Hi' can anyone give advise?Ive rebuilt a 318 for a 68 vali used hi comp pistons, a magnum cam big tho still hydraulic, airgap performer manifold and 600 vacume carburetter on msd ready to run billet distributer. the heads have been mildly ported and 360 valves fitted.ive taken it to dyno places and spent hundreds but have ended up tuning better myself.I have a problem with plugs failing after just a few hundred k's & then strong smell off unburt fuel. ive tried all the distributer centrefigural settings and beleive have the best setting, also have had carbureter tuned down but still have the same problem.My engine builder said he had advanced the cam by half a tooth to improove the responsivness. im thinking would this be the problem where the fuel is delivered to early now perhaps and the spark is now late' somthing ? or could it be somthing else. it does dyno at 220hp at rear wheels its not really lacking but if any1 may have a idea it would be much appreciated?ps what happened to just the old interorgator gas anylist machines cause no1 can tune these anymore!
first... the old scopes have died do to lack of replacement circuit boards... and almost no body has a set of schematics .. lack of service parts requires you to replace them with something else.. most fuel system tuning is done these days with either narrow band heated oxygen sensors.. or the more expensive wide band oxygen sensors ... tells how much oxygen is left in the exhaust.. gives you an accurate idea of air fuel ratio..there are also detonation sensors that bolt to the sides of the engine block.. or screw in.. these are actually piezo microphones and generate electrical signals to be picked up and displayed if the engine is detonating.. what number spark plugs are you using.. at what gap.... you have a ready to run HEI.. but with which coil... i had a friend that found his car would slow 3/10th if he ran the spark plugs more than 3 passes...have you ohmed the spark plug wires?? verified that they are less than 1,000 ohms per inch.. is there visible damage to the spark plugs.. where the electrodes are eroded.. or are they carbon coated and starting to misfire..
Your having the same problem because the engine is so lean it's about to self distruct...Never detune a carb lean to make horse power. Find the power someplace else...Never push a stock cam ahead it will fall off at the higher RPM. I read this post and I just get so Pizzed this guys make a living tuning engines and they don't know what they are doing. Stay away from these guys!!!! Why in the world did you tune down a 600 cfm carb. It sounds to me your making power because the engine is so lean. Your blowing the Plugs apart because of that. If anything you don't jet lean. Jet for max power. Your not running a 1/4 mile. Ask the engine builder if the intake valves are burnt if he is going to replace them for nothing?1.The raw fuel you smell is the fact the plugs aren't firing to burn the fuel. Get rid of your dyno guy and engine builder. 2.Put the cam straight up and make sure the timing chain hasn't stretched. Why did he do that on a stock cam is assinine. 3.The carb put the stock jets back in and tune the engine for that. 4.Because your so lean I would do a cranking compression test.5.If they removed springs in the distributor go back to the stock set-up that MSD had for a power curve. If the engine bogs then adjust the advance spring buy putting in a little set.I would just put everything back to the stock settings, and tune from that point. Then make one change at a time. You make a TOO HOT a sprk plug in the engine also...Bob
I had the 600 cfm tuned down besause it was the new silver plated from rocket performance and it was jetted up high to suit a wider range of aplications.it was running so rich that the plugs went black in days and you couldnt breath from the fumes. Its jetted now as a normal 600 would be. Before the mixure screws didint change a thing now it can be adjusted.I know what your saying about the cam. Its a magnum 180 cam ive seen other 318 engines make as much as 400hp using the same but why it was advanced i dont understand. I will dial it in myself agin to marks & go from there.
