Ok so i think it's my distributor. I have some weird cheapo one called procomp I think? I forget off the top of my head. But i set it to 35 degrees total timing at 3000 rpms and my base timing is 19! And that's with a stock cam. Isint that way to advanced? And I think that's why when I turn it ill either get crappy low end and good high end power or good low end and crappy high end power. Also I set my primary jets from a 72 to a 68 and I still get no surging at 65 mph like the Holley tuning guide said. I guess I have to go lower but if I'm not getting surging at 68 and the guide says to come up two steps from surging wouldn't my next logical jets be at least 65's? That seems super low. I also put in a 105 power valve. I still have less power then my old 305 and horrible gas mileage.... Any ideas guys?

 

Sorry guys I thought you were talking about something else.

 

The est? Did you even read any of the thread before you posted?

Procomp distributors are pretty much junk. When you set total timing at 3000 are you sure it's still not advancing after that? You may have like 40 or 45 degrees at 4000.
Don't worry about base timing. You can't really have too much and with a stock cam and i doubt it will ever fall to low.

As far as the jets try 66 if they surge then put the 68 back in if not try 64.

Do you have a vacuum advance on the distributor? If not that's like another 2 or 3 mpg your not getting.
Those procomps really are junk, try and find a buddy who has an old hei laying around and use it.

 

Are you confusing your base timing with your initial? Base timing at 19* won't even start the engine, it would kick back. 19* initial is fine, as is 35* total. Where the heck are you in New Jersey, I will show you how to get it right...

 

I think you like MrPackstin are a little confused. There is no computer controlling the engine. It is a holley carb and a regular non computer controlled distributor. Base timing and initial timing are the same thing.

 

Seriously? You asked...

We set base timing with the vacuum advance disconnected, which is our base timing. We then hook our vacuum advance to a constant vacuum source, which is our initial. Whether a constant vacuum source or "timed" vacuum source, base and initial are not the same thing. This can be done with vacuum, or with voltage, and it needs to be done otherwise your timing is LOCKED. Why not disconnect the vacuum advance in your own particular setup and set your base timing to 19*, being that it is the same thing as initial as per you and see where that gets you. Incidently, ECM's need a spark reference as a base other wise the SA main table is completely skewed.

So... so much for base and intial being the same thing...

Perhaps you are the one who is confused lol...

 

... and for the sake of clarity for those who are reading along and can't distinguish between the two, those who run their vacuum advance distributor's with a constant vacuum port on the carb or intake manifold are REPLACING their base with their initial because the moment the engine is started the vacuum advance is already advancing, it does not mean that they are the same thing, they are simply bypassing the base and immediately starting with the initial. Some people prefer that method, while others prefer a timed vacuum port which has you idling at your base (no vacuum advance), but then switches to initial timing upon sensing engine vacuum.

 

I am just bowing out of this one...hope he doesn't blow it up, got to be careful who you take advice from. Good luck with car.

 

Bowing out of what lol? If you disagree then disconnect the vacuum advance and/or EST bypass wire for fuel injection and set your base timing to 19* BTDC, then plug the vacuum advance back into a constant vacuum source and/or EST bypass wire back in and see where you are in terms of ECM "base" advance. There is no "base advance", there is only "base timing". There is no "inititial base", there is only "initital advance". When engines accelerate the air entering into the cylinders gets there quicker than the fuel and spark, thus the reason we have pumps shots/acceleration enrichment and spark advance, as this keeps combustion where it needs to be and happy. Base is not initial unless you run initial during idle, but that does not make it base because your already advancing. Engines 101 my friend...

 

No No, I am with you on this one and aware of the OP's concerns. Originally, I stated "No...disconnect EST and set to 6* BTDC" mistaking EST for vacuum advance hose in this case.

 

I don't know who told you that but base and initial are the exact same thing same thing. It is the number the distributor is set to before anything is added whether its added from mechanical, vacuum or ecm.

 

alright so i figured out my issue. its not my timing, its not a pump cam, its not my secondaries opening to soon, its the size of the jets in my secondaries for sure. and since i have a sub-par holley 750cfm I cannot adjust the jets on my secondaries. what i found works best so far is putting the heaviest spring (black) in so the secondaries dont open for a while but regardless once i peg it the whole thing bogs and takes forever to get going. (and by forever i mean like probably 6-8 seconds to get from a rolling 20mph to 60mph) since ive put the heaviest spring in im able to give it like 60% throttle before it starts to bog and i think thats the best im gunna get with this carb which kinda sucks. there is a big swap meet coming up in the end of September in e-town where im gunna try and find a 650cfm dp on the cheap but im stuck with the 750 for now i guess. i really wish i did a little more research on carbs before i bought the 750. i never would've got it knowing what i know now. thanks for a the help though guys, the info i get on here is literally priceless and it saves me 1000's by just fixing or in this case tuning my car myself instead of taking it to the shop. ill post my results here if i ever get a 650. once everything is all said and done im gunna take it to a local dyno shop and see how she does. im hoping for 300hp to the wheels but well see..... lol

