Chickenman35

Most newer DP's no longer have a Secondary Power Valve,,,but that's a good point. Also you can't be too carefull with Power Valves.

For years I've always used the tried and true ( Suck on it and see if it sticks to your tongue method" . Recently I bought a Moroso Power Valve tester that I can hook up to a Mighty Vac. I found 2 bad PV's that passed the " Suck Test " ( Tiny, tiny pinhole. ) and one that was sticking. Power Valves are Cheap. If it's been back firing it's always good insurance to replace the Power Valve....although the Newer Holley's are suppossed to have " Blowout protection". Don't know if Heavy Chevy's has this untill we get the list number.

heavy_chevy29

i would like to thank everyone that has helped me out.

i did what Chickenman35 told me to do and the car runs great. i replaced the pink cam with the blue cam. i put 69 jets on the primary side in place of the 71 jets that were originally on there. i also replaced the pump nozzle with a 31 on the primary side in place if the 28 that was on there. the car runs great now. i have little tuning left but all the major problems are gone. thanks you Chickenman35 and all the others that helped out.

Chickenman35

jimmy_mac

This is a great technical post, and I'm glad the problem was fixed, but if the carb was working fine before the problem started, how could fine tuning it with different sized jets, cams, and pump nozzle fixed it on its own. I suspect the real problem, ie a clog or vacuum leek was fixed in the process.

That's like having your vacuum advance on your distributor not working because your vacuum hose has a big hole in it and you fix it by replacing the whole distributor along with the hose. Then saying you fixed it by replacing the distributor.

I'm not saying tuning the carb with the above is a bad thing, I'm just saying there is a difference between trouble shooting a problem and tuning. Particularly when there was no problem before hand with the same exact parts.

sqzbox

It's almost hard to believe that a couple of jet's and a pump shot fixed all the problems he had unless , it wasn't all that bad as he claimed! But oh well, like I said before "It's hard to diagnos the patient over the phone! He (heavy chevy) sure had enough feed-back on the subject to keep him busy lookin'. Glad things are better now and hope it didn't cover up some other short commings. Kudo's for Chickenman on this one! Still can't agree on that intake vacuum port though. (Git er done!).:hail:

heavy_chevy29

all i know is that it works now and it didn't on saturday. now im happy.

sqzbox

YEEEEE HAAAW! Burn a moostang for me! I really hate them Moostang's!

EvilCartman

iTrader: (1)

Just for chits and giggles tonight I changed my pump cam from a green one to the blue cam. Bit more snappy throttle response was the result Gonna try a different squirter size next. Also heard the beginnings of an exhaust leak for the first time at the header flange Got worse after an hour of driving grrr.

Chickenman35

Just for giggles....change your Vacuum advance from Ported Vacuum to Manifold Vacuum. I'm betting that you''ll notice even better throttle response. ....and maybe decreased 60ft times

I'll post a thread in the near future discussing the Pro's and Con's of Poeted vs Manifold Vacuum. I'll start a new thread dispelling some myth's.

LilJayV10

iTrader: (5)

Thats good to hear heavy fixed his problem. I have a 406 that I am starting to tune on. I am going to use alot of the info I read here and probably start a new thread because I don't want to start posting questions in heavy's thread.

Chickenman35

Heavy_Chevy and I PM'd quite a bit back and forth. He'd covered all aspects. He looked high and low for a vacuum leak...never found it. He made some changes that I recommended , but not exactly as I specified. I finally phoned him on Saturday. Got him to setup his carb exactly as I specified...and Voila....Car is running beautiful. BTW...ignition sysytem was all brand new and good parts as well. Moroso Helicore wires, new Summit distributor, new Coil...no carbon tracking...we covered everything.


