keyman Posted July 16, 2012 Report Share Posted July 16, 2012 Is there any way to find optimal timing besides a dyno? I have been setting at 34 btdc but how do I know if more/less would be better? In 355 in Sportmod. Has anyone used a timing chain tensioner, used to keep slack out of chain for more accurate timing? What timing lights are best? Link to comment Share on other sites More sharing options...
KISS_Racing Posted July 16, 2012 Report Share Posted July 16, 2012 Is there any way to find optimal timing besides a dyno? I have been setting at 34 btdc but how do I know if more/less would be better? In 355 in Sportmod. Has anyone used a timing chain tensioner, used to keep slack out of chain for more accurate timing? What timing lights are best? Well here is my take and I'm not trying to not tell you secrets. What does your engine builder tell you? Did they degree the cam. Here's one I will shoot myself in the foot for and tell a company secret, but since you asked. Has your distributor been worked? What fuel are you using? What plugs are you using? What is the gap of your plugs? On tensioner if the rules say you can use one then do... Again not trying to be vege you just asked a broad question... By the way, the engine builder should be the one who can get you close.... Link to comment Share on other sites More sharing options...
keyman Posted July 16, 2012 Author Report Share Posted July 16, 2012 Well here is my take and I'm not trying to not tell you secrets. What does your engine builder tell you? Did they degree the cam. Here's one I will shoot myself in the foot for and tell a company secret, but since you asked. Has your distributor been worked? What fuel are you using? What plugs are you using? What is the gap of your plugs? On tensioner if the rules say you can use one then do... Again not trying to be vege you just asked a broad question... By the way, the engine builder should be the one who can get you close.... That is the a problem because I bought both motors from another racer, he could probably tell me who built them but I'm sure at this point that would not do much good. Since timing is such a critical element I was wondering what others do. Even if your engine builder tells you what to set it at is there no way to check that it is at the optimum setting Link to comment Share on other sites More sharing options...
jwmbishop Posted July 16, 2012 Report Share Posted July 16, 2012 More important than "all in" timing number is RATE of advance. Too much too early or not enough until too late leaves a lot more on the table and can do more damage than the all in number. Each cam has a timing curve it really likes - and the distributor can be curved to their recommendation - but port shape, volume, velocity and quality of atomization all effects the final output - so only a dyno really reveals the truth. Once the advance rate is set - the all in number is simply a reference for repeatability. But keep in mind the curve does not effect the post RPM performance - if you are all in at 3400 changing the curve does NOTHING to the performance from there up. There is no need for a timing chain tensioner on a stock block SBC if you are using a good true roller. If you have enough slack to NEED a tensioner you are already chasing a moving target. The tensioner is more for a block that has been line bored and lost a couple of thousanths of bore center spread between the cam and line bores (thus introducing slack on a new chain set right out of the box) than it is for a stock block. ANY slack (even if taken up by a tensioner) results in being out of time - retiming the start event with a slack chain means the ending event is off! Why use a 40.00 part to extend the life of a 40.00 when a 80.00 part gives the same result with fewer wear points? Even on flat tappets I have always preferred a thrust bearing over just the surface and button setup on the cam drive (thrust effects not only the lifter - but because of the helical drive on the dist it effects timing as well). Torrington style is my 1st choice - you can still dial in .001 to .002 - Torrington is ball bearing so has a longer service life with less precision, the roller style more for precision at the cost of shorter service life. Manley 73141 has served me well over the years! Like Mark pointed out - your builder is the best source - and as he has a vested interest - probably more reliable than anecdotal forum information... Link to comment Share on other sites More sharing options...
jwmbishop Posted July 16, 2012 Report Share Posted July 16, 2012 Even if your engine builder tells you what to set it at is there no way to check that it is at the optimum setting reading spark plugs - you want to be as advanced as it will run and still be a minimum of two degrees under any sign of detonation! Link to comment Share on other sites More sharing options...
dancer52 Posted July 16, 2012 Report Share Posted July 16, 2012 You guys make me feel dumb...lol...so here is my dumb advice....20 years, lots of different motors...bomber to latemodel.... 32 degrees.... its safe....to finish first, you must first finish.... Link to comment Share on other sites More sharing options...
