C4 Big Block Swap
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C4 Big Block Swap
Hey guys,
I'm getting ready to create a my dream car of many years--> a manual trans big block Vette. I have the car, a 1987 Z51 with 4+3, and I have the engine, a 454 that I built with appropriate goodies. My question concerns the flywheel, clutch, bell housing for the swap.
I know all the bolt patterns fit. My concern is regarding whether the larger big block flywheels and clutches will fit the Corvette bell housing. There's the 153 tooth, small flywheel, and the 168 tooth large flywheel. Then, as well, there are 10.5" clutches, and 11". Can anyone advise me as to if the larger flywheel, and/or the larger clutches will fit the stock C4 bell housing??
Yes guys, I know. Everything from the firewall back is going to break.
Yes guys, I know. An "LS" is a better swap.
I don't care! I want this!
;~)
Vettepilot
I'm getting ready to create a my dream car of many years--> a manual trans big block Vette. I have the car, a 1987 Z51 with 4+3, and I have the engine, a 454 that I built with appropriate goodies. My question concerns the flywheel, clutch, bell housing for the swap.
I know all the bolt patterns fit. My concern is regarding whether the larger big block flywheels and clutches will fit the Corvette bell housing. There's the 153 tooth, small flywheel, and the 168 tooth large flywheel. Then, as well, there are 10.5" clutches, and 11". Can anyone advise me as to if the larger flywheel, and/or the larger clutches will fit the stock C4 bell housing??
Yes guys, I know. Everything from the firewall back is going to break.
Yes guys, I know. An "LS" is a better swap.
I don't care! I want this!
;~)
Vettepilot
Intermediate
Joined: Feb 2024
Posts: 40
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From: Rochester Hills Michigan
You can use the smaller flywheel with no problems. For an example go to SPEC clutches website and "spec" your car. They list a number of different clutches depending on your HP goals. they also sell the flywheels that will make the whole thing a "bolt in" deal. I bought the Aluminum flywheel with the two piece rear seal bolt pattern. They vary the materials used in the discs and the pedal pressure is pretty reasonable. I have the super twin and the pedal pressure is right at 35lbs. I have the same concerns about breaking everything behind the clutch.
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Well, here's the thing. I would rather use the larger 168 tooth flywheel and 11" clutch too, if it will fit.
In general, Chevy is great about interchangeabilty, but I could see them making a special bell housing for the Vette for packaging considerations that might not fit the larger flywheels and clutches sometimes used on the big blocks. That's what I'm trying to find out...
Thanks,
Vettepilot
In general, Chevy is great about interchangeabilty, but I could see them making a special bell housing for the Vette for packaging considerations that might not fit the larger flywheels and clutches sometimes used on the big blocks. That's what I'm trying to find out...
Thanks,
Vettepilot
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Because bigger flywheel = more leverage for the starter, and easier starting. After years of fighting difficult hot starting on my large, high compression hot rods, it's something I always consider. And there's not much room in a C4 for the 27 series, 1000 amp battery I normally run on such a rig.
Additionally, a dual disk clutch is more expensive, can be problematic, and can cause shifting and/or synchro problems. Extra mass spinning on the input shaft has consequences. There's no free lunch. I like an old fashioned 11" clutch here...
Vettepilot
Additionally, a dual disk clutch is more expensive, can be problematic, and can cause shifting and/or synchro problems. Extra mass spinning on the input shaft has consequences. There's no free lunch. I like an old fashioned 11" clutch here...
Vettepilot
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Joined: Jun 2004
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Just a couple thoughts:
Aren't 153 tooth flywheels standard in early C4s? (My '84 has the small flywheel) This usually means a different bellhousing than a 168 tooth setup. Given that it's an hydraulic clutch in C4s, are you going to be able to find the bellhousing you need if you go with a 168 tooth setup?
