Damon

Temp sensor in the head shouldn't make much difference vs. in the intake. I've heard of maybe 10-15* difference but nothing more that that. If you're sure it's not actually overheating then I'd be guessing you've got some air trapped in the system. Beyond that I'd be looking at the sensor or the wire running to it. Grounded = full hot.

Confuzed1

iTrader: (4)

Correct me if I'm wrong, but doesn't "Grounded = full hot" - even when the engine is stone cold?
- It's not like that. The gage is reading that it's cold - when it's cold. As said above, I don't think it's overheating because it doesn't boil over after I shut it down when it says it's 260 pus degrees....

I just picked up a cheapee mechanical temp gage from Autozone and I'll compare against my factory gage.

Damon

Yes. I'm saying the sender could get to a certain temp and then malfunction to "fully grounded" or some other odd thing might be going on that causes erratic behavior.

Confuzed1

iTrader: (4)

Well, I proved some odd thing is happening. I got good news and bad news...

Good news: I started it up, and when my mechanical temp gage reads 210 degrees, my factory gage is already in the red (260 degrees +) - so the factory gage is off at least 50 degrees in the upper range for some reason. So I know now for sure my factory gage is junk.

Now the bad news: My brand new Jeg's electric fan control kit didn't start the fan up at all, and I had to shut the engine down at 220 degrees before it overheated. I may just post up in the "Product Review" board about this. It only worked once when I first started the engine for break-in and now it doesn't work at all. This is literally the 4th fan control kit I've had on the car, and I can't seem to find one that is the least bit reliable. It's supposed to turn the fan on at 200 degrees, off at 185 degrees when using a 195 degree T-stat.....like I have.

It's gotta be a bad fan switch right??? I disconnected the wire from the switch and grounded the wire - I heard the relay click and the fan started right up....

JohnBlazeLTZ

Hey there...
I have a Flex-A-Lite Universal Monster fan on my Caprice. It has a nice fan control kit that relies on a radiator mounted T-Stat to get the fans to kick on and off. (I don't know if you have tried that one yet.) One thing though...beware that when mounted in that way...the engine is getting much hotter then the rad. at least is what was explained to me a handful of times. I have had to set mine at around 180* on the stock Temp read out to get it to come on early enough. So these fan control kits with a radiator T-Stat can be as much as 30-50* off in some cases.

junkcltr

iTrader: (1)

There are different coolant temp. sensors with various ohms. Make sure you have the right sensor for your gauge. If it is not correct then the gauge will read incorrectly.

For the fan setup I use a Dodge (van/minivan) coolant temp switch. It switches on at 200*F. The switch turns on the coolant fan relay. I picked it out of the catalog at the local parts store (real parts store, not Autozone, PepBoys, etc).
It screws right into one of the coolant holes on the intake (performer RPM).

jwscab

I've used a GN fan switch, which might be a little hotter than you want, but less so than a factory switch.

I also used the painless temp switches, and they seem to be OK, but a little pricey.

good tip on the dodge fan control, junk.......

Confuzed1

iTrader: (4)

I'll just go ahead and pick up a temp gage sensor at the Chevy dealer then and try it. (so it should have the proper OHM range)

A dodge fan switch huh? Sounds like it's in the right range for mine, but I'm a bit concerned about installing it in the intake though...with a 195 degree T-stat, the fan would never turn off would it?? I mean, the T-Stat opens at 195, temp increases to 200, then fan comes on and cools engine below 195 degrees, T-stat closes.....heats back up to 200.....I don't get it.

Confuzed1

iTrader: (4)

OK- yet another new problem. I have my initial timing set at about 12 degrees advanced. it idles well, but when I gave it a good blip of the throttle, I heard a VERY LOUD - BAM - through the carb...I mean it sounded like a gun went off!! It was so bad it shut the engine down!! Luckily it did start right back up and it doesn't sound like it damaged anything....

Should I try advancing the timing more?? I'm almost afraid to do anything. I know the firing order is right since it idles smooth like it's firing on all cylinders. (And I checked for the heck of it)

I don't want to ruin this blower! It can't be good for it. It has a 750 DP Holley on it, and the squirters seem to shoot a nice stream into both sides.

