That level of bouncing is not indicative of a good tune. That cam will allow you to use MUCH more than 12 degrees of initial lead and shouldn't have much erratic needle movement at all on a larger motor with a dual plane manifold. Now, I'm not saying you should run the ragged edge here like I do, but my smaller and higher compression combo uses 54 degrees of initial timing and pushes just a hair under 16" of vacuum at 900 rpm. Which tells me that there is plenty more to be had there in your combo. What was your total advance number and at what rpm did it all come in at? Have you done a compression test yet to verify peak cranking pressure and to make sure everything's fairly even across all 8?
Will check later this afternoon, I don't think the rings are seated yet, gotta change water pump then I can run it more.
Eventually,you are going to want to get bigger heads & at a minimum 750 carb.Your top end is choking down that 408 badly,it will never realize its full power capabilities,just a suggestion.You have a very sharp car.
Don't underestimate the power potential of a good port job and larger intake valve(if you don't already have the 2.02's) on that head. My Chev's "little 170cc" RPM heads are not even pro-ported(around 190cc now) and it did 563hp around 6,600 rpm and also carried decent power way out past 7,000 where I like to manually shift my auto. And just as an FYI/"note to self" for later use.. just heavily streamlining the guides and working the pocket for a nicer/longer throat and gentler seat entry radius gains power.. EVERYWHERE. They're not very thick for huge jumps in port size.. but there's plenty there to be had. With so many CID airspeed will be very high at higher rev's, so increasing the CSA of the pushrod pinch.. and not necessarily the port/gasket entry itself.. also helps with further gain without losing any low end or throttle response. You gettin' it all figured out and broke in yet?
Yeah I do have the 2.02's in them already, seem to be pretty good heads from what I can tell so far, and I forgot, the cylinder head shop did do a little milling on the surface so that changes the static compression ratio...
nice. have to also remember that dished valves subtract another 1-2 CC's too.. but you already got so much excess here in the first place it's a non-issue anyways. "uh-oh, bud.. you lost 2 ft/lbs of torque!.. ahhh, that's ok cause I still got 450 left". hehe
Going back to the beginning on the timing, something is still badly off, drove it today and was real sluggish no real power to it, I have already double...no triple checked the timing, checked the distributor twice now, I am going back and bring it up to TDC on the compression stroke and re stabbing the dizzy and work from there, I know it's just some little thing I may have done improperly and I will find it, on another note I love the TREMEC! it shifts perfectly, what should the optimum plug gap be, gonna pull them and recheck and see what they look like.
Spark plugs Frank, only plugs I know of in the TREMEC are fill and drain plugs, it came out like that cuz of it being an afterthought.
lol.. now you know you should'a edited that with an extra return key-stroke on the keyboard just so's Frank didn't pop in and catch you on it. Yeah,.. return back to baseline and start from there. Do you have the vac advance pot running to manifold vacuum?.. or ported/timed?.. and are you sure the diaphragm is still good/sealed? No handheld vac pump required if you simply suck on the hose and seal it against the tip of your tongue to see if it holds and maintains vacuum. What was you final timing curve? Initial, centrifugal portion and @ what rpm it's "all in", and total number? Also if you are actually using the advance pot.. it is VERY important to know the amount of advance its adding into the equation. The reason I say this is because this is one of the biggest issues I see with guys deviating from the stock initial and mechanical timing settings. There's sometimes upwards of 20 degrees of additional timing being added with some factory style diaphragms.. and that's just WAYYY too much to add to an already aggressive enough performance timing curve. Adjustable units are almost a mandatory accessory to have here.. and be sure to check the one you have as it may even have adjustment capability from the factory. Also consider the opposite affect that lower manifold vacuum has on it's overall functional abilities. With your combo and a decently hot ignition box/coil.. I'd start at no more than .040" gap and see if it would tolerate just a bit more without issue. Despite its hotter ignition system, I only run .035" plug gaps on mine but that's simply because of its higher compression ratio and cylinder pressure. If you get your combo dialed in tighter.. you may very well find that it can go to around .045 - .050" gaps no problem.
here's another way to go as well. A little more work involved.. although not much when you already have your disty out.. and fully reversible when you're done. Spin the disty's shaft to LOCK YOUR TIMING OUT AT 36 DEGREES and run it again. This will eliminate MANY variables all in one shot and take you away from the disty curve as being the main culprit here if things don't immediately improve. Not sure whether it'll start with that much lead or not.. mine does with 12:1 but needs a hi-torque starter.. but you can always just "twist in" a bit less advance for initial start-up.. and then quickly twist it back to 36* for testing. If you've never run heavy timing before right at idle/off idle?(regardless of their vacuum source, vac advance pots don't count here because their supplementation completely "falls away" under quick/heavy WOT throttle blips).. I can tell you without one single shred of doubt that you will be absolutely floored at the extra "functional and non-disappearing" engine vacuum and throttle response improvements that can be had.
