muggsyjack

I have a 750 Vac. Secondary carb on a 305, open headers, long dur. cam and torker manifold. Th-350 Trans, 4.10 rear gears and 3500 stall converter. Car has run 8.6795 in 1/8th mile. 81+ MPH. After runs, plugs look fine. Light tan electrode.

Question #1

How do I know if secondaries are opening correctly? Car seems to build RPM slowly, I am guessing the lower vac. caused by cam is delaying full secondary operation. There is no miss or anything, it seems like car gradually accelerates in both 1st and 2nd gear.

Question #2

The is an off idle hesitation at times. is this related to idle circuit issues? It will hesitate very momentary and then recovers fully without backing off. It is most noticable at lower rpm launches.

I have bought a tuning manual. I now see where transition slots may prevent clean idle circuit operation. I have already put a 65 power valve in because my idle vacum is 13.

Any insights would be helpful.

Chickenman35

You have three things effectively killing bottom end torque. Long Duration camshaft...what are the specs? Open headers ...kills bottom end torque. And the Torquer manifold.

There is much better technology than a Torker available today. A Torker kills bottom end grunt on a 350...let alone a 305. Old, old technology.

On a 1\8th mile track I would recommend a Dual Plane such as a Performer RPM .

If..and only if the engine is built to the nuts with lots of compression and good heads, would I consider going to a Single plane such as a Victor Junior. If you can pull 7,000+ RPM out of your 305..then go with a GOOD single plane. A Torker is not a good single plane. It's time has come and gone.

Run a full muffler system. You need TORQUE with a 305. Open headers kill it.

You should be able to run a fairly soft spring on the secondaries. A long yellow would be a good starting point. Attach a paper clip or rubber O-ring to the secondary rod off the diaphram. Then you can tell how far the secondaries are opening. Don't be surprised if you see no more than 1\2 to 3\4 opening on the secondary. That is not an indication of a problem. It's probably only how much air the engine will pull.

What accelerator cam are you using and what size shooter? More details on your engine please. Such as timing. compression, head specs, camshaft specs etc.

muggsyjack

Cam is 235 duration @ .050, .488 lift. Using 1.6 roller rockers. Carb is 750 Vac. secondary. Timing is 20 static w/38 full mech advance @ 3000 RPM. Compression is 10.5 to 11.0 to 1. Cranking compression test was 220 PSI.

Heads are weak point. Stock 305 HP heads w/1.94/1.50 valves and 3 angle valve job. Milled to improve compression. Minor relief around valve to unshroud.

Ignition is Accell dist w/300 series box.

Send me your E-Mail and I will forward video of car on single pass. Engine runs clean just does not wind out as quickly as I would expect.

Is not a dog, 8.6795 @ 81+ in 1/8 th mile.

Chickenman35

Ok...sounds like a fairly potent 305. Is that .488 lift with 1.5 ratio rockers or the 1.6 rockers. Just curious.

Sounded like you were complaining that it was weak in 1st and 2nd. Quote: There is no miss or anything, it seems like car gradually accelerates in both 1st and 2nd gear

What RPM do you launch at? What spring do you have in the Secondaries now. What Pump cam and Shooter size do you have?

I still think that the Torker and Open headers hurting you. I tried a Torker on a fairly stout 350 years ago and it just killed my bottom end performance. Car was lazy just as you described. What RPM do you turn?

A Performer RPM will pull strong to 7,000 but has a slightly fatter torque curve than a Victor JR. In side by side Dyno tests there is surprisingly little difference in the HP figures between a Performer RPM and a Victor JR.

Circle Track tested both the Victor Jr and a Performer RPM a couple of years ago and found they were neck and neck. The Perf RPM made a bit more Torque on the Bottom end and the Victor Jr made a bit more HP on the Top. The Difference was something like 12 ft\lbs of Peak Torque gain with the RPM vs about 10 HP Peak gain to the Victor JR at the top end. Mind you this was on a very well built ARCA series motor...350 cubic inches. A 305 is going to be lacking in Torque compared to a 350....so I still swing to an RPM


The open headers aren't helping you either. A proper full lenght dual exhaust, with an H or X pipe and Dual mufflers such as Flowmaster's would really bump your bottom end torque and cost you nothing in HP. In fact you would probably pick up a bit of HP. Proven time after time in dozens of articles....

