hey all, I just had a question about trying to tune this new 350 i dropped in to my pickup. Here's the story- I pulled the 350 out which got about 16 inches vacuum (at 4500 feet elevation) and 130 compression each cylinder. A good motor, still passed smog and got about 11.5 mpg around town with rochester 4 barrel. I pulled it in favor of a 350 crate engine (base model replacement) with about 850 miles that came out of our T-bucket and has set for a couple years. Got it installed, and had a hell of a time firing it up, depsite confirming all the TDC marks and valve operation on cylinders 1 and 6. It backfired and blew the accelerator pump seal out so I had to swap carbs to a somewhat unkown condition Rochester. I got it fired, but it ran rough, timed it at 12 degrees, and set the mixture with a vacuum gauge. The highest vacuum I could get at that point was 15, in the yellow zone. Rebuilt the old Rochester I was originally running. Still, only 15 inches. I started rotating the distributor without paying attention to the timing marks, and can get it up to 16 inches of vacuum. If I leave it at that setting, it's timed at about 30 degrees! If I retard it back to 16 degrees, it REFUSES to fire up in the morning cold. I have to really advance it (which is counterintuitive right?) to get it to fire. In that case, it's at about 40-50 degrees advanced! I have NO idea what is going on here. I've narrowed it down to the timing tab on the water pump cover and the harmonic balancer timing mark cover (an aftermarket cover with all the marks up to 50 degrees in white letters, easier to read than the little notch on the balancer). If I time the engine off of the mark on the balancer it refuses to run- could it have slipped, or were there different marks on balancers for different years? I bought this brand new from Summit. Also got the balancer cover from Summit, and the TDC mark does not line up with a balancer notch. If I time the engine to achieve the most vacuum at idle that i can get, it runs strong with more power than it had before, but it SUCKS gas at twice the rate it did before. If I time it at 12-16 degrees, it won't fire up cold and it runs rougher. What could be going on here? HEI ignition, I ran a compression check and each cylinder was at 140- could it still be breaking in or did I screw something up? Vacuum gauge is steady so it doesn't seem like a flat cam or valve problem. Would the thing run good at all if the timing chain jumped a tooth? Please help- gotta get this figured out before driving the truck towing a trailer with all my posessions to Washington! thanks
Pull all the plugs and then verify that the TDC marks are correct. I used to just stick a small screwdriver down the plug hole while turning the crank with the damper bolt. A small wooden dowel will also work if you are worried about messing up. Turn the crank REAL slow once you feel the piston coming up to TDC you will probably need to reposition the screwdriver once or twice. Rock the crank back and forth once at tdc to get the highest point and then look at the timing marks. If they are within a degree or 3 that is not your problem.
There are 2 or three mark locations on balancers and numerous tabs, plus whatever variations aftermarket introduces as actual changes or just sloppy work... You cannot figure out what a given group of random parts are meant for...just stop and determine ACTUAL TDC from scratch, not a hard process. Buy the blocker tool or make one: Smash porcelain out of an old sparkplug (Pretend it's the head of the guy who made your timing tab), heat ishell as hot as you can on stove when wife is out or use torch if you have one to soften the temper of the metal. Tap the hole, oft 3/8, and run in a long bolt with locknut. Screw into #1 with that cylinder on its compression stroke, bolt protruding into cylinder maybe 3/8" more than electrodes did. Slowly turn engine with wrench till piston stps against your bolt (File it to smooth end, by the way!), then rotate in opposite direction til it hits. Mark both places on balancer where it matches zero on tab, measure exactly half way between your marks, that's TDC. Probably easiest way to fix is to keep tab, mark balancer with new mark and contrasting paint.
After you verify No1 position and readjust the timing with no change. Then start looking for a vacuum leak at carb, intake and all the vac hose connections.
Yep. start with confirming TDC. So many dif. ones. Also the balancer could have spun on the hub knocking the mark off. If it is old and the rubber is coming out or cracked, get a new one before you need a new rad.
i'd say it's TDC. I had the same problem on my T over the summer.. Seemed to like way too much advance. Pulled the heads over the winter to find my timing marker was off like 6deg. I did it the rigorous way with a degree wheel and a piston stop. That way you can get it to less than 1/2 degree
Another thing...ponter markings are sometimes...imaginative...on aftermarket ones. After you verify TDC, do some quick arithmetic so: Measure from center of balancer bolt to tab, the radius it is following. Compute how wide a degree (or 5, whatever gives a useful number rather than something like .2732), measure, and see if degree marks correspond with observable reality. I think on some of these parts, they just mailed a sketch on an old napkin to the Chinese... And might as well find TDC accurately. the measuring is a one minute job, add 10 more minutes to beat an old plug to death if you can't borrow the tool.