 

Welcome to this weeks installment of! THE THREAD THAT NEVER DIES!!! Hahaha just kidding but this carb is still giving trouble. I set the jets to 62's with still no surging. I'm not sure if I should still keep stepping them down or not. Also, the carb stumbles HARD when you stomp it. It almost stalls out if you really peg it. But once it works through that it pulls nicely. I have the yellow spring in there now which seems to be working nicely. Also, my timing is at 13 with no vacuum line hooked up. But like 30 a tilde with the vac line hooked up. And I know it says tune the air/fuel needles to highest vacuum but mine are only turned out 1.5 with a vac of 22. Is that normal? One other thing that is weird is my carb actually idles higher when warmed up. Cold it idles around 700. Hot it picks up to around 950. Shouldn't it be the opposite? Could my pump cam and jet be the cause of my problems?

 

The pump cam, not the jets.

 

You can play **** and ***** all you want changing cams and jets but at the end of the day poor atomization is going to kill your combo with a 750. Find someone to trade with or sell and get a 650.

 

depends, are you not going to get a cam and heads any more?

 

thats exactly why im trying to make my 750 work because eventually i am gunna get heads and a cam. my goal is this spring so ideally i want to make my 750 work for now. im going to put 60 jets in tomorrow and has anyone ever checked out this video? that is also an issue i am having. im gunna grind down that lever so it only rests on the pump cam and not the spring. ill post my results. just ordered a set of pump cams too.

 

well if you have the same issue it would cause a stumble. Did you try moving the pump cam to position 2, That might be enough to get it off the spring.
Also a 750 will tune out and work just fine on your engine. Especially if its a vacuum secondary. There is absolutely no reason your engine wont cruise fine on the mains of a 750. You will not have poor atomization or booster signal.

 

Even with heads and a cam a 750 is still too much carb unless you are spinning over 7000 rpms. I have no idea why so many people insist on over carburating

 

One other thing. When you are cruising, try doing it in forth on the highway instead of fifth. The higher rpm will make it run of the mains more rather than a mix of the main and the idle circuit like at low rpm.

A 750 is not to big for a cammed and headed 350. There is a reason why every single dyno session with a 350 or 383 when they increase the carb size from 650 to 750 and to 850 it makes significantly more power. And with the better boosters in the newer carbs it's not an issue with low booster signal at cruise and low rpm like it was 30 years ago.

 

you reposting something that is not the problem is not helping the op with his question. there a alot of poeple with mild 350's and 750 holley dp. myself included i know at least 6 with that setup, the whole reason i bought mine is when i was getting my stuff together from going to 305 to 350, i went around at the track and asked what the faster guys were running and that was it.

back on task, i dont think its whats in the vid because that would be an of idle stumble and you said its from like 20 to 80 when you stomp on it. that would be past the part of the throttle. to me that seems like the secondaries are the issue. i just dont know anything about vacuum secondaries. to me it seems like the jets should be adjustable and i cant figure why they wouldnt make them adjustable. thats the reason i got my 4150 with mechanical secondaries, it easy to see in the pit if its opening because if it works when you open it by hand its going to work when you use the petal. then all you have to worry about is jets. you ever take a look at the plug after mashing the throttle and cutting off the engine?

 

after thinking about it more maybe it is the cam not having enough duration to take up the time that it takes for the secondaries to open. like jabot said there is different holes on the stock one or you could get a even longer duration one and change it

 

Just because a lot of guys do something it does not make it right. I wish him the best of luck but a 650 DP will support a 400hp engine all day and when back to back dynos are made most 350s reving under 6500 rpm only gain 2 or less HP from a 750 and often drop 10 or more tq down low.

I hope he can tune it for drive ability on a stock L98 but a better course of action would to get a 650 or 600 cheap, rebuild it then sell it when he gets the new parts.

Even if he builds a monster that needs a 750 he will have to re tune so he will most likely save time and hassle.

 

Right on holeys website the cutoff for a 650 to a 750 is over 6000 rpm in a 350ci. Over 6000 you go to a 750. And they gain much more than 2hp and don't loose low end torque. I have no idea where you are coming up with these numbers.
I dyno tune multiple carbed cars a month for years and have never had a problem getting a 750 to drive and perform correctly on any 350 engine and is no more difficult to tune than a 650 on a 350.

 

Are we going racing here or trying to get to work in the Morning ? I am running a Old school Barry Grant Mighty Demon 750 on a very warmed over 358 with nitrous
mechanical secondary's no choke for a DRAG-RACE summer cruise to car-shows machine. for a stock or close to stock 350 manual transmission car 600-650 double pumper is the best way to go period .. for bolt it on and run .. you can tune a 750 but why ?? The best thing about pro-comp parts is they make your wallet fit in pocket better cause you have less money in it MSD--MSD--MSD

 

Because he has it already and there is no reason to buy another carb!

yea nothing worse than buying crap procomp parts and having to buy the good stuff anyway.

