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Post by mark on Sept 29, 2014 19:13:36 GMT -5
Looking for some information and feedback. I know starting in 1972 Chrysler (along with the other manufacturers) starting detuning engines, dropping horsepower and compression. How was this accomplished? Heads, pistons, cam??? The reason for asking is I'm looking at a very low mileage 1974 440 and if I should get it I would like to un-detune it but on a budget, changing only what's necessary to bring back the H.P. and compression. I know the bore and stroke remained unchanged. This would be a weekend driving street engine, not anything radical or for racing. Would this even be worth the effort?
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Post by Nacho-RT74 on Oct 1, 2014 21:16:00 GMT -5
mainly just lower compression height pistons... then year after year, camshaft were being replaced
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Post by 1ol74charger4me on Oct 1, 2014 22:39:16 GMT -5
Using what the motor has which is probably unleaded heads, you have to mill excessively to increase compression requiring you do the intake also. Best bet is new pistons like Nacho explained. Basic hop up stuff. Earlier motors had forged cranks, holleys or 6 pak, bigger cams. If it was me, I'd have to take it apart for piece of mind anyway. New gaskets, 3 angle valve job(40 year old seals), new cam, new pistons, bearings, double roller chain, hone it, assemble and go. 74 has positive value in hardened seats in heads but low compression, cast crank, smog cam. All 440s can run with a little work. You just have to decide how fast your money can go.
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Post by Nacho-RT74 on Oct 8, 2014 9:48:35 GMT -5
open chamber heads were basically the same CC from 69, so there is not a Compression drop there
Magnum camshaft used on HiPo engines was available on engines from factory still up to 74. After that, not anymore.
So lets say about a 74 440Magnum. installing on it the earlier stock pistons, nothing fancy, you'll get same power than a 440 Muscle car era (69/71). The only BIG difference would be the crank, being cast on 74 and forged on earliers, but ACTUALLY that won't be a diff on power ( if we can say that )... in fact MAYBE you get more power from a cast crank engine being lighter, since makes rotation mass lighter.
way bettwer could be using KB HyperHeutic pistons about same price than stock replacement but higher compression height than stock, including earliers stock pistons.
so pretty much easy get power from them on the cheap, making a basic rebuilt job using the right parts
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Post by mark on Oct 9, 2014 20:21:17 GMT -5
I appreciate the responses and feedback. Since I have some unwanted free time I started looking into if these engines had actual h.p. drops or just a revised rating system. From what I've found from lots of web searching there were h.p and compression drops as part of the detuning. I had hoped Chrysler made the change in one specific area but it appears they didn't. (Don't know what the other manufacturers did, don't care. Mopar or nocar.) From what I've found they were numerous suttle changes. I've read the cams were milder, intake valves got a little smaller, cranks were changed since compression dropped and from what I read on allpar, for the 340 anyway the same piston and rod was used but the wrist pin location was changed affecting the compression height. I don't know if I can tear this engine apart since it's low miles and in good shape. It was wishful thinking the detuning change was just one component. Again, thanks for the responses.
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gip63
Forum Regular
Posts: 257
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Post by gip63 on Oct 9, 2014 20:35:09 GMT -5
I have a book called Mighty Mopars and it gives a lot of info on engines. The main areas changes took place were cams, compression, an carbs. At the height of power compression was 10.5:1 and the six pack was hot. According to the book the 440 was almost the engine the Hemi was and made more torque at less RPM. I have a engine like yours but was rebuilt two years ago and I want to do the same thing. I'm eyeballing a six pack right now, I just think they are cool  |
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