So it begins. Alright, recently I put a set of 882 heads and a B&M 144 on my car. Today was the first day I had the chance to do any real testing due to vacationing. My car now runs at 230-250 fans on all the time via switch where as it ran 200 before. Would colder plugs help this maybe? The sc started killing out my engine. Literally under 1500 rpms it would just act like it was binding and kill out. I hadn't touched the huge bolts so I don't believe it was a tightening issue. Especially after running it hard seeing as how I was far from the house it worked it's self out. It now idles smooth and runs good, no binding or dieing/surging when slight load applied. New problem is it runs about 20 vac at idle, half throttle results in 10 vac, and WoT will net 5lbs boost after 2.5K rpms. According to the pulley formula on my 305 I should be netting around 9. Have yet to see it reach above 5. I have no off the line power at all. Literally can't even break the tires loose. Use to be able to with ease on my N/A setup. Now if I floor it from a dead stop it just bogs, then picks it's *** up gradually. Car runs beautifully at WoT, and normal driving now. Just no torque what so ever off the line, bogs off the line, maximum of 5lbs boost and extreme heat output. Any Ideas? Carb is a holley 670 street avenger. Never had any problems out of it. bought it brand new. Vac is 20 at idle. Oil psi is 60 under load 30 at idle hot, rockers are adjusted. Timing is advanced to 10 degrees base.

 

i am thinking possibly you destroyed the blower...

with you mentioning it being tight beforehand..and wanting to kill the motor..its all i can think of...especially since after you went and beat on it..it loosened up..

im not sure if those b&m have the teflon tipped rotors or not, but its possibly you wore the blower out, tolerances got sloppy...and its just not building the boost it should because of those clearances...

its all i got man! if i were you, id yank the blower apart, and look at the tips and lobes on the blower, check for galling/excessive wear.

 

You can check for lobe-to-case contact just by pulling the carb, yanking the blower and looking while spinning the blower over by hand. Look for any places on the rotor tips that have obviously had metal scraped off of them. If there was contact it will happen first between the lobes and the lower edges of the inside of the case. Doesn't sound like the problem, though. Rotor-to-case contact sounds like a hundred guys with Lousiville Sluggers hitting the blower at the same time- an unmistakable sound once you've heard it the first time.

Sounds like either just running too lean or inadequate ignition to keep up with a boosted application.

Yes, you should run colder plugs (a step or two colder than stock is fine for a street application) but it won't affect your engine's running temps. It does take a little more cooling system than a stock engine.

 

You increased flow, and are now running 1.94 intake valves, correct....?

Sounds like your timing is off, and the carb needs to be adjusted....

 

Am I reading this right....?

 

Yeah, advance is 10 degrees. I don't believe it was a lobe contact due to the fact it didn't sound like metal to metal. It sounded like a belt screetching or if you were to throw something in the bades that spun around with them like Styrofoam type sound. It was only binding under load. That all worked it's self out tho. Weird I know. As far as the valves i'm running whatever was in them stock. They had a 3 angle valve job, new springs and seals. Thats all i know about them. Use to run on my s-10s 350 fine. Made good power. Plugs don't indicate a lean situation. Holley said since a 700 cfm carb is what's needed for a stock 350 a 670 should be enough for my stock 305. Makes sense if you ask me. As far as the cooling system goes. It's a single fan setup hard wired to an interior switch. I bought a high flow water pump and put it on also. drpped down from a 195 to a 180 stat. Still see high temps.

 

The car runs beautifly now. Just hot and no low end what so ever. It picks up it's *** after 2500 rpms at wot. Just nothing what so ever before that.

 

I know it's making more power high up in the rpms cause when I hit 3rd racing my buddies lt1 car my clutch slipped pretty bad. His lt1 still pulled my car by 2 cars by 70mph tho. That's not much different from before.....

