Dodge Challenger R/T 426 Hemi - what makes this V8 engine so revered? | Tyrrell's Classic Workshop

Dodge Challenger R/T 426 Hemi - what makes this V8 engine so revered? | Tyrrell's Classic Workshop

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00:09
well hello and welcome to another tyrells classic workshop this time around we're looking at something a bit different and this is part of my life that people watching the channel haven't particularly been aware of and a little bit left field it's a big horsepower american v8 and people uh we're used to seeing the italian exotica the miuras the countaches the porsche 911 rss and it could end there but the funny thing is uh i've been in the engine tuning business for 40 years and i've tuned a lot of
00:41
american v8s along the way of different performance and different power outputs over the years different specifications different modifications so this has been very much part of my life but this is the first time i've featured a big american v8 on the channel and what i wanted to start with the dodge challenger rt426 hemi and as soon as you say the word hemi any american drag racer or v8 nut is guaranteed to go weak at the
01:11
knees because it was such a powerful word that chrysler actually trademarked it in the mid-1960s when this engine first came out this is a 1970 car and it's it's such an iconic trademark such a and i don't like using the word iconic but i think we can get away with it here but um hemi really does carry an enormous amount of weight not just physically but also in terms of admiration and all that sort of stuff so we've got this car here it's 426 cubic
01:44
inch seven liter v8 unlike most american v8 it didn't start life as a fairly humble engine that was developed up the way to produce big horsepower like a lot of the cars of the 1960s this car was a detuned racing car engine so chrysler went racing with this engine in the nascar series it became so successful ford actually objected and had it outlawed on technicalities which was something ford did quite regularly at that time because they carried enormous weight in nascar racing but the
02:16
engine itself in stock trim as it is here produces 425 brake horsepower at 5000 rpm and 490 pounds per foot of torque at 4000 rpm now they sound like big numbers but you've got to remember that there were all sorts of twists and turns within american horsepower ratings at the time the you had the sae rating and then you had the din rating which were two different things but what increasingly happened was that
02:46
during the late 1960s insurance companies actually became very scared of ensuring anybody with a with a muscle car a proper serious muscle car which this most definitely is so the manufacturers started to under quote power ratings and this engine is running completely stock so it's got two four big barrel carburetors on the top which i'm going to tune and it's got standard valve springs standard camshaft standard everything really forged pistons ford's crankshaft which came as stock on this engine but
03:18
otherwise even the headers the exhaust manifolds are cast iron they're reasonably efficient but they're not as efficient as a proper set of stainless steel extractors so net result is this engine actually in reality produced a lot more than 425 brake horsepower but if you started doing some modifications to it and reintroduced some of the race bits that chrysler had taken off you can get up to 700 horsepower out of one of these engines fairly easily this is a serious serious engine
03:51
in 1970 they made 83 000 dodge challengers and 137 of them had this engine and a manual gearbox and you had to pay 25 extra it gets a bit complicated with the options like dana rear differentials and all sorts of different things upgrades that come with the engine but you had to pay at least 25 percent a quarter of the purchase price just to upgrade from the next most powerful
04:22
engine the 440 six-pack to this 25 of the cars value extra just to upgrade to this particular engine no wonder they're so venerated in uh in u.s muscle car circles we're going to be tuning this car taking it for a drive and i'm just going to delve a little bit into the technicalities of why the hemi works so well let's have a look okay so there are three reasons why the hemi combustion chamber is better than
04:55
the more conventional of that period combustion chamber designs and i've got uh two cylinder heads here this is a fairly conventional cylinder head and this is a ferrari cylinder head from the 1960s that we got in for an engine rebuild so reason number one is flame propagation this here does not go around the full bore this combustion chamber the cylinder head is flat so the spark plug sparks the mixture explodes and it can't get past here and
05:26
this gap is very narrow between here and the piston wasted energy the the air air and water like the path of least resistance they're lazy so it's got to work to get past here it's not very good really second reason is gas flow or volumetric efficiency more air you can get through an engine the more powerful it is the more gas it explodes the more powerful it is very simple volumetric efficiency so air comes into the inlet port here it
05:56
goes into the inlet valve it comes in like that you get the spark exploding and the mixture comes out the exhaust there so the air is effectively because you have an engine is designed so that the exhaust gases actually suck partly suck the next charge of mixture into the cylinder but it's got to do that it's got to travel across and then out again very very complicated not straightforward third reason why this is not so good is because the valve diameter is limited
06:28
it's flat the valves are at the same angle so they can't be skewed in any way to get more size out of them so then we move on to this cylinder head which is a hemi head very similar to the one in the dodge so reason number one there's your spark plug right in the combustion chamber it explodes the whole thing spreads beautifully through that hemisphere of the combustion chamber and you get really good flame propagation that's reason number one why