While you are thrashing around down there... To ensure you don't find your timing getting mysteriously wierd in the future, after checking condition mark a painted line all the way across your balancer and/or centerpunch center ring right next to punchmark on outer ring. Then when things look strange, pop off the pulley and look. They really do go adrift with age and rubber failure.
If the chain actually "jumped a tooth" or moved after installed, it's a serious problem. If you are talking about it being accidentally installed a tooth off of center, unless you are way off, this isn't your problem. Degreeing a cam simply pulls the curve up or down a little in basic terms. I would start with all the above advice: find where your marks should be, then mark your balancer to your pointer.
Also when setting timing by vacuum you will end up with way advanced timing. You can set it to the highest reading and back it off and double check with the timing light. Total should be in the 36-38 degree range with the vac advance blocked. You can also just set the total by reving the engine until it stops advancing and turning the dist to get the mark you want, and leave it there.
thanks- that's kind of what i was addressing, whether setting timing by vacuum would give you the best power and mileage. I have found it obviously doesn't help mileage! Well, thanks for all the help- I checked the timing mark, and yes, it does line up with the TDC mark when the piston is at the top of its range, within two degrees. SO, I checked timing throughout the rev range- if I set it at 12 degrees, it runs OK, I can get 15 inches of vacuum, not near the 16 I had with the previous engine (and this ignition that I swapped on). When I rev it up, it will only advance to a total of 20 degrees (without the vacuum advance). So obviously something there is screwed up right, it should advance to 35 degrees or so without the vacuum advance am I right? WITH the vacuum advance, it will only advance to about 40 total (with initial set at 12 degrees). I swapped the cap and coil, and the modules, and lubed up the advance weights. They seem to move freely, no binding. Still, same ignition curve where it would only advance to a total of 20 degrees (40 with the vacuum) I am going to swap back on the points ignition that was originally on this new engine I swapped in, and see if it changes anything. When this engine was in the t-bucket with points it only needed 8 degrees initial to run well. When the HEI that I have on there now was installed on my old engine, it only needed 8 degrees to run well. I have no idea what happened during the swap but it's messed up now! thanks everybody
update: swapped the ignition with the points- ran exactly the same as it does with the HEI, can still only get to 20 degrees when the initial is set at 12, and 40 with the vacuum advance. Is there anything internal in the engine that would prevent me from getting to 35 or so degrees of total advance without the vacuum advance? Swapped the HEI back on, can get it to 15 inches vacuum at 12 degrees when it is fully warm. Just barely at the green point, though the elevation doesn't help. What is perplexing is the old supposedly tired engine was getting 16 The engine has about 1100 miles on it now- will it take a long time before the rings fully seat and give me more vacuum or is this engine douched?
Usually you have 20 degrees of advance in the dist only when fully advanced say at about 3-3500 RPM depending on the springs, you have to rev it to see when it stops advancing. Now if you did that and it only gives you 20 total you have a prob, are you plugging that vac advance at the dist? With 12 initial and 20 in the dist your total would be 32 so in theory you could go up to 16 initial. If you bump the initial up see what that does to your total. Total is more important than intial provided it is no so advanced it wont crank when hot. I cannot think of anything internal in the engine other than there is a problem with the damper and timing mark. Check that again making sure you go up to the stop and then back to it like Bruce L suggested. I had a damper made for a timing pointer mounted at the top of the balancer used with a long water pump and because I am using a short pump I had to use a different tab and I had to do just what he decribes to get true TDC.
Also vacuum depends on other factors like the cam, i can only get 15 out of mine with the cam I have, a steady reading is really what you want.
You need to find somebody with a distributor machine so you can find out what your distributor is actually doing. I would also try another timing light.
