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(with Purple92)
Base your decision on facts or what a couple of engine builders think. More than one. Guys that have built a few thousand engines each. They're not on this forum cause they are too busy. I know of one who chimes in occasionally but haven't seen him in this thread. Unless you get lucky and someone has built this exact 427 combo and has had either good or bad luck with it. Haven't heard that here either. Best comment I heard was factory 400s lasted a long time. Now that's a fact. What stroke and rod length do they have? Was it ideal? Was it as good as a 350? I don't remember. Google says 4.125 x 3.75. Google says some ran a 5.7" typical sbc rods and some ran a .135 shorter 5.565" rod. The original 400s ran the shorter rod and they lived long lives. Not sure where the 5.7 came from . I'd figure out the stroke to rod ratio and compare it to the 427 variant. I am assuming you could build the 427 with different rod lengths if you could find a piston to match. There has got to be a minimum length needed to clear the crank, and I did see a 6.0" listed.
So based on that math the 427 SBC has the same rod ratio as a 400 SBC, and the 400 lived a long life. That's based on facts and not opinion. I'm a scientist so I put way more faith in verified facts, not opinions or theories.
i will talk to your builder next week. If he says the right things that make sense to me, I can proceed. As I said on phone yesterday, you are one of the few that listens to what I want instead of telling me I want something different. It really comes down to a torque curve that mirrors an LS5 Corvette engine. Apparently nobody ever wanted the LS5 back in the day......and GM built it anyway,.
Last edited by Shovels and Vettes; Nov 10, 2019 at 11:31 AM.
you mean it would win a race by speed, but the LS5 would launch and accelerate faster pushing me back in the seat till it topped out and the the 383 would fly by. I am not racing. I want acceleration up to 60 and then I am done. It seem very few people can comprehend the difference. Plus you would have to rev the 383 to 5000 to get the torque the LS5 does at 2500 rpm.
Last edited by Shovels and Vettes; Nov 10, 2019 at 05:10 PM.
Did anyone see the power graphs in post 61?? I am not sure why it is not clear what that torque curve will feel like in the car. Seems to me the only argument would be that the torque curve shown would actually not be the same in real life. If anyone has charts that show same torque curve as these AND power at 5000 plus, let’s see it because that seems to be the argument from the race boys.
Last edited by Shovels and Vettes; Nov 10, 2019 at 05:10 PM.
funny. Instead of remarks how about providing some technical information, which is what this forum is for. Otherwise you are just trolling for your own fun. I am here to find information, but it’s always tedious seperating facts from race boy egos.
you mean it would win a race by speed, but the LS5 would launch and accelerate faster pushing me back in the seat till it topped out and the the 383 would fly by. I am not racing. I want acceleration up to 60 and then I am done. It seem very few people can comprehend the difference. Plus you would have to rev the 383 to 5000 to get the torque the LS5 does at 2500 rpm.
Just took my buddy for a little drive if your not a bodybuilder this thing would snap your neck. It will literally blow the tires of in every gear I just did it . There is no way an Ls5 will even though the front end is heavy
funny. Instead of remarks how about providing some technical information, which is what this forum is for. Otherwise you are just trolling for your own fun. I am here to find information, but it’s always tedious seperating facts from race boy egos.
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Me and you build two engines, yours will have a 4.00 inch stroke mine will have a 3.00 stroke we will both use quality parts. You use 6.00 rod with your 4.00 stroke, I use a piston that is normally used with a 3.50 stroke and a 6.00 rod length the piston needs no oil ring supports, to atach it to my build make it work with the 3.00 stroke I now have to use a 6.250 rod length. Now your rings are traveling 4.00 inches in the bore mine 3.00 inches so your rings are doing 25 percent more work and that is not all. Both are engines are now at bottom dead center to change direction come back up. How much side loading of the rings and piston skirt with your 4.00 stroke and 6.00 rod, well the rod is now at a pretty bad amount of angle trying to force outward before it starts to slide upwards. Now you are making both the rings and pistons skirts work harder more wear added to the other 25 percent. My cranks rod pins are further away and the 6.250 rod has the piston at a much better angle. Now both our engines have to do this 5000 times per minute x 8 cylinders. Now I'm not suggesting you try to to use a 3.00 stroke for a good tq build engine. The extra 17 cubes the 4.00 stroke to a 3.75 stroke, then oil ring supports and smaller base circle cam, it's not worth it.
Last edited by Little Mouse; Nov 10, 2019 at 05:52 PM.
