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Old 11-14-2010, 11:16 PM
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no power/backfire through carb/timing? 355 build

Hello everyone, im new to the foum here and i hope someone can throw some ideas at me, ive been working on a friends 73 nova for a couple weeks in our spare time, and we are having quite a few issues with it, now i figure since im kinda a ford guy that this is the reason for this car giving us so much trouble, karma maybe? haha, anywho below are the specs of the motor and then details of the problem, sorry for it being a lengthy read,

current motor and car specs
350/ 30 over
coyes double roller timing chain, crank gear advanced 4*/not check with degree wheel.
lunati 10001lk barebones cam and lifter kit .443/.465 lift, 214/224 duration @.050, replacing 10000lk
summit racing double hump head copies
2.02/1.60 valves/ springs rated up to .550 lift/
1.5 roller tip rockers
pro products air gap intake
edelbrock 1406 carb
long tube headers into flowmaster copies
stock mechanical fuel pump/ no fuel pressure gauge/unknown fuel pressure
unknown age HEI dizzy
stock th-350
4.10 gears out back

now, im pretty green when it comes to carb motors, and hei distributors, especially of the bowtie sorts, i'm more aquainted with Ford EFI motors, mainly because of my love of the Foxbody Stang haha. But im getting pretty aquainted with the different technology.

so heres the issue with a little back story. He had this motor put together about 6 or 8 months ago, and it wouldnt get out of its own way, idled fine, sounded ok, but driving down the road it was complete trash, so we went to trouble shooting, he was almost positive that the installed the crank gear 4* retarded, not advanced, so we figured ok we would change that and install it straight up to see what happened. while in there we decided to change the cam to the 10001lk, because the original 10000lk was pretty wimpy, we figured that didnt help things. also changed from edelbrock performer intake, non rpm, to the pro products air gap.

so while we disected the motor, and got to the crank gear, low and behold it was actually advanced 4*. so we left it the way it was and installed the new parts and buttoned it back up. the old cam looked fine, no worn/wiped lobes or odd scarring and the lifters looked fine, pushrods and such check out as well. we broke in the new cam, and tried to dial in the timing the best we could, idles fine, sounds decent, but starts hard, kinda hangs a bit like the starter is dragging or it was a very high compression motor, crank over twice or so then pause and then fire up, so i figured timing is messed up. at first it was shooting compression out of the carb occassionally on a failed start, but no fireball, so we figured that maybe we had on of the rockers too tight, so we went back over them again but nothing was out of the ordinary. we have also watched to make sure all of the rockers are moving the same distance as the others to help rule out a flat lobe on this cam, but they all seem match the others, the wieghts in the dizzy were all rusted up and such so we got a new weight and spring kit from mr gasket and installed the lightest springs and no vacuum advance. under the advice of an old racer friend. now i understand some, if not a ton of people think the mr gasket kit is junk, but it was what i could get in a pinch. so we took it out for a test drive, it ran worse than before until we tuned on it a bit with timing and such, seriously this thing should be running circles around my little 5.0 stang, but its not.

now on the road it is really down on power, to compare it ran like the 2.0 cavalier i have, and if you stomped it to the floor it would cut out and pop through the carb, sometimes a fireball. havent had any backfire throught the exhaust. so back to more tuning, ran a compression test and all cylinders where pretty equal around 170, vacuum test show a kinda low vacuum around 15 hg at around 800 rpm idle. currently initial timing is around 17* and total around 30, without vacuum advance. with vacuum advance hooked up its close to 50 at idle. check for vacuum leaks around everything and havent found anything. all vac ports that arent used are capped even replaced the hoses that went to the tranny modulator valve just to make sure, it had a kink in it. vacuum is still at around 15hg at idle. with it set this way we were able to get a little bit of horse powder back out of it, but you had to baby the throttle to do so, slowly increasing the throttle would get it going and you could actually pull in the secondarys for a little boost, kinda caught me by surprise. but still its almost like riding a 5hp go kart, a really big one haha, although at this point that would be more fun. also it smokes from the drivers side tail pipe a very little bit after you are hard on the throttle at in park, kinda grayish in color, not white like water. but its pretty faint, but only from the drivers side exhaust, true dual exhaust.
so we are kinda at a stand still at what to check, firing order has ben checked and check a million times and plug wires are on the correct post of the dist.

the age of the dizzy is a factor and the edelbrock carb was use when he got it, age unknown as well,

would the crank being advanced cause these issues?
do you have to time the spark differently when the crank/cam is advanced/retarded?
bad accelerator pump in the carb?
failing coil or ignition control module in the HEI dizzy?
Bad distributor period?
bad fuel pump?

any ideas would be appreciated, our lack of experience has us learning some things by trial and error but we are at witts end and its tying up space in my garage.

also the cam was installed dot to dot, crank timing mark at noon and came at 6, and a timing tape has been installed on the balancer/damper.

again any help or ideas will be greatly appreciated, thanks

matt.
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