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I took my 383 apart...what do you think? #1320704 10/15/12 07:07 AM 10/15/12 07:07 AM
Joined: Dec 2010 Posts: 208 Norrland, Sweden Swedcharger67 OP enthusiast
Swedcharger67 OP enthusiast Joined: Dec 2010 Posts: 208 Norrland, Sweden	I bought my 67 Charger with a 383 4bbl from 1971 in it. The engine is bored 0.030, has Eddy RPM intake and 750 Holley vacuum secs, Hooker headers. Compcams 21-224-4 grind XE274H is installed straight up. Intake closes @ 63 ABDC. Heads are 346 open chamber. I measured about 120 psi cold cranking pressure WOT. Now with the engine apart I see that the flat top pistons are 0.130 down the hole, calculate the static compression to 7.2:1, and the dynamic compression to 4.4:1. How do you think this engine was running? 7421409-PA041421_1024.JPG (229 downloads) Martin, 67 Charger, 512 cui, E85, MegaSquirt MS3X sequential ignition & injection

Re: I took my 383 apart...what do you think? [Re: Swedcharger67] #1320705 10/15/12 07:54 AM 10/15/12 07:54 AM
Joined: Nov 2004 Posts: 843 Suffolk,VA I ireland383 super stock
ireland383 super stock I Joined: Nov 2004 Posts: 843 Suffolk,VA	Probably ok but no barn burner. What head gaskets were on there? What are your plans for this motor? You might want to run some KB400 pistons, steel shim gaskets, mill the heads some, and degree the cam. This will wake it up some.

Re: I took my 383 apart...what do you think? [Re: ireland383] #1320706 10/15/12 08:16 AM 10/15/12 08:16 AM
Joined: Jul 2009 Posts: 413 Norway (old world) Oyvind Mopar mopar
Oyvind Mopar mopar Joined: Jul 2009 Posts: 413 Norway (old world)	Like a stock Volvo, but more thirsty...

Re: I took my 383 apart...what do you think? [Re: Oyvind Mopar] #1320707 10/15/12 10:16 AM 10/15/12 10:16 AM
Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska	heavy car/small engine/low dcr live every 24 hour block of time like it's your last day on earth

Re: I took my 383 apart...what do you think? [Re: Oyvind Mopar] #1320708 10/15/12 10:21 AM 10/15/12 10:21 AM
Joined: Jan 2003 Posts: 75,094 A Banana Republic near you. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,094 A Banana Republic near you.	Quote: Like a stock Volvo, but more thirsty...

Re: I took my 383 apart...what do you think? [Re: Oyvind Mopar] #1320709 10/15/12 11:35 AM 10/15/12 11:35 AM
Joined: Dec 2010 Posts: 208 Norrland, Sweden Swedcharger67 OP enthusiast
Swedcharger67 OP enthusiast Joined: Dec 2010 Posts: 208 Norrland, Sweden	Quote: Like a stock Volvo, but more thirsty... �yvind, you get the Nobel prize! Your description gave me a good laugh, and it's very accurate! Engine power is comparable to an ordinary Volvo, but consumes 3x more fuel! This engine is a good example of how to NOT build an engine! Martin Martin, 67 Charger, 512 cui, E85, MegaSquirt MS3X sequential ignition & injection

Re: I took my 383 apart...what do you think? [Re: Swedcharger67] #1320710 10/15/12 11:40 AM 10/15/12 11:40 AM
Joined: Jan 2003 Posts: 75,094 A Banana Republic near you. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,094 A Banana Republic near you.	Quote: This engine is a good example of how to NOT build an engine! Martin welcome to the world of 383's , piston choice is lacking and most that rebuild them do not know this .

Re: I took my 383 apart...what do you think? [Re: JohnRR] #1320711 10/15/12 11:46 AM 10/15/12 11:46 AM
Joined: Dec 2010 Posts: 208 Norrland, Sweden Swedcharger67 OP enthusiast
Swedcharger67 OP enthusiast Joined: Dec 2010 Posts: 208 Norrland, Sweden	Quote: Quote: This engine is a good example of how to NOT build an engine! Martin welcome to the world of 383's , piston choice is lacking and most that rebuild them do not know this . Yep, that's it, lack of compression kills the engine. Martin, 67 Charger, 512 cui, E85, MegaSquirt MS3X sequential ignition & injection

Re: I took my 383 apart...what do you think? [Re: JohnRR] #1320712 10/15/12 11:49 AM 10/15/12 11:49 AM
Joined: Oct 2012 Posts: 1,106 Northeast V VincentVega super stock
VincentVega super stock V Joined: Oct 2012 Posts: 1,106 Northeast	The 241 Red Ram started with 7.1:1. Obviously that's way too low for modern fuel and performance expectations.. but the good news is you could have put some boost on it, or run paint thinner in a pinch Looking for 1975 through 1978 B body 4 door sedan sheet metal or parts cars - monaco, fury, coronet. Please let me know

