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Board Moderator & Exner Expert 10K+
  
Location: .Norfolk..Mafia.. ,England UK | Check previous Page for more PIC,s..........
Edited by Rebels-59 Coronet 2008-01-03 1:23 PM
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Expert
Posts: 3402
 
Location: Chestertown, NY ( near Lake George) | If you look closely it does not look like the intakes are inserts, only the exhaust, could be wrong the pics may mask that, anyway the exhaust is all that is required , nice pics good looking valve work. Just finished the same job on my 331, which as I said had factory steel exh. seats. Also recommended at this time is machining the intake guides for modern PC valve seals. They do make a seal that will work with the double springs.
Edited by Shep 2008-01-03 3:15 PM
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Expert
Posts: 1918
Location: Hell's Outhouse - a.k.a. Buckeye, Arizona | Sorry, fellas. This is all Greek to me. I'm not even in the same solar system as you guys where mechanics are concerned.
I think I may just have the hardened seats installed. I went with the lead additive on every fill-up with my '57 Lincoln after leaded gas went off the market in 1993 (at least, here in AZ it did) - after 3 years, it got beyond old. The thing is, I want the Coronado to be as low maintenance as possible after she's roadworthy. The variables ain't worth the worry - she'll get the seats..... |
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Elite Veteran
Posts: 709
Location: Poznan, Poland, Europe | So...these are the famous hemispheres ? Never seen them in closeup. Looks like they really match the name. And I was always thinkink that valves are supposed to be the same size, not one being bigger and one smaller...but what do you expect from a guy who always has to think hard before deciding in which way the screw rotates to go out. |
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Exner Expert 19,174 posts. Neil passed away 18 Sep 2015. You will be missed, Neil!
Posts: 19146
Location: bishop, ca | The intake valve is always considerably larger than the exhaust valve, owing to the fact that each cylinder requires a larger volume of unburned air:fuel mixture to be sucked (via the vacuum created when the piston descends) into the cylinder, than is the volume of burned mixture which exits thru the exhaust valve, and, the unburned mixture is not under any great pressure, so the smaller exhaust valve opening tends to speed up the flow of the gas in leaving the cylinder.
Also, the exhaust valve extends down into the combustion chamber, during the exhaust-cycle, so it gets hotter than the intake valve (which only receives the cold air:fuel mixture, and it has a larger surface area to dissipate ambient heat, than the smaller exhaust valve.
Because the exhaust valve is smaller & gets hotter than the intake valve, it can get oxidized (burned) if not allowed to cool off, and the gas octane/air:fuel ratio; the spark-timing (when the plug fires in relation to the piston being at TDC), and/or the camshaft timing ( allowing the exhaust valve to remain extended/open, in the combustion chamber ) can all contribute to burning exhaust valves, or causing other operational problems.
The exhaust valve ( steel ) seat-insert acts as a heat-sink, and a cushion, to the valve, in allowing excess heat to get transported to the internal water jackets.
Leaded gas deposited lead around the exhaust-port, which served to cushion the exhaust valve's impact on the
cast iron cylinder head. The lead may also have served to cool the exhaust valve.
The benefit of a hemispherical combustion chamber is : better gas-flow thru the combustion-chamber (in a straight line), mo-better burning of thegasses, due to the centrally-located spark plug, better heat dissipation, owing to the lack of nooks & crannies inside the combustion chamber, and MORE gas getting into & out of the c.c., by virtue of the larger valves that can FIT inside the c.c. .
Also, a Hemi can efficiently process BOTH lower and higher compression ratios, and gas-grades/quality, due to its inherent operational efficiency!!!
The drawback is that the system is more complex (& therefore more costly to produce) than a "wedge" c.c. , which has its intake & exhaust valves lying side-by-side, instead of across from each other, and with the spark plug intruding into the c.c. at a sharp angle.