Big blocks are heavy. You're just compounding the handling degradation if you go with a heavy flywheel and starter arrangement. A stock later C4 lightweight PMGR starter will spin a big block with ease. And, they're not as sensitive to heat as the older heavy(!) starters.
Aren't 153 tooth flywheels standard in early C4s? (My '84 has the small flywheel) This usually means a different bellhousing than a 168 tooth setup. Given that it's an hydraulic clutch in C4s, are you going to be able to find the bellhousing you need if you go with a 168 tooth setup?
Big blocks are heavy. You're just compounding the handling degradation if you go with a heavy flywheel and starter arrangement. A stock later C4 lightweight PMGR starter will spin a big block with ease. And, they're not as sensitive to heat as the older heavy(!) starters.
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Joined: Jul 2010
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Just a couple thoughts:
Aren't 153 tooth flywheels standard in early C4s? (My '84 has the small flywheel) This usually means a different bellhousing than a 168 tooth setup. Given that it's an hydraulic clutch in C4s, are you going to be able to find the bellhousing you need if you go with a 168 tooth setup?
Big blocks are heavy. You're just compounding the handling degradation if you go with a heavy flywheel and starter arrangement. A stock later C4 lightweight PMGR starter will spin a big block with ease. And, they're not as sensitive to heat as the older heavy(!) starters.
Aren't 153 tooth flywheels standard in early C4s? (My '84 has the small flywheel) This usually means a different bellhousing than a 168 tooth setup. Given that it's an hydraulic clutch in C4s, are you going to be able to find the bellhousing you need if you go with a 168 tooth setup?
Big blocks are heavy. You're just compounding the handling degradation if you go with a heavy flywheel and starter arrangement. A stock later C4 lightweight PMGR starter will spin a big block with ease. And, they're not as sensitive to heat as the older heavy(!) starters.
As far as the weight, yeah. However, I am taking weight off in other areas in the front, plus moving the battery to the back, etc., etc. The big block has aluminum heads, intake, water pump, etc. It looks like the weight issue will be manageable, plus, this swap has been done before. It's been a "dream car" for me for many, many years and we're going to make it happen...
I was going to go with one of the aftermarket high torque starters. You think the stock, permanent magnet starter would work? I have no personal experience with those on a large displacement, high compression engine.
Thanks,
Vettepilot
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Joined: Feb 2024
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From: Rochester Hills Michigan
It all depends on what you call large displacement and high compression. I have been running a 10.75:1 565 CI Big Block on a 153 tooth flywheel and ZF trans for years. The single disc goes up to 920 or 930 Lb/ft of torque. I have the super twin that is IIRC 9” diameter and the flywheel and pressure plate are aluminum. I have no issues with shift quality or as I mentioned pedal pressure. With big block torque you don’t need the steel flywheel mass to keep the car drivable.
I do run a good aftermarket starter, and a 000 gauge wire to a trunk mounted battery with zero hot start issues. I recommend that you focus on these areas and keep the clutch simple.
I just started tearing down my 95 to install the 565 that had been living in my 67 Camaro with Corvette bell housing and ZF trans. I have always thought it would be a pretty cool and fun setup. Good luck with your build!
I do run a good aftermarket starter, and a 000 gauge wire to a trunk mounted battery with zero hot start issues. I recommend that you focus on these areas and keep the clutch simple.
I just started tearing down my 95 to install the 565 that had been living in my 67 Camaro with Corvette bell housing and ZF trans. I have always thought it would be a pretty cool and fun setup. Good luck with your build!
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Well, nobody has specifically answered my question about 168 tooth flywheels and stock, original C4 bellhousings. From a hint here, and info from other sources, it seems that it probably will not.
So, luckily I had not bought the flywheel yet, and I will just go with a 153 tooth flywheel and a high torque starter. I too think aluminum is probably ok for a big block, non-drag racing car. An aluminum flywheel might also help the trans and rear end live a little longer...