ive seen a few of those machines on ebay i was thinking it might be handy to have as they do make life easy and show a torqe curve. Im using ngk bp5es and bp4es spark plugsive tested the power coming from the msd everything there seems ok. once i solve this initial prob i might chance gaps slightly higher for a longer spark and try get it close to perfect
Does the engine make the Top RPM range? Then there is something going on. That could be one of the problems. A nice long spark is nice. But here is a problem that can occur. When the spark is that wide believe it or not the flame can actually get blown out by the incoming charge of fuel&air. Close the gap. I don't know what your using as a Gap but go to a .032 or .035 for a street engine. Are you running a .065 gap. I used NGK plugs in my Race Engines for years. I used Autolite Plugs also. I would never buy a Champion plug ever. The ground electrodes blow off the plug. I'm am not going to debate you but as I said I would put all the things back to stock. Then make one change at a time. I would definetly do a cranking compression test. Maybe your problem is there.put that cam back straight up If that carb was so rich why didn't you call the manufacturer up. Or put another one from somewhere to see if the carb changed something. Its possible the carb has an interal leak. The floats are they where they should be? You have to get back to a basic setting.Check your engine oil also I'll bet it smells like gas. The Cam can't be advanced a half tooth. Is that what he told you? Its either 1 full tooth or it doesn't match the crank sprocket or the cam gear. What did he actually advance the cam or the crank sprocket teeth. Before you work around the ingition or cranking the engine. Dis able your ignition. Pull the fuse! Check you TDC verses you timing marks. You can do that will a compression gauge, or hold you finger over the hole. When you do this make sure the battery is good. Or put a charger on it. Bob
thankx bobIve been using the plugs where there set in packet which is the .035 gap that seems to be good i was told i could start off by opening a point bigger at a time to try find best gap but i have played with that b4 but with the engine not been right to start with ive been leaving it at .035It has good compression i used paper to find top dead in number 1 one time and it blew out and hit garage roof. ive a comp tester but havnt tested the compression.The oil seems ok no real petrol smell but i do change it fairly often as engine is basically new maybe three times so far.ive used lighter springs in the msd and have eliminated pinging tho after a while if engine is driven over 100kmph for a period it does start to heat up a little and has pinged. I might start as by what your saying is to set the cam back. im not 100% he said half a tooth im not sure what hez done until i look i guess.The carburetter i brought as best suited for this engine as i didnt stroke it or id use a 750 but the 318 seems not to like allot of fuel as b4 it just had a 350 two barrel. i did speak to allot of carburetter experts and where i got it and it was recomended just to be rejeted to suit more the 318,' it all wasnt cheap to do as its turned out i shoud have fitted the 360 crank and had the 355 maybe thats my problem! but you could be right starting from scratch with timing i think its the way to go
To add with the rpm im not sure i havnt a taco on it i think around 5000rpm, it seems to start to loose power at 160knpr on dyno, b4 that point it makes around 220 at the wheels. I would of thought it to pull allot longer than that and make a bit more.....
dragr33 I'll try and answer your 2nd post first. If the cam is over timed, it will run out of steam early. In other words it won't pull to it's potential. It could have flattened the valve springs some also. Trying to get it up in RPM you could have experienced valve float, so minor you didn't know it. Were the valve springs matched to the cam? If you can borrow a 600 or 650 cfm carb try it, and see if that helps. I ran my 402 Big Block Chevy with a 750CFM carb, and that was plenty for it. Thats nearly a 100 more Cubic Inches then you are running, and my engine was modified a lot more. I'm glad to hear your making some progress.Bob
Making some progress. Havnt had much time till now.mainly starting from scratch as you said is what im doing, i would wish to be in position to borrow and test other carbies but i dont know anyone. im just going thru settings one by one starting with a manifold vac gauge to find where it is to perhaps change power valve. i herd theres a tab on the arms for float inside bowl so il be checking level that way.il also check secondary is working and im not sure ive a holley hi volume pump ive herd can be as hi as 8psi so just to be sure and without getting a regulator i just have a new standard to try. basically checking and then trying to set this carbie to suit better.i also got new ngk iridium plugs to try.also the centrefigural spring and bush kit for distributer'' going by holley tech its our distributer or ignition. i think its the bush is to small and im getting not enough advane. its going to be a long day or two days trial and error and road testing to get it better set up. its a 280h magnum flat tappet cam with that been advanced im also going to set it back i got the cam card is it called and everything from manufacturer.dave