Not saying that the car is a dog...just that you could have a better combo. Carb tuning may help...but you still have some basic problems with your setup.

However...simple things first ( and cheap ) ...so post the info on the carb, launch RPM's , shift RPM's etc... and we can go from there.

Chickenman35

BTW...cam duration and vacuum readings have no affect on the opening rate of the secondaries. It is entirely dependant on airflow velocity.

Holley's have a very sophisticated VS circuitry ( Much better tha the Demon's but that's another subject ) . Initial opening is controlled by a Pitot tube that is connected from the Primary Venturie to the Vac Diaphram. There is a an air bleed in this circuit that balances the circuit to ensure a smooth operation and to ensure that the Vac Secondaries will close.

Once air velocity in the Primary Circuit reaches a sufficient value, enough vacuum will be applied to the Vac Diaphram to start the Secondary opening. On the Secondary side there is an additional opening that is connected to the Vac diaphram and to the Primary Vacuum circuit. The Secondary feed provides two basic functions.

1) Provides a stronger signal to diaphram as the secondary throttle blades open.

2) Acts as an an additional air bleed when the Primaries close. Along with the Main air bleed this ensures rapid bleed of of vacuum to close secondary throttles rapidly

Chickenman35

A couple of suggestions off the top of my head to get you going. These may change once you post back with the info requested.

) Secondary spring. I'm thinking a long yellow spring should be a good starting point. May be a bit light. Get a quick change cover kit if you don't already have one. Check opening amount with the paper clip trick.

2) Pump shooters. I'm thinking you'll need at least a #35 shooter with the Torker. Try a Blue cam in the #2 hole. Get a hollow shooter screw.

3) Transition slots. No more than .040" exposed on the primary side. Open the secondary side a bit more if necessary to close the primary blades a bit.

muggsyjack

.488 is with 1.5 rockers. Closer to .520 w/1.6. Thought this may help compensate for heads. Carb is out of box except for 65 power valve.

Launch is at 2000 RPM. Anymore and car tries to creep, brakes won't hold. Shifting at 6500 RPM. Have tried lower points to no great impact. Fifteen passes total, all in 8.67 to 8.78 range. MPH remains somewhat constant.

I would post vid of single pass but is too big for board upload. Considering testing dual plane and/or 1.5 rockers.

Chickenman35

RPM range certainly within that of a Performer RPM.

Still need to know what shooter, and cam you have. List number of carb would help a bit...although a physical check is best.

I think I'd try 1.5 rockers on the intakes only. If ET drops then an indication that the engine want's less cam.

Video's hard to tell ( unless something grossly wrong ) what the ngines actually doing. What looks great on video can feel like crap in the car. You're the best judge of what works.

What do you have in the back for brakes? Drum or disk? Drums will actually hold better against the convertor than disks. Drums have a self-servo action. Disks don't.

Either way an adjustable proportioning valve will help you out. Crank more brake Bias to the rear.

muggsyjack

Carb is 3310-3. Power Valve was changed to 45, not 65. I also have a 35 if needed. Otherwise it is same as delivered. choke is wired open. Running 5 PSI per gauge. Using in tank TPI pump w/Mallory regulator. Cannot run pressure higher because gauge bounces. Installing new gauge on cowl to verify pressure during run.

Drum brakes in rear w/new shoes. Cylinders good, m/c good. Rear tires start pulling free between 2200 and 2400 RPM.

Looking at spring specs w/assortment. Stock spring may be issue. Will try long yellow and straighten transition slots/idle plates.

Should I order a trick kit for cams or are they separate?

muggsyjack

I may be chasing ghosts to a degree. Last time I raced it was a dragbike running 10's.

muggsyjack

Also have one inch spacer under carb. Used single plane in expectation of nitrous addition at some point.

Chickenman35

OK..3310-3 comes with a #25 shooter out of the box. Tech specs don't list cam, but it probably came with a white or a red cam. Either way not enough initial shot. Your 3,500rpm stall convertor helps mask some of the problem.

Order the cam assortment. Always nice to have the different profiles to play with.

I'd still recommend the Blue cam in #2 hole. As for shooter...try a #31 and then a #35. See if that gets rid of your tip in hesitation.

Rear brakes. Drums should be able to hold the rear wheels. May take a while for shoes to bed. Do you have a line-lock on the rear drums or do you do the two foot shiffle?