;~)
Thanks guys,
Vettepilot
So, luckily I had not bought the flywheel yet, and I will just go with a 153 tooth flywheel and a high torque starter. I too think aluminum is probably ok for a big block, non-drag racing car. An aluminum flywheel might also help the trans and rear end live a little longer...
;~)
Thanks guys,
Vettepilot
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Only the stock 10 1/2 inch 153 to flywheel will fit inside the bell housing of a 4+3.
I just went through this because I built a pretty stout 406 with a SR intake and wanted to use an 11 inch flywheel and pressure plate that I know would hold but it would not fit in the Bell
I ended up using a stock flywheel with a upgraded pressure plate and a standard organic disc and iit held up.
I just went through this because I built a pretty stout 406 with a SR intake and wanted to use an 11 inch flywheel and pressure plate that I know would hold but it would not fit in the Bell
I ended up using a stock flywheel with a upgraded pressure plate and a standard organic disc and iit held up.
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Thanks! Right there is the simple answer I was looking for here.
However, thanks to all responders and thanks for the other info!
And THANKS for not trying to talk me out of it, and for NOT saying "LS".
(Yes "LS" engines are great. NO, they are not the ONLY engine.)
;~)
Vettepilot
However, thanks to all responders and thanks for the other info!
And THANKS for not trying to talk me out of it, and for NOT saying "LS".
(Yes "LS" engines are great. NO, they are not the ONLY engine.)
;~)
Vettepilot
Tech Contributor
Joined: Jun 2004
Posts: 20,905
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Well, nobody has specifically answered my question about 168 tooth flywheels and stock, original C4 bellhousings. From a hint here, and info from other sources, it seems that it probably will not.
So, luckily I had not bought the flywheel yet, and I will just go with a 153 tooth flywheel and a high torque starter. I too think aluminum is probably ok for a big block, non-drag racing car. An aluminum flywheel might also help the trans and rear end live a little longer...
;~)
Thanks guys,
Vettepilot
So, luckily I had not bought the flywheel yet, and I will just go with a 153 tooth flywheel and a high torque starter. I too think aluminum is probably ok for a big block, non-drag racing car. An aluminum flywheel might also help the trans and rear end live a little longer...
;~)
Thanks guys,
Vettepilot
Regarding the starter, the stock C4 PMGR starter works well on a big block, and they can be found at reasonable prices compared to too many aftermarket starters. I've used one for years on my '69.
Post some update pictures when you start getting into this project.
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To answer the exhaust question:
From my studies, there are a number of BBC-->C4 exhaust options. Sanderson headers is often mentioned as one. Apparently various block hugger headers, and other short/intermediate headers will work. Long tube headers are more difficult, but I've seen some done where one tube is cut and re-routed, and they then work.
Being a bit of an engine/performance purist, I tend towards long tube headers on my builds. However, this one might be different. Do I really want long tube headers hanging down low on an already very low slung car to inevitably get bashed?? I don't think so. I don't believe lack of power/torque will be an issue here, and I will be happy with a more logical intermediate length header on this one.
Just how fast do you actually need to fry the tires, anyway??
;~)
Vettepilot
From my studies, there are a number of BBC-->C4 exhaust options. Sanderson headers is often mentioned as one. Apparently various block hugger headers, and other short/intermediate headers will work. Long tube headers are more difficult, but I've seen some done where one tube is cut and re-routed, and they then work.
Being a bit of an engine/performance purist, I tend towards long tube headers on my builds. However, this one might be different. Do I really want long tube headers hanging down low on an already very low slung car to inevitably get bashed?? I don't think so. I don't believe lack of power/torque will be an issue here, and I will be happy with a more logical intermediate length header on this one.
Just how fast do you actually need to fry the tires, anyway??
;~)
Vettepilot
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Just a musing here...
This 454 that I am going to use is a refreshed and updated hot big block that I drove in my Blazer for 20 years. In the Blazer, I got 12.5 to 13 miles per gallon on the highway. I thought that perfectly acceptable for a rowdy cammed big block with a carburetor in a clunky Blazer.
