Disappointed by the BB
Thread Starter
Team Owner
Joined: Nov 2004
Posts: 20,715
Likes: 25
From: Sorrento Italy
Disappointed by the BB
I've owned for more then a decade a fully modded and lightened C3 (1260 kg), the engine was a 406 575 hp jewel built by American Speed of Ill... I've sold the vette and have recently bought a show conditions rebuilt 72 Nova, with a 454 engine with supposedly 1000 miles on the clock, seller claimed to have 500+ hp, 5 speeds trans (absolutely fantastic) and 4.11 gears...The car is beatiful, a true muscle car.
Just that Comparing my C3 SB with this new 454 I feel quite didappointed, the way it speeds up revs is totally different, it sounds thundering but the revs are not there, over 4k it becomes lazy, it just does not enjoy being over 5k, while my C3 406 raged up to 6k like a turbo motor...
I'm now thinking about changing the engine with a built low compression 406 race engine.
Your comments will be appreciated, tks.
Just that Comparing my C3 SB with this new 454 I feel quite didappointed, the way it speeds up revs is totally different, it sounds thundering but the revs are not there, over 4k it becomes lazy, it just does not enjoy being over 5k, while my C3 406 raged up to 6k like a turbo motor...
I'm now thinking about changing the engine with a built low compression 406 race engine.
Your comments will be appreciated, tks.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
I've owned for more then a decade a fully modded and lightened C3 (1260 kg), the engine was a 406 575 hp jewel built by American Speed of Ill... I've sold the vette and have recently bought a show conditions rebuilt 72 Nova, with a 454 engine with supposedly 1000 miles on the clock, seller claimed to have 500+ hp, 5 speeds trans (absolutely fantastic) and 4.11 gears...The car is beatiful, a true muscle car.
Just that Comparing my C3 SB with this new 454 I feel quite didappointed, the way it speeds up revs is totally different, it sounds thundering but the revs are not there, over 4k it becomes lazy, it just does not enjoy being over 5k, while my C3 406 raged up to 6k like a turbo motor...
I'm now thinking about changing the engine with a built low compression 406 race engine.
Your comments will be appreciated, tks.
Just that Comparing my C3 SB with this new 454 I feel quite didappointed, the way it speeds up revs is totally different, it sounds thundering but the revs are not there, over 4k it becomes lazy, it just does not enjoy being over 5k, while my C3 406 raged up to 6k like a turbo motor...
I'm now thinking about changing the engine with a built low compression 406 race engine.
Your comments will be appreciated, tks.
Melting Slicks
Joined: Apr 2019
Posts: 2,504
Likes: 1,166
From: Northern Wisconsin
The big block motors were known more for low end torque, not so much for high rpm performance. That is not all bad, though. That low end torque is impressive on the street, where most muscle cars are driven. Some engines (especially big blocks) have long intake runners, and that is extra good for low rpm torque, but extra bad for high rpm performance. If the intake manifold of your engine has long intake runners, replacing it with a shorter style should help move your rpm up, but at the same time, you will loose some low end torque.
Burning Brakes
Joined: Jun 2010
Posts: 1,165
Likes: 93
From: Bellmore NY
Right there is the problem.
You knew what you had in your 406. And a well built 406 can really deliver the goods.
Without knowing what parts are actually in the motor, one can only speculate what kind of power it really makes.
A 454 can easily make 500hp. It can also easily make 350 depending on whats actually in it.
Race Director
Joined: Mar 2016
Posts: 14,399
Likes: 8,204
From: Napa Valley California
Did the seller provide you with a dyno sheet and sales receipts for the components supposedly in the engine?
Claiming 500 hp on a new engine sounds like an excellent selling point.
Big blocks can produce massive torque and strong hp up to and over 6500.
A 500 hp engine isn’t going to be as fun to drive as one putting out 575 hp, whether Its from a BB or a SBC.
My personal opinion is that you will be much happier if you build the BB in that Nova, but I’ve been a BB guy all my life.
Claiming 500 hp on a new engine sounds like an excellent selling point.
Big blocks can produce massive torque and strong hp up to and over 6500.
A 500 hp engine isn’t going to be as fun to drive as one putting out 575 hp, whether Its from a BB or a SBC.
My personal opinion is that you will be much happier if you build the BB in that Nova, but I’ve been a BB guy all my life.
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Le Mans Master
Joined: May 2003
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From: Fernandina Beach FL
2023 Restomod of the Year finalist
2020 C3 of the Year Winner - Modified
Melting Slicks
Joined: Jul 2005
Posts: 2,649
Likes: 863
Might I suggest "investing" a few hundred dollars on a chassis dyno session to see what power you're really making.
It's entirely possible that the carb or timing is screwed up, and IMHO - the best possible way to get things sorted out is to run on a chassis dyno where they can see things like Air / Fuel ratio in real time.
It's entirely possible that the carb or timing is screwed up, and IMHO - the best possible way to get things sorted out is to run on a chassis dyno where they can see things like Air / Fuel ratio in real time.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
First time it correctly. Then if still unhappy pull a valve cover and see what you have for heads. And measure valve lift while valve covers are off. Under half inch it is a junk truck or mercruiser cam. Building a better mouse trap, it still will never be a rat trap...