 

882's come with a 1.94" intake valve, much larger than the stock 305 intake valve your engine came with, and when you increase flow, you decrease psi. Take two straws, place one in your mouth and take a deep breath through it. Now, place both straws in your mouth and take a deep breath through both. Much easier the second way, right? That is because you decreased the amount of pressure needed to fill your lungs with air. As for a 10 degree BASE, that is way too much timing, as well as the reason why she is a dog off of the line, not to mention the reason why she is overheating. Pull the vacuum line off of the distributor, and set your base timing to 4 degrees....

 

Ok, i'll go change the base timing and pull the advance, i'm assuming plug it off too. i'll run it and let you know what's up. give me 10 to 15 minutes.

 

Ojk, well it seemed to run a little better and cooler like that. Still couldn't break the tires loose. Only ran it for about 2 miles then had a new issue. The gasket between the blower and manifold blew out. Completely on the drivers side..... needless to say it was a rough ride home. Any idea where I can get this gasket?

 

Btw, according to flow charts, even tho my old heads had smaller valves, they flowed more. 20cfms more intake side actually. I've noticed the 882's run out of breath about 5000 -5500rpms, where as my 416s shifted about 6k.

 

4-degree base is where you want to be, and you will gradually increase it until you find the engine's sweetspot, but any more than 6-degrees will more than likely result in an overheating issue. A vacuum leak will cause hesitation and bogging, and being that your gasket blew completely out you were more than likely running too lean at idle this whole entire time, which will effect your idle to part throttle transition. Were you always at 20" of vaccum at idle, or just after you installed the blower? If you can't get your hands on a new gasket, I would just use some quality silicone based gasket maker for now (let it set), and once everything is buttoned up, check for vacuum leaks, but you'll eventually want to get another gasket once you get the chance to. You hooked your vacuum advance back up after you set you base timing, correct....?

 

Flow characteristics change when boost is presented into the equation. In a naturally aspirated engine, port velocity is always the key. But when it comes to boost, the size of the valve is what really matters....

 

I see, didn't know that.

 

And yes, it always made 19-20 vacuum at idle. a little throttle drops it to 10, almost half drops it to zero, and wot makes boost.

 

I can run to advance and get the gasket now if you'd think they have it. Or napa, or is it a special order type deal. And no, I didn't hookthe vacuum advance back up. I thought I wasn't supposed to. My bad.

 

Anytime you open up the intake path for the incoming air, your going to decrease the amount of psi needed to fill the those cylinders, as a larger diameter will make it easier for the added pressure to do its job. Whether you open up the ports, or literally change the size of the valves, its going to be effected one way or another. Just like with oil pressure, when you spin a bearing, pressure will drop, because a spun bearing creates more room for the oil to get through....

Here is the gasket....

http://cgi.ebay.com/ebaymotors/New-W...Q5fAccessories

 

calling advance. the Holley site says they carry them.

 

Well that's that. Have to order it from holley. I'm leaving tomorrow for work so I guess I'll just have to finish this up when I get back in 20 days. On the timing. It's currently set at 4 degrees advance. Now I should hook the vacuum advance back up correct?

 

Oh yes, you need to hook the vacuum advance back up and not keep it locked, as that is the only way to balance your air and fuel w/spark as RPM's increase. With a 4-degree base, and no vacuum leaks, that engine should pull extremely harder than it did before you installed the blower, and if it still lies down from the getgo, then it has to be somewhere in the carburetor setting. Everything else is okay though, eg; spark plug gap, spark plug wires (no arcing), firing order, and coil, correct....?

 

yes sir. It runs great for normal driving. Just wasn't boosting like I thought it should and had no low end. Rtving at the moment. How long should this stuff set?

 

Alrighty, 4 hours later. I just ran it with the new timing setup and adjusting my mixture screws. It's a much happier first gear. Difference is night and day. Can't wait to go to the track next month!

 

Im glad you have worked the problems out!. I would seriously replace that RTV with the original gasket. be careful on those big bolt torque settings from the blower to manifold.

 

Fine work, sir.

My experience with these little mini blowers lines up pretty close with yours. Not much timing advance is neeed or wanted. I run 8:1 compression (but on a larger motor) and still run only 8* of initial advance (28* total advance fully revved up at WOT). It doesn't seem to like more than that for making power and I don't want to push the limits and risk detonation.