Car sat for a year, but I put fuel stabilizer in the tank when I parked it because I knew it would be parked for a while....

jwscab

almost sounds lean to me....it's hard to say....most times, a severe lean will be a pop, where a severe rich will basically just 'chug' bad.

check the squirter pump cam for any play. there shouldn't be any. you might also want to change the pump cam to shoot fuel sooner. if it's set up incorrectly, like most people do, they put that 0.015" clearance on the pump arm at rest, which will cause a bad lean spot. the 0.015" clearance measurement is meant to make sure the pump arm doesn't jam the diaphragm at full throttle, that's when the feeler guage is used. I don't know if that is your problem, but I see it all the time, just pointing that out. at closed throttle, there should be NO slack in the pump arm.

also do you have vacuum advance or mechanical advance in the distributor? vacuum will drop timing as you crack the throttle....did you check initial with the vacuum disconnected(if you use it)?

Damon

Agreed, it does sound like you got a lean "pop". Obviously, that's very hard on a blower since it's basically a big one-way valve into the engine.

Accelerator pump would be where I'd look first, especially if it revs smooth when you open the throttle slowly, but pops when you snap it open quick.

Confuzed1

iTrader: (4)

jwscab:
- Yeah, I think it's too lean too. As I said above, the squirters seem to shoot fine, and there's zero play in both arms with the throttle shut. It's a "Pro-Sytems" 750 carb that was set up originally when the engine was still N/A. I had just bumped the jets up to 76/86's and this happened. Doesn't seem to jam at full throttle. Had the vac. advance disconnected when it happened. Sounded like a M80 went off!!

Damon:
- Yes, air doesn't flow very well out the top of the carb with the blower on, and as I said - I DON'T want to kill it!! You described it right though...if I transition the throttle smoothly it doesn't backfire. But if I blip it - BAM!

I'm seriously thinking about taking this thing to a dyno tuning place that has people the have dealt with supercharged cars to get it set up right....I afraid I'll hurt it trying to tinker with it, and end up spending just as much in carb parts, time etc. when it's all done anyway. Sound like a good idea, or am I going overboard you think??

EDIT: I've been thinking this out for awhile (yeah, I'm slow) and I think I might know what's possibly going on, but I'm away from the car for a bit working so I'll run this by you experts out there before I get home to try it....maybe it's just a theory, but......

-I don't recall it backfiring when I had the PCV disconnected and plugged. There is a vacuum port on the back of the blower that is for constant vacuum, and just before it backfired, I had connected my PCV hose to it. There is no connection large enough on the intake to connect the hose to, so I figured hooking it up to the blower port would do the same thing....but maybe not? Maybe I'm pulling too much air in through the PCV causing a lean condition that resulted in a backfire? What do you think???

Damon

You sure the port is for vacuum? Remember that it'll pull vacuum even below the blower while you're just idling. If the port is down low, below the lobes, it's a boost/vacuum port. If it's up above the lobes it's vacuum only.

Easy enough to try out your theory, though- just cap it again temporarily and see if the problem goes away. A properly functioning PCV system shouldn't cause this kind of problem, but as a diagnostic aid, try out anything that comes to mind and might point you in the direction of the real problem.

Confuzed1

iTrader: (4)

Yes, the port is above the lobes, so it's vacuum. I figure on a N/A car, when the throttle blades are closed such as at idle, vacuum at the PCV is at it's highest. If you blip the throttle open, vacuum at the PCV drops until engine RPM's increase. I don't think it's working that way when I plug the line in above the lobes on the blower - correct?

flrtin1

Confuzed....how warm was the engine when it backfired?

Confuzed1

iTrader: (4)

I really didn't look, but I'd say less than 220...

flrtin1

Well if the engine/intake temp was not up to close to operating temp (180) that would be a fairly normal thing to have happen with a roots S/C especially if you are not running a choke setup......you will find that when you start the car you need to sit and let it get up to operating temp before you drive it or it will be sluggish like that......not saying you dont have another problem just let it warm up before you try to trouble shoot it.

bluechev

damn i want one!

Damon

Well, I got a functional PCV system on my roots-blown 383 and it works just fine. Anywhere above the lobes functions almost exactly like a N/A engine. It's only below the lobes that thing can fluctuate between vacuum and boost.

flrtin1

Yep Damon is right on.......any port under the throttle plates and above the rotors will work.