Re: I took my 383 apart...what do you think? [Re: JohnRR] #1320713 10/15/12 11:54 AM 10/15/12 11:54 AM
Joined: Jan 2003 Posts: 16,376 D dogdays I Live Here
dogdays I Live Here D Joined: Jan 2003 Posts: 16,376	If everything you say is correct your pistons have a compression height of 1.802" which is lower than I am used to seeing. Stock replacement 383 pistons generally come in at around 1.840 - 1.850". The advice to install different pistons is right on, if your numbers are right. Other possibilities are: 1. You mismeasured the distance from deck to piston top. It must be at true TDC and you measure to the top of the pin area so piston rock doesn't affect the reading. 2. The block is unusually high, it's supposed to be 9.980" from deck to crank centerline. 3. Someone got carried away rebuilding the rods and shortened them. A 0.030 over 383 has approximately 797cc swept volume. To get to 9.5:1 compression for a street engine on pump gas you need 797 / 8.5 = 93.8cc above the piston. As your 346 heads can measure out to 92cc, you can see that you have a dilemma. I calculate 0.130" of piston travel to be 30.7cc. Is this close to what you got? One more thing: The 383 is easy to overcam. Your cam is probably contributing to the problem. It needs to be advanced at least 4* from straight up to close the intake valve earlier. R. PS: I have a lot of respect for you Scandinavians building MOPARs!

Re: I took my 383 apart...what do you think? [Re: VincentVega] #1320714 10/15/12 12:00 PM 10/15/12 12:00 PM
Joined: Dec 2010 Posts: 208 Norrland, Sweden Swedcharger67 OP enthusiast
Swedcharger67 OP enthusiast Joined: Dec 2010 Posts: 208 Norrland, Sweden	Quote: The 241 Red Ram started with 7.1:1. Obviously that's way too low for modern fuel and performance expectations.. but the good news is you could have put some boost on it, or run paint thinner in a pinch Yes, you are right. I guess the 241 had a dyn compr ratio DCR not much lower than the 7:1, and that makes a difference. Even my engine would probably be pretty ok with a DCR of 7:1, even though I personally want to see it higher. Martin, 67 Charger, 512 cui, E85, MegaSquirt MS3X sequential ignition & injection

Re: I took my 383 apart...what do you think? [Re: Swedcharger67] #1320715 10/15/12 01:22 PM 10/15/12 01:22 PM
Joined: Jul 2010 Posts: 295 Vallejo, CA D ditchdrift enthusiast
ditchdrift enthusiast D Joined: Jul 2010 Posts: 295 Vallejo, CA	All i have to add, is that thing probably sounded.... so dull that i would cry. If you dont want to rip the bottom end apart, i would use a very thin head gasket, get heads with smaller cc's and advance the cam to increase cylinder pressure.

Re: I took my 383 apart...what do you think? [Re: ditchdrift] #1320716 10/15/12 02:27 PM 10/15/12 02:27 PM
Joined: Jan 2003 Posts: 3,920 n.e. pa. 6 65rbdodge master
65rbdodge master 6 Joined: Jan 2003 Posts: 3,920 n.e. pa.	see the 5th line in my signature but really if you can get it up to 9:1 that will be plenty. it will take a lot of head milling, new pistons or both to get it up that high. a combo of milling the deck on the block and some off of the heads should do it. this will require an adjustable valvetrain or shorter pushrods.

Re: I took my 383 apart...what do you think? [Re: 65rbdodge] #1320717 10/15/12 02:45 PM 10/15/12 02:45 PM
Joined: Jan 2005 Posts: 1,647 IL 7 71383beep top fuel
71383beep top fuel 7 Joined: Jan 2005 Posts: 1,647 IL	Been down this road before on the initial build for the 383 in the bee I used to have. Must have been rebuilt by the same knuckleheads except they billed me for a Comp Cams 268H and put it a POS cheapo cam from Elgin or something. During the second build they fond it to be at 7.8:1 when they opened it up. Best thing I did was go to closed chamber 516 heads with a decent valve job and bigger valves. Ended up with 9.2:1 and that 383 became a beast. Compression is King! '73 GK6 Challenger Rallye - 340 4-Speed

Re: I took my 383 apart...what do you think? [Re: dogdays] #1320718 10/15/12 03:03 PM 10/15/12 03:03 PM
Joined: Dec 2010 Posts: 208 Norrland, Sweden Swedcharger67 OP enthusiast
Swedcharger67 OP enthusiast Joined: Dec 2010 Posts: 208 Norrland, Sweden	I agree on the piston rocking, that might have affected my measurement slightly. I have a spreadsheet where I just plug in all my data, and nothing helps on this engine with the pistons that far down. I plugged into the spreadsheet that I have Eddy Victor 75cc heads, and a Hughes Whiplash cam for low compression engines, and this cam even advanced 4 degrees...the static and dynamic compression is still a far cry from any acceptable numbers! I attach a pic showing the numbers with Eddy Victor 75cc heads, Hughes Whiplash smog-cam advanced 4 degrees... 7421868-CR_Victor_Whipl4adv.JPG (92 downloads) Last edited by Swedcharger67; 10/15/12 03:05 PM. Martin, 67 Charger, 512 cui, E85, MegaSquirt MS3X sequential ignition & injection

