Messages

1

Originality / Any documented z28s w/o black or white stripes out there?

« on: August 06, 2021, 03:15:18 AM »

I ran across photos if that early Maroon/Red car (not sure who owns it, But Id love to)
And i was wondering if we have any documented examples of cars with special order stripe color, or if any Z28 were done with unusual stripe combos like the early Maroon cars

If i read correctly,  black, dover, and cortez silver Non-Z28 could have had red stripes - so I wondered if we have any factory mistakes?

Cheers

2

General Discussion / Re: Burgundy Z with Red stripes

« on: January 03, 2020, 10:10:54 PM »

I believe this car is at Mecum Florida - saw it today -
nice - but ugly in my opinion

3

Maintenance / Z28 - 4053 mods when running the 140 cam

« on: September 21, 2019, 11:30:28 PM »

Other than jetting -
Does anyone have any advice on tweaking a 4053 to run better when the 140 cam is used?
Idle or high speed air bleeds or anything

Thanks in advance?

4

Maintenance / Re: Clutch shudder - tuning wuestions

« on: August 20, 2019, 01:16:14 AM »

a shudder or chattering on pull away as the clutch is engaging is almost always caused by the clutch itself. If the clutch is the problem resurfacing the flywheel and installing a new clutch is the solution. Clutch chatter is often worse when pulling away in reverse. A stock "OEM" type clutch is what I would recommend. Aftermarket performance clutches have a much higher tendency to chatter but may be necessary if the engine is highly modified. Engine tune up and mount problems usually will show up at other times as well as when the clutch is engaging. Rough idle, under load at low RPM, engine acceleration while standing are examples. A new clutch will chatter if it gets engine oil, transmission lube or grease used during installation on the disc. A new pilot bushing is a "must have" when replacing the clutch. These are my opinions based on experience and I hope they are a help.

I would agree 100% except  -  this is my 3rd clutch and 2nd flywheel with less than 1500 miles and virtually no change in the shudder -

At first I installed a new McLeod 20# flywheel with their twin disk RST setup -    a lot of guys reported chatter so I wasn't worried - but couldn't live with it.  I contacted McLeod and they sent me their Super Street Pro which has a ceramic pad on the flywheel side and organic on the pressure plate side -   they said since it had such low mileage on the rST that I could easily get away without a resurface on a near new flywheel (we're talking less than 300 miles)

So - I put that clutch in - and made one error -  I put the Throwout bearing on incorrectly, as in, the fork's retaining clip on the back side of the TOB instead of in between the flange - stupid mistake, and I'm not a rookie at this -  - at first the clutch seemed smooth - but as it got warm, the TOB would not engage/disengage properly - and would make noise as I depressed the pedal -

SO - all that came out - and I learned that from the TOB not engaging the clutch properly, there was uneven wear on the flywheel -  so I pulled all that off - had the stock 40lb flywheel Blanchard ground, and installed an OEM type (made by Ram) clutch - fully organic with a bit more holding power.

That started off seemingly smooth but still had a very slight shudder -  I'm guessing nothing was solved but the problem slightly masked because fo the added inertia weight of the 40# wheel -  - but now a few hundred miles in - its still shuddering on take off.

When I put the car back together last year - I did replace the motor mounts with new rubber mounts and I had an energy suspension poly mount for the trans -  that's how the car sits.

tomorrow - I'm replacing the trans mount with an OE rubber mount - and I have 2 new Rubber motor mounts coming from HeartbeatCity - if the new mounts don't solve the issue - then it can only be the clutch fork or the bell housing - both of which are original and were not problematic before.   


I SUPPOSE I goofed up the fork when I had the TOB on incorrectly - but I highly doubt that -   I'm beginning to worry that I screwed up ANOTHER clutch with all this shudder - when its looking more and more like it never was a light flywheel or clutch problem to begin with.   

