[malibu man]

I don't know if this is the right forum but I get a very bad hesitation when I activate the kickdown. It is actually right before the kickdown is activated because the rpms are still low. Say i'm going along at like 1500 rpm down the road and I kickdown the accelerator pedal, the rpms will lower for a second or two and then the rpms will raise and it will downshift. After the kickdown works the car breaks loose pretty easy though. Is the detent spring too light in the valve body, does the modulator need to be set, or is it engine related such as a mis-sized or mis-tuned carburetor? I'm guessing carburetor but I wanted to get some opinions here also.
Thanks

 

[charbilly2001]

Check the operation of your carbs accelerator pump first to make sure you are getting a decent pump shot.

After you have done that I would then look at the secondary opening rate of your carburetor (assuming you have a 4bbl) and see if they need to be slowed down a bit. Your secondaries may be opening too soon and giving you a passing gear "bog". You don't mention any backfire which leads me to think that your secondaries are opening too soon rather than your accelerator pump shot being weak.

The transmission downshift rate is pretty much "fixed" and is normally fairly rapid. Not likely to be the cause of your hesitation.

 

[malibu man]

Thank you charbilly!

I might as well get a different carb then check to see if it does this. So would you recommend to stay away from mechanical secondaries on my engine since this does this? I'm currently running vacuum secondaries with I think one lighter spring in the secondary. I think the guy before me had done that to the carb. Also, do you recommend the quick change kit for holley? What's your opinions on the Quadrajet carbs?

Thanks

 

[charbilly2001]

Walnut Grove, Seems to me that that is in the St Paul area isn't it? I am origionally from Crystal, Mn which is where I lived before I came to California.

With respect to your car it is entirely possible that you have too light a spring in your vacuum secondaries. The way to find out is to put a heavier spring in the pot.

With respect to mechanical secondaries they usually come with either a secondary accelerator pump or some sort of air dam that can be adjusted for its opening rate. I have used just about all kinds of carbs over the years and I have found that they all work fine once you figure out the tuning combination for your car.

I am currently running a Quadrajet on my car and have no bog problems when downshifting. I happen to like the "streetability" of the Quadrajet over all other carbs I have used but that is just my opinion. To each his own I guess.

One thing I will say for sure is that for you to go get a different carb is not , in my opinion , a good idea. Stick with what you have until you figure out the solution to your hesitation problem. This is all about learning how to diagnose tuning problems. Changing carbs will teach you how to change carbs...not how to diagnose problems. Keep trying different combinations of secondary springs and or accelerator linkage (cam) adjustments or any other tuning adjustment that works until you get rid of your hesitation. Learning how to do that will prepare you for the next diagnostic challenge your car hands you.

Good Luck!

 

[malibu man]

Yeah Walnut Grove in in the southwestern part of MN. I'm pretty familiar with Crystal myself. Don't they have a grain truck box manufacuring plant up there called Crysteel?

I might as well get a different carb since i'm undercarbed. I'm running a 600cfm Holley 1850 on my 383 with 10.7 CR and 292* Duration. I'm currently rebuilding a 750 cfm Quadrajet out of a 73 Buick Century so maybe that would be better. What carb would you recommend since I need one anyways? So should I try to tune this one anyways since I have it?

Thanks

 

[AdamLym]

Trevor, I saw the pic of your plugs a while back - get that holley tuned up!! You're running rich BIG TIME. You have plenty of carb for your application. I had a 600 holley on my 406 for about a year, and it was more than enough to spin it to 6500 and run mid 13's at over 100mph in the 1/4 with 2.56 gears and a stock converter. I'm betting if you get it leaned out and get some nice tan plugs, with a proper timimg curve you'll be rid of your hesitation. That cam/converter/rearend combo is not helping your situation one bit either.

 

[malibu man]

Thanks Adam!

Those plugs were pretty bad. They always ended up that way ever since I got the 600 holley and put it on my 350 a couple years ago. I'm pretty sure the secondary spring is one lighter than stock. If I remember right I got the carb from Bills Camino off the forum. I traded my Edelbrock 1407 750 for it.

So you recommend I:
1)Stick with this carb.
2)Retune this carb.
3)Check timing and possibly re-adjust it.
4)Get lower gears in rearend.

This brings up a lot of priorities and things that I might want to fix and plan for the future like the rear end and the octane of gas that I will end up running.

Let's start with the first one. This carb will provide enough airflow right? Next one. What should I do to the carb, in order, as far as tuning is concerned. Next one, is their any happy medium on the timing so I can run so I can run pump gas with my 10.6:1 Compression and 8:1 DCR? Last one, maybe I should get a different rear end first and then mod that one and put lower gears in it. I really don't think the 8.2 10 bolt will hold up to this engines profile and possible performance. I've been told to go with a 8.5 rear, and 8.875 12 bolt rear, or a Ford 9". Should I plan for the future while doing these mods or should I just go along one step at a time?

I need to start doing some of this stuff instead of asking questions and bothering all of you like i've done for the past couple months.

I feel sorry for you guys.

You don't know how I appreciate all of the encouragement and advice.

 

[odie]

After you get the carb, timing, etc. squared away & if you still have the problem, you might take a look at the setting of the kickdown at the carb & where the kickdown mounts at either the manifold or carb mount, etc. If you're using a factory kickdown cable, most have an adjustment to lengthen or shorten the distance from the mount to the "stud" on the carb, which will effect when the transmission downshifts. I had one kicking down "out of time" with the carb once & caused a hesitation at one extreme of adjustment & a roaring motor without the kickdown happening quickly enough at the other extreme. It took a little tinkering to get it right (but it was a lot of fun running down the road testing the kickdown !!). As the other posts say, you'll want the carb & timing functioning right first. Good Luck...Odie.

 

[odie]

After you get the carb, timing, etc. squared away & if you still have the problem, you might take a look at the setting of the kickdown at the carb & where the kickdown mounts at either the manifold or carb mount, etc. If you're using a factory kickdown cable, most have an adjustment to lengthen or shorten the distance from the mount to the "stud" on the carb, which will effect when the transmission downshifts. I had one kicking down "out of time" with the carb once & caused a hesitation at one extreme of adjustment & a roaring motor without the kickdown happening quickly enough at the other extreme. It took a little tinkering to get it right (but it was a lot of fun running down the road testing the kickdown !!). As the other posts say, you'll want the carb & timing functioning right first. Good Luck...Odie.

 

[Joey B]

Malibu Man,Isn't Walnut Grove, MN where Little house on the Prarie was supposedly to be set?

 

[malibu man]

Thanks!

I'll just do what smokumchevy told me to do on my carb and timing. Then i'll post back.

Joey,
Yes that is correct. They have some sort of a pageant and supper in the late summer every year. We get a lot of tourists then so I try to stay out of town on the weekends, weekdays aren't as bad. The town isn't very big, under 1000 people I believe.