dancer52 Posted July 16, 2012 Report Share Posted July 16, 2012 oh yea...timing chain tensioner.....tried it on a latemodel....engine guy said i had to have it.... timing mark still jumped around some....next time he rebuilt it...said I didnt need it... motor ran the same...and timing mark looked the same with timing light...... in my opinion...the tensioner cause more timing chain wear...now if you rebuild your motor twice a year...sure...it might make a tiny difference... Link to comment Share on other sites More sharing options...
abrungot Posted July 16, 2012 Report Share Posted July 16, 2012 I'm with you AJ.. just sitting here with my Dum Dum Lolly pop reading! You guys make me feel dumb...lol...so here is my dumb advice....20 years, lots of different motors...bomber to latemodel.... 32 degrees.... its safe....to finish first, you must first finish.... Link to comment Share on other sites More sharing options...
jwmbishop Posted July 16, 2012 Report Share Posted July 16, 2012 You guys make me feel dumb...lol...so here is my dumb advice....20 years, lots of different motors...bomber to latemodel.... 32 degrees.... its safe....to finish first, you must first finish.... I have ran several that really came alive around 34 - and one even at 38 (well built by Lunati and ran in a high humidity low temp weather pattern)! But 32 is a good rule of thumb and safe starting point (and where I always set em after breakin). As much as possible with no detonation is where you always want to be. The ragged edge could fall off and bite your rear though if your fuel supplier is inconsistent with octane - or if your fuel sits vented over the two off weeks, or the hunidity drops suddenly as temps climb etc. That extra bit of advance could be costly beyond the 2-5 ponies you are hunting! Link to comment Share on other sites More sharing options...
poorboy Posted July 16, 2012 Report Share Posted July 16, 2012 one thing I might add is to degree your balancer and make sure 0 is really 0, I have never had a balancer that was closer than 4 degrees and had some up to 12 degrees off. That will make a huge difference in what you think you have. Your 32 could be 44. Link to comment Share on other sites More sharing options...
Boernebullet Posted July 16, 2012 Report Share Posted July 16, 2012 Keyman I will help you, First, are you running cast or forged pistons? Second, what cylinder heads are you using? Greg Spreen 830-249-2235 Link to comment Share on other sites More sharing options...
4cylfordz Posted July 17, 2012 Report Share Posted July 17, 2012 timing has allot to do with your fuel type as well as its quality, anywhere onthe range of 32-36 is a fairly good place to play around for total advance. any less and they will run hot more and they will detonate. long rod engines typically like more timing. guessing it's a dirt track your running on and you can go +- a degree depending on wet or dry as a less will gain some low end and more will lend top end. an advance curve kit it one of the most underapreciated tuning methods out there. e ever had a slow start with a locked distributor and felt a stumble? most rollers chain sets are tight enough to not require a tensioner. though a block that has been line bored and ended up between a stock chain and a -.005 set I would install a tensioner if rules allowed. erratic timing has more to do with distributor runout as well as camshaft endplay than chain tension. timing lighs I prefer a advanceable light. digital are more accurate though knob type are good if checked and callibrated every now and then. no secrets here lol Link to comment Share on other sites More sharing options...
jwmbishop Posted July 17, 2012 Report Share Posted July 17, 2012 First, are you running cast or forged pistons? I see where you are going with that. So let me ask your opinion on hypers? I have em in my 383 and have gone so far up in advance and down in mix that I popped a head gasket on first throttle run - no damage to pistons at all. Wondering if that was flukish... Link to comment Share on other sites More sharing options...
Boernebullet Posted July 18, 2012 Report Share Posted July 18, 2012 Just Flukish Link to comment Share on other sites More sharing options...