 

i misspoke when i said pro comp. i meant "proform" http://www.summitracing.com/parts/pro-66941bk/overview/ it is a real bottom of the barrel piece that i bought when i was broke and needed my car up and running for work. i know this is an expensive hobby but sometimes you just dont have the cash yanno? lol

 

my ultimate goal is to have it more like a weekend worrier type ride. still 100% streetable and that can cruise all day but still have some power. for now its my daily driver until i can scrape enough cash together to get something else but it will have to last me through the winter thats for sure. I jumped the gun on what I thought was a good deal on my 750 off ebay when I really didnt know what I was looking at because I was so used to TPI and so new to carb. what I saved in money I've more then spent in headaches and time. Live and learn I guess. Going back there is no doubt I would have a 650DP with electric choke on my car now but I have to work with what I have . (if you guys know anyone that has a 650DP thats looking for a 750VS let me know!!! lol)

 

Proform is not bad. I use their carbs all the time and never had an issue. I actually prefer them over holley for the price. And quick fuel carbs actually have proform parts in them. I have only used that distributor once and didn't have an issue. It's the same as any other hei distributor.
Believe me I know about not having the cash. But one thing I have learned over the years from myself and watching others is most of the time you are better off buying a good used piece rather than say new procomp or some no name piece on ebay.

 

Not trying to get you down just help. I know that often used 750s sell for more than 650s.

You may be able to get a 650 and rebuild it and sell the 750 for more than the rebuilt 650 cost.

I just helped a friend do that with his 750. Cost us $100 to buy the carb and the rebuild kit and then sold the working 750 for $170

 

You got that right, take your time and look for good deals. Look at craigs list daily and browse the wanted for sale area here. Usually better prices than ebay.

I have got some amazing parts for my cars and bike by being patient and looking around.

I got a nice and completely rebuilt WC T5 for $500 and sold my NWC used unit for $350

 

update!!

got my pump cams in! threw the blue one in but it dint help much, put it in the second position, or second screw hole and it was a noticeable improvement. still bogs in the beginning but not to hard. idle is fine and i think full throttle is fine cause after it bogs if i have it pegged itll start burning out and even squeak the tires in second. but the transition from idle to particle throttle is pretty jumpy. still drive-able but really annoying. and its right where you would normally have the pedal to accelerate normally so i feel it every time i stop and then have to go again. the only way to avoid it is to give it like 70% throttle until i get up to cruising speed which forces me to look like a douche driving around town and wastes my gas. my question is: which pump camp should i put in now? i personally think its the squirters and not the pump cam. if i had to step down my jets from 72's to 60's would the squirters also need to be smaller to even everything out? also, just throwing this out there. i have unburned oil coming out of my tailpipe. any idea how that could happen? its a fair amount, if i leave my hand by the pipe at idle for maybe 5 seconds i'll have 20-30 specs of oil on my palm. Thanks for all your help so far by the way. Were so close!! i owe you guys a smokey burnout video when I finally get it running right. hahahaha, thanks again!!

 

Try a bigger squirter now to get the shot in the engine sooner. But there is definatly something else wrong, probably with the carb internally. A stock 350 should not need that much pump shot. And no it is not due to a 750 having poor atomization on a stock 350. That is just not the case. 25 cfm more per barrel will just not cause that issue period.
After doing a bit of research there seems to be a bunch of issues with the street avenger carbs and fueling and bogging. In some cases nothing has fixed it and I think that may be your issue. I bet the reason the person was selling it is because they had the same problem. Plus you bought it used so who knows if there are other problems.
If you can I would just get another carb and call this one a loss. Pick up a nice 650 dp and call it a day.

 

Are you sure it is oil? Water and gas get dark like oil from carbon in the exhaust.

At this point I would try any other carb just to see if it makes things different. Rule out the carb as being bad.

 

huh? I've compared procomp dizzy's side by side next to a $300 'name brand' dizzy, and they seem find. No wobble or play in the shaft, pickup looks good.

What exactly is "junk" about these distributors?

-- Joe

 

Let me know how they are after 50,000 miles.

 

Well what exactly do you expect to happen to it? It's an aluminum shaft turned on a lathe.

If you have no technical or engineering to add, simply say "I don't like China". But to call it junk without backing anything up is somewhat absurd.

-- Joe

 

From what I have seen around the forums the wiring is the weak link not the distributor.

 

Ahh. That makes sense. I have not had a problem with mine, but I suppose if the module crapped out I'd replace it with a good module. I think I paid $45 for this billet distributor and it's as nice as MSD/Accel.

But as far as the distributor itself I mean, if it's not machined improperly on day one, I can't see it suddenly becoming a problem down the road. It's not that complicated of a design

-- Joe

 

I never said I do not like China. I have and will continue to use quality parts from china.
I have only personally seen 2 of these on a car. One distributor was about a year old and all the weights were rusted stuck. Now this isn't exactly that uncommon but not after only a year. The other was a few years old and had almost 50,000 miles on it and the internal seal went and there was oil in the top. This was probably due to the bushing wearing but it was never checked. Just thrown out.