I also run 16* of vacuum advance on top of that for part throttle operation. Originally I ran it to a full manifold vacuum source on the carb (worked fine) and then switched to a fitting below the blower (boost referenced, basically, but only for manifold vacuum, no retard under boost- just goes to zero like usual). Also works fine- no real difference I could notice, but it's now guaranteed to never pull in even the slightest amount of vacuum advance under boost.

My idle mixture settings were pretty similar to when I ran N/A, but my carb was already set up with a richer idle system to start with. Still wanted a little more fuel with the blower at idle and light throttle.

Still, it's odd you aren't making more boost and having to get above 2500 to see it. My combo makes almost full boost at any RPM, even way WAY down in the RPM range when I used to run a stock stall converter. When the pedal goes to the carpet it instantly reads 5 PSI and works it's way up to maybe 5.5 PSI in the upper RPMs. Low end torque is huge and instantaneous. Not brutal lke nitrous, but like the engine's 100 cubes bigger than it really is in the low-mid RPMs. However, it definitely starts to run out of breath around 5000-5500, even with my good flowing AFR heads. The ancient blower design just gets very inefficient in the upper RPMs and isn't moving a ton of air upstairs in the RPM range, despite the boost indicated on the gague. I don't shift over ~5700-5800 for that reason. With a stock cam you probably wont want to shift even that high.

My motor is a 383 with an old set of AFR heads and a slightly over stock cam (214/224 @ .050). To boost against the larger cubes I had to use a larger 7" bottom pulley (vs. 6" stock) in combination with the stock 3.07" top pulley. It still only makes about 5 PSI of boost, but that's plenty on a larger cube motor to turn the car into a very traction-limited ride. Hooking the tires anywhere below about 30-40 MPH is basically impossible, no matter how slowly I bring in the pedal.

 

Ivelostcontac - Glad you got it dialed in...even though I'm having a hard time understanding how you did it..
Street Lethal -I don't get this....does the above mean 4 to 6 degrees retarded mechanical timing ...or 4 to 6 degrees of mechanical advanced timing?? -Which is still low unless he's adding more advance by hooking up his vacuum advance canister to full manifold vacuum to add more initial timing (which makes sense)?? Is that what he did, or am I missing something...I'm confused..no pun intended (maybe)
Hey Damon - I didn't realize you were running the vacuum advance at full manifold vacuum and not ported (timed) vacuum. So when you are running it on boost referenced (on the intake) - the vacuum advance diaphragm has no issues going from vacuum condition to pressure? I wasn't sure what would happen putting 4-5 pounds of pressure on the advance...I thought about trying it myself.

 

His timing was set at a 10-degree base and he was overheating, which should immediately tell you that he might not have been running a ported vacuum line for the distributor, and full vacuum at that high of an advance of a base would have more than likely caused the increased temps. Since full manifold vacuum sounded like it was being used, 4-degrees is where he wants to be, initially, so he can then start to dial everything in from there. If he would have set base timing to 4-degrees, but then told me that he was still continuing to overheat, then it would have been a different story. Ported vacuum as far as I'm concern was strictly for emission purposes, and although there are advantages for both, from a performance perspective, I will always lead towards a full manifold vacuum source....

 

Sorry Street Lethal, but Running at a 10 degree advanced base and overheating doesn't tell me much. Add 10 degrees for a manifold vacuum source advance and that's around 20 degrees advanced - or 10 degrees initial depending on how the vacuum can is set up. Neither seems unrealistic to me depending on other things.

-I run 16 degrees initial mechanical advance myself with no overheating whatsoever. But I presently run a ported timed vacuum, so nothings added on at idle - I wasn't sure how he was running his since he didn't say.

From what I've experienced, retarded timing at idle causes overheating and until the timing is advanced to the point of pinging or detonation very little extra heat is generated..you need to be up to, or past the point of detonation before overheating occurs due to over-advanced timing.

You were telling him to set his timing at only (-4) to (-6) degrees of timing at idle...since you use the (-) sign before the numbers, I didn't know whether you were saying "minus" 4 to 6 degrees, or 4 to 6 degrees BTDC.