Confuzed1

iTrader: (4)

Thx Damon....this has me really frustrated. I'm gonna hook the PCV hose to the back of the carb, the power brake hose to the upper port on the blower. I think I have some kind of lean issue since it is a "pop" if you want to call it that. To me it sounds as loud as a gun going off. Gotta be the carb, timing or both. I'm gonna damage this thing fooling around.

I just have to face it....I just don't have all the testing equipment, carb tuning stuff etc. that I really need to play with this thing plus, I'd spend numerous hours trying to get it right (I'm a rookie at blowers) -all while risking damage to the engine/blower. I'm normally not the type of guy that takes his car to a shop for repair, but in this case I'm going to....I just have too much $$$ wrapped up into this engine to skimp out now.

The same machine shop that did my engine machining got a Mustang chassis dyno installed this past year. I've asked them to tune it for part/full throttle, set the timing curve, and dyno the thing next Thursday. I also requested I receive all the A/F, EGT, timing and carb tuning info, etc. for anything they change on it. They say since it's fall and everything has slowed down for them, he'd give me a "good deal". They figure 4-6 hours to get it tuned......We'll see.

So far as my temp gage goes, I just went to NAPA and paid 38 bucks for a new gage sending unit, and it's still not reading right. My mechanical gage is reading 195 degrees, my old factory gage reads 240 degrees. There has to be something wrong with the gage itself. I originally went to my local GM dealer for a temp sending unit, and they want $72.60 for one!!

I'm picking up a new 4" steel cowl hood for it tomorrow. It only took 7 weeks for it to arrive....

Confuzed1

iTrader: (4)

Allright guys....I've beem thinking and researching pretty hard to try and figure out what all this backfiring is all about. I installed a new Accell 5200 series street billet small cap distributor on the engine along with the blower. I read the instructions on the advance curve it comes with, and here's what it says:
It also says:
Now, I've always read on here that your mechanical advance should all be in by around 2800-3200 RPM's, and have a max of around 32-36 degrees total (initial plus mechanical) so is my advance all goofed up for my car causing this backfiring??? I never changed the factory setting.

Call me slow, but I just can't figure out the chart Accell has on their instructions on how to select the proper springs for the advance curve. It throws me off when they say "Set Initial Timing at 1,200 RPM" or 1400 RPM etc....what do they mean by that?? I had my MSD figured out, but these directions with the Accell I don't get.... Where's a good starting point for springs/stop bushings if my initial is 14 degrees?

Here's the distributor I have: http://store.summitracing.com/partde...5&autoview=sku

jwscab

I didn't see where the instructions said to set initial at 1200 or 1400 rpm. They made mention to intial timing at 900rpm, which sounds about normal.

you have some conflicting information in your last post. what do you mean by 'never changed the factory setting'? factory setting of what?

the curves are pretty straight forward. each chart shows you how fast the timing comes in based on the springs. each horizontal line corresponds to the limit of timing with each bushing (blue, black, etc). so the lightest spings will move the advance the fastest, the total timing however is determined by the bushings.

I'd probably set base(initial) timing to about 10 degrees at whatver idle is, leave no stop bushings (as delivered from factory), and put the lightest springs in. this will give you around 32 degrees total timing by about 1500-1700rpm.

I never got a clear answer, are you using the vacuum advance?

Confuzed1

iTrader: (4)

-Thanks for the reply jwscab!

Open the PDF file for the instructions. Figure 2A through 2D on Page 2. In the box at the upper left inside each figure (or spring combo) on page 2 it refers to, for example on figure 2D "Curve w/2 Heavy Gold Springs - set initial timing at 1400 RPM's" - I don't understand that. Do they mean that with those springs, it will not start mechanically advancing until that RPM or what? -BTW, that's what I meant by the "factory setting". My distributor came out of the box with 2 heavy gold springs installed with no bushing like figure 2D. I have not changed that. Could my advance be coming on too slowly causing it to backfire??

I do understand that the lighter the spring, the faster it will advance since they counteract the advance weights. The bushings limit how far the mechanical advance will move since it limits how far the weights swing out. With no bushing, it will move 20 degrees. (allows weights to swing out as far as they can go)

With a black bushing installed, it'll only move 16 degrees, etc. (Page 3, Figure 3) . So - if I set my initial timing at say, 14 degrees BTDC, and I use the black bushing, my total mechanical advance will be 14+16 which will equal 30 degrees of total mechanical advance correct??