Confusing that he says it worked OK at one point as you mentioned. Only thing I can figure is that he was having trouble starting he car with the wimpy GM Metric starter. He may have reduced his timing enough ( 8 deg BTDC ) that the setup he had on the carb just plain wouldn't work. He's going to try some more timing...the engine will like it , but he will probably have to get a Gear Reduction starter. Standard Metric strter barely adequate for a 350...let alone a 409


Hard to Diagnose or tune over the Internet or phone from 3,000 miles away...... but Dan's pretty dog goned happy with the results

EvilCartman

iTrader: (1)

I'm not running any vacuum to the distributor at the moment. I haven't been for about 2 1/2 years now hehe. I think right now one of the best things to help my 60' times is more traction. My first time at the track I was expecting 2.3 to 2.4 at best but on the 3rd and 4th run I did a 2.21 then down to 2.19. This was done on 215/65/15 regular street tires and rolling into the throttle quickly.

I think my base timing is set at 18 degrees right now for a total of 38. Next time out I'll mess around with it some. What do you think about stepping up from a #31 squirter to a #35 on the primary side? Yeah a 750 is huge on a 305 but damn it runs so much better than the Holley 670 I had lol.

Chickenman35

A #35 might be a bit too much fuel. May get lazy on the launch. Subtle difference between a " Lean Bog " and " Rich Bog ". Only way to tell is to try it out.

BTW, if you run the car on the street you're killing fuel milage by not running a Vacuum advance. Vacuum Advance will not affect WOT performance at the track ....except for running Manifold Vacuum which may reduce your 60' times. But it is critical for the street.

Quote from David Vizard's book " Performance with Economy". Page 81 Quote:

" As far as economy is concerned, vacuum advance control is the single most important ignition factor affecting part-throttle economy. If economy is in any way a consideration, under no circumstances should any engine be operated without a distributor that has a functional and thoroughly tested vacuum advance mechanism". End Quote.

Vacuum advance will also reduce plug fouling if you're having this problem.

onebad82z

iTrader: (7)

I chased a mid range part throttle miss for around a year on my Z...turns out the vacuum advance was causing it to detonate and seem like a miss.Removed vacuum advance from MSD pro billet and car has ran great since.Some cars just don't like a vacuum can..mine being one.I have even hooked it back up to see if it was a fluke..miss was back.But then again my motor is a little more strip than street.Very imformative post though..I also swapped to a blue cam from the green (like Evil Cartman) on my Demon 750dp..improved throttle response was the result..but I am at a 42 squirter right now..may try a 45 this weekend to see if it improves a 'lil more.

sqzbox

If you really want to hook it up again, it sounds like your pulling total adv. at too low an rpm. You should have an adj. adv. rate built in. If you bring it all in say 250-500 more rpm the miss might go away or take a few *'s out of the total (I'll bet you don't want to do that!!) If you have a vacuum pump you can check the diaphram for leakage also. Might even need bigger jets in the primary's but I'll let chickenman handle that one!

onebad82z

iTrader: (7)

The vacuum can was on a brand new MSD pro billet and checked fine..I swapped to the MSD believing that the new Summit HEI (less than 2 years old) was giving me the miss.That vacuum can also checked fine...although it was the Crane adjustable unit mentioned elsewhere(Highly recommended Heavy Chevy!).The stock Summit provided can sucked so I swapped it..the Summit can gives way too much advance.So I spent $200 to find out all I had to do was unhook the vacuum can and the car ran great...but I wanted a pro billet anywayAs far as bigger jets...I am at 80's on the primaries right now..78's had a real slight surge at cruise.Plugs are coloring great so I left it at that for the summer and the car loves it.And you are correct..I do not want to take any timing away from the total..the car put down the most rwhp with 36 degrees..so it stays.I may play with the advance rate next year and try hooking the can up again..but I also keep telling myself if it ain't broke don't fix it...lol

billhelton

***, what an enormous amont of info on this thread!!! I have but one question - will all this tuning also apply to a 600cfm vacuum secondary? I just installed a new 355ci in my 85 sc. I'm now in the process of trying to find all the little things that always pop up. The dist. is new GM HEI w/vacuum adv, new rotor, plugs, wires, Holley 600 VS, Edelbrock Performer RPM intake, small Lunati street cam (458/458 lift, 110* lobe separtion, 216* duration). Like Chicken, I've built race engines for more years than I like to remember, but always had the luxury of a carb specialist. Just want the carb to perform well.

Thanks in advance.

onebad82z

iTrader: (7)

The steps of carb tuning and methods discussed will work on a 600VS..obviously most of the specific parts mentoned may not work being they are for a 750dp..but some may.Get your timing set and tune the carb step by step.Make one change at a time so you can see and feel the difference it makes..good or bad.I have learned everything I know about carbs from these boards and the 'ol trial and error method.Ask questions..do searches..there is endless info on this board.Having a good pile of parts for the carb never hurts either..such as jets,squirters,pump cams and the such is also important.

billhelton

I already started some of the improvements. Adjusted the timing to 12* initial, 32* with vacuum, adjusted float level, idle mixture and idle. What a difference. Can't wait to try some of the other ideas. I don't think this car has ever run so good. Of course, before, it had a 305, now a 355.

sqzbox

Sounds like you have a 6210 universal 600 cfm right? There is a little bit you can do to it but not much. Sounds like you've allready taken care of the primary's but, you can stretch the secondary's too. Instead of a secondary metering plate they have a small plate screwed onto the body inside the rear fuel bowl. If you remove it look on the bottom edge and you will see two small holes. These are the same as secondary jets only permanent. Being made of aluminum they are easy to drill larger. I accually stretched mine with a torch tip cleaner like a file (sic) I think they were about #62-#66 I kept filing til they looked about the same size as a couple of old #70 I had. Imidiate difference was top end power from 3000 rpm on up. It was and old top 25 tips &tricks for more performance in hot rod magazine years ago! Thought you might want to know!!

EvilCartman

iTrader: (1)

Got home today with a package waiting for me... Dave Emanuel's book " Holley Carburators " by SA Design Now it's time to read up a bit Used book for 14 bucks and it had a recipt from Chicago Corvette Supply for what looks like a yoke and a 63/79 posi unit... 950 bucks date 06/16/90 hehe

sqzbox

Hell, that's half of what I payed for my whole car!!

EvilCartman

iTrader: (1)

hehe that's 50 bucks shy of what I paid for mine

sqzbox

Did it come with a motor?

billhelton

When you guys are specifying particular jets, are you suggesting based on carb size or motor size? Right now I have 65 primary, and 70 (equivalent) in the secondary. It also has 31 squirter. This weekend I'm going with a blue cam. Any other suggesttions?

Sqzbox - You're right about the carb. It's a 80457S (electric choke), but I believe it's the same as the 6210.

EvilCartman

iTrader: (1)

Yup paid 1000 bucks for the car, drove it home, pulled the engine out 2 weeks later and found 4 flat lobes on the cam. The car has come a long ways since I first got it.

sqzbox

Jet size I think depends on the carbs cfm rating to produce the correct air fuel ratio (around 14:1) Your pretty close on yours. You might even try 66's or 68's in your primary. Used to be at the track, after you started running consistent times you could step up on the size till the car started to run slower times, then go back (trial and error). Since you have a mild cam, intake, hot ignition, Headders? and low gears you could probably move up to a 650cfm. With the increased air-flow goes larger jets and more tunebility with the secondary's and increased top end power.
Smaller carbs produce more throttle responce and bottom end to mid-range power. larger carbs work better from mid-range to top end power. It all depends on application. I would prefer low-mid range for auto-cross because of the rpm range. For drags, mid to top end. If your driving around on the street all the time, low end torque and power works good. If your drag racing top end is what you want because after you launch at the line your not going to see anything under 2500 rpm anyway!
Too small a carb is like a restrictor plate is to nascar. It hold you back. There are so many different equasions to consider (cam size, valve size, comp. ratio, gears) that there isn't a certain size, it's only round about, then fine tunning. Chickenman35 could probably help you more on this, I think he's lost more sleep staring at holley's than I have. There is a formula for figuring correct cfm for cu. in. but I can't remember it. cubic inches x 2 always worked for me as a base starting point. For example,
my 360 AMX I used a 650, could have gone bigger, but it was a daily driver, weekend warrior, and trip taker 1000 mi back and forth to calif. from arz. My 440 GTX worked real good with a 780 cfm. on the street . My 440 dart GTS had a 800 but it had a crane hi-lift cam and sucked gas pretty good (about 9 mi to the gal. cruising) The GTX got 17. Your 355 and cam could use a 700 on the strip but milage would suck on the street. The bigger those venturi's are the less that engine has to work at sucking air in, and that means more power. Air fuel ratio is the key (jet size) Have I repeated my self too many times? I need to quit this before it turns into a novel!!!!!:lala:

Chickenman35

Been working my butt off the last couple of daze so that's why I've been kinda quiet.

One suggestion...change the stock vacuum can for a Crane Unit or 15 deg GM can. The stock HEI units normally run 20 deg. This is because the stock HEI mechanical curve does not give a lot of total advance, so it needs to be made up with vacuum advnace to get the correct total for cruise. The Crane is limited to a max of about 15 degand can be adjusted to less if necessary.

Bill...I'd recommend that you change to the Crane can. At cruise with 12 deg initial, some mechanical advance and 20 deg of vacuum adavnce you could be running close to detonation. Depends on your setup. A 15 deg can will put your advance curve in the optimal range.

When you start adding static advance you need to cut the vacuum advance down a tad. I've found that 15 deg cans are about ideal. The Crane Adjustable unit is the way to go.

With 10.3 to 1 compression, Aluminium heads, 218\228 @ .050 cam.....I run between 14 to 16 degrees lead and 15 degrees in the Vacuum can. Car absolutely loves this.

NOTE!!!! Gasoline quality highly affects what you can run for initial lead. I'm in Vancouver, Canada. Canada has a bit better quality gas than most places in the US. ( Comparing equal brands and grades). I'm note going to go into all the details right now of why...but it is generally true.

I also run Mohawk gas which is an Ethanol blend. Most of the forced induction guys up here run Mohawk .....it's good for at least 2 to 4 deg extra static advance on a supercharged\turbocharged car.

At 14 to 16 deg initial lead ( with a 15 deg vacuum can giving 29 to 31 deg total. I of course run manifold vaccuum ) The car will diesel on a hot day with Chevron 94 Octane. It will not Diesel on Mohawk 94 octane. Plus the car will run noticeably smoother and it makes more power on the dyno

Just a couple of things to consider.

billhelton

Well, I had to change the carb to a 650 DP. The 1850 just wasn't handling it. My question is this - Is it possible to get a carb straight out of the box that is set up perfectly? I never have, but this one sure seems to be right. The idle is good and smooth, acceleration is great with no ping (ref 12* with full port vacuum), and it's a neck breaker when I hit passing gear from 35-40mph.

The only problem I see is the vacuum. I only have about 9", which I'm sure is the cam. No matter what I do, that's all I get. Should I change the power valve to accomodate this (now has a 65), or leave it alone?

Also, in an earlier post it was recommended to go to a blue accelerator cam. Is this still recommended? I can't believe it can get better.

In all honestly, this motor seems to have about the same get up and go that my 99 SS had with the LS1. I know it can't be, but it sure is nice.