Funny thing: in 1958, when CHRY introduced the Wedge-series of engines, it claimed ALL of the above Hemi-benefits as pertaining to the new Wedge-engine (in other words: they lied!)
Edited by d500neil 2008-01-03 8:14 PM
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Exner Expert 19,174 posts. Neil passed away 18 Sep 2015. You will be missed, Neil!
Posts: 19146
Location: bishop, ca | Mark: your Coro-nado (not to be confused with a TORO-nado!) looks to be sporting a 4-bbl carb! |
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Elite Veteran
Posts: 709
Location: Poznan, Poland, Europe | So the Hemis didn't have to depend only on the postwar octane increase , to gain extra performance, as other brands had to ? And that's why the '61 DeSotos 361 run on regular while other's 361 with higher compression on premium (as they say on allpar.com)?
Edited by FinFan 2008-01-04 3:54 AM
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Expert
Posts: 1918
Location: Hell's Outhouse - a.k.a. Buckeye, Arizona | d500neil - 2008-01-03 6:24 PM
Mark: your Coro-nado (not to be confused with a TORO-nado!) looks to be sporting a 4-bbl carb!
Yep, she sure is, Neil! But, I think she's still "only" 200 hp, unless I'm confusing the Fireflite plant with the Firedome plant somehow - if they had different plants.
I've only seen the '55 DeSoto listed with the 291 cid hemi rated at 200 hp, but I've no idea if that was for the Firedome or Fireflite - maybe the Firedome was rated at 200 hp with a 2 bbl with a 15-25 hp hike for the 4 bbl Fireflite?
Or maybe that's just a wild hope..... 
Either way, I'm not into making her some sort of Speedway Special - if she can handle regular 75-85 mph cruising speeds on the freeway, I'm cool. Yeah, you D-500 hot shots may leave me in the dust, but there's STILL something to be said about being fashionably late.....   |
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Expert
Posts: 3402
Location: Chestertown, NY ( near Lake George) | d500neil - 2008-01-03 8:01 PM
The intake valve is always considerably larger than the exhaust valve, owing to the fact that each cylinder requires a larger volume of unburned air:fuel mixture to be sucked (via the vacuum created when the piston descends) into the cylinder, than is the volume of burned mixture which exits thru the exhaust valve, and, the unburned mixture is not under any great pressure, so the smaller exhaust valve opening tends to speed up the flow of the gas in leaving the cylinder.
Also, the exhaust valve extends down into the combustion chamber, during the exhaust-cycle, so it gets hotter than the intake valve (which only receives the cold air:fuel mixture, and it has a larger surface area to dissipate ambient heat, than the smaller exhaust valve.
Because the exhaust valve is smaller & gets hotter than the intake valve, it can get oxidized (burned) if not allowed to cool off, and the gas octane/air:fuel ratio; the spark-timing (when the plug fires in relation to the piston being at TDC), and/or the camshaft timing ( allowing the exhaust valve to remain extended/open, in the combustion chamber ) can all contribute to burning exhaust valves, or causing other operational problems.
The exhaust valve ( steel ) seat-insert acts as a heat-sink, and a cushion, to the valve, in allowing excess heat to get transported to the internal water jackets.
Leaded gas deposited lead around the exhaust-port, which served to cushion the exhaust valve's impact on the
cast iron cylinder head. The lead may also have served to cool the exhaust valve.
The benefit of a hemispherical combustion chamber is : better gas-flow thru the combustion-chamber (in a straight line), mo-better burning of thegasses, due to the centrally-located spark plug, better heat dissipation, owing to the lack of nooks & crannies inside the combustion chamber, and MORE gas getting into & out of the c.c., by virtue of the larger valves that can FIT inside the c.c. .
Also, a Hemi can efficiently process BOTH lower and higher compression ratios, and gas-grades/quality, due to its inherent operational efficiency!!!
