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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | it's been about two years since my 241 hemi rebuild and it now has approx 1500 miles on it, not even broke in yet. ,,,engine runs great and I am thinking about installing a set of Ross forged high compression 10.1 pistons in the 241 hemi. question is , will my old stock rod length work with these new domed piston ? I'm assuming they will because the dome is the only thing different protruding into the cylinder head chamber. will I have to rebalance the rotaing assemble again with the new pistons ? I'm pulling the engine out anyway and would like to make a change on it It does have a step up on a reground neilson's cam in it already with ported and polished heads. what are your views ? I'm NOT looking to race the engine by any means but am looking to increase horsepower and the fuel mileage on the dodge. you can see the full step by step Hemi rebuild full atricle in search of " rod knock in my 241 hemi" Thanks guys
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 IMG_3209 50.JPG (101KB - 181 downloads)
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Elite Veteran
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Location: Peoples Republic of Oregon | Nice to have a 4-bbl on the little guy!
Swapping pistons is not a huge job but expect to rebalance the package. Shop around for the best buy on the forgings as prices do vary with the source. The pistons and rings will be the only parts that you will change.
Keep in mind that the clearance on a forging will be a little greater than on a casting so there is some room for fussing/mis-measuring. The forgings will be extremely accurate so measure the bores several times. Be sure to note any taper in the holes.
Tell the piston 'guy' everything about the cam.
...as for not answering my phone, my hearing isn't all that great anymore and the shop is noisy at times...most folk leave a message.
Good luck.
Edited by wayfarer 2015-08-31 12:52 PM
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Expert
Posts: 3778
Location: NorCal |
In addition to the info above, it really helps if you can tell them the current measured deck height and the exact measured volume of the combustion chambers; the published factory specs (if you can even find it) are usually way off. |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | wayfarer - 2015-08-31 11:40 AM Nice to have a 4-bbl on the little guy! Swapping pistons is not a huge job but expect to rebalance the package. Shop around for the best buy on the forgings as prices do vary with the source. The pistons and rings will be the only parts that you will change. Keep in mind that the clearance on a forging will be a little greater than on a casting so there is some room for fussing/mis-measuring. The forgings will be extremely accurate so measure the bores several times. Be sure to note any taper in the holes. Tell the piston 'guy' everything about the cam. ...as for not answering my phone, my hearing isn't all that great anymore and the shop is noisy at times...most folk leave a message. Good luck. Thanks for the info wayfarer . very heplful I was hoping you would have anwered my post . and yes wayfarer ... that 4 barrel really wakes the 241 hemi up for sure. The shop that build my eninge says he knows the sales person at auto tec said he used to work for JE pistons. and could get the domed piston at a reasonable price . I did stop in and talk to the engine builder that put together my 241 hemi .. he says it would require new piston rings and probally need to rebalance erverything again. but says everything you were mentioning too wayfarer. How much mopar power do you think the domed 10.1 piston from 7.5 would add to the baby hemi? |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | 57chizler - 2015-08-31 1:32 PM In addition to the info above, it really helps if you can tell them the current measured deck height and the exact measured volume of the combustion chambers; the published factory specs (if you can even find it) are usually way off. thanks 57chizler .. good info ! |
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Expert
Posts: 3400
Location: Chestertown, NY ( near Lake George) | Pretty high compression for a steel head motor if it actually works out to10:1, lots of 91 octane and some timing curve rework to avoid defamation. |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | Shep - 2015-08-31 3:51 PM Pretty high compression for a steel head motor if it actually works out to10:1, lots of 91 octane and some timing curve rework to avoid defamation. hi shep I thought you could run more compression in a hemi and won't detonate vs say a bb mopar ? john |
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Expert 5K+
Posts: 7409
Location: northern germany | dodge59 - 2015-08-31 6:26 PM
Shep - 2015-08-31 3:51 PM Pretty high compression for a steel head motor if it actually works out to10:1, lots of 91 octane and some timing curve rework to avoid defamation. hi shep I thought you could run more compression in a hemi and won't detonate vs say a bb mopar ? john
that is true but domed pistons have 2 major drawbacks: weight and the shape that directs the exploding gasses towards the piston rings. one reason why bb engines live longer.