UGH - back under the car we go

5

Maintenance / Re: Clutch shudder - tuning wuestions

« on: August 18, 2019, 03:31:55 PM »

i'm digging into it on monday -  its entirely possible the points have gone out of adjusment - but timing was still where I left it - so i don't think thats the issue.

the motor mounts could be the culprit - although i'm certain they are not the wrong ones - i would think that if they were shorter the fan would hit?

they were def snug on the frame when I installed th emotor last year - but i suppose one could have ripped some how.

will report back asap

thanks

6

Maintenance / Re: Clutch shudder - tuning wuestions

« on: August 17, 2019, 07:50:41 PM »

Def not the pump arm or the squirter. I have a 31 in it now   

Any ideas What else might be causing the chatter?

7

Maintenance / Clutch shudder - tuning wuestions

« on: August 16, 2019, 03:06:21 AM »

Trying to tune out a clutch shudder on take off

Stock 1969 302.  With 1970 Lt1 cam
Manifolds, transverse exhaust
4053 with 72/76 6.5 and 8.5 and a 31 squirter

I don't believe timing is the issue as Ive had it everywhere frok 12initial/36wot to 20/42. With and without vac advance and no appreciable difference

The car is responsive and pulls great for being all corked up. 

The only thing i think is different in my carb,  previously i had 80 or 82 jets with a PV blockoff
And was running rhe 6.5pv up front when I had the 30/30 and it was smooth on take off

With the added 4-5” vaccuum at idle that the Lt1 cam creates, - do i need an 8.5 pv up front?At 900rpm idle, im getting 14-15”hg

Thoughts?

8

Mild Modifications / Re: l88 flywheel in a Z28

« on: August 01, 2019, 12:06:42 AM »

I ordered a Ram HDX for it = organic - 30% stronger than stock - should be good

9

Mild Modifications / Re: l88 flywheel in a Z28

« on: July 31, 2019, 02:52:14 PM »

I have two Mcleod clutches -  the twin disk RST which I really wanna like - and the super street pro.
the Super Street Pro pedal feels like a toy -   I kinda liked the twin disk pedal feel -  but the noise from not having any sprung hubs is terrible.... SO I'm going with a Ram this time.

10

Mild Modifications / Re: l88 flywheel in a Z28

« on: July 30, 2019, 01:35:05 AM »

got it -  stock 40# it is.

11

Mild Modifications / l88 flywheel in a Z28

« on: July 29, 2019, 04:38:51 PM »

who has done it?
any chatter or shudder on take off?

I have a #30 wheel in there now and a McLeod Super Street Pro and it shakes on take off -  i'm approaching 300 miles on the new clutch -  McLeod says give it 500 miles - but I've driven tons of cars with fresh clutches that were smooth as silk


curious if anyone has tried the lightweight flywheel with a torque-less 302 to see how the take offs are.  My car has 3.73s and M20

12

General Discussion / Stock DZ302 ideal performance....

« on: August 27, 2018, 02:14:06 AM »

Pretty sure I have the car running to optimal performance

You cam literally feel a solid kick in the pants at/around 5000/5200 rpm on up.
Starts pulling at about 3k but really wakes up at 5k
This through stock manifolds

Is this just he secondaries finally opening all the up or just where the 30-30 cam finally wakes up?

13

Maintenance / Re: another 4053 question

« on: August 24, 2018, 06:07:26 PM »

I def do not have too much transfer slot exposed,  if anything. Not enough
There is play in my secondary throttle shaft but that would mean - vaccuum leak, not pulling fuel from there.

Question- should the primary side transfer slots be exposed equal to the secondaries?   I just pulled and flipped the carb, and Id have to make a full turn to turn and a half on the curb idle screw to get the transfer slot on the primary side exposed, which would then raise the idle up to 1700 or more- and it would still run with idle mixtures all the way in.

Advice now?  Carb has two new power valves - suppose one could
Be bad so ill check and replace again.