The drawback is that the system is more complex (& therefore more costly to produce) than a "wedge" c.c. , which has its intake & exhaust valves lying side-by-side, instead of across from each other, and with the spark plug intruding into the c.c. at a sharp angle.
Funny thing: in 1958, when CHRY introduced the Wedge-series of engines, it claimed ALL of the above Hemi-benefits as pertaining to the new Wedge-engine (in other words: they lied!)
Neil, nicely done, hit all the points on the money!
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Expert
Posts: 3967
Location: DFW, TX | Not bad Neil - that's all spot-on information.
Mark - your 4bbl 291ci '55 Fireflite was rated at 200hp, the Firedome for the same year was exactly the same engine with a 2bbl carb and rated at 185hp.
This might give everyone some additonal information on engine ID and ratings. http://www.hothemiheads.com/hemi_info/hemi_engine_id.html |
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Exner Expert 19,174 posts. Neil passed away 18 Sep 2015. You will be missed, Neil!
Posts: 19146
Location: bishop, ca | James, the Hemi ALLOWED a higher compression ratio to be utilized, for better performance (making the gas work harder, or, being able to squeeze more thermal energy out of it, by compressing it further, than before, and by burning all of the mixture; the earlier engine designs just didn't work efficiently )
and, the Hemi design could require and utilize an increased octane rating DUE to the increased c.r.; the higher octane rating was necessary to prevent improper gas combustion-timing (pre-ignition/detonation/pinging).
The creation of the Hemi head design allowed the gas companies to increase their octane ratings, because, now, there was a market FOR it!
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Exner Expert 19,174 posts. Neil passed away 18 Sep 2015. You will be missed, Neil!
Posts: 19146
Location: bishop, ca | And, James, altho the Hemi's might "officially require" a higher octane rating, as long as the c.r. is under 10.0 (let's say), the Hemi can PROCESS and USE efficiently a much lower octane ratio gas than that which the factory would (have-to) "recommend" , for the general-buying-public's various, even negligent, high-speed/high-load driving (worst-case-scenario)
"Hey: we TOLD you to use Premium gas" (to that person who just blew up his engine, pulling a trailer, up a mountainside, in August).
The Hemi can PROCESS higher-octane gas, so, the higher octane was 'required', to maximize the engine's performance.
AND, I just realized that I forgot to mention, above, that the Hemi's "dome" allows its centrally located
spark plug to have an "extended(long-ish)" electrode, penetrating deep into the middle of the c.c.,
creating a quick, complete, efficient burning of the air:fuel mixture.
AND: the centrally-located sopark plug causes a flame-front which pushes straight-down, into the top
of the piston.
A wedge c.c., with its sharply-angled spark plug, causes a lateral flame front, that pushes across the top of the
piston, and which tends to cause the piston to descend in its cylinder in an inefficient sideways
momentum-direction, increasing friction (heat) and wear to the cylinder & piston rings.
Edited by d500neil 2008-01-07 7:22 PM
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Expert 5K+
Posts: 7423
Location: northern germany | d500neil - 2008-01-03 8:01 PM
The drawback is that the system is more complex (& therefore more costly to produce) than a "wedge" c.c. , which has its intake & exhaust valves lying side-by-side, instead of across from each other, and with the spark plug intruding into the c.c. at a sharp angle.
Funny thing: in 1958, when CHRY introduced the Wedge-series of engines, it claimed ALL of the above Hemi-benefits as pertaining to the new Wedge-engine (in other words: they lied!)
unfortunatly this isn't the only drawback. to make an unblown hemi more efficient it requires a domed piston to raise the compression ratio, which adds weight to the piston which is VERY bad and the shape of the domed piston is less than ideal since the exploding gases are directed more towards the piston rings.
i don't care if they lied or not but the B/RB engine, probably the most reliable V8 engine ever build, was a mayor improvement over the early hemi.
Edited by 1960fury 2008-01-07 7:17 PM
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Exner Expert 19,174 posts. Neil passed away 18 Sep 2015. You will be missed, Neil!