Thanks for your replies.

sqzbox

Glad to hear your happy with that 650! Is that a spread-bore or square hole? I had one (square hole) on a 360 ci. and never had to mess with it for two years when I sold the car. (9 lbs might mess with your power brakes if you have them depending on your idle rpm. If a problem starts with them getting real stiff at idle you might want to look into getting a vacuum resivour can.
Chickenman can help U more on the power valve and cam issue.

billhelton

It's a square bore. Just never got into the spreadbores.

sqzbox

Yeah, me either. the spread-bore might get a little more hwy. milage but who cares? Nobody I know ever put a holley on for milage! The square hole has so much more part throttle performance! Did you ever take your car to the strip with the 600? I'm interested in the time comparison between the 600 and the 650. Guess that will be next season huh? You know U can klick on chickenman's profile and send him an E-mail if he doesn't get back to U on that P-valve and cam thing right ? Ok man, Have fun. Hey check out the thread on Gen Eng board "Knock in my new engine" and see what happened to that guy He had to do a little extra work but he did right shuting down early or it could hav been alot worse!!

Chickenman35

That's a very low vacuum reading for that cam. It's not overly huge. Heck I could pull 11" with my Xtreme Comp ....236\242 @ .050". Check for vacuum leaks. How much static timing are you running? Should be around 12 deg initial with no vacuum advance hoked up. Low vacuum reading can be an indication of retarded timing.

I'll say it one more time....hook the Vacuum advance up to manifold vacuum. It will smooth out your idle...you will pull more inches of vacuum at idel and you will get better response. There are absolutely no drawbacks to running manifold vaccuum, once you set things up properly.

Some people don't agree with me on this...but it's a proven combination.

I'll really have to get going on that " Ported vs Manifold vacuum " article...but I've been so busy lately

6.5" Power valves fine.

sqzbox

He's got it hooked up to Man. port! (full port) Sometimes I think U read too fast!!

Chickenman35

Welll I didn't understand what he meant by : Quote: (ref 12* with full port vacuum) To ME that meant ported vacuum.

sqzbox

Would you like to use a tire iron on me?

Chickenman35

Nahhh...that would be too quick and mercifull

sqzbox

Burnout on me would be nice and slow! I love the smell of burning rubber! Then recuperation wouldn't be so bad and I'de have really cool marks to show off!

Chickenman35

Back to Bill's problem before we turn this into an S&M Forum!!!

Triple check for Vacuum leaks. Try a different vacuum guage.... ( sometimes the simplest things..... )

9 deg seems awefully, awefully low for that cam combo. Mind you the 110deg LCA doesn't help. What is the comp ratio of your engine?

billhelton

Sorry about the confusion. The advance is connected to manifold vacuum, so I have 12* static plus vacuum.

I think the gauge I'm using is not real good. I've had it for probably 25 years. I've checked for leaks half a dozen times, with water, all to no avail. I think I'm going to get a new gauge this week.

The real purpose of this post was carb mods. With the 650, should I still go with a different cam or leave it alone for now. I does run VERY good.

The C/R is 8.7. (Stock!?!)

I've also ordered a Crane vacuum advance (like you suggested).

Chickenman35

OK the CR answers a lot. With that low of compression the 110 LCA will kill idle vacuum. You should have gone with something around 114 deg to 112 deg minimum with that CR. A tighter LCA reduces dynamic compression.

Still...9 inches awefully low...Could very well be the guage.


Back to your carb. If it came with Pink cams I believe that you will get even better throttle response at tip in by trying the Blue cams in the #2 hole. Both Primary and Secondary. You'll use less fuel as well. It all adds up....

Your Primary shooter is probably a #28. You may want to stick with that or go up to a #31. Secondary shooter likely a #31...I'd leave that alone.

Sounds like things were pretty close out of the box. Nice when it works out that way

Keep an eye on the plug color and fuel milage. DP's are usually jetted a tad rich on the Primary side. You may want to jet down a couple of sizes...but get some miles on it first and see how she runs.

billhelton

The cams that came with it are red. The primary and secondary nozzles are both .025. I agree with you to stick with it for a few miles and see what happens. I check mileage over the first 1000 miles or so and get back with you.

I also agree that the gauge is probably worn out. I'm going to get a new one today. I'll post what the difference is.

Thanks for your reply.

billhelton

Chickeman35, you're awesome!!