Either way I'd recommend an adjustable proportioning valve to crank in some more rear bias. That should do the trick. Premium lining are a must.

Stock secondary spring is a silver or "plain" spring. Fairly stiff on a 350. Definately too stiff for a 305.

Power valve has little affect in Drag Racing. As long as it's at least 2 points lower than vaccuum reading at idle in gear it will be fine. Power valve tuning has more affect in Road Racing.

Having a re-think on your Torker....your high stall convertor ( 3,500rpm ) and 4.10 gears are probably masking it's poor low end performance. Convertor allows the engine to flash past the weak point of the manifold. Still...there is better technolgy out there. I'm thinking a Victor Jr might give you a bit more HP over the Torker. Still a lot of manifold for a 305 though...

Brilliant thought!!!! Why not give Edelbrock's Tech line a call? That's what they're there for. I've had pretty good service from them. The odd time that I got someone that was in over their head ( New guy ), they immediatley switched me over to a senior staffer.

BTW..I've used Nitrous on a dual plane before...no problemo. Just check the spray bar orientation before purchase.

Chickenman35

Couple of other tips. Remove the choke assembly entirely. Install a K&N stub stack...this will really help flow through the carb. Might be worth a tenth all by itself.

Pablo

iTrader: (1)

Stick with the single plane, 95% of the rpm your car is in is where single planes build more power. Dual planes only give more signal to the carb on low end by making it appear smaller, I think the longer runners giving more low end perf. is neglible. I have run FI on my single plane and I have low end to spare, so i think its mostly vac. signal. The runners are tuned for low rpm anyways. With a dual plane youll also have 1 half of the engine with a much bigger plenum than the other and more disparity between runners.

Now if you have the ORIGINAL torker i would suggest you get rid of it it is an X manifold and they are pretty terrible. The Torker II isnt bad though, I have one and as you know i trap a hair away from 105 with a 305 with full exhaust, and smaller cam.

If you are going to swap manifolds id definately go with a victor junior. I think you should put some more work into the heads though before you think of anything else, just removing all the casting irregularities from a set of 416s has to be a huge gain.

muggsyjack

Have cams and squirters ordered. Already swapped spring. Will try your recommendations. May not get to track until next week.

Appreciate the help.

icebird_1981

with VS the car is suppost to gradualy accelerate smoothly, u r not suppost to feel the secondarys open and if u do that means they r opening to soon.

muggsyjack

changed spring, replaced nozzle and cam..... Engine runs crisper, response is improved. Will be going to track next Friday night to test...

Chickenman35

muggsyjack

Special thanks to Chickenman.....his tuning tips helped to drop best time down to 8.3559 @83.03 in 1/8 th mile.

Chickenman35

Wow...over 3\10's in the eighth mile and nearly 2MPH. That is good...Excelllaaaant

muggsyjack

Tonight ran an 8.3445 @ 83.26 MPH w/1.8936 60' time.

The next question is: I have the long yellow spring in and there is no bog present or any indication of secondary opening. Should I try next lighter spring in secondary?

Plugs look great, light tan w/little sap buildup on outer ring.

Chickenman35

Go for it. Your Et's will tell you if you went the right direction. You should not be able to feel any secondary opening. If you do, it usually means the spring is too light. At that MPH and ET you can be assured that the Secondaries are opening. Note: they do not have to open all the way....opening rate is more important than amount. A 305 at 5,500 RPM with a 780 VS may only pull the Secondaries open 3\4 of the way. That's fine. That's all the air the engine needs.

What happens is that you get a slightly lean condition if the secondaries open too soon. Not enough airflow to start the secondary boosters flowing properly. This lean condition is very subtle...you may not be able to feel it...although a dyno should show it...both in HP\Torque production and A\F mixture.

Doesn't last long, but when you finally get enough airflow through the secondaries, the boosters start flowing and that is the slight " kick" that you can sense. You've passed through this slightly lean area and now are getting a correct booster signal.

Dragstrip a very good way to set up VS carbs. The ET and MPH will not lie.

83 Z28 HO

Hmmm, on my stock crapajet I can BARELY feel the secondaries open with I floor it from a stop or slow roll. Odd. But I'm getting a 600 or 650 and disconnecting the computer so.

bidle98

I had a holley on my 406 and I had the same hesitation sometimes and I did have slow rpm build up. I figured out that my converter was not big enough and to play around with the power valve and squirters.I havve just a little bit bigger cam then you do but same mite apply.