07:02
it's better reason number two is it comes in the inlet port there into the valve you get the explosion and the mixture goes out through the exhaust there and sucks the inlet directly across much much easier to get the next charge of air into the combustion chamber and the third reason is that the the valves are angled so you can get a bigger diameter if they were flat you could get less if they're angled you get bigger valves
07:31
net result a hemi engine is naturally disposed to work much more efficiently than a wedge or a bathtub or any other type of combustion chamber enough of the nerdiest in earliness let's get back to tuning the car well we have an expression in england the proof of the pudding is in the eating and uh this is a very big pudding with lots of big pudding bowls in it
09:02
and um yeah i mean it's a big car we uh it's it's amazing how different american cars are on european roads and vice versa uh i'm just making sure that the engine is thoroughly warmed through it is of course because i've been tuning it but i just want to get the oil circulating get everything thermally stabilized it's a bit of a cat at the moment you've got the power brakes very
09:32
heavily power assisted steering and the ride is not too bad the suspension is pretty firm as you'd expect bearing in mind the power but it's not too bad and the seats comfy i mean this is definitely it's the american dream it's uh driving on a freeway on a sunny day with your friend playing the guitar in the back yeah it's all going on but not quite on an english b road but anyway what is certainly going to be going on is what's under the hood under the
10:05
bonnet um so we'll just move this pistol grip shifter down uh into second gear and let's uh see what that performance is actually like fantastically quick uh it's a good job it's a dry road because this would be an absolute handful in anything other than dry conditions and what an amazing
10:45
really considering the car is so big what an amazing unleashing of power this thing has got just incredible yeah as i mentioned earlier um as far as these cars were concerned the benchmark was acceleration cornering wasn't really an issue because uh the sort of cars that these cars the sort of roads that these cars were built for were straight and wide and you could see a long way you didn't need to particularly stop on
11:25
a six months or go around sharp corners although of course that was part of the fun when you got nearly 500 horsepower under your right foot but um on particularly 1970s technology tires but the acceleration is what really sets this car apart and a not to 60 time in period of 5.4 seconds 5.3 seconds was supercar territory worldwide the car that uh
11:57
that most probably closest in performance was the ferrari daytona on acceleration and that was quoted by ferrari when it came out in 68 69 as 5.4 seconds not to 60. so this was amongst the fastest accelerating cars on the planet at the time not just in the us an amazing achievement and i repeat this engine is in stock trim this is detuned this engine for road use
12:27
it was it started life as a racing car engine not the other way around like a lot of american v8 they started life as a stock engine that like the wonderful small block chevy that just gradually got altered and breezed on and changed and became a very very credible racing car engine but this was designed from the start with those wonderful hemispherical combustion chambers to be completely uncompromising and this is about as tame as it got
13:00
425 which is what uh dodge claimed for the engine brake horsepower there was such a lot of confusion at this time around sae and din horsepower you had different different readings and different ratings and but what dodge consistently did as is the other manufacturers of the time with these cars was they played down the horsepower ratings and actually under quoted and i i've seen these on dinos making even in standard stock trim close to 500
13:33
horsepower which is way above the uh claimed 425 and we get these wonderful this wonderful sweet spot of 1970 uh v8 mopar and detroit iron and aluminium and the results are just fabulous i'm going to just open those hemi combustion chambers up again yes what a beast i've just run out of gear that was second gear
14:09
i just run out of gear it's amazing the way the nose lurches up on this car when you accelerate the raw power and the raw torque just literally causes the back of the car to sink down and the front to rise up amazing and the way this engine revs i mean normally american v8s you you know when they're running out of power at the top and you know when the gas flow is beginning to slow down um this engine
14:46
is uh is just wants to carry on going even with the stock cam stock headers those cast iron headers instead of some as they called extractor tubular steel headers on the exhaust manifolds on the engine um already this thing is just it wants to rev and rev and rev and this is a big engine it's seven liters four 426 cubic inch what a thing it thrives on being thrashed this car absolutely
15:24
thrives on it and this shifter this pistol shifter which looks like uh some sort of crazy after-market thing is actually original equipment standard and it's a real joy to use it just fits perfectly yeah you feel like clint eastwood with a cult 45 in your hand waiting to uh to uh shoot up some um you know department store burglars or something it's
16:07
this is living the american dream yes well that concludes another tyrol's classic workshop video and if you particularly fancy this car it's coming on the market classic car auction website very very soon within the next few hours or days so keep a lookout for that don't forget to like share subscribe and also if you want to catch up on things that are going on um more generally to do with tyrol's classic workshop please
16:48
follow my instagram account and we'll be back with something else very soon you

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