ideal 4053 jetting for stock 302/30-30/manifolds

[aaronz28]

getting my stock DZ302 back on the road this week -  and have a few questions.

i'm getting a high rpm break up - but i think i know where/what that is - as for the carb...
i know 68-72 was stock jetting - but i also know that is WAY lean.

the motor is true 11:1, installed a NOS 3849346 cam with factory - 0-stamped rockers. - lash is set and checked at 30/30 -
ignition is 38wot, with initial around 18 -  car fires up beautifully, and I have no issues with idle at 950.
its got 70-76, with a 6.5 and 8.5 and a yellow spring - and its pretty doggy - even for a gutless 302 with manifolds lol.

one thing that seems odd - idle mixtures are only 1/4 to 1/2 turn from bottomed out with about 10"Hg at idle... so i'm slightly concerned about the mixmatch of new/old Holley parts.

the carb is an old 4053 with original metering blocks, on newer 4053 baseplate -   i still have the rest of the repop 4053 which might get put back together tonight if I can't sort this original out.

something just doesn't seem right about the way it runs - its rather sluggish to get off the line, seems ok mid-range wise - but never really pulls hard.

Years ago, I borrowed a buddy's o2 -A/F tailpipe rig and I got the best readings with 72-76 with the stock manifolds... does that sound right to you tinkerers?

Thanks

[X33RS]

Stock jetting is 68 front and 76 rear with 6.5 power valves front and back.

A lot of this is going to depend where you live, the altitude, and more importantly the DA the car is regularly driven in.
 
I'll assume you're also running the stock DZ intake.  In which case stagger jetting will give you best results if you're really picