Flexicoker Posted June 23, 2010 Author Share Posted June 23, 2010 This is something I can do... I need to have it running this weekend, however. So I can install the spraybar and spraybar cam towers now, with either cam, and send the other cam and rockers to get ground at my convenience. Which cam should I make the 'hot' one? If I've got the spraybar either way, does it matter if its internally oiled as well? Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 23, 2010 Share Posted June 23, 2010 Some grinders balk at regrinding drilled cams, the solid one will likely be a better bet. While the head is off, don't forget to open up the oiling restrictions in the top of the block to the recommended size (in the Blue Book) for good top end lubrication. With the crap oil these days, this helps. With the holes opened, you will have plenty of oil up top as long as your oil pump is in good condition. If you haven't installed a turbo/auto pump, now would be a good time to do so for additional flow capability. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 23, 2010 Share Posted June 23, 2010 If the cam grinder will grind the drilled cam, I'd do that one. Then you can run spray bar and internal oiling, which shouldn't be a problem with a turbo pump. Again, that's what I should have done. Check the brazing on your spray bar and make sure it's not coming apart before you run it though. Tony, re swapping the A cam in, wouldn't it be easier just to use the later cam, get an adjustable cam gear and retard the cam a degree or two? With the lift and duration being damn near identical, I bet the result would be damn near identical Then you don't even need to take the cam out of the head. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 23, 2010 Share Posted June 23, 2010 But that costs $240, now doesn't it? And some dyno time to get it 'just right'. It's not just a retardation, the opening and closing events are slightly different as well. A couple cam degrees makes a big difference even though it doesn't seem like much. There is someone making nice replacement spraybars now out of billet aluminum, with 'cooling grooves' on it. Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted June 23, 2010 Share Posted June 23, 2010 There is someone making nice replacement spraybars now out of billet aluminum, with 'cooling grooves' on it. OOH - where / who??? Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 23, 2010 Share Posted June 23, 2010 But that costs $240, now doesn't it? And some dyno time to get it 'just right'. It's not just a retardation, the opening and closing events are slightly different as well. A couple cam degrees makes a big difference even though it doesn't seem like much. Big difference? By whose determination? Again, not enough to take the time to swap them out, IMO. I haven't priced out an adjustable cam gear lately. If they were ~$100 I'd be curious to try that route. You really should have one to set the cam per the cam card with your regrind anyway. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 24, 2010 Share Posted June 24, 2010 I use the Tomei from Japan, they have a nice etched degree wheel and are accurate. A couple of degrees makes a big difference. Our torque band went from 6000-7500 flat and level when the cam was 'straight up' compared to a 2 degree change resulting in that SAME LEVEL OF TORQUE being available from 4500-7500. It just opened up the bottom end and didn't seem to change anything up top. Having your torque plateau widened by 1500 rpms would be classified as a 'Big Difference' in my book. If you want to dispute that is not a 'big difference' we will have to agree to disagree. It was the difference between not being able to 'pull the spread' at speed and breaking records. Before the change when doing drag strip testing we would shift to third and you could literally count 1...2...3 before the wheels broke free and the car started accelerating again, passing through the traps at 13.08 at over 100mph and spinning the wheels all through the end of the 1/4 mile (3.36 gearset, and stock diameter street radials.) Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted June 24, 2010 Share Posted June 24, 2010 So Tony - was that a 2 degree 'retard' in cam timing that yielded those results? Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 24, 2010 Share Posted June 24, 2010 It was 1999. I would have to look at the dyno sheet from our testing, we both advanced and retarded the cam up to 4 degrees in each direction and took the position that gave us the best torque. I remember for our application that 2 degrees was the ticket. This DOES NOT mean that 2 degrees is some magic number and this is where you set every cam. We spent $200 in dyno time testing the cam in various positions and took the one that gave us the best torque/HP split. Subsequent testing with different induction systems on the car gave similar results. The only way to know is buy a sprocket and try it on your particular build. Someone said: 'Big difference? By whose determination?' so this was illustrative of such an instance. Best $200 we spent in 'performance modifications' to that point. $200 for Dyno Time. Until you do that, you're just guessing. The torque and HP we picked up from that change allowed us to pick up our first record at ElMirage. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 24, 2010 Share Posted June 24, 2010 Again, context. Big difference in moving a stock cam a couple degrees vs using another stock cam that is already relatively retarded? Or big difference comparing stock cam to an aftermarket cam? Or big difference timing a cam that is better optimized for the job at hand (whether that be mileage, low end torque, hp, etc) and getting the most from it? I think you'll get much more out of swapping in a much larger than stock regrind than you will out of changing the timing on a stock cam a couple of degrees. Degreeing the bigger cam is what should be done, and don't waste time swapping in a smaller cam or retarding a stocker. My point with the cam gear was that you could probably swap the gear alone and get similar results to going to the early cam with a lot less labor, not that changing cam timing doesn't make a big difference. Context helps. I feel like we're going round and round here. If you think that swapping in an early cam is going to produce a power increase larger than raising the compression from 8.3 to 9.8, I'll just say that I think you're wrong. You bashed the P79 as the wrong head to start with. For most people and the motors they build, I think you're wrong. As far as what to do to make more power, there are many ideas about that and an infinite number of solutions to getting more power. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 24, 2010 Share Posted June 24, 2010 "My point with the cam gear was that you could probably swap the gear alone and get similar results to going to the early cam with a lot less labor, not that changing cam timing doesn't make a big difference." If that's what you meant to say, you should have said it in the beginning. The response is the same: the opening and closing times on the valves are different early to late and "a couple of degrees makes a big difference"... The later cams are not the same as an early cam with overall advance / retard. And even with a stock cam, gains are to be had by degreeing it to the engine it's installed into....stock or not. The original question was 'should I shave the head 0.080" while it's off'.... "NO" Coming from someone who did it above I believe the answer 'in retrospect' was it was a waste of time and money as well. This is all from leaking / weeping coolant. "ALUMA-SEAL" Argue about an aftermarket cam all you want, you have obviously missed the absurdity in the original posts, missed it when I pointed it out, and now have steered the conversation so far off track that YES we are 'going round and round'.... For the THIRD time my original statement was "LEAVE IT ALONE IT'S NOT WORTH THE TIME AND EFFORT" Is this clear to you yet, JM? Flexicoker seems to have gotten something out of it. IMO I don't see the advantage of turning an otherwise strong-running bone-stock engine which runs on regular gas into a (for all intents and purposes) IDENTICALLY PERFORMING engine which REQUIRES permium fuel to run around. You can get at least 147 RWHP on a stock low compression, stock EFI'd, F54/P79 on REGULAR GAS. If that engine isn't there yet, I'd suggest he spend time optimizing what he has FIRST before making the universal mistake of cutting, modifying, and altering a subpar/subperforming engine! You can put a Holley Dominator on that 318, but it doesn't mean it's actually a 'performance upgrade'. How many people spend a couple grand on their engine, and then are disapointed that the ratty looking stocker that rolls onto the dyno after their car rolls off spins it up to an equivalent number, or even higher (been there, in the ratty car...) All this 'incremental' stuff is just that: Incremental. It still is a system and some stuff just doesn't make sense to do first. Like milling the head for compression when you have sparkplug wires that are leaking to ground and misfiring at the top end. Not saying that is the case here.... but like I said in the beginning: What quantifiable result is he expecting to obtain from this modification? He's worried about the cost? If you are worrying about the cost of a marginal or incremental modification: SKIP IT! Like you said: CONTEXT. Read what the OP wrote, and consider he's worried about the $$$ expended. It's not YOUR car JM, it's his $$$ and his car. My advice would be 'pass on this one at this time and keep the car reliably running on regular fuel until you CAN afford it without reservation...' Quote Link to comment Share on other sites More sharing options...