I wonder what it will get in the much more svelte Corvette?? I will likely at EFI at some point, which should help...
Vettepilot
This 454 that I am going to use is a refreshed and updated hot big block that I drove in my Blazer for 20 years. In the Blazer, I got 12.5 to 13 miles per gallon on the highway. I thought that perfectly acceptable for a rowdy cammed big block with a carburetor in a clunky Blazer.
I wonder what it will get in the much more svelte Corvette?? I will likely at EFI at some point, which should help...
Vettepilot
Tech Contributor
Joined: Jun 2004
Posts: 20,905
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
To answer the exhaust question:
From my studies, there are a number of BBC-->C4 exhaust options. Sanderson headers is often mentioned as one. Apparently various block hugger headers, and other short/intermediate headers will work. Long tube headers are more difficult, but I've seen some done where one tube is cut and re-routed, and they then work.
Being a bit of an engine/performance purist, I tend towards long tube headers on my builds. However, this one might be different. Do I really want long tube headers hanging down low on an already very low slung car to inevitably get bashed?? I don't think so. I don't believe lack of power/torque will be an issue here, and I will be happy with a more logical intermediate length header on this one.
Just how fast do you actually need to fry the tires, anyway??
;~)
Vettepilot
From my studies, there are a number of BBC-->C4 exhaust options. Sanderson headers is often mentioned as one. Apparently various block hugger headers, and other short/intermediate headers will work. Long tube headers are more difficult, but I've seen some done where one tube is cut and re-routed, and they then work.
Being a bit of an engine/performance purist, I tend towards long tube headers on my builds. However, this one might be different. Do I really want long tube headers hanging down low on an already very low slung car to inevitably get bashed?? I don't think so. I don't believe lack of power/torque will be an issue here, and I will be happy with a more logical intermediate length header on this one.
Just how fast do you actually need to fry the tires, anyway??
;~)
Vettepilot
Adding a third u-joint and link guide to the steering linkage is an option, but I just prefer simplicity of operation for some components on the car.
Heel & Toe
Joined: Jul 2007
Posts: 24
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The reason I was asking about exhaust was because I was thinking of using the factory exhaust manifolds. The Factory Appearing Stock Tire racing series requires oem iron manifolds and they are making some serious HP to be running deep in the 9 second range with the big blocks they are using. Just curious what people think about that. It does have the advantage of not hanging down too low.
Intermediate
Joined: Feb 2024
Posts: 40
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From: Rochester Hills Michigan
The reason I was asking about exhaust was because I was thinking of using the factory exhaust manifolds. The Factory Appearing Stock Tire racing series requires oem iron manifolds and they are making some serious HP to be running deep in the 9 second range with the big blocks they are using. Just curious what people think about that. It does have the advantage of not hanging down too low.
I don't want to go too far off on the OP's thread, but there are a couple of things to consider with the stock manifolds. The F.A.S.T. guys put a bucket full of money into the manifolds and they still restrict the power. They are 2.5" outlets also. I have a hand ported set on my C10 with a 496 in it. They are nice and quiet as a plus. I have the parts to do a custom set of headers for my 95, but I would like to keep it simple. I purchased a set of C3 Big Block 2" primary (#68090) hookers and have heard they require modifying one tube or notching the frame. I think I am about four weeks away from doing a fit up. The plan would be to cut off the collectors and weld on something a little more performance oriented such as a 2" to 3.5" collector and extend the collector 18" or so. That is all dependent on what fits.
so the Big Block has an 8" deep pan vs the SB 7.5" pan. In the name of keeping it simple there is no plan to try and go with a shallower pan. I have one picture I will share here that shows the pan to header fit-up. the heads have raised ports (0.600") but it looks like there will be no hang down on stock ports. I will try to update my thread as I progress through the fit-up process. this is the thread:
https://www.corvetteforum.com/forums...eed-build.html