F-BIRD'88

your 1/8th mile ets amd mph convert to 13.10@105.4mph

not bad at all.

I'd try increasing the initial timing to a full 35deg.
remove the mechanical advance springs and weights and tie wrap the mechanism fully advanced. reset timing to 32-36 deg.

This motor will make maximum hp at near 7000rpm.
This car needs more rear gear ratio to use all the motor up in the quarter mile. I'd move up to 4.56's... 4.10 are not enough gear.

The cam may respond to being advanced a few degrees.

The old edelbrock torker is infamous for a pesky off idle stumble.
Carefull tuneing of the shooter size, pump cam and initial timing setting will get rid of the flat spot.

The 750VS secondary opening rate can be further tweeked by
using a Quick fuel technology lower vacuum diaphram housing with the adjustable vac bleed rate screw (looks like a idle mixture screw on the lower housing). But will take carefull tuning
as to much opening will cause the car to bog.

220PSi is a lot of cylinder pressure for street pump gas.
Try some race gas. (110 octane)
Try some 12-18" long collector extensions to enhance the torque ...

Chickenman35

Weakest point in the combo is the heads by far. Huge HP to be gained with better heads. AFR's would be my choice...although the Edelbrock RPM's are nice as well. Valve train on Edelbrocks not up to the task though. Too wimpy of springs for your combo. I went to Isky 8005a's on my motor with a Comp Cams 236\242 @.050" and .575\.590" lift ( with 1.6 ratio rockers ). I'd definately go with Aluminium.

Edit: With your current heads no point winding the motor up. They just can't flow enough air. Just about anything would be better than the stock 305's that you have. I would choose some good quality Aluminium heads such as AFR, Holley or Edelbrock with a suitable combustion chamber to keep your 10.5 to 11 to 1 C\R. Keeping you C\R around 10.5 to 1 with Aluminium heads will enable you to use a good quality pump gas no problem.

Edit: Intake? I'd go with a Victor JR. No use changing intakes till you do something about the heads...they are the cork in the system right now. But you probably already know that.

Note editing!! Got in late last night at 2:00AM Got your post confused with one above and thought you had a 406

Heads still the weak point...but not nearly as bad on a 305 as on a 406 LOL!!

muggsyjack

Per Chickenman suggestions, we made carb changes and car responed well. Flat spot/stumble gone. Car will now light tires if you stomp from an idle. Using new 12" wide Goodyear Nascar slicks off E-bay. Traction is an issue at present.

Current best time is 8.3345 @ 83.74 MPH w/1.89 60' time. Tach shows 5000 RPM at the finsish line in 3rd gear. We know the heads are weak point. Currently have them off to match gaskets, open as much as possible and remove casting flash. Current best is arrived at by shifting at 6200/6300 RPM. Tried both higher and lower and car slowed.

Hoping current effort allows improved breathing. Anything would probably help. Also adding shift kit and 90/10 shocks to improve transfer and gear change. Son says 200 to 300 RPM lag before shifts.

The 305 was originally intended as a throwaway motor for me to become more familiar with tuning and son to get used to car/drags. Did not really expect it to respond as good as it has. All components are lower grade. Especially the heads. Could not use original swirl port models as they would not breath above 4000 RPM. Cam is Summit cheapo. Springs are off brand (they are strong as I keep bending my spring compressor removing them). Heads were milled to hell and back. The manifold is a $40 Torker2 off e-bay. The engine had been rebuilt prior and only had 20k on it. New bearings, rod bolts and high volume pump is only bottom end investment. Even dumped original hyd. roller setup as the valvetrain weight would be too much for stock diameter springs.

Overall engine runs good, enough so that no one believes it is a 305 2 bolt POS. I like sound of open headers and it is loud. Most guys are running some type of muffler. I have 45 degree turn downs to keep exhaust from heating fuel lines and trans.

We would like to see 12's N/A before adding nitrous. Since the car is running last part of 1/8th in weaker band, 1/4 mile should be in the high 12's.

How much gasket matching, general opening and cleanup will help I cannot even make a guess. I have all the tools required from racing two stroke triples years ago. Any improvent will show.

I had originaly installed 1.6 rockers to help heads breath better. Maybe I would have been better using 1.5? Any comments?

I appreciate any input as I am relatively green on current trends. I am more familiar with AFB's than Holleys.