And yes, I do have a vacuum advance, and I plan to use it. But from my understanding of that, it has no bearing on advancing the timing when I tromp on the throttle. It advances the timing above and beyond whatever the mechanical might be at that RPM under part throttle/light load operation. That's why I have not fooled with it yet. I haven't hooked up a vacuum hose to it so far. When I do, I plan to hook the hose into the "timed" vacuum port on the carb (no vacuum at idle) - That's correct right??

That would be great, cept that it doesn't idle as smoothly with only 10 degrees initial....it seems to get smoother idling with 14-16 degrees initial. I already have a high torque starter so starting it with 14-16 is no problem. Will my engine be able to take that much advance that quickly? (32 degrees by 1500-1700 RPM's)???

-Sorry this is so long, I didn't get my screen name by accident! lol Thanks in advance for any replies! (no pun intended)

BTW, I drove 2 hours to pick up my steel 4" cowl hood...looks sweet! Don't know if it fits yet though.

jwscab

yes, I see it now. they are basically saying to make sure you set the initial below when the mechanical advance starts to occur, so for the first chart, don't try setting initial at say 1000rpm, you will already start having mechanical advance added.

if it wants to idle with 14 degrees, then sure, use the black bushing, and set your initial to 14, and you will have 30 total advance. sounds like a good starting point. does it idle well below 900 rpm? if not, they use the springs that will set the mechnical advance curve above the idle rpm.

if it came with the 2 heavy gold springs, definitely change them out, they will cause a lazy advance curve.

as for vacuum advance, it might work better ported, or direct, you would have to see what it likes. if you don't use ported, it will add advance at idle, which might help. You might not need it at all.

it still sounds like a lean pop however, you should get that checked out. Are your power valve(s) boost referenced? I don't recall if we talked about that...

BTW who makes a steel cowl hood for thirdgens?

Confuzed1

iTrader: (4)

Well, things went from bad to worse. I added the two lighter silver springs and a black bushing to the distributor. After a few smaller backfires, it started but refused to idle at all. I know I did nothing wrong to the distributor, it was a routine advance change.

Had it running until it warmed up, and ran smooth if I held it at 1000 RPM's but if I let go of the gas, it would stall and spit fuel from the carb - but not a full-fledged backfire or anything. Plugs are soaked with fuel. The carb just decided to start dumping....

Gonna try it again tomorrow, but I switched to a 650 Speed Demon I had lying around since it appears the 750 Holley will need a rebuild or at least gone through. I want to see how differently it will run with the Demon, since it ran good on my N/A setup. I know it's smallish for the blower, but it will give me an idea hopefully if the Holley was the root cause of my problems with this. I don't get it...it idled well at 800 RPM before this happened, although it would backfire through the carb if I blipped the throttle too fast.

The hood I got on Ebay. Just search for 82-92 Camaro 4" steel cowl hood, and a place called Tamraz's sells them. Seems to be great quality, but I seriously doubt it was made in the US.

lt1z350

iTrader: (2)

figured I would chime in and try to help. I have a efi turbo set up now but have worked with a lot of carbed blower setups like b&m 671s in the past. First for the advance with boost and depending how much you need to be very conservative with the total advance. I had help tune my buddies 351 single turbo carbed car and we set the msd dis at 28 degrees total and locked it. starts on 28 degrees and doesnt move. this is a car that on 12 lbs made 750 rwhp with a t-76 and a holley type 750 carb. Your carb you are running if it doesnt have(most dont ) back fire protectors you will have killed the power valve and now why it wont idle. It is just dumping fuel. Do you have a boost gauge? if you pull it up slow it wont make boost and when you blip it quick will make a lb or 2 maybe more which will cause it to go way lean and pop. You need a blower specific carb to be safe. it will have special annular discargers and huge excellerator pumps with agressive rated for the boost. a roots blower is so quick on boost it is hard for a carb to keep up unless it is made for the applicaton. i have seen this more than once . If you are running 8 or more lbs I would get a msd boost retart set up that pulls timing for every lbs it makes. it is very safe that way. get the right carb or get the specs off one and change yours over but until you change that power valve it will not run right.

