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Chevy 454 Big Block, Mark IV, 7.4l - Rebuild and more Power.

RayzWorld

RayzWorld

Registered Member
Joined
Jan 2, 2025
Posts
37
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20
Location
Houston, TX
Hi everyone,

I'm wanting to rebuild and add more power to my Big Block somewhere around 500hp. I keep getting lost in the lingo and I'm hoping someone can give me some advice or opinions about what to purchase and what route would be best to achieve this goal.

Thanks for your Time.
 
I would be happy to help you select the components to build your BBC, 500 HP is no problem and we can make all the parts work together in your vehicle.

Can you tell us what vehicle it is, what engine you have to rebuild, what drivetrain parts, gearing, tires, and what you plan to use it for?

You can also call me at my shop at (262)495-8861
 
1986 Chevy K5 Blazer, 454 Big Block, Mark IV, 7.4l. TH400 transmission. The Axle gears I'm not 100% on, but I do know the front is a 10 bolt GM and the rear is a full float 14 bolt. The tires are currently 38 which I feel are pretty good, but then again I hear 40s are better so I'm on the fence. I wanted the vehicle to be 3 day weekend truck so freeway use, overlanding, and minimal towing.
 
folkenheath said:
I would be happy to help you select the components to build your BBC, 500 HP is no problem and we can make all the parts work together in your vehicle.

Can you tell us what vehicle it is, what engine you have to rebuild, what drivetrain parts, gearing, tires, and what you plan to use it for?

You can also call me at my shop at (262)495-8861
Click to expand...
Where are you located?
 
That’s a workable budget and FOLKENHEATH can absolutely put a plan together that will make all components work together ( keep that in mind - everything must compliment each other ).

He will need to know the gear ratio , induction type and exhaust to give you best results.
 
tarussell said:
That’s a workable budget and FOLKENHEATH can absolutely put a plan together that will make all components work together ( keep that in mind - everything must compliment each other ).

He will need to know the gear ratio , induction type and exhaust to give you best results.
Click to expand...
Thank you, I dont mind reworking the Axles so if they can tell me what ratios I need i will most definitely make them so that everything is copacetic.
 
RayzWorld said:
Thank you, I dont mind reworking the Axles so if they can tell me what ratios I need i will most definitely make them so that everything is copacetic.
Click to expand...
If you can find out a little more about your 454 like what it may have come out of - and what type of cylinder heads ( casting numbers will tell all ) such as peanut-port or older oval-port; the more info at hand the better the plan will be.

Note: you can pop a valve cover to retrieve the casting numbers.

Keep us posted on what happens - big blocks are GREAT !
Glad you are wanting more power - it’s addictive.
 
RayzWorld said:
Where are you located?
Click to expand...
I'm in WI, but I did live in Houston for one year if that counts for anything. ;)

I agree with the guys, what heads do you have to work with? Casting numbers will be under the valve covers.

How is your ignition system and exhaust system?

Plan to keep it carbureted?

I am going to some general questions here from my cam form, it will apply to the whole engine rebuild...I deleted some stuff as we will be changing it, or you already answered it....if you don't know the answer, leave it blank...

-------------------------------

Cylinder Heads:

Cylinder Heads ported or Stock

Combustion chamber size:

Runner Volume:

Valve Sizes:

EFI or Carb:

Throttle/Carb model:

Intake Manifold Model:

Intake Manifold Type:

Torque Converter Size/Stall:

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
 
Don’t get overwhelmed with all the detailed questions - it’s all part of getting exceptional results and spending your budget wisely.

Think of this as part of the fun of building your truck - researching this information is part of learning and the fun of it all.
 
tarussell said:
If you can find out a little more about your 454 like what it may have come out of - and what type of cylinder heads ( casting numbers will tell all ) such as peanut-port or older oval-port; the more info at hand the better the plan will be.

Note: you can pop a valve cover to retrieve the casting numbers.

Keep us posted on what happens - big blocks are GREAT !
Glad you are wanting more power - it’s addictive.
Click to expand...

tarussell said:
If you can find out a little more about your 454 like what it may have come out of - and what type of cylinder heads ( casting numbers will tell all ) such as peanut-port or older oval-port; the more info at hand the better the plan will be.