Thanks

14

Maintenance / another 4053 question

« on: August 24, 2018, 12:01:43 AM »

so - I rebuilt the 4053 on my all stock Z, did some stagger jetting, took the car for a spin -she runs absolutely GREAT. BUT i'm concerned about the idle mixtures, and raw fuel odor at idle.

jetting is staggered, 73/71 on the primary with a 6.5 pv,  79/77 on the secondary with an 8.5

with the carb flipped, you can barely see the transfer slot on the secondary side - i err'ed on the side of too little transfer slot showing.

with the engine idling at 950,  (started with the idle mixtures 1/2 turn out where it seemed to run best prior to the rebuild/rejet)

timing is about 20 initial with 38max wot, using full manifold vaccuum,   I have a pink pump cam in the #1 and a 31 squirter -   the car is super responsive, and pulls very strong all the way up.

when I was adjusting the idle mixutres with a vac gauge, i could seat both and the idle went up - backed the curb idle down again, with both mixture screws seated and still get my highest vaccuum reading of over 12-13in - almost got to 15" hg, but that was with the idle around 1050.

what should I be looking for?  I'm to believe that seating the idle mixures means that its pulling fuel from somewhere? or is it pulling air from somewhere?

the bowls have been off several times, so i could see a bad gasket seal - but no obvious fuel leaking, and again, it runs better than ever.

any help woudl be great.

Thanks

15

Maintenance / Re: ideal 4053 jetting for stock 302/30-30/manifolds

« on: August 22, 2018, 12:12:19 PM »

Pump cams are color coded and have 2 or 3 holes to use, so lots of adjustability there.

I run the pink cam in the #1 hole and it works flawlessly on the 302.  I upped the squirter size to 31.   My throttle response it crisp and quick.   A lot of that will be in the timing as well.

Mine likes to have 16 initial and currently running 36 total.  I have (adjustable) vacuum advance adding 10 degrees and it's all done by 8 inches of vacuum, much like a factory B28 can.  I welded the slot on the arm to limit what I wanted.  .250" of movement is all that's needed.   I've switched back and forth from ported to manifold vacuum.   Since I drive most of the time up here at 5,000 ft altitude I found mine just prefers manifold vacuum.  Ported is okay, but it tends to run a little warmer that way, and mileage was down with around town stop and go driving.  I have much cleaner and crisper idle with the added timing using manifold vacuum.  Also helps the little 302 that has a pretty rowdy camshaft from the get go make a little more vacuum as well.  With a true 11:1 compression it runs beautifully on 91 octane, and even with the summer temps hovering 100-106 this summer, I never see the engine over 185 degrees shooting it with a inferred gun.  All stock cooling system and the original 49 year old radiator.   So there are some things you could look over and try, see if that helps.

Here's an idle clip of mine.   https://youtu.be/IZ0HlEY7b74 
 
I run what the PS guys call a cheater cam.  It's pretty close to factory spec but it's closer to advertised lift after lash is figured in with a .330 lobe and a tight lash of .014" (.481" lift vs .455").   This was done for a few reasons (take advantage of rules) but one was to also keep valve train beating to a minimum.  It idles near stock and produces stock like vacuum, makes plenty of off idle grunt for a 302.  I can lug it down to 25 mph in 4th gear, with 3.55's out back, about 1100-1200 rpm, and adding throttle easily picks up speed without complaining.  Makes it nice to drive around town with minimal shifting when you get behind slow people.

As far as valve lash, that 90 degree method posted above works fine. 2 at a time assures the lobe is on the base circle, I know engine builders that use it and it works.  What I do is one at a time, rotating each lobe to max lift and then 1 complete crank rotation (= half cam rotation) assuring each lobe is on the base circle, with the biggest difference being I have to rotate the engine over a lot more, and it's more time consuming,  but for me it's just being picky.   Either way, base circle is what you're trying to accomplish and is most important. 

you were gonna get me those lobe numbers -   from sYc forum.