Confuzed1

iTrader: (4)

Thanks for replying lt1z350.
I knew I blew the power valve, and I replaced it with an old one I had. Didn't make a difference, but I don't have a way to check them so the one I replaced it with could've been blown too I suppose. No place to get a new one today. I intended to check it by turning in the air/fuel screws in all the way to see if it would stall, but I couldn't get it to idle enough in the first place.

The carb sat for a year, and maybe that did it in....not sure. I'm being conservative with the boost to start with. It's a small blower and it supposedly made 5 lbs. of boost on a not so radically built 350. On my 400, I'm assuming even less boost - maybe 3-4 lbs. at most. Once I work out these issues, I plan to chenge pulleys and see if I can get up to 8 lbs. max.

I already have a MSD boost timing retard box installed. Have not had the opportunity to really tromp on it to go into boost due to the backfiring issue. I really hate to switch out the carb to a blower specific one, especially since I already have 2 carbs already - almost new (at least very low miles)
- 750 Holley Pro Systems carb (600 bucks)
- 650 Speed Demon (300 bucks)
- So you can see, with the $$ I have wrapped up in carbs already.....

-but that being said, with trouble I'm having, I'm still seriously considering it. Edelbrock sells one for this blower. It's a 800 CFM and "calibrated for boost" - supposedly.

lt1z350

iTrader: (2)

sell the two and get the one or see if you can change the bigger holley over with parts that match one of there blower specific ones(squirters, cams jets so on)

flrtin1

My 2cents here....I started back in 86 on the first blower (B&M 144) with a set of Carter Comp Series carbs on the Z..........they are still on the 420 today 22yrs later and I have been nothing but happy with them. Now unfortunately Edelbrock absorbed Carter a long time ago so you can no longer get them... with that said the last 6-71 and 8-71 I have built have been with the Edelbrocks, while not perfect I think the advantages much outweigh the problems with using the Holleys (not bashing JMO).

Confuzed1

iTrader: (4)

Which "two"??....I have a 750 and a 650. If I sell them both, I need another carb. May as well get a blower carb then.

On a VERY GOOD NOTE...I tried the 650 DP Speed Demon on the car today, and it's a totally different engine!! I got it dialed in pretty close, I changed the jets up to 76/87, timing is at 18 BTDC, idling a bit high at 1100 RPM's but not running at full rich on my cheapie narrow band A/F ratio gage (at least it's on the gage finally). NO BACKFIRING!

I was actually able to take the car out for a spin for the first time since this all began!! I had to get gas anyway....can you believe I went through an entire tank of gas while trying to tune this thing?!? Can you imagine???

This car is gonna be real fun! Unlike when it was N/A, the engine doesn't seem to labor whatsoever when I drive it. I didn't even give it half throttle because I know this carb is undersized and I don't wanna risk it going to lean and detonating- but none the less, this thing is FAST! It was pretty darn quick before (although it burned oil before, still don't know why) - I had to look really stupid with that big grin on my face while I was driving it!

I can only imagine what it's gonna be like with a bigger carb and everything set right!!! I gotta get my Holley 750 straightened out!! I'm still scheduled to get it tuned and dynoed this week, but with the Holley like it is, I'll have to cancel....

It's not over yet though...I still need to hook up my vacuum line for my MSD boost retard and my vacuum advance on the dist. Also need to install my new hood, boost gage and fix my temperature gage - yeah, it's a Thirdgen...

Confuzed1

iTrader: (4)

Ha Ha....I'll show my age...I remember Carter carbs too. Most either loved em or hated them. What I really remember though is that Q-jets were called Quadra-junks. or Quadra-bogs - but as I grew older and finally ended up with one, I realized it was a myth. Most people just didn't know how to tune the secondary AV and they would bog badly. lol

My original 305 HO had the CCC version Q-jet. I went with DR rods and B hangers, tweaked the secondary AV just right and it ran great!

In hindsight, I agree a Edelbrock would've been more trouble free with a blower especially. But for all out power, I'll pick the Holley every time due to it's tunability - for those that really know them (not me)...but I'm learning the hard way like I always tend to do.

