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Post by bustedknuckle on Jul 14, 2015 15:19:13 GMT -6
Our car is strong and fast but the starts are killing us. it's sluggish until the RPM picks up a bit. I'm going to advance the cam timing to get more torque in the lower RPM range. What is a good starting point 4*? We have a falcon tranny in it so high gear is a must.
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Post by flipflopoo1oo on Jul 15, 2015 15:06:41 GMT -6
Assuming you are running a locked or welded distributer with no vacuum advance as most do! Bummer if so--- Back to the cam-- if solid lift a bit of thought and a few searches might help! Where are you now is the thing! If advanced you may loose top end torque by moving it to the lower side with exhaust numbers in question! Check your compression and match your fuel first as well as a dist. up grade! Most I see leave a hundred horses floating around in the you need to do it like this coral! Not changing what isn't wrong is a big help to get started on this road of many changes to fit the next in line! too low of ign. timing down low is a torque killer as well as to high it locked and no advance to clean it up if too much octane or jetting!
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Post by bustedknuckle on Jul 15, 2015 15:47:19 GMT -6
Plenty of top end. We've ran it up to 7800 and was still pulling. Much more than we need on our track. All I want to do is move the power band down in the RPM range. Not running a locked distributor but no vacuum advance, mechanical only, built for our specifics. carb and fuel is where I want it also built to our specifications. Not leaving anything on the table.
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Post by flipflopoo1oo on Jul 16, 2015 6:40:16 GMT -6
That you know of if going by the book??? Are you still running a power valve in your carb-- reading the plugs to get closer to lean--- is your fuel controlling your stroke timing and piston speed correctly or are you having to run your ign. timing under 38*-- ? Always good to close the exhaust number correctly! Where are you now and 2 degrees at a time if not checking first! 108 seems to be my best on intake valves as vacuum is torque but its that exhaust number that does the most good HP wise! This is with a 110 LS on the cam and 1.6 rockers always! Even fan belt ratio's can change it all!!!
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Post by flipflopoo1oo on Jul 16, 2015 6:51:51 GMT -6
Try dumping the P/S pump pressure at low speeds! That vacuum advance will keep it clean and lean on those slow starts! Weak fire power can loose you plenty ! A HEI with out the correct up grades won't make ours run! Check out my dist. upgrade post! I can't tell you how much it puts out but it jumps 1.6 inches from pin to pin with no ground in sight and it gets out of the cap and not just a click inside! Good luck finding all you need!
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Champ2x36
Pit Crew
Just an old racer!
Posts: 10
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Post by Champ2x36 on Sept 11, 2015 9:09:50 GMT -6
Bustedknuckle, as a general rule 2* timing change will move your powerband up or down 100rpm. Advancing or retarding cam timing also changes valve to piston clearance, either direction moves one of the valves closer to the piston. If you're pulling strong to 7800 you are running a fairly "big" cam, so this is something you'll want to keep in mind. Generally you can only change the rpm range 300-400 rpm. You may want to consider changing your cam to something with less duration. I had a 355 that did the same as your describing, it was a little "lazy" off the corner, but about at the flagstand that thing came to life, nobody pulled me on the big end. Changing to a cam with 10* less duration helped that engine a lot off the corners. With solid lifters, Opening up the valve lash by a few thousandths can help, but don't go over about .005 looser or you'll be really slamming the valves closed, the lifters will be coming back down on the cam past the closing ramps, and wipe lobes pretty quickly.
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Post by flipflopoo1oo on Sept 12, 2015 2:10:05 GMT -6
1.6 rockers instead of 1.5s helps get your topend back with duration staying the same but more lift at .050 ! Push rod length and length can leave the push rods hitting the heads if not so machined to clear! More valve clearance retards the cam timing trading tit for tat in some cases! Geometery is everything when thought of in cam profiles! Who would think pushrod length could do so much at tune! Just think it all threw and check all clearences!
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Post by flipflopoo1oo on Oct 8, 2015 1:08:39 GMT -6
Getting rid of reversion by closing the exhaust sooner has been the key factor for years to put frost on the intake and let exspanion build the compression rather than using up horses to make it the hard way! I'm no physics major but just a country boy with ideas of said factors that relate to designs in theories that have been proven by our winning more than most ever thought possible by my shade tree justice in making things better by hook or crook in my head! Gift or curse I know not but some winning now all over this Earth and not limited to just US now has blessed this good ole boys heart! They are amazed at how simple minded thought has built such results in all fields of motion! From the use of small runners increasing velosity to get it there cooler to the down sizing of molicules in sending more threw small ports faster inabling the burnning of twice the fuel just in the a main than most do all night cleanly while running on the vurge of lean to produce more horses-- it can and has been done! Stay on top of your game by your thoughts and not the pack around you by conforming also to the follow the leader racing I see every where I go or each one requesting help!!!
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