Edited by 1960fury 2015-08-31 6:53 PM
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | 1960fury - 2015-08-31 5:52 PM dodge59 - 2015-08-31 6:26 PM Shep - 2015-08-31 3:51 PM Pretty high compression for a steel head motor if it actually works out to10:1, lots of 91 octane and some timing curve rework to avoid defamation. hi shep I thought you could run more compression in a hemi and won't detonate vs say a bb mopar ? john that is true but domed pistons have 2 major drawbacks: weight and the shape that directs the exploding gasses towards the piston rings. one reason why bb engines live longer. my engine builder said to me today that the new pistons they make now days are much lighter even lighter than the flat tops i have in the hemi right now. He said if he has to balance the rotating assembly he would be taking weight off the crank because those flat tops are hevier .. |
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Expert 5K+
Posts: 7409
Location: northern germany | dodge59 - 2015-08-31 7:40 PM
1960fury - 2015-08-31 5:52 PM dodge59 - 2015-08-31 6:26 PM Shep - 2015-08-31 3:51 PM Pretty high compression for a steel head motor if it actually works out to10:1, lots of 91 octane and some timing curve rework to avoid defamation. hi shep I thought you could run more compression in a hemi and won't detonate vs say a bb mopar ? john that is true but domed pistons have 2 major drawbacks: weight and the shape that directs the exploding gasses towards the piston rings. one reason why bb engines live longer. my engine builder said to me today that the new pistons they make now days are much lighter even lighter than the flat tops i have in the hemi right now. He said if he has to balance the rotating assembly he would be taking weight off the crank because those flat tops are hevier ..
that could be true but the dome requires extra material, so if they manage to make the domed pistons lighter they could make new flat tops even lighter. also i hope the new, not time proven, lighter aftermaket? non mopar? pistons are as sturdy as oe ones.
Edited by 1960fury 2015-08-31 8:07 PM
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | 21 century maybe companies are making pistons out of the hyperheutectic metal formulas or better. . don't know . |
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Elite Veteran
Posts: 888
Location: Peoples Republic of Oregon | •the domes on a 241 piston are not huge...the combustion chamber is only in the 75 cc range
•hypereutectic is for casting not forging....forgings typically use something like a 2618 T61 or 4032 T62 alloy
•you should see 40-50 hp with the forgings (7:1 vs 10:1)
•the Hemi chamber easily supports a full point of compression more than a typical wedge chamber. |
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Expert
Posts: 3400
Location: Chestertown, NY ( near Lake George) | wayfarer - 2015-09-01 12:09 PM
•the domes on a 241 piston are not huge...the combustion chamber is only in the 75 cc range
•hypereutectic is for casting not forging....forgings typically use something like a 2618 T61 or 4032 T62 alloy
•you should see 40-50 hp with the forgings (7:1 vs 10:1)
•the Hemi chamber easily supports a full point of compression more than a typical wedge chamber. Agreed on the Hemi being more detonation resistant but with milder cams that do not bleed off much dynamic compression at low engine rpms, detonation can still be an issue. |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | how about some prices on these pistons.... anyone ?
I found one manufacturer alot cheaper than Ross........ Venoila
I'm surprise to see all the manufacturers make HP pistons for chryslers and desotos but no domed high compression pistons for the 241 dodge ..I mean pistons that are on the shelf. . I would think there is a big demand for HP 241 pistons if they were available. what gives ? baby hemi is pretty desireable engine .
everyone likes a little more horsepower.
 (my hemi crank installed 40%.JPG)
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my hemi crank installed 40%.JPG (194KB - 122 downloads)
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Expert
Posts: 3035
Location: N.W. Fla. | Guess they're more popular than the low deck Dodges. |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | these are the 241 hemi domed pistons
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ross 10.1 241 pistons.jpg (47KB - 149 downloads)
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | engine is out and disassembled ready to go to the speed shop tues. |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | engine is out and disassembled ready to go to the speed shop tues.
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pullin the hemi out again 50.JPG (121KB - 120 downloads)
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | one head , piston and head gasket dropped off at the speed shop.. they cc'd the head combustion chamber at 70*. movin right along. just need a few more specs on engine . and then send the flat top piston to venolia . |
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Extreme Veteran
Posts: 537
Location: Upstate NY | I am seeing many blogs about early hemis being sluggish and not worth the hype of current day early hemi fans. I personally could care except for the extremely high rebuild costs what engine is on my 57 Desoto but it happened to be a 341 hemi. I found it to be more than adequate for power with a 4 barrel carb. It was not sluggish at all. I can only assume that the recent articles are referencing the renewed interest in the early hemi and some feel that the wedge and poly were less masculine??? I also have a 58 Desoto and the 361 wedge is a great engine with an equAl amount of thrill (for me) when pressing the gas. So can I assume we are not talking about the classic car fan who loves his car but rather the performance parameters of the drive train?? For sure newer technology produces better power per cu in but I don't want a 300 HP 6 cylinder or I would have bought one. This site (for me) is about the classic car as it was built and the joy and nostalgia of owning the "car" not the drive train. I'm not trying to offend anyone and I know there is that group that is all about the drivetrain but the old drivetrain for it's time was pretty cool and the cars in there entirety were sensational. We all have a place here. My old hemi ran great for me! Thanks
My two cents again. |
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Elite Veteran
Posts: 888
Location: Peoples Republic of Oregon | Opinions are akin to belly-buttons; we all have one and all are different.....