Right now I plan to work on the 750 Holley again to see if I can get the car running worthy enough to get it dyno tuned. Pretty sure the power valve blew when I backfired a few times so I'm changing that out, also manifold referencing it. Then I'll bolt it on and try it again!

lt1z350

iTrader: (2)

like I had said you back fired the power valve clean out of the other and sure the 650 was ok still. that was what i meant. sell both carbs to pay for one good blower specific 750 or larger. If it runs good on the 650 go with it for now. it wont run lean if you jet it high enough. Not sure if you watch nascar but if so think of it as a restrictor plate. you can tune it to it just fine and not hurt a thing but just wont make max power with it. as long as the air fuel mix is correct you will be good. really need a good wide band and playing with fire without one and boost. My first time out with my turbo and 5 lbs of boost saw 14.7 at wot and the car felt great but at that ratio if i hadnt richend it up would have melted it down. now at 11.5 it is a different beast on only 5 lbs. you can get cheap ones from moates.net or a ebay for used ones. 150 and you are set with a safety rope you shouldnt boost without.

Confuzed1

iTrader: (4)

Ok - you just threw me off when you said sell both...
I kinda thought you meant to get a blower specific carb, but I wasn't sure.... I'm still considering going with a blower specific carb, but really, after much research the only thing I've seen different between a regular NA carb and blower specific carb is that the blower specific one has a manifold referenced power valve - and it's jetted up for boost. Other than that, I'm not seeing any huge differences. I called Holley tech just yesterday and they sent instructions on how to manifold reference my carb over. And oh yeah, I listened to ya - my power valve is shot due to the backfiring. I don't have the ball check to protect it.

I'm not going totally without any A/F indication, I have a narrow band A/F gage in the car that I used when it was NA. Not totally acurate I know, but it'll get me closer than doing this blind for now. A wide band O2 meter is in the plans. I want to give the 750 one more try to see if I can get it running halfway decent - if it works out, it's getting tuned on the dyno where the A/F will be set up right. Funds are limited, so right now I think the money is better spent getting it set up right, and if it doesn't work - well, a blower specific carb and wideband is on the list this winter!!

lt1z350

iTrader: (2)

sounds good keep me posted on how it goes with the 750.

djamel

Wow you got a handsome car to go along in the streets. You did a good job of fixing the problem parts. About the power valve being shot due to backfiring, I think it needs cleaning out by the mechanic, maybe a gasket is blown and its leaking oil and water into engine. Keep us updated ok.

AKS_Racing

My neighbors car...

Aaron

Confuzed1

iTrader: (4)

Been a while since I've posted on this...busy-busy. Well, I went ahead and bought another power valve for the 750 and tried it out. Bottom line is - it just doesn't run right at all.

I can't get the transfer slots set at .050" (so a square is seen) at all and maintain any idle under 1200 rpm's. I end up having to close down the blades so much on the the primary and secondary sides, that the transfer slots are basically closed off. Then yeah, it'll idle lower but it wants to surge and my A/F meter is all over the place. Initial timing was set at 16 degrees BTDC. Of course, I couldn't advance it any more because that just made the idle go up even more...

I put the Speed Demon 650 back on it, and it idles nicely at 800-900 rpm's with no surging. It just runs better with it.

BUT - I think I know what might be happening with the Pro-systems 750 carb..the primary throttle blades have holes in them about 1/4" diameter. I think it has the holes because the carb was initially set up when the engine was NA, and had a larger duration cam in it. I *think* that's why the baseplate on that carb had holes in the primaries - to add air to the mix because the car had low manifold vacuum with that cam. That's the only conclusion I could come up with as to why this carb will not to run right with this blower. -Does that make sense to the carb guru's out there?? -Because I'm not 100 percent sure...

The Demon I have on it now has the "Idle eeze" feature to work around drilling holes in the butterflies, which I don't need with this smaller blower cam, so I'm not really using it.

Damon

Yep, that's about right. The holes are drilled in the throttle plates to allow more air in at idle without having to open the throttle and expose too much of the idle transfer slot. A very common mod with big lump cams. Of course, that's now working against you since you are getting TOO MUCH air through at idle with your milder cam and you can't close the throttles far enough to compensate for it.

Confuzed1

iTrader: (4)

Thanks for the reply Damon. So I wasn't overthinking this then...maybe that also contributed to the lean backfire I had when I first tried the 750 on it before I blew the power valve out...

It does seem to run great with the 650 Speed Demon on it, although I really haven't given it full throttle yet since the engine's still not broken in.