4cylfordz Posted July 18, 2012 Report Share Posted July 18, 2012 kinda curious on input of the forged vs hyper topic. while what your combination does have a recipe for disaster for any piston i give some hypers credit when installed in the right manor. kinda like dealing with a kb piston (not saying i use them) but in my previous experiences when given the right amount of p2w clearance and more importantly the top ring clearance they took a butt whoopin at 7500rpm for many many laps and are still sitting in a box in very useable shape. Link to comment Share on other sites More sharing options...
jwmbishop Posted July 18, 2012 Report Share Posted July 18, 2012 kinda curious on input of the forged vs hyper topic. while what your combination does have a recipe for disaster for any piston i give some hypers credit when installed in the right manor. kinda like dealing with a kb piston (not saying i use them) but in my previous experiences when given the right amount of p2w clearance and more importantly the top ring clearance they took a butt whoopin at 7500rpm for many many laps and are still sitting in a box in very useable shape. I have +.040 kb134s (9.8:1 ratio, and we did blueprint to .032 top end gap and .0019 wall) in it ... When I started it after that hard run and steam/smoked a five house area around my driveway I saw $$$$ signs pass before my eyes. I was really surprised that I had no land to wall contact, and no scores from butted end gaps. Just a head gasket and back in business (after going back up two steps in jet and back down to 32 all in lol). I chose the KB specifically because of the tighter wall - the pre-build analysis noted that a "high and sudden cylinder pressure spike could exist at high load\high RPM conditions so barrel rock could occur and should be addressed with tight control of piston clearances and skirt design". What was ironic about that - when I plugged in 2.02 valves the warning went away, but also the estimated torque value at 2000 to 3000 RPM decreased (5k-6k went up - but this is a towing engine, not racing). Hypes are not near as structurally strong as forged (they are in fact still a cast piston) - but with the heat quality of the high silicon it seems to me they don't become "soft" and allow the ding that starts the rest of the damage until a much higher temp (even than forged) so the additional strength isn't needed as much. Back when I WAS in the shop full time we used EngineTech Hyper rebuilders series for regular street engines (they compensate for decking and boring so return to standard displacement and valve clearances in most cases) - never had a piston related comeback. some of those got ran in the local street stock class and I am not sure how they did as there would be no comeback as there would be no real warranty - but no one ever complained either! Link to comment Share on other sites More sharing options...
keyman Posted July 26, 2012 Author Report Share Posted July 26, 2012 Thanks for the info guys. Just to clarify its a 355 Jeffs performance motor with Eq heads stock Hei, stock 4412 on racing gas running at 3800 to 6700 rpm. Thats about all I know and I have another motor that is similar. Givin all the components (weather,internals,fuel,balancer and dial in timing lights) a number does no good. 34 with a balancer/timing light off 3 degrees is what I am concerned about. (and yes I know how to check tdc)but you see what I mean. I guess the best way would be to make sure timing mark is correct and dyno at 32/34/36 (with my timing light)to see the best power curve in the desired range? I've been checking plugs but don't really see any difference. Just want to make sure I'm not wasting dyno time and I am about to change motors so I want to repeat the process with the new motor and compare results. Link to comment Share on other sites More sharing options...
jwmbishop Posted July 26, 2012 Report Share Posted July 26, 2012 Thanks for the info guys. Just to clarify its a 355 Jeffs performance motor with Eq heads stock Hei, stock 4412 on racing gas running at 3800 to 6700 rpm. Thats about all I know and I have another motor that is similar. Givin all the components (weather,internals,fuel,balancer and dial in timing lights) a number does no good. 34 with a balancer/timing light off 3 degrees is what I am concerned about. (and yes I know how to check tdc)but you see what I mean. I guess the best way would be to make sure timing mark is correct and dyno at 32/34/36 (with my timing light)to see the best power curve in the desired range? I've been checking plugs but don't really see any difference. Just want to make sure I'm not wasting dyno time and I am about to change motors so I want to repeat the process with the new motor and compare results. Yea - in the context you put that it does make sense to dyno it. You could do the same with practice laps - but I have not yet met the driver who is so constant that you would have good precise comparison. Plug check is mainly to make sure you are not going over the edge and damaging. Even if your dyno results show good at 34 OR 36 you should plug check every outing - weather, especially humidity and barometric changes - can get you in trouble real fast. The plain truth is - the best power is made in the moments just before scattering of the shrapnel! SO you are really only balancing power with longevity and defining your fine line! Link to comment Share on other sites More sharing options...
keyman Posted July 27, 2012 Author Report Share Posted July 27, 2012 Don't like shrapnel and actually I am looking for consistency and reliability not max power. What do plugs look like or what should I look for when detonation occurs. Link to comment Share on other sites More sharing options...