JMortensen Posted June 24, 2010 Share Posted June 24, 2010 Beating a dead horse here, but seriously... WTF? My point with the cam gear was that you could probably swap the gear alone and get similar results to going to the early cam with a lot less labor, not that changing cam timing doesn't make a big difference. If that's what you meant to say, you should have said it in the beginning. The response is the same: the opening and closing times on the valves are different early to late and "a couple of degrees makes a big difference"... Really? Read my earlier post again? This wasn't clear enough? Tony, re swapping the A cam in, wouldn't it be easier just to use the later cam, get an adjustable cam gear and retard the cam a degree or two? With the lift and duration being damn near identical, I bet the result would be damn near identical Then you don't even need to take the cam out of the head. Regardless, I'll stop here. I think I broke my dead horse beatin' stick. Quote Link to comment Share on other sites More sharing options...
sledz Posted January 14, 2015 Share Posted January 14, 2015 Yes this thread is old sorry. I have been reading up and gathering all the info to do this mod for what I thought was a good one until I came upon this thread and feel stonewalled. My head is apart and is ready to send pieces out to get machined and now I am wondering if this mod is truly worth the trouble. Does anyone have true experience with this? I do know of one over at classiczcar that I have talked to and he loves it and has a lot of experience with it, just looking for others to confirm if they have done it. Thanks.. Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 14, 2015 Share Posted January 14, 2015 Be aware - http://forums.hybridz.org/topic/120923-got-my-head-rebuilt-and-shaved-i-fear-i-might-be-screwed-help/?do=findComment&comment=1131881 Buy the Honsowetz and the Monroe books. $20 - $30 spent to save hundreds. Quote Link to comment Share on other sites More sharing options...
sledz Posted January 14, 2015 Share Posted January 14, 2015 I have both and have read them. the how to modify book does not even talk about later the later P79 but a lot of nice to dos for sure. The Mod seems pretty straightforward, shave the head .080, shim up the towers and outer springs 0.80 inner .40, install shorter valves, pick a performance cam, springs and retainer, figure out the geometry for the lash pads and run with it. End up with an updated head with higher compression which seems logical for a performance engine!? Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 14, 2015 Share Posted January 14, 2015 My impression is that increasing compression ratio doesn't buy you much, these days. It's essentially a very dated way to increase power, from back when the fuel available could handle the increased cylinder pressure. If you're running high octane racing fuel, that's a different scenario. The most effective way to get more power for the L6 engines, today, using pump gas, seems to be to either/or/and get tuneable engine management if you're running EFI, and port the cylinder heads. Over and over you'll read that the intake ports on the stock L6 heads just won't let enough air by to get the power up. Without porting the only way to get it through is with a turbocharger. That's just what I've picked up. The .080" shave and different valves is a way to get bigger valves in to the early heads, I believe. The P79 already has them. Quote Link to comment Share on other sites More sharing options...
sledz Posted January 14, 2015 Share Posted January 14, 2015 Yep the work and cost is just not worth the gains.., I think I'll get of my "Horse Power High" and get grounded. I have my 240 engine out to paint the compartment and had this combo to go in and was looking to maximize it... I think I will keep it simple and save some cash. Thanks. Quote Link to comment Share on other sites More sharing options...
madkaw Posted January 14, 2015 Share Posted January 14, 2015 I thought the idea for all the work on the P79(which isn't a lot of work really) is to take advantage of the more modern combustion chamber that has good quench characteristics. The head can handle the higher compression better because of the good chamber design thus fighting of detonation. I don't think it's a bad idea at all. It would cost a lot more to have an older head reworked to produce the same quench characteristics. The idea is to be able to run a more aggressive timing with a decent CR ratio that gives the power! Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 14, 2015 Share Posted January 14, 2015 The quench discussions always seem to spin out. It's not even clear that the stock heads quench area does any useful quenching. But if you did chamber work then shaving to get compression back makes sense. I was mainly pointing out a bang for the effort issue. If you're going to work on the head, porting seems to give the best return. A set of new valves seems spendy for a small bump in CR. Not an expert, just read a lot. I could be way off. Quote Link to comment Share on other sites More sharing options...
tamo3 Posted January 14, 2015 Share Posted January 14, 2015 Quote Link to comment Share on other sites More sharing options...
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