dragr33 I'm glad to hear your making some head-way. I know it's so hard to undo what someonelse has done. Because your really going at it blind. (I have been there). If you have a way to check the Fuel Pressure 8-PSI maybe a little high if the carb has a stock needle and seat. 6-PSI should be Okay for a street engine. If your plugs are sooty when you check them. I would start there,lowering the fuel pressure or finding a Viton needle and seat for the carb.It's Okay that you don't have another carb to try. We can work getting yours back to where it should be. The NGKs are good plugs. I ran NGK's and Autolite's in my race engines. AC Delco makes a good Spark Plug too. The NGK's you have now, are they extended tip or a retracted tip? I would set the spark plug gap to .032-.035 for now. You want to get the engine to run. Then you can start tuning it to get the power it should have. Keep me posted, and we can get it to run better. One thing at a time. Then we can tune it! Bob
yes im pretty new to it, especially the very technical side of things' advance curves, power valves etc. The time i spent not doing it i was on the internet finding out as much as i could, i think 14 housr 1 day. Ive owned a few fast 8's when younger but i worked in a sevice station with the interorgator machine & just use to put my car on it. Since ive owned turbo cars ive brought and just payed for all the good stuff so to say.. Im really into the mopar seen now and have a 68 vip and a 68 regal both with a 318. But yes having it all back to a stock setting is hard having the airgap and holley and msd on it. i do have a new stock fuel pump but couldnt get a gasket today for it so left it for now. ive herd the holley hi volume can be from 6.5 to 8 psi and the carbie i got is good for just 7 psi. it might still be a prob but il get gasket asap.i started today by taking few things off front of engine, fan belts etc so as to see the timing marks. I highlighted the marks with liquid paper and ran engine and took not were it was at different revs. I then started playing with bushes and springs and took note again. At the end of the day the blue bush with two heavy springs with distributer set at 12 degrees b4 top and straight away you could hear the difference it even had a really nice note from exhaust and no more rich smelling grey black smoke. during that time i used a boost guage from my skyline that has vacum on it and set the primary mixtures getting 15 inches of vacume. also the kickdown lever was moving to early puting trans into i think over drive i also fixed that problem. i know now i need a 6.5 size power valve which il buy and install. im not sure what size in it now but i will see when get it and gaskets so left inside of carburettor alone today. with the plugs i got or i had ordered them were iridium bp5ix when went to buy they were $180 so i put deposit thinking i dont want to use them yet and kill them so i got ngk bp5es for the tune. I think il drive it for a bit and see how it goes. if it stops failing plugs il put the good ngk plugs in & see how they go. But havnt got hopes up yet its good it seems to be but i know my luck. il let you know how its going again soon. thank you very much for the help its been really good to be able to speak to somone with some real proper knowledge cause some of those forums OMG!!!
Dragr33A quick and simple way to figure out what power valve to use is 1/2 your intake manifold vacuum. So for 15" of vacuum you will need a 7.5 power valve. When you get the cam back to a straight up setting the intake vacuum may come up. Thats a good thing. I would not use a good spark plug until you have all the problems taken care of. The nice thing about the paper white it shows up really nice when you put a timing light on it.
Dragr33:Good Luck Bud. Take your engine apart and if you have a service manual thats the best way. If you need more help, I'll be here it may take a little longer.MERRY CHRISTMASBob
Thankx mate & yeh 7.5 thats right half the vacume. As i said ive no hopes up yet its right. The tech for msd,holley,ngk were a great help too!Ive a 660 rambler classic with a rebuilt engine, i tuned it to a tea, i wish this val was as easy!Anyhow merry christams to you to thank you heaps for the help,' im pretty sure il be back again soon tho!!