Ok last time out there I noticed with a brand new vacuum gauge, if I hooked it to manifold vac, it went nuts, on the timed port it was much more steady but very low, almost no reading at all, I have a hi torque mini starter on it, plugs were gapped at .035 when I installed them, my next time out,(don't know when that will be, working a lot) I will try and do some of the suggested things and find info on what you have asked for, just not able to get to it right now, thanks for the help/suggestions so far, at least I have a direction to go, can't find my compression gauge so might have to purchase another.
I hear ya.. most of us gotta work harder just so's we can afford to play harder. What you are describing here is exactly as I said above. Your vac advance pot is adding far far too much timing advance with the full manifold source.. and probably still too much in the high-idle/mid-range rpms as well, if I had to guess(which is why your vacuum is still lower than anticipated). So, why not just entirely do away with the vac pot for now? Tons of the racier guys don't even use them anyways so it's not out of the ordinary at all. Stick a.. 5/32" ???.. allen wrench into the vac-pots metal hose nipple to see if you can engage the allen and tighten it up?.. might already be factory adjustable and that will surely fix you right up to keep moving forward. And remember that the timed port is subject to the exact same manifold vacuum level(all from the same source) but is just "timed" to only come into the mix during above high idle speeds and higher throttle angles.. such as cruising on the highway at 2,400 rpm or lightly bumping through the gears.. but then "goes away" again at higher angles and WOT. Basically, "ported" creates a mid-range sweet spot of vacuum assist to aid you within an.. rpm AND load based.. "window".. and "Full" creates a constantly used(as soon as the engine fires over) and ever evolving amount of timing assist based solely on engine loads/throttle angles from the very bottom of the rev-range on up. This added "timing control" is obviously possible because either way you go, it's directly attached to the manifold vacuum which is considered to be a major indication of overall efficiency. Remember all the old "mileage/efficiency gauges" from years ago?.. and I do know for fact that some semi-new'ish vehicles still use them to denote fuel efficiency levels in digital fashion.. average/estimated MPG is based on throttle angles/manifold vacuum levels. Mainly because largely closed throttles directly contribute to higher amounts of engine vacuum. So, when loads are highest, throttle is opened further and vacuum goes down to reduce the amount of "under-load" timing assist. This is closer to perfect than just having a smaller "window" because higher loads reduce the octane tolerance of an engine which in turn also reduces timing lead tolerance.. all else being equal. So, having it based entirely on load vs throttle angle over a much broader rpm range makes much more sense for improving power and efficiency under a larger "window" below peak torque rpms. Bigger window below peak torque = bigger potential part throttle gains on the street. Unfortunately NOX will go up and it'll start to stink more.. but lower rpm efficiency will undoubtedly improve. There will be many opinions about "this port or that port" subject.. but trust me here, unless you do major amounts of very illegal and very high speed highway cruising, 100+ mph.. you generally always want full manifold sourced vacuum for your ride. I would also add some caution in regards to the break-in time under loads for any "untuned engine".. do not try to hold power too long or get even close to overrev until the motor is dialed in. Without proper timing you can wash your walls and rings which is never good at all. IOW, best to look at this as a "3,500 rpm powerhouse".. rather than quickly trying to find out how all your cash added up by stabbing your foot deeper into the throttle. I would be looking to get it as close as possible to barely adding any vac pot timing assist to this motor. Set initial timing to 18-22 degrees at idle(I know it sounds high but just just once try to twist that disty while you watch the vac gauge go up.. and you'll "see and hear" what the motor wants and likes. Carb settings will need to be adjusted several times along the way. Then get your cetrifugal lightened up a bit and limit its travel(much harder to do with the factory stuff). Then add the vac pots tightest diaphram setting of around 8 degrees of timing assist to fluff up the light throttle torque and response. You will not be disappointed.
Found 3 non firing cylinders today, didn't have much time to work on it but that's one problem, spark plug wire electrodes were burnt into at the cap, Taylor wires were only 15 months old.