Posts: 19146
Location: bishop, ca | The wedge was lighter and simpler to manufacture.
The Japs have even copied the Hemi head design.
There are few, if any, inherent design perameter benefits for a wedge combustion chambered engine, beyond weight and manufacturing costs.
The wedge c.c. design DOES promote better low rpm torque, than a Hemi head engine---that's about "it".
Of course, nowadays, Hemi heads are being cast out of aluminum.
Edited by d500neil 2008-01-07 7:36 PM
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Expert 5K+
Posts: 7423
Location: northern germany | neil, we had that topic a while ago. wedge vs early hemi:
http://www.forwardlook.net/forums/forums/thread-view.asp?tid=12685&...
hemis are great (BIG BLOCK based hemis) the hemi head design is superior, never said the contrary (that doesn't mean that the EARLY hemi is a good engine) the question is, if a lighter simpler cheaper engine with wedge heads can easily produce more power than "our" cars can handle, who needs hemi heads?
neil, did you know that the chrysler early hemi is based on a german ww2 engine that powered the generators for these huge anti aircraft spotlights? not so nice history for an american car engine
Edited by 1960fury 2008-01-07 8:00 PM
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Exner Expert 19,174 posts. Neil passed away 18 Sep 2015. You will be missed, Neil!
Posts: 19146
Location: bishop, ca | Thanks, Sid; heheheheh; during the past years, probably everything's been cussed/discussed.
BTW, did you see that postcard, recently, that featured a red 56 PLY convertible, in a western downtown shopping area, somewhere,
which had (aftermarket) fender skirts on it?
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Expert 5K+
Posts: 7423
Location: northern germany | d500neil - 2008-01-07 7:56 PM
BTW, did you see that postcard, recently, that featured a red 56 PLY convertible, in a western downtown shopping area, somewhere,
which had (aftermarket) fender skirts on it?
no,post it please  |
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Expert
Posts: 3155
Location: NY & VT | Re: the early Hemi's origination: the Deusenberg J/SJ's engine with hemi combustion chambers (and DOHC!) predated WW2, and I've seen it reported that Chrysler's famous engineeering team, the 3 Muskateers (Owen/Skelton/Breer) and Bob Roger were most influenced by the Deusy when coming up with the early hemi chamber design, I believe by Jan Norbye in his Postwar Chrysler book issued in the '70s IIRC, but it's been years...it's packed in some box somewhere, bought back when I had my 300-C connie (just one of several FLs I wish I'd kept!). RA in NY |
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Veteran
Posts: 279
Location: Norway | Hey! Done allready?  Nice!
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Expert
Posts: 3155
Location: NY & VT | Whoops... gettin' old! - that was FRED ZEDER, Owen Skelton & Carl Breer - the 3 Muskateers - who designed the Hemi... there's an old SAE paper on it somewhere, will ask my son who is a member..... brain fade |
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Expert
Posts: 1918
Location: Hell's Outhouse - a.k.a. Buckeye, Arizona | 55 Savoy - 2008-01-22 2:15 PM
Hey! Done allready? Nice!
Tee-hee! I wish.
Further incentive, just the same..... |
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Inactive by Request
Posts: 1292
Location: Lovely place | 1960fury - 2008-01-08 1:37 AM neil, did you know that the chrysler early hemi is based on a german ww2 engine that powered the generators for these huge anti aircraft spotlights? not so nice history for an american car engine :( Thats exactly why I moved to Germany. I found a really perfect new old stock (build year 1944) German V2-missile which is now my parts source for my 325 Hemi. The only problem I have with the Hemi - after the mods the engine always wants to go to London, England! Perhaps it needs a reprogram. I'm not sure what happens with the engine when it reaches the destination. But I bet it will be a thrill to drive! Cedric
Edited by Sisu 2008-01-23 9:17 PM
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God willing, count me in as a FLer in 2009!!!
