70 Javelin 390 Rebuild

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   I have to rebuild my 390 and would like some input as to what is the best way to go.  I race this car and would like to get into the high 11 sec to low 12's.  Engine currently has edelbrock aluminum heads, 11-1 pistons, cam uses hydraulic lifters-.516/.534 lift, duration of 291/297. Has an edelbrock Air Gap highrise with an edelbrock 800 carb.  The car currently runs 12.5-12.7.

Any advice would be greatly appreciated.

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Silvertip Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Fan Joined: Mar/15/2020 Location: BC, Canada Status: Offline Points: 4	Post Options Post Reply Quote Silvertip Report Post Thanks(0) Quote Reply Topic: 70 Javelin 390 Rebuild Posted: Aug/30/2021 at 10:56pm
	I have to rebuild my 390 and would like some input as to what is the best way to go. I race this car and would like to get into the high 11 sec to low 12's. Engine currently has edelbrock aluminum heads, 11-1 pistons, cam uses hydraulic lifters-.516/.534 lift, duration of 291/297. Has an edelbrock Air Gap highrise with an edelbrock 800 carb. The car currently runs 12.5-12.7. Any advice would be greatly appreciated.

PROSTOCKTOM Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: Jun/20/2010 Location: Indiana Status: Offline Points: 2450	Post Options Post Reply Quote PROSTOCKTOM Report Post Thanks(0) Quote Reply Posted: Aug/31/2021 at 12:20am
	What is your duration @ .050"? Rear gear ratio? How much stall on your torque converter or 4-spd? Slicks? Tom
	Molnar Technologies Full Service Dealer - Crankshafts & Connecting Rods 1969 AMC Rambler Rouge Race Car 1974 AMC Hornet Hatchback, Wally Booth Outlaw Nostalgic Pro Stock Race Car Project

bcsideshow Members Profile Send Private Message Find Members Posts Add to Buddy List Supporter of TheAMCForum Joined: May/19/2010 Location: Kenosha Status: Offline Points: 1226	Post Options Post Reply Quote bcsideshow Report Post Thanks(0) Quote Reply Posted: Aug/31/2021 at 10:46am
	I have a similar build with best time at 12.4. I run through the lights around 5000 rpm. I have a 727, 2500 stall and 3.54 gear. 275/50 -15 drag radials. I suspect if i were to change to a 411-454 gears, higher stall and maybe the new victor intake i'd be high 11's.
	1969 SCRambler "B" 1970 AMX 390 Auto 1968 AMX 390 Auto 1970 Rebel Machine Project 1969 AMX 390 4SPD Project 1969 AMX 390 Auto Project 1969 Javelin 390 project 1997 Cherokee lifted 1998 TJ Lifted

PHAT69AMX Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jul/07/2007 Location: West Virginia Status: Offline Points: 5918	Post Options Post Reply Quote PHAT69AMX Report Post Thanks(0) Quote Reply Posted: Aug/31/2021 at 2:31pm
	SilverTip - Many opinions, mine ? Go with a Solid flat tappet camshaft of about 235 degrees at 50. Schneider Cams recently updated their web page and increased the number of available AMC V8 solid flat tappet cams they offer for purchase. An AMX 2-seater needs only about 300 HP at the tires to run 12 flat at 109 mph with everything working at peak efficiency, soo a 400+ HP motor should get ya there, Motor HP over 400 is just insurance / fudge factor, and a well built 390 is capable imho. Timing Advance Curve & Carburetion being big factors, as well as, as mentioned, stall, gears, & tires. But that's just one opinion of one hobbyist, not a professional or business owner. Self made below chart is Physics based and assumes 100% efficiency of available RWHP. Values result from actual car & driver WEIGHT and MPH obtained. The MPH is "easy" to obtain... the related "ideal" matching ET can be pretty "tough", but doable. Run the car down the track as good as it can, and get the MPH, regardless of the ET. Make sure and hit the return road scales on that run and get an actual exact as-raced weight. There ya go, that's how much HP it made that pass... Then the pain... oh my look how inefficient I / it is... ( too slow ET for the MPH ) Now ya gotta get after it finding all the little inefficiencies... or throw more money at it to make more power since what's there isn't being used LOL Peace Edited by PHAT69AMX - Aug/31/2021 at 2:43pm
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BassBoat Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Aug/29/2008 Status: Offline Points: 1718	Post Options Post Reply Quote BassBoat Report Post Thanks(0) Quote Reply Posted: Sep/03/2021 at 10:44am
	I know of one case where a guy picked up 70 HP on the dyno with a port matched torker and 800 Quick Fuel Holley over an air gap and Edelbrock 800. Edelbrock heads respond well to modest porting and another 50 HP is on the table. With bigger valves and more extensive porting probably good for 100 HP. I would send those heads to Knowleton for their CNC porting with big valves. That alone will get you the power you need. I have run solid lifter cam as PHAT69 suggests but for your build with 11 to one you can probably go to 245-250 on the intake duration. The only issue with a bigger cam is you will lose low end for the gain on top end so converter if applicable and gearing need to compliment the new power band.

BassBoat Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Aug/29/2008 Status: Offline Points: 1718	Post Options Post Reply Quote BassBoat Report Post Thanks(0) Quote Reply Posted: Sep/03/2021 at 10:49am
	I just googled your cam specs and there is a Comp Hydraulic ROLLER cam with those exact specs. If that is the cam you already have, you probably don't need a bigger cam.

Ken_Parkman Members Profile Send Private Message Find Members Posts Add to Buddy List AMC Addicted Joined: Jun/04/2009 Location: Ontario Status: Offline Points: 1813	Post Options Post Reply Quote Ken_Parkman Report Post Thanks(1) Quote Reply Posted: Sep/03/2021 at 11:27am
	Need more data - what are the gears, converter, mph, 60' etc. 11-12 second cars is where the launch of the car becomes much more important. I have seen a good converter make 1 second improvement without touching the engine. The engine may already have the power, just not getting it to the ground right.