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Me and you build two engines, yours will have a 4.00 inch stroke mine will have a 3.00 stroke we will both use quality parts. You use 6.00 rod with your 4.00 stroke, I use a piston that is normally used with a 3.50 stroke and a 6.00 rod length the piston needs no oil ring supports, to atach it to my build make it work with the 3.00 stroke I now have to use a 6.250 rod length. Now your rings are traveling 4.00 inches in the bore mine 3.00 inches so your rings are doing 25 percent more work and that is not all. Both are engines are now at bottom dead center to change direction come back up. How much side loading of the rings and piston skirt with your 4.00 stroke and 6.00 rod, well the rod is now at a pretty bad amount of angle trying to force outward before it starts to slide upwards. Now you are making both the rings and pistons skirts work harder more wear added to the other 25 percent. My crank is further away and the 6.250 rod has the piston at a much better angle. Now both our engines have to do this 5000 times per minute x 8 cylinders. Now I'm not suggesting you try to to use a 3.00 stroke for a good tq build engine. The extra 17 cubes the 4.00 stroke to a 3.75 stroke, then oil ring supports and smaller base circle cam, it's not worth it.
i understand and you make sense. Just because the industry has produced this 427 sbc it does not mean its the best choice when reliability and longevity matters. This was my original question and you have answered it.
Last edited by Shovels and Vettes; Nov 10, 2019 at 07:35 PM.
I guess I have to bring up the fact that a 454 BBC also has a rod ratio of 1.5, and they are known to last a long time. They certainly don't self-destruct in 16,000 miles. or 50k or 100k for that matter.
Since an LS5 was brought up, here is the power curve for an 1970 454 LS5 that the OP wants to emulate if possible in a SBC.
These are known to produce great low end torque, with a long flat torque curve that practically starts at idle, and the smallish factory cam makes them run out of breath around 5000-5500.
GM says they peak at 390HP at 4800 rpm. Some here not so lovingly refer to it as a truck motor because of that.
The OPs proposed 427 SBC would actually have within a few ft lbs of this low end torque level (maybe 20 lower), and make a little more high rpm HP (maybe 20). I find it amazing that a SBC can be made to mimic a BBC so closely.
All this without the weight penalty of a BBC or the severe parts penalty from swapping over to all BBC headers, exhaust, pulleys, brackets, rad, etc.
It sounds like he wants to re-use his excellent existing heads/manifold/carb. So we are only talking a short block change.
This would be many thousands less than the LS5 route. Or a compete crate motor for that matter, of any size.
I would guess an LS5 clone could be built for $3500+ with another thousand or two for the other BBC bits. $5-6K kinda expensive.
I think this 427 SBC is a great idea, and should give him that punch in the gut he wants, in any gear, at any rpm. For way less $ than the above.
Any larger cam than the factory LS5 one starts to degrade that low end at idle torque level, but obviously adds great power at the top, for either large cube motor.
He's not building a race engine but neither is the LS5.
So does anyone think this 427 SBC short block could be built for around $3500? Best guess? More or less?
Last edited by leigh1322; Nov 10, 2019 at 09:00 PM.
Very often, I suggest sbc L31 iron Vortec TRUCK motors/heads because they have so many features folks desire ...
... Affordability, Availability, Durability, Reliability and good Performance with potential for much more.
NO serial production passenger CAR was delivered with sbc L31 iron Vortec ... only with serial production Trucks and as Goodwrench replacement motors.
If L31 iron Vortec had been available in only Cadillac Allante, I'd still recommend that Truck motor.
It's my understanding the Big Block BBC has its earliest roots in Trucks when it was introduced (as an adjunct to smaller sbc) ...
... as a larger & more powerful W motor for Trucks; then subsequently for larger cars.
3500 short block w/cam & lifters ... just barely ... IF he did it himself ... lotsa guys can do a great job of it, standing on their heads ... plenty others think they can But will wreck it.
FWIW ... my post # 102 has links to LS5 hp/tq specs & curve direct from GM
For those within the "plenty" group ... the point/estimation is moot.
-addendum not edit-
and so, on the heels of my post # 116 with a conditional concurrence w/ post #114 ... TS FB questioned my estimation ... then ...
... when I replied with this post # 117 ... TS FB deleted his post questioning my "estimation".
Being older, a classic and hot rod mechanic, and a driving instructor I have been blessed with getting to drive all kinds of Vettes. Some of the most disappointing models are the low powered BBC. The 390 Hp 427 and the totally junk end of the era 454's. They were installed in family wagons and trucks. They absolutely have no getup and go. They are not TQ monsters they are slugs!
Being older, a classic and hot rod mechanic, and a driving instructor I have been blessed with getting to drive all kinds of Vettes. Some of the most disappointing models are the low powered BBC. The 390 Hp 427 and the totally junk end of the era 454's. They were installed in family wagons and trucks. They absolutely have no getup and go. They are not TQ monsters they are slugs!
Being older, a classic and hot rod mechanic, and a driving instructor I have been blessed with getting to drive all kinds of Vettes. Some of the most disappointing models are the low powered BBC. The 390 Hp 427 and the totally junk end of the era 454's. They were installed in family wagons and trucks. They absolutely have no getup and go. They are not TQ monsters they are slugs!
Explain the torque graph above and how those torque numbers do not launch the car forward at low RPM? If you can explain it, maybe I will believe it.
Last edited by Shovels and Vettes; Nov 12, 2019 at 03:01 PM.
Yes
(with Purple92)