Note: you can pop a valve cover to retrieve the casting numbers.

Keep us posted on what happens - big blocks are GREAT !
Glad you are wanting more power - it’s addictive.
Click to expand...
Well I'd have to pull the engine out to see the casting numbers. The information I put together was from the front cast numbers. Which have told me the year and that it came from a 73-74 corvette.
tarussell said:
If you can find out a little more about your 454 like what it may have come out of - and what type of cylinder heads ( casting numbers will tell all ) such as peanut-port or older oval-port; the more info at hand the better the plan will be.

Note: you can pop a valve cover to retrieve the casting numbers.

Keep us posted on what happens - big blocks are GREAT !
Glad you are wanting more power - it’s addictive.
Click to expand...
Well I'd have to pull the engine out to see the casting numbers. The information I put together was from the front cast numbers. Which have told me the year and that it came from a 73-74 corvette. The heads i wanted to replace since they are iron and have a reputation of not performing and causing over heating. That's just from what I read.
 
folkenheath said:
I'm in WI, but I did live in Houston for one year if that counts for anything. ;)

I agree with the guys, what heads do you have to work with? Casting numbers will be under the valve covers.

How is your ignition system and exhaust system?

Plan to keep it carbureted?

I am going to some general questions here from my cam form, it will apply to the whole engine rebuild...I deleted some stuff as we will be changing it, or you already answered it....if you don't know the answer, leave it blank...

-------------------------------

Cylinder Heads:

Cylinder Heads ported or Stock

Combustion chamber size:

Runner Volume:

Valve Sizes:

EFI or Carb:

Throttle/Carb model:

Intake Manifold Model:

Intake Manifold Type:

Torque Converter Size/Stall:

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
Click to expand...
Well damn... let me try and answer
1. I want to change the heads with aluminum.
2.i want it to idle like it's about to die i want that classic vehicle that has power.
3.manifold I want a new one.
4. If I need bigger heads then I'll be totally fine with that.
5.EFI, no to the carburetor.
6.The torque converter i know nothing aabout and would like input into what I should get.
I guess what I'm trying to say is that if I need to replace everything but the block then I'm willing to go that route to accomplish the goal. I want a big cam and I read the compression should be high to achieve higher power gains.
 
The Headers will be new, I just need to figure out which ones will function and not hit the cross member. I have a jacked up truck so I don't think Shorty Headers will work on the truck.
 
nvrenuf said:
Be careful, aluminum heads and EFI just ate half your budget.

Don’t be quick to turn away from iron heads, they’ll work fine with a good combo AND an adequate cooling system.
Click to expand...
Interesting. Everything is read said to get away from iron heads. 1. Was extra weight, 2. Was the performance is not as good. If I can stick with iron heads and still get what I want out of the engine then that helps with the budget. I don't know if that effects the frame since the K5 Blazers are known to have a weak point in the in the engine bay if you ever do any flexing. Again I'm overwhelmed with all the information from Google and YouTube videos.
 
Here is the best place for K5 mods. If it's possible someone here has probably done it.
there are plenty of K5s with big blocks. K5 are not light race cars, yes the weight can add up, but new aluminum heads will be at least a 3rd of stated budget. Weight vs cost.
If your engine is truly an early 70s Vett engine and unmolested the heads will make 500hp easy. You may have an Ls6 or Ls7.
 
There are certainly big benefits to aluminum heads, weight savings and big power potential is definitely real but that doesn’t mean all iron heads are junk.

Honestly, 500hp from a bbc is pretty easy without getting radical or the need for ultimate magazine article parts.

Like Wes said, you’ll find all kinds of squares here from mild to wild and there’s not a tube chassis in sight. There are some boxed or reinforced frames but it’s typically not because the motors are tearing them apart.

That said, watch the frame for cracks behind the steering box as that is a big problem area (regardless of engine).
 
From personal experience….make the truck as usable as possible. Not a one trick pony! Better to have truck do many things good, than a truck that only does one thing great!
 
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