar’s go big or go home spec. Might be worth the research to see what his specs are just to know what that had and where to go from there.