Chickenman35

Did you send me a couple of Mpeg's of your car from your wife's computer or was that someone else?? Didn't look like Nascar slicks to me??? I'm confused.

Switching to 1.5 ratio rockers on the intake may help. That's what I would try. Your RPM range looks good. A 305 does not have a favorable rod to stroke ratio...so big rev's ( over 6,500) won't really help....particularily with your current heads.

Concentrate on unshrouding the Combustion chamber on the Intake side. Stick with the 1.94's. 2.02's in those heads will cause too much shrouding and will actually cost you HP and Torque. Even if it costs you some compression, open up the cylynder wall side area by the Intake valve. Don't go past the Bore limits of course.

Bowl area porting, valve guide slimming, short side radius and Roof of Intake port is where you'll get the most gains.

The open headers are hurting you....nice as they may sound. Build a good full lenghth system. Dual 3's with an "H" pipe or "X" crossover and a couple of Big Flowmasters. You will pick up lots Torque and HP. Dual 2.5's would probably be fine for a 305....but hey...you're gonna go with a bigger motor later on....Right?

muggsyjack

Yep. The two MPG files were from wifes PC. Her machine has connection and software for camera. One is prior to carb changes and one after. The car is running good overall. I think we may be able to go a little faster yet though. I am hoping port work will free up power a little. The gasket match is terrible on one head....the other not as bad, but still not good.

These are Nascar 12 X 27.5 X 15 Winston cup slicks D-6340. They were put on new. The old tires were 10 X 27 X 15 Hooters series tires, they were used. They seem to work okay once heated. I honestly did not think the 305 would break them loose as easily as it has. We are geared to run 1/4 mile but the 1/8 mile track is easier to get to and not as busy. We are able to get more test time in. The 1/8 mile track does no track prep. The 1/4 mile does and I will be able to launch a lot harder there.

I have 90/10 struts coming to get better weight transfer along with a manual shift kit for trans.

Hopefully I will be able to get done for Friday test and tune.

One other note, I used head gaskets from a 350 because the original heads were to be world SR305 and that was specced. When Summit called after a couple weeks and said it would be another 16 weeks. I bought cheapo "high velocity" heads to get engine together. I have found a set of proper 305 head gaskets and will use them when it is put together. They fit bore properly and are about .005" thinner. I have .070" piston to valve clearance so this should not be an issue.

muggsyjack

Lighter spring (short yellow) works fine. Best ET is now down to 8.11 at 85.45 in 1/8 mile. 60 foot of 1.85 is still of concern. NASCAR type slicks will not hook well. Must do Funny car type burnout to get hot enough and it still spins.

Thinking of removing plate style secondary setup. Plugs look rich after run.

Any thoughts on conversion?

F-BIRD'88

The secondary metering plate will not in itself, cause rich plugs but fuelbowl vent slosh at launch will.

So can accelerator pump shooter fuel suction. (pull over)
Remove the accelerator pump nozzle and check for the little anti pullover check valve and that the right O gaskets are under the shooter.
Change to and anti pullover style shooter.

Connect the fuel bowl vents with a piece of rubber vacuum hose as per the pic. Cut a hole at the highest point.

You'll pick up a lot of head flow with a full port job.
Don't be shy, You can't make these heads too big.
they flow amazingly well with full porting and large valves. 235-240 intake and 180+ exhaust.

But once you do that its really going to love the rpms.

Then you'll really want the 4.56's

Some M/T et streets and a Airlift air bag in the rear will help it hook a lot.

A Performer RPM air gap will add over all torque and not give up much top end if at all.

F-BIRD'88

Here is a pic of a adjustable vacuum sec lower housing

Chickenman35

Looks like the increased Secondary opening has fattened the mixture from your original setup. Back then, I believe you said that the plugs were a nice tan color. The increased air flow on the secondary side also increases fuel flow.

Metering plates ara PITA IMHO. Makes tuning so much more difficult.

I'd purchase the Secondary Metering Block conversion Part # 34-13 ( Or 34-13S for " shiny finish).

Along with that I's get the " Whistle Vents " part # 26-40. Installing these , along with the "hose" trick, should eliminate any fuel slosh problems.

A set of " Quick Jet Change " Fuel bowls will definately make jet changes easier, with lees chance of fuell spillage.

Part # 34-25 for the Primary side ( 34-509 for Chrome finish ) and # 34-27 for the Secondary side ( 34-511 for Chrome finish ).