Your 341 is a fine example of a factory hot-rod engine. Great balance of physical size, displacement and output. Some of the EarlyHemi engines are less-than-enjoyable
in stock trim because of the anemic compression ratio. Again, your 341 does not suffer from this. Also, compared to current day cam profiles, all of the early engines were
using very mild grinds; perhaps they did not know how far they could go and still maintain driveability for the older car buyer. That is why the 300 and the Adventurer were
created.
In terms of power available, any of the EarlyHemi engines can achieve 1hp/cu-in without breaking a sweat. The various wedge headed units require a lot more work.
Expensive to rebuild ? Yes.
Gobs of eye appeal? Yes
Good for every project? NO. |
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Extreme Veteran
Posts: 537
Location: Upstate NY | Fair enough and obviously you know a lot about these engines, so I respect your view. i wasn't trying to annoy anybody. It was just a bit mich to keep reading the early hemis were sluggish. I felt the need to point out that to a performance person this may be true but to the average joe that just loves the old cars and the way they performed at the time, anything beyond was a waste of money and time. Who cares what the pistons are made of? |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | up date >
I should have the new high compression 10.1 pistons for the 241 hemi by the end of this week or next from venolia pistons . then it's time to check to see if the engine needs to be balanced again or not. then .... assemble.
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Expert
Posts: 3035
Location: N.W. Fla. | "sluggish' Hmmmm, well, the low deck Dodge, Desoto & Chryslers were typically 7-7.5 C/R 7 small CID, with 2 speed trannys in fairly heavy bodys . |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | the domed 10.1 pistons have arrived from Venolia today.
They look awsome ! The weight is very very close to the old flat tops . speed shop says they can just take a little off the new pistons to compensate the difference. so there will be no need to balance the rotating assembly . that's good. $$$.
moving right along . |
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Expert 5K+
Posts: 9681
Location: So. Cal | Good move to go with higher compression. It will allow you to run a hotter cam too. But yes, the baby hemis are always more expensive. 331 pistons are harder/more expensive to get than the 392 pistons.
I also have run 10:1 in my 392 for many years on regular fuel and experienced far less ping issues than my 10.2:1 340 motor on premium.
Show us a pic of those bad-boys on the rods when you get a chance. |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | <p>worked on the 241 hemi yesterday .. my brother and I assembled the hemi . here are a few pics of pistons.. I'll load up some pics of it all together tomorrow.</p>
Edited by dodge59 2015-10-24 11:17 AM
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 (piston stick out of head II 55.JPG)
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dome piston sticking out if head 55.JPG (172KB - 155 downloads)
piston stick out of head II 55.JPG (153KB - 136 downloads)
IMG_5768 55%.JPG (203KB - 191 downloads)
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | 241 hemi with 10.1 pistons all assembled and ready to be installed in the 54 dodge pace car.
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10.1 hemi all ready to be installed 50.JPG (92KB - 115 downloads)
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | Hemi's in the hole
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Expert 5K+
Posts: 9681
Location: So. Cal | Nice job. Those pistons look great in there. Should be a nice power addition. Looks like you swapped to an aftermarket intake, I presume to be able to use a bigger carb?
Edited by Powerflite 2015-10-25 8:09 PM
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | all buttoned up and running.
the 241 hemi runs excellent ! One STOUT like hemi !
throttle response is awesome !.
more torque and hp. yeah !!!
video below here >>>>
http://s446.photobucket.com/user/stroker402/media/MVI_5792_zpsvzuwp... |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | <p>all buttoned up and running. the 241 hemi runs excellent ! One STOUT little hemi ! throttle response is awesome !. more torque and hp. yeah !!! video below here >>>> http://s446.photobucket.com/user/stroker402/media/MVI_5792_zpsvzuwp...