- I have maybe 50 miles on it. The only time I gave it 3/4 throttle, I must've been doing around 30 MPH in 2nd gear and the rear tires broke loose instantly, so I know it has some power for sure!

So far the engine looks good! First and foremost and for the first time EVER, the engine IS NOT SMOKING after the rebuild, if you've read any of my posts when the engine was NA in the past, I tried EVERYTHING to find out why it burned oil to no avail, and I'm still not sure what I did to fix it this time, just glad it's not burning oil at all now!! There's very little blow-by in the crankcase, no oil or water leaks. I ended up replacing my new defect cooling fan switch for another, so it's running now. And of course, the snow started flying up here so it's also....parked....

So....back to my carb situation. It seems I could:

1. plug the holes in the primary blades on the 750 - not sure how yet or how well it would work...
2. spend more $$ on the 750 and just buy a new baseplate for it.
3. sell both the 750 AND the Speed Demon for a loss, and buy either a Demon or Holley blower specific carb - or:
4. just run it with the Speed Demon (but is it too small?)

-Which one would you do?

EDIT: Yeah, I know I said in a previous post that if the 750 didn't work, I'd just buy a blower specific carb, which isn't off the table either...just getting a concensus from you guys.

Damon

For now, I'd run it with the carb that works- the Speed Demon. Yes, it's a bit too small, but not so as you'd notice anywhere but at the track. And you do want to have some fun driving this thing before winter sets in, don't you?

You can play with the 750 if you like in your spare time. You can replace throttle plates fairly easily- just remember to grind off the backside of the threads that poke through before you unscrew them- the factory mashes them down so they can't unscrew. When you put the new ones on just use some LocTite on the threads. I have a feeling there may be a bit more worng with that carb than just the throttle plates, though. I'd do a complete going-through on it before you try it again.

If that doesn't work out then consider selling both and buying a bigger (possibly blower-specific) carb later when you have a big pile of cash laying around doing nothing.

Confuzed1

iTrader: (4)

I wish I coulda had more fun with it, but the snow has been flying around here like crazy already, so it's parked for the winter I'm afraid...

I've been doing mega researching on what my best route could be when it comes to manifold referencing mods on the carbs I currently have now. I was trolling around on the BG website, and they actually claim that their 650 Speed Demon carbs outperform most 750 cfm carbs so far as low RPM torque and HP goes on most engines. They don't get into why this is, and maybe it's just them blowing smoke to sell more carbs...I still tend to believe a 750 will outperform a 650 in the upper rpm range though....

On another note however, I've found out that Demon carbs are easier to modify for PV manifold referencing than a Holley is. All I need to do is purchase a Mighty Demon 650 "blower specific" carb baseplate (part# 121215) and bolt it on to my existing Speed Demon carb and it will allow the PV to reference manifold pressure - to the tune of 175 bucks - but it's a bolt-on proposition with no drilling or port plugging required.

With my Holley, I need to modify the baseplate by drilling holes and plugging some existing ports - and I need to change out the primary butterflies too - it's still cheaper yes, but it'll never operate on a N/A engine again. So if the 750 doesn't work out right after I mod it for some reason, I have an expensive piece of junk - decisions, decisions......

Have you noticied how much more $$ they want for "blower specific" carbs?? It's stupidly outrageous!! "Blower specific" carbs (at least draw-through ones) just aren't that much different from regular N/A carbs to warrant that type of price increase!! I still may end up doing this, but I'll feel totally robbed as soon as I send the money to them...

lt1z350

iTrader: (2)

the blower specifc ones are way different. My buddy has a turbo mustang and he showed me the paper work that came with the carb and from the annular discharge to the size of the air bleeds is made to work with the boosted application. Now his is blow through too which makes it more radical. I hadnt checked in a while and saw about the holes in the blades. I had to drill holes in my 58mm tb on my car for the larger cam i had and now with the small cam and turbo idle was too high so i used expoxy to close the holes back up and have had no problems with it not staying in place for over a year and alot of driving. Just scuff the plate up so it has something to stick to. close them up and see how it goes and convert the holley. Or do what i said before and sell the two you have and buy one made for what you are doing. Shop around ebay. Maybe you can find someone going away from a blower and who would be willing to trade a blower carb for one or two regular ones. wouldnt hurt to look.