Primary side Quick change Bowl is generally more usefull than Secondary side. The Primary kit also includes a nifty Jet removal tool.

For jetting: A stock 3310-3 comes jetted with 72 jets in the Primaries and a 134-21 Secondary plate , which is equivalent to a #75 jet.

I think you'll find it's a bit fat on the Primary side. I'd try #70's and see what the ET does. Keep a close check on plug colour and for any signs of detonation.

If you drive your car on the street, I usually like to run the Primary side lean and mean. Good for keeping the plugs clean and general fuel economy. Then I jet up a couple of jet sizes on the Primary side for the Track.

If you change to a metering block on the Secondary side, don't be surprised if you have to go up considerably in Secondary jet size. While a 134-21 plate has an equivalent fuel flow as a #75 main jet, the metering plates and metering blocks have different air bleed and emulsion tube sizing, This of course affects total fuel flow.

I'd try some 76,78 and 80 jets in the Secondary side as a starting point. See what the ET does.

I'm thinking that 70's in the Primary and 78's in the Secondary with the metering block conversion would be a safe starting point.

Baseline it with the Primary side jetting. IE: Get the best ET you can ( with good plug color ) using your current metering plate setup. BTW...right everything down in a log.

Then if you convert to a metering block setup...adjust the secondary jetting till you get the same performance as your baseline. That should put you in the ballpark. This is where an Air\Fuel monitor can help. Good for establishing a baseline....just don't rely on them 100%. They are only accurate near Stoich ( unless you get a Wide Band o2 sensor...Mucho dollars ). Go with what the motor wants but they are a usefull tuning " Tool ".

Chickenman35

Couple of other things to check. How much clearance between the top of your air cleaner lid and the airhorn of the carb? The more the better. If the lid gets too close to the airhorn it can choke off the carb and cause excessive richness on the top end. Minimum clearnace is approx 2". I like to see more. I run a 5" tall K&N air cleaner on my car with an Extreme Top filter.

A hood scoop or bulge is necessary to run this much clearnace. Couldn't tell if you had a hood scoop or not.

Get rid of the choke assembly and install a K&N " Stub Stack ". This will really smooth airflow into the carb. Can easily gain you 5 HP.

muggsyjack

Have old style Mopar Pro stock hood scoop. Air cleaner is 4" tall X 10" diameter K&N style on 5" velocity stack base. I did make a couple of runs without it. Just to be certain there was no restriction. Element was to be good for 1200 CFM at some minor amount of static drop.

Plugs went from light tan to dark tan. May be normal buildup after 22 runs. Gonna stick new set this weekend. Wondering about jets vs plate to get more control.

Gonna also try white (lightest) spring too. Short yellow is not causing bog or transition to secondaries. Cam in combination with porting is apparently working well.

Just installed new MT drags slicks tonight. Expect to drop 60' at least .15 or better. Current best is 1.85 60' with the 1/8 mile closing out at 8.11 @ 85.45 MPH. Should car spin too much, it drops et on 4-1 ratio. If I run a 1.86 60' the ET is 8.15/16.

Also had trouble with spinning in second gear.... noticed change in incremental times.

What is the effect of carb spacers on a combo like this? I am currently using a 1" spacer. Would increase to 2" create more ram effect? Noticed when we pulled heads that intake prts on 2&6 and 3&5 looked like there was more black goop built up. Does a torker two have trouble with equal distribution? May have caused in part by balky needle/seat that I replaced because of flooding.

Expect to see 7's Friday night w/new slicks.

Considering adding mufflers, trouble is not much room to tuck up in frame. Also not much clearance when going up trailer.

muggsyjack

per your advice, I dumped choke assembly and installed quick change spring housing.

muggsyjack

Have air bags, boxed control arms and adjustable panhard bar. No tire hop at all , rear is stable. Also added 90/10 struts in front. Hits stops on launch with tires spinning.

Since port work, car now pulls strong to 6500 RPM before there is a drop off. Lauching at 2200 RPM and shifting at 6500 is what produced best current ET.

Will keep car geared as is, optimized for 1/4 mile. 1/8th track is best for launch and tuning through 2nd gear. If we were only gong to 1/8th, we would use 4.56 gears.

Chickenman35

If you've got room for it, definately try a 2" open spacer. Will help the fuel droplets to make the turn before hitting the plenum floor. May even out the fuel distribution.