 (10 to 1 hemi pic pass 50.JPG)
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10 to 1 hemi pic pass 50.JPG (238KB - 135 downloads)
10 to 1 hemi pic drv 50.JPG (235KB - 139 downloads)
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | <p>this fresh rebuilt 241 hemi with 10.1 venolia pistons is installed into my 1954 dodge royal 500 convertible INDY pace car. The stock compression<a href="http://s.ltmmty.com/click?v=VVM6ODE0MjY6MzI4NTpyYXRpb3M6ZjdjNDA1NmFlODA2MTJhM2EwMWU3Mjc4MDAwNGNlOGI6ei0yNDQ5LTgwNzc1NTQ3OmZvcndhcmRsb29rLm5ldDoyNDEzNTg6NzFlNzI1ZmFmYmQyNmU2ZDQ2ZjBjNjcyNTNmNGJiM2I6NTkwNDQxMDQ2N2VjNGRmM2JjNmMwM2NiMjFlYmVjMWY6MTpkYXRhX3NzLDU4OXg4MTk7ZGF0YV9yYywxO2RhdGFfZmIsbm87OjU4MjI2NTI&subid=g-80775547-d0481c46838848baa9f155e04d807170-&data_ss=589x819&data_rc=1&data_fb=no&data_tagname=A&data_ct=image_only&data_clickel=link" target="a652c_1446218129_forwardlooknet" title="Click to Continue > by mediaplayer"> ratio<img src="http://cdncache-a.akamaihd.net/items/it/img/arrow-10x10.png" border="0" /></a> is 7.5 for 1954 . quite a big upgrade to 10.1 . also has one step up in the cam specs by Neilson cams , engine is balanced and the heads are all worked over for better flow. . pertronix electronic ignition . oem offenhauser 4v intake manifold with the stock oem 2191S wcfb 4v carb. Quite the package ! excellent throttle response ,, runs awesome ! </p>
Edited by dodge59 2015-10-30 11:09 AM
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | got the hemi out of the road for a test run . I set the timing at 6* btdc for starters and is not pinging at all, stock is 4* . what would you guys recommend for this baby hemi ? I had timing set at 8* before I upgraded to the domed pistons.. and never pinged there either. It has gobbs more torque and HP now than before. I'm thinking 8* is tops what do you think ? |
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Elite Veteran
Posts: 888
Location: Peoples Republic of Oregon | I'd bump it 2° at a time until you hear the noise then back it off 3°.
The goal is easy starts, no rattle, no heating issues, and so on.
Do not go over 35° total lead. |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | <p>the hemi is not fighting itself when starting. soooo I could go a little more timing , then the back off like you said . I probally should put some more miles on this fresh engine. give those new domed pistons time to settle in. Thanks wayfarer !</p>
Edited by dodge59 2015-11-02 7:33 PM
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Location: North Australia | That looks sweet '59, nice job. I am curious, what sort of HP do you think this little engine is producing?
Steve. |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | Thanks Steve !
since it is still mopars smallest cubic inch hemi , It does respond to improvements made. I would say the 241 hemi puts out 200 hp give or take . stock is 150 hp w/ 2 bl . but with 10.1 forged pistons now and a little bump up in the cam specs , oem offy 4v intake manifold , wcfb 2191s carb , ported /polished heads , gasket matched , pertronix electronic ign. w/ curved dist and a fresh engine rebuild , it's a pretty healthy little hemi. still haven't installed the true dual exhaust yet. that may help also. |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | Found the happy spot on the hemi.. 8* btdc.
very good throttle response , and no slouch out of the gate.. It's true colors shine on the freeway.. no need for passing gear ! it's has the balls just pushing the pedal down.
very very Happy with it's performance !
and this hemi is moving my convertible with ease and that is a heavy car.
don't under estimate these baby hemi engines. they have lots of power.
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | hope this video comes through.
http://s446.photobucket.com/user/stroker402/media/MVI_5792_zpsvzuwp... |
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Expert
Posts: 2312
Location: Arizona | Worked for me! |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | one more thing I wanted to say about my 241 hemi . I've only put on aprrox. 70 miles on it so far and everytime I take it out it gets stronger and stronger. unbelievable ! Here's an comparison I made >>> I owned a few 273 commando 235 hp engine cars over the years , darts and cuda and this little hemi feels way stronger than they ever did. this 54 dodge convertible weighs alot more than a 65 dart-cuda. I am really impressed with this hemi's performance !! so my guess the hp is at least 200 maybe more .
Edited by dodge59 2015-11-06 7:05 PM
 (10 to 1 hemi pic pass 50.JPG)
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Expert
Posts: 2312
Location: Arizona | what rear axle ratio does the car have? |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | stock 3.54 gear ratio stamped on the pass side near oil filler hole. |
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Expert 5K+
Posts: 9681
Location: So. Cal | These early hemi motors can easily put out 1 hp/in^3 when built with good upgrades. So I would expect you to be getting around 230 to 240 horsepower. |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | Yes powerflite ... that is what it feels like . love in it !
I just can't believe the torque it has now to move this heavy car effortlessly. |
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Temporarily suspended to cool off
Posts: 316
| oh wow... I didn't know we could sexual content on this message board! |
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Extreme Veteran
Posts: 537
Location: Upstate NY | Very nice car and I am sure it performs well with all your hard work. The engine looks fantastic. |
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Elite Veteran
Posts: 1018
Location: Milwaukee Wisconsin | Thanks bbrasse1 ! It' Great to here a Nice comment once and awhile !
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Expert 5K+
Posts: 9681
Location: So. Cal | Now what are you going to do with the green car you pulled it out of?
That yellow convertible is pretty sweet!....except.... that I am not a fan of continental kits.
Edited by Powerflite 2015-11-11 12:11 AM
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swapping out flat tops for dome pistons early hemi