First things first - I got a new vacuum gauge and mine was pretty bad, off by about 3" at idle. As for leaks, I checked again and found nothing until-- I was re-reading the instructions for the gauge and it mentioned timing could cause low vacuum. Well, I had unplugged the vac adv to plug in the gauge. I plugged it back in and was going to use the big vac tube on the back of the carb and voila! the hose was loose as a goose. I found a smaller vac hose, put it on and 15"!! No wonder I couldn't find any leaks.

Thanks for all the help you guys have given. I really appreciate it.

billhelton

Sqzbox, you mentioned a 440 Dart. Let me knock your socks off. My MOTHER got a Hemi Dart!! The old bird could drive it pretty good, too. In 71 when I cam back from 'Nam I bought a new Charger RT 440 from Mr. Norm in Chicago. I told him exactly what I wanted to do and they built it. It has TWO 1050s on a cross-ram manifold. Talked about lousy mileage - about 5 mpg. It would pass everything on the street except a gas station!! But it was FUN!!

sqzbox

Yeah the dart was bad *** but I can't take credit for building it. I bought it off a friend (can't believe he sold it to me). When I got back from Nam I bought a brand new AMC Javelin SST. I didn't know it had a T/A 360ci in it till I burned up a couple of valves in the first 15'000 miles using reg gas like the book said. My uncle
(best mech. Iv'e ever known) took the heads off to do a valve job on it for me, fliped the first head off and said "holly S**T look at the size of those valves" needless to say Prem. gas was used from then on! Car ran a hole lot better and I put 86'000 mi. on it in two years as fast and as far as I could. It's a wonder I never killed myself, But who cared? I didn't! I just survived a year getting shot at everywhere I went what could posibly hurt me now RIGHT. Welcome home brother! A/co 101st AVN Bn.
Commanchero's 70-71 :rockon:

billhelton

I was attached to the 101 AVN Bn from Feb 66-May 69. Then Nam til jun 71. I was a weather guy in the AF attached to 101st at Ft Campbell. Went to Nam w/SF. (Not really Nam, but real close. It was classified )

sqzbox

What a small world it is! I was a door-gunner on a UH-1H Huey.
Flew many mission's for MACV-SOG including N. VN and Laos and partisipated in Lom Son 719 (A sad attempt to Vietnamize the war). One of our mission's was even writen about in Newsweek Mag. By Kevin Buckley (Siagon Bureau Cheif for newsweek) after my chopper draged his butt and several others off a fire base in laos at night. (Didn't think I was comming back from that one).
Unfortunatly 4 brothers are still laying on top of a hill on the Laos border. Johnson, Berg, Woods, and Dempsey. An attempted recovery this summer failed to find the correct crash site as coordinants were crude then compared to now. I call my black flag I fly every-day the "MIA-POW- LBH flag (LBH standing for Left Behind). If you'd like to visit our web site sometime our add. is
http://www.a101avn.org Once again, welcome home!

billhelton

Never made it to NVN. Spent all my time in Laos and NW Thailand. That's some beautiful but hard country. Tough to live there. One day we should try to get together a tell war lies.

Thanks for the welcoming. Keep the Black Flag flying.

sqzbox

Thanks! What part of tenn. do you live in? I drive a semi and I'm through there all the time. Even tomorrow, on my way to Ala.
Before the Moderators jump our stuff for non automotive topic's
you might want to click on my profile for E-mail address. C-Ya!

Chickenman35

Glad you found it. Car running great and 9" of vacuum just didn't ad up. Vacuum leak and bad guage explains a lot.

Red cams...#240's? A bit on the wimpy side IMHO. If you find any tip in hesitation you might want to try something a bit more agressive. What List # did you get? There are different part numbers for 650DP's and the specs do vary.

Late models of List 4777 ( Revisions 1 through 6 come with a #28 shooter ). I'm suspecting that you didn't get a List 4777 DP.

If it's working good...leave it be