Last edited by derekderek; Jul 5, 2020 at 06:52 AM.
Burning Brakes
Joined: Aug 2013
Posts: 1,071
Likes: 322
From: palm springs ca
When I worked a a Chevy dealership I got a work order to adjust the valves on a ChevyII. I went to the holding lot and drove it around the block to warm it up. It was a hand full and I expected a 427 under the hood. Nope it was a SB.
Years ago I was told that you could measure HP by the amount of exhaust the engine produces. That seemed to make sense as the SB would rev to 7,000, and the BB much lower, therefore the SB was actually producing more exhaust. His formula was HP = the CFM of the exhaust.
Just something to think about.
Another fellow had a 302 SB in a Camero and it was OK but not great till he put a 4:11 in it and it came alive on the street runs. Seems that small blocks made it with RPM and as said in the other post Big blocks make it lower. There was a service manager there that told of a 454 that was de-stroked to a 300" engine. The purpose was to break a speed record at the salt flats. He said it would rev up a storm.
dom
Years ago I was told that you could measure HP by the amount of exhaust the engine produces. That seemed to make sense as the SB would rev to 7,000, and the BB much lower, therefore the SB was actually producing more exhaust. His formula was HP = the CFM of the exhaust.
Just something to think about.
Another fellow had a 302 SB in a Camero and it was OK but not great till he put a 4:11 in it and it came alive on the street runs. Seems that small blocks made it with RPM and as said in the other post Big blocks make it lower. There was a service manager there that told of a 454 that was de-stroked to a 300" engine. The purpose was to break a speed record at the salt flats. He said it would rev up a storm.
dom
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.
The BB in my 1233 kg C3 revs damn quickly. I have a lightweight flywheel/pressure plate combo, a timing curve to get efficient combustion, and a low backpressure exhaust system. What's the specs on your setup?
Team Owner
Joined: Jul 2004
Posts: 40,404
Likes: 791
From: Redondo Beach, California
Back in the day, the BB cylinder heads came with rectangular intake ports and oval port intakes. You need to have the rectanglar ports.....they are big. I had a piece part built L88 427 in a 1969 Coupe. The L88's were reputed to produce flywheel 550 hp...they of course had rectangular ports. The L88's had a 12.5 compression ratio, which needs 104 octane. I had the piston domes milled down 0.1 inches to get it down to 11:5 compression. I had sidepipe headers that were virtualy unmuffled. I think the carburetor I had flowed about 1000 cfm. It definately came alive at high rpms. It took a while before I could drive it without becoming frightened.
If your BB seems to be falling off at hgher rpm, first guess is it's running out of air. Rectangular ports? Free flowing exhaust? Big carburetor? Also, the cam? The L88 cam had a lot of overlap, so much so that the engine had very little off-idle power, but realy came alive at high rpm..
.............................
Stored the 69 in a sortage unit when I moved to Australia. It was stolen. I think the manager of the storage facility took it. He may have thought it was a real L88 car. 1969 L88's auction off at a little over $1 million today..
If your BB seems to be falling off at hgher rpm, first guess is it's running out of air. Rectangular ports? Free flowing exhaust? Big carburetor? Also, the cam? The L88 cam had a lot of overlap, so much so that the engine had very little off-idle power, but realy came alive at high rpm..
.............................
Stored the 69 in a sortage unit when I moved to Australia. It was stolen. I think the manager of the storage facility took it. He may have thought it was a real L88 car. 1969 L88's auction off at a little over $1 million today..
Last edited by 68/70Vette; Jul 5, 2020 at 01:17 AM.
Thread Starter
Team Owner
Joined: Nov 2004
Posts: 20,715
Likes: 25
From: Sorrento Italy
Thanks for all the inputs and comments.
I can only say that the seller of my Nova is a well known dutch american musclecar dealer, I visited his premises in Holland before deciding to buy the car from him (he had 20+ cars in stock) and he's also an engine builder.
It took 6+ months to find the right Nova and the car was rebuilt from ground up, I didnt look in details for the engine components, I just trusted his claim of a meaty 500+ hp output.
I'll send detailed pics of the engine later on.
I can only say that the seller of my Nova is a well known dutch american musclecar dealer, I visited his premises in Holland before deciding to buy the car from him (he had 20+ cars in stock) and he's also an engine builder.
It took 6+ months to find the right Nova and the car was rebuilt from ground up, I didnt look in details for the engine components, I just trusted his claim of a meaty 500+ hp output.
I'll send detailed pics of the engine later on.
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
Thanks for all the inputs and comments.
I can only say that the seller of my Nova is a well known dutch american musclecar dealer, I visited his premises in Holland before deciding to buy the car from him (he had 20+ cars in stock) and he's also an engine builder.
It took 6+ months to find the right Nova and the car was rebuilt from ground up, I didnt look in details for the engine components, I just trusted his claim of a meaty 500+ hp output.
I'll send detailed pics of the engine later on.
I can only say that the seller of my Nova is a well known dutch american musclecar dealer, I visited his premises in Holland before deciding to buy the car from him (he had 20+ cars in stock) and he's also an engine builder.
It took 6+ months to find the right Nova and the car was rebuilt from ground up, I didnt look in details for the engine components, I just trusted his claim of a meaty 500+ hp output.
I'll send detailed pics of the engine later on.