thanks all- I have tried another timing light, same exact readings. So yes, with 12 initial, the reading tops out at about 20 degrees, even at 4,000 RPM (with the vacuum advance plugged). Now, it did that with two different distributors, one HEI and one points, and with two different caps and modules on the HEI. WITH the vacuum advance it tops out at 40 degrees with 12 initial. So, is there ANYTHING in the engine that could be causing this, not the distributor? Timing should be the same whether engine has internal problems or not? I have also tried three different plug wires just to make sure they weren't misfiring and giving me a bad reading. I can fire it cold with the choke manually held down (this stupid Edelbrock intake with no thermostatic choke mount is for the birds), but it takes a while, but when it does fire it idles nice. With the old engine and the Weiand intake, it would fire easy but idle rough until it warmed up. I don't understand that one Aside from double and triple checking the timing marks, I am ready to swap cams and intakes, JUST to double check that the chain didn't jump or cam didn't go flat. My vacuum reading is steady, but still only 15. I am pulling the vacuum off the manifold, which gives me the same reading as the ported source on the carb (which is the same source I used on the old engine that did much better) I'm getting 9.5 MPG compared to the 11.5 I was getting with the old engine. Man, I really screwed this one up big time. I need to drive this truck, pulling a trailer, up to Seattle in two weeks
This may or may not be part of the problem, but for me to understand more on timing would someone clarify it more for me? Question is: With the timing mark on the balancer at 8 degrees before top dead center (clearly marked on stock timing tag and piston at correct compression rotation) should the distributor rotor pointer be slightly before it gets to the number 1 post on cap or slightly after? Just trying to make sure that when dropping in distrib not one tooth off. he
i have the same problem with it starting up in the mornring too but when hot one crank starts ups no problem. i dont think i'm getting all my hp out of mine. its 300 hp corvette 327 with 202 heads headman headers a duntov cam edelbrock street master manifold and hei this thing should rip but i have the same problem with timing my dis sit's way to the left and cant turn it anymore its in a 55 chevy truck and the motor sits close to the fire wall is there a advance kit to put in the hei to make it better i dont no the name of it mabe some one can come up with it. i have some pics of my motor .billy
Any more solutions/ideas ? Hellmet-nice motor-it should fly. Possibly putting a "small" HEI or a pertronix electronic change over in a points distrib. Summit Racing and others should have adjustable vacuum stuff you are looking for
nope- never resolved As it sits now, HEI is in, new module cap and rotor- didn't fix it, old points distributor didn't change anything. Several different carbs didn't help either. Still only getting 15 inches, and very hard starts in the morning. I also notice now that I get pinging under full throttle at about 3000+ rpm Timing is set right now at 12 degrees, but if I retard it anymore it won't even idle. My thought is that the cam is either a) a very poor grind designed to pass smog tests since it is a replacement engine b) damaged due to improper initial break in/startup c) is off a tooth or two d) I have improper lifter preload, I read that it causes poor manifold vacuum and low throttle performance. I bought a new towing grind cam, fuel pump, fuel filter, distributor curve kit, adjustable vacuum advance, plug wires, timing chain and gears, thermostat and some other bits, and was going to swap them today, but I leave Monday, there is no way I have enough time to finish and make sure it works and still depend on it to haul me and everything I own up there! I have way too much to do right now as it is. I just went with a U-Haul and will have to come back to it in a month or so. Luckily I have a storage space for it here. I'm getting 9MPG, and I was getting 11.5 before the swap I would swap the old engine back, but I already sold it! doh! thanks for all the help guys
Check your valve adjustment. And while you have the valve covers off confirm the timing marks by using valve overlap. Watch #6 while you turn the engine over by hand. When the exhaust valve is almost closed and the intake just starts to open (overlap) you should be on (or damn close) to tdc #1. If the timing marks are off your cam timing could be off. The chain has to be really bad to jump a tooth. I'm not going to go through the way I adjust valves now because I don't have time, but I use the firing order and turn it over by hand, it's a lot cleaner. Watch when you adjust the exhaust, if you have to back them way off to get them into adjusment you could have valve seats going away. Jeff
Interesting reading guys........ I've a 58 Lincoln 430 that i rebuilt & have had similar thoughts & worries but, as PRO STOCK JOHN pointed out, it can sometimes be a dying fuel pump & I bought a rebuilt one & that failed after 300 miles ( seems the top diaprhagm doesnt like our detergent enhanced fuels here in UK.....yet my 58 Buick Limited pump has never failed in 12 years! ). Car starts better now & idles great, had an earth wire break in distributor which didn't help & have now set timing at every mark from it's recomended 3 to 6 minimum & max sparking & at 3 it starts well & has bottom end but little power & at 6, has more power but backfires. Oddly the other day I drove it some 20 miles somewhere & it felt lifeless, yet on the way back it ran great, so can't help fearing I still have a fuel problem ( carb has been rebuilt too ) or electrical intermittent break down. Found all your advice re checking tdc very interesting & whilst confident it's dead on from the starting ease & from memory of using the screwdriver in number one cylinder trick I may re check & possibly try & get a new balancer as mines wobbling as much as Jane Mansfield's wonderful breasts!! I sure hope BUSCHANDBUSCH gets his problems sorted & if anyone can advise any further on mine I'd be grateful. Regards, Steve
Steve it sound like a distributer advance issue. Not being able to drive a car and hear it run really makes it hard to pin down problems. Check the mechanical advance and make sure it's free. Make sure the vacume advance is moving.
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