Re: I took my 383 apart...what do you think? [Re: dogdays] #1320719 10/15/12 03:12 PM 10/15/12 03:12 PM
Joined: Dec 2010 Posts: 208 Norrland, Sweden Swedcharger67 OP enthusiast
Swedcharger67 OP enthusiast Joined: Dec 2010 Posts: 208 Norrland, Sweden	Quote: ...A 0.030 over 383 has approximately 797cc swept volume. To get to 9.5:1 compression for a street engine on pump gas you need 797 / 8.5 = 93.8cc above the piston. As your 346 heads can measure out to 92cc, you can see that you have a dilemma. I calculate 0.130" of piston travel to be 30.7cc. Is this close to what you got?... You can see from the spreadsheet pic I posted that I have the same numbers. Martin, 67 Charger, 512 cui, E85, MegaSquirt MS3X sequential ignition & injection

Re: I took my 383 apart...what do you think? [Re: ireland383] #1320720 10/16/12 11:04 AM 10/16/12 11:04 AM
Joined: Dec 2010 Posts: 208 Norrland, Sweden Swedcharger67 OP enthusiast
Swedcharger67 OP enthusiast Joined: Dec 2010 Posts: 208 Norrland, Sweden	Quote: Probably ok but no barn burner. What head gaskets were on there? What are your plans for this motor? You might want to run some KB400 pistons, steel shim gaskets, mill the heads some, and degree the cam. This will wake it up some. I checked the numbers with KB400, quite a good choice, compression height 1.908, 6cc dome. With Victor 75cc heads it would give 10.4:1 static, and still allow for a bit of milling of the deck (0.027)...assuming the dome can fit there... But, I have a 400-block ready for a stroker kit, so that's the path I'm going to follow... Martin, 67 Charger, 512 cui, E85, MegaSquirt MS3X sequential ignition & injection

Re: I took my 383 apart...what do you think? [Re: Swedcharger67] #1320721 10/16/12 11:30 AM 10/16/12 11:30 AM
Joined: Jan 2003 Posts: 75,094 A Banana Republic near you. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,094 A Banana Republic near you.	Quote: I checked the numbers with KB400, quite a good choice, compression height 1.908, 6cc dome. With Victor 75cc heads it would give 10.4:1 static, and still allow for a bit of milling of the deck (0.027)...assuming the dome can fit there... But, I have a 400-block ready for a stroker kit, so that's the path I'm going to follow... I personally think that KB400 is a poor choice , but with the limited choices for pistons I guess one takes what they can get. Good that you have decided to go the 400 stroker route , those victors would be a bad choice to put on a stock stroke low compression 383 , you can cut your open chamber heads enough to get that 75cc number.

Re: I took my 383 apart...what do you think? [Re: Swedcharger67] #1320722 10/16/12 12:17 PM 10/16/12 12:17 PM
Joined: May 2008 Posts: 5,399 Aurora, Colorado 451Mopar master
451Mopar master Joined: May 2008 Posts: 5,399 Aurora, Colorado	I have a 383 almost built the same. It was disapointing, weak low end power, decent power in the mid range, but nothing special, and not much top end. It was all done by 6,000 rpm. The 346 heads are correct for 1971. I think they were only used in '71, and maybe part of '72. A set of KB zero deck flat tops should help.

Re: I took my 383 apart...what do you think? [Re: JohnRR] #1320723 10/16/12 12:43 PM 10/16/12 12:43 PM
Joined: Dec 2010 Posts: 208 Norrland, Sweden Swedcharger67 OP enthusiast
Swedcharger67 OP enthusiast Joined: Dec 2010 Posts: 208 Norrland, Sweden	Quote: Quote: I checked the numbers with KB400, quite a good choice, compression height 1.908, 6cc dome. With Victor 75cc heads it would give 10.4:1 static, and still allow for a bit of milling of the deck (0.027)...assuming the dome can fit there... But, I have a 400-block ready for a stroker kit, so that's the path I'm going to follow... I personally think that KB400 is a poor choice , but with the limited choices for pistons I guess one takes what they can get. Good that you have decided to go the 400 stroker route , those victors would be a bad choice to put on a stock stroke low compression 383 , you can cut your open chamber heads enough to get that 75cc number. Yes, I used the Victors in my calculations just to see how small chambers would affect the compression...disappointing result with the pistons about 0.130 down. Martin, 67 Charger, 512 cui, E85, MegaSquirt MS3X sequential ignition & injection

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