Confuzed1

iTrader: (4)

...And totally different from a draw-through setup, agreed. Many more modifcations are needed/done to "blow thru" blower carbs as opposed to "draw thru" blower carbs, which - at least - kinda justifies why they are more expensive than a carb set up for a "draw-thru" blower application.....
I'd rather just change out the butterflies instead of using expoxy really. Two new little round butterfly blades can't cost that much, can they? I'll look into it..
Oh, you can bet I've been looking....but I never thought about offering to trade up though...might not be a bad idea.

Confuzed1

iTrader: (4)

Just for info - I found that new butterflies (or throttle plates) costs under 15 bucks, so I'm getting those and decided to drill and plug the Holley as needed to convert it over. Maybe I can take pics and post it up in the carb board....

On yet another note, the air cleaner I have is not fitting under my new cowl hood like I hoped it would. The pre-made hole in the hood wasn't placed right when it was made.... When I go to close the hood, the rear edge of the air cleaner hits the edge of the hole in the hood about 1/2". I could just trim up the hole in the hood and widen it 1/2" in the rear where it's hitting, but after looking at it even closer, the hole in the hood is also off side-to-side too. It's much closer on the driver's side than the pass side....so I'm still thinking up a way I can get an air cleaner on the car and make the cowl functional....

EDIT: Allright, I don't think it's the hood that's really off after taking a couple more measurements from the edge of the carb airhorn to each fender - guess what? Might sound crazy to some, but I think the engine is actually not centered in the engine bay!! I'm guessing it's because of the torque arm on these cars that runs down the driver's side. The engine is closer to the pass. side fenderwell than the driver's side fenderwell by a bit more than an inch...closer to two! Tried to take pics of where it was hitting with the hood partially shut, but they didn't come out well enough. With a blower, this air cleaner needs to sit up inside the actual cowl - and that's using a drop base AC...but in order to line up properly, it needs to move diagonally toward the front drivers side corner....no one sells a diagonal offset drop base air cleaner...this is really frustrating....open to any ideas. Looking at maybe getting an oval air cleaner, but I bet it'll sit up too high...

Confuzed1

iTrader: (4)

- Are there any websites/companies that make any kind of universal pre-fabbed air intake kit designed for cowl hoods? I've searched and can't seem to find any...

jwscab

i think moroso used to make a cold air pan for cowl hoods. I remember having an air cleaner, two pieces of aluminum that you rivet together, one of which had an air cleaner hole in it, and some soft runner weatherstripping type stuff to seal to the hood.....maybe check summit....

edit: yep,here it is:

http://store.summitracing.com/egnsea...03632&D=303632

Damon

The engine isn't centered in the engine bay. The hole in your hood probably is. I had to trim mine to fit especially at the rear. I think trimming to fit is just part of the process with an aftermarket hood.

Try these guys out for a cowl induction setup:

www.ramairbox.com

You will definitely have to modify this to fit, if it'll even fit under the hood at all. They don't even pretend their stuff is a bolt-on.

Confuzed1

iTrader: (4)

Thx Damon, I discovered that to be very true. Of course, that throws all my careful measuring off that I did before I bought the hood. Thanks for the link, I didn't realize they sold things other than there Ram-air boxes.

Unfortunately, I didn't see anything that would work on my car though. All the fresh air setups I've seen for cowl hoods assume the top of the carb is even with, or far below the hole in the cowl hood, where on mine, practically my entire carb sits inside the cowl itself.

I have approx. 2 1/4" to 2 1/2" of room between the air filter mounting flange on the carb, and the top of the cowl itself. Not much room at all. I think I'm gonna try getting a 2" drop base air cleaner, and using a 3" or 3 1/2" thick air filter element and see if I can mount some kind of cake pan below the air cleaner base with that with the Moroso foam that I saw at Summit. Of course, first I have to cut the hole bigger in the hood itself since it doesn't line up...just glad to hear it's normal I guess.. - I'll figure something out....

jwscab - Yeah, I seen those "kits" from Summit. I can't figure out why they only make those pans square and only 12" wide though... The hole is a standard 14"...

DAVECS1

iTrader: (2)

You could cut the hole out big and rivet a new piece of aluminum on to the hood with a new hole in the correct location. Also Moroso sells an offset air cleaner that is what I am using on my blower.