Most single plane manifolds, including Victor Jr's and Holley Strip Dominators come with a plenum volume that is too small for a race 350. Adding a 2" spacer brings the volume just right. This is intentional on the mfgs part ( according to Vizard and Roe ). Having a spacer of the correct dimension makes machining of the plenum and runner entrance very difficult. Also much easier to put a shorter spacer on an engine or remove it entirely, if that is what the engine wants, than to mill off an inch or two of aluminium. Might be too much volume for a 305...but maybe not.

Carb flooding, even once, will make plug readings useless.

BTW...just reading one of Vizards books ( How to build horsepower Volume 2 ). Tested one of the K&N Super Stacks similiar to what you have. By adding a machined down K&N stub Stack that fits inside the Super Stack....resultant gain of 10 ft lbs throughout the RPM range.

chad89ta

i have an rpm on my 350 that i will trade for the torker,its 1 year old looks new,,,,,the torker is one of the best intakes ever,

muggsyjack

Chickenman, Some questions and current changes:

Went with white spring. Works fine. No bog or secondary transition noticed. Car has run a best of 8.11 in 1/8 mile.

Could not get traction, combination Nascar slicks and cool weather. 60' no better than 1.86 after long funny car burnout in second gear, looked nice and still spun. 60' all over the place due poor tire performance. Got into third round and broke out every pass until last in poor lane.

Changed to 28 X 10.5 X 15 M-T drag slicks. Taller tire slowed 60' to 1.9 range, consistent but slower. Took 1" spacer off torker and 60' dropped to 1.84. Ran a best of 8.14 w/spacer off.

Choice of add power low end or change converter, current converter flash stalls at 3200 RPM at launch. Installed dual plane air gap manifold and 230 duration crane cam in hopes low end power will improve 60' time.

Cam timing on less agressive cam has later exhaust closing point, eariler intake closing point and more overlap. Old cam timing points indicate a really cheap generic grind. LCA on new cam is 106, old cam was 114.

Should I put in smaller squirter with dual plane? Will dual plane wreak havoc with current secondary spring setting? We will not be able to run until Jan. 1st or 2nd.

muggsyjack

Another unique occurance. While running the torker one night, I checked timing. The advance springs had both broken off freezing timing at max advance, 37 degrees. I fixed it and car slowed a little, especially 60' time. Next day I fixed timing to max all the time and 60' dropped back down along with ET.

Engine starts okay but it is laboring a bit. When I try to run dual plane, do you think it will be worthwhile to go back to a timing curve?

Chickenman35

With the convertor that you have you may as well lock in the Timing. Weld the advance mechanism solid. For starting, wire in a separate switch for the ignition. Crank with the ignition off...then flip thye switch. Starter won't labor then. Or get a MSD starter Retard...switch cheaper though.

On welding the advance weights. Phase the distributor rotor first. Get an old distributor cap, mark the cylinder#1 on the side with a black marker. Cut the top off the distributor. Edit: Bring #1 to 37 deg BTDC. Remove springs and weights. Adjust advance mechanism so that the rotor tip is directly in line with the distributor tower contact. Now tack weld.

Chickenman35

The cam change should make quite a difference. The tighter LCA will increase low end torque and the mid range. Can you post the complete specs on the old cam vs the new cam? PM me if you wish.

The Dual Plane should also increase your low end torque. Don't use an open spacer on the Air Gap RPM.....at first. From what I have read they don't like them. Run a Four hole spacer as a baseline. I'd experiment back and forth with spacers. They can be an essential tuning tool.

You should get a stronger booster signal with the Dual Plane . This will affect several area's. It is going to cause the secondaries to open sooner...so you might want to back up a step or two on the vacuum spring.

What are you at with pump shooter and pump cam now now?

You may have to jet down slightly with the manifold and cam change...do this last. Shouldn't be much if any.

Make only one change at a time. I'd suggest spring... then shooter...then jetting if necessary by plug color.

The manifold and cam change should give you a bunch more bottom end. Don't think you need a convertor change...3,200rpm at launch should be just right. A full lenght exhaust with an X or H pipe and mufflers will also add bottom end torque if you need it.

If you need more top end...you can always retard the cam 2 to 4 degrees. I'm thinking you won't. 305's don't like to rev...poor rod to stroke ratio. Keeping it below 6,500 will be your best bet IMHO.