That being said, I agree with you, there's advantages to both souces of vacuum for the advance. I may try boost referenced manifold vacuum/pressure myself to see if there's any difference. I was always concerned with pressurizing the vacuum advance instead of it being under a vacuum - I know they aren't designed to run with pressure on them, but if it doesn't hurt anything....

 

You sure you weren't intending on that pun earlier on? Nobody is claiming for such an assessment to tell you as an individual. It is something known as the process of elimination, which is why I already pointed out in reference to your first query that if the overheating persisted, then if would have been a different story, but it didn't. That being said, he was obviously running too much timing....

He is running a 670 Street Avenger, which ideally comes with three ports if I remember correctly. One of which is ported vacuum, and the other two are full vacuum. We can sit here all day and speculate as to which one he was using, but again, had the overheating issue not been resolved, then we can continue this particular discussion, but apparently it did. Many people are unfamiliar with ported vs full, and rather than sit here and explain it to him, because the guy obviously just wants to get in the car and enjoy it, I told him to pull the vacuum advance and set base timing to 4-degrees (notice where the dash is being used after the 4, but I will get to that in a second)....

Both too much advance, as well as too much retarding, will cause overheating issues, but there is more to it than just that, as the amount of rate for both mechanical and vacuum advance come into play as well. Everyone is looking for that happy medium, and every engine is of course different. That being said, the majority of us usually work with only one side of the timing tab, the advanced side, as there is more of an area to work with on that side for a reason...

Did you just say that I used the "-" before the numbers that I quoted? Are you sure about that lol? I most certainly used the "-" after the numbers I quoted....

Just use a check valve if your worried about pressurizing the advance canister. We had similar issues running vacuum secondaries with a turbo, and were concerned that the added pressure would force the secondaries closed....

 

OK then Street Lethal, I sense you are taking my responses to this post as "calling you out" , which I'm not intending to do whatsoever. I know you're pretty well versed on most engines in general. I'm not used to seeing (-) marks either before or after the numbers, so I was looking for clarification on that, and there's really no more to look into it. Call me slow (guess you did already) - but I was just trying to understand the whole thing...

I have no idea how a "Holley Street Avenger" carb is set up since I don't normally goof around with vacuum secondary carbs. I'm sure you know already that Holley and Demon DP's have both sources of vaccum available also.

Did you use a check valve on the advance with the turbo because you had issues, or was it to prevent any possible issues?

 

Don't take my words the wrong way, as we've both been on this website for a very long time, and it's hard to tell when somebody is being friendly or sarcastic, and my words are definitely being used as friendly....

I was forced to use a check valve before the turbo was even installed when we were still running w/the carburetor, which is something that I really should have pointed out. Fuel had a tendency to work its way into the distributor cap because of a bad advance canister (or so I was told, which now I believe it was just moisture), so we were forced to use the check valve. By the time we installed the turbo, the check valve was already on the vacuum advance line, and it worked really well. Not so good for the secondaries though, as once a particular amount of boost was realized, it started to break up pretty bad (this was with a carb hat). I was told that I could eliminate the check valve for the secondaries by using a carb enclosure box, but by that time I went back to TPI....

 

That's why I originally hooked it up at the carb- so it would never see pressure against the diaphragm. I just got a bug up my butt one day and tried it down on the intake. So far, no problems (almost a year). I only drive it around occasionally on the weekends so I don't know if it would ruin the vac advance diaphragm over long term daily use. Maybe eventually it would but those little suckers are pretty tough.

 

Just out of curiosity, should I change where I have my Timing advance vac line run to? It's currently ran to the port on the left hand side of the carb obove the fuel rail near the front bowl assuming your looking at it from the front of the car. Passenger side. Small port. There is another port down near the front of the carb near the base of the carb. I have my Vac controlled air vents on it. Break booster on the big port. I think there is another port capped off somewhere. At the beach, (myrtle) can't check at the moment. Currently have Boost guage hooked up on the manifold.