4cylfordz Posted July 27, 2012 Report Share Posted July 27, 2012 Don't like shrapnel and actually I am looking for consistency and reliability not max power. What do plugs look like or what should I look for when detonation occurs. grab any chiltons or haynes manual and hunt for the plug pictures (its the only page in color in the whole book). itll show ya all ya need to know about reading plugs Link to comment Share on other sites More sharing options...
jwmbishop Posted July 27, 2012 Report Share Posted July 27, 2012 Don't like shrapnel and actually I am looking for consistency and reliability not max power. What do plugs look like or what should I look for when detonation occurs. Start at 32 degrees all in. FIRST you got to have the right heat range plug: The ground strap indicates the heat range of the spark plug. If the "color" of the ground strap "changes" too close to the ground strap's end, (located above the center electrode), then the heat range is "too cold", meaning that the strap is loosing heat too quickly to the base ring. It is not able to burn off deposits until near its end. If the "color" of the strap changes near where it is welded/attached to the base ring (last thread ring), then the plug heat-range is "too hot", because heat is not being transferred or cooled from the strap to the base ring quickly enough. The strap might begin to act like a "glow-plug". Eventually causing pre-ignition and/or detonation later on. The proper heat range is when the "color" is at the half-way point on the strap. This means the plug is neither too cold or too hot. THEN you have to have the right jetting: The air/fuel mixture ratio shows up on the base ring. This is the last thread ring, it has the strap welded to it. You want a full turn of light soot color on the base ring!!! If you want to tune for maximum power, then you want 3/4 to 7/8ths of a full turn of light soot color to show up on the base ring. This is on ragged-edge of being too lean, but will make the most HP in most engines. To be safe, leave it at a full turn of light soot color. If the base ring has a full turn of color, but there are "spots" of heavy build-up of "dry soot" on top of color, then jetting is too rich. ****If the base ring has a full turn of color with some spots of heavy dry soot, then jetting is too rich, EVEN IF the porcelain is "BONE-WHITE", jetting is still TOO RICH.**** THEN look for detonation and increase timing (but keep in mind this will also effect heat and mix indicators - adjust accordingly) The porcelain shows up pre-ignition and detonation (timing/octane). It will not accurately reveal jetting/air/fuel ratios. To look for the first/beginning signs of detonation, search the white porcelain for tiny black specks or shiny specks of aluminum that have fused to the porcelain. When detonation occurs, part of the air/fuel mixture explodes instead of burning, the explosion is heard as a "metallic knock", this audible knock is the result of a sound shock-wave, this shock wave travels back and forth across the clearance volume "disrupting" the cooler boundary layer gases that cover the entire clearance volume area. This disruption allows "more" heat to be transferred into parts, especially, domes/piston tops,...along with the very rapid rise in pressure like a hammer blow, pistons can get torched with melted sides and holes !!! With the early signs of detonation, the shock-wave will also rattle rings causing the tiny amounts of oil that now gets by rings, to be fused to the white porcelain as tiny black specks, also fused as specks are soot that was clinging to clearance volume surfaces in the relatively "still-air" of the boundary layer. One step beyond the black specks, will be tiny specks/balls of aluminum coming off the pistons that will be fused to white porcelain,....the next step to be reached is occasional pieces of the porcelain being broken-off as detonation gets worse, etc. Soon after that are holes, blown head gaskets, broken connecting rods, etc. Link to comment Share on other sites More sharing options...
keyman Posted July 27, 2012 Author Report Share Posted July 27, 2012 Thanks Jw, the first article I read on this said the ground strap color change showed timing. I think I will use your method cause I know you know your stuff! Link to comment Share on other sites More sharing options...
Boernebullet Posted July 27, 2012 Report Share Posted July 27, 2012 IMCA Southern Sportmod Engines are only 9.5 to 1 compression, 32 degrees isn't even close with EQ Heads 830-249-2235 Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.