You're moving in the right direction....Merry Christmas and may Santa bring you some 7's

muggsyjack

Old Cam:

Summit
w/ 1.5 Rockers
.488 lift intake/exh. 292 Adv. Duration. 114 LCA

Valve timing @ .050 tappet lift
Intake: Open 8 BTDC Close 46 ABDC Max. Lift 109 Dur. 234
Exh. : Open 56 BBDC Close 2 BTDC Max. Lift 119 Dur. 234

New Cam:

Crane Blue Racer
w/1.5 Rockers
.465 lift intake/exh. 292 Adv. Duration. 106 LCA

Valve timing @ .050 tappet lift
Intake: Open 13 BTDC Close 37 ABDC Max. Lift 102 Dur. 230
Exh. : Open 45 BBDC Close 5 ATDC Max. Lift 110 Dur. 230

Both cams are installed 2 degrees advanced. Also using 1.6 roller rockers.

The numbers are close until you look at timing points. The Summit cam appears very conservative in overlap. I remember the benefits of a free flowing exhaust and port overlap from racing two strokes. I am wondering if maybe the old cam did not allow full scavenge/burn. There was more soot than expected in chambers and exhaust ports when I took heads off. After a run w/clean plugs. The plugs are light tan. No sign of soot on outer ring, aluminum on electrodes or overheating. No sign of black smoke either. I looked under car during launch.

Currently using blue cam, high flow screw and #35 squirter nozzle. Will drop back two springs for initial run, presently have white spring in.

Appreciate all your help and happy holidays.

Chickenman35

I'm thinking that with the Dual plane you'll probably be able to drop down to #31 shooters

muggsyjack

Started engine tonight. Sounds different. Crisper exhaust note. Throttle response is improved...tried a couple of launches, bottom end pull feels stronger. Works suspension more than before. Will update after Jan. 2 test and tune.

MIKE 1985

any updates yet with the dual plane and cam change

muggsyjack

Will be testing tonight at track. Will post results after mid-night. Keeping fingers crossed that we will see improvement. One note though, backed off on shooter size to #31 and stumble appeared on test launches. Had to go back to #35 nozzle.

muggsyjack

Weather was warmer than last month, 73 degrees at track. New best time of 8.10 @ 84.8 MPH w/ 1.7966 60' time.

This is the fastest the car has ever run at this temp. The previous best time of 8.11 @ 85+ MPH w/ 1.85 60' time was set at 42 degrees.

Put clean plugs in, look great. Timing locked at 37 degrees. Trick of spin then ignite works fine for starting. Left white spring in and still no bog apparent. Even tried adding stop to help secondary open a little at launch. Still using #35 shooter.

Was a little disapointed, wanted to see car in 7's.

Made 5 passes, slow night due to oil downs.

8.2007 @ 84.25 w/1.8317 60'
8.1580 @ 84.48 w/1.8268 60'
8.1372 @ 84.22 w/1.8131 60'
8.1311 @ 84.71 w/1.8199 60'
8.1013 @ 84.84 w/1.7966 60'

No definite conclusion yet. Fastest off the trailer pass. Car has gone faster than previous runs at warmer temps. Is it possible that a 30 degree change in ambient would create a 2 or 3 tenth difference?

On next to last pass, noticed engine RPM was not coming up as high as expected. Driver (son) said all launches were above 2,000. Was supposed to be launching at 2200 RPM. This is likely reason for 60' improvement.

F-BIRD'88

Hummm
are there 330' times and MPHs on your time slips?
better ? worse? the same?

The exhaust may respond to some restriction and pipe length. (may be over scavaging) Try some collector extensions.
may have to run the jetting and timing up and down again.
See what the motor likes

Still think you're using too much timing (37deg) ( indicates a lean(er) AFR at high rpm) ( slow burn speed)
If so, a richer mix will make more power with less timing.
higher MPH. Something to try. Bigger jets less timing.

might try a standard silver carb sec spring to see what happens. (faster, slower, same)
On my car after trying all the springs, jets timing etc etc.
went back to a standard spring and ran my best et and MPH. Weird but true.

Is the car's front suspension toped out as the car goes down the track? Suspension rise limiters will help the front end stay down at high speed. So will a front end chin spoiler.
go back to 1.5 rockers on the exhaust side. usually 1.6
intake and 1.5 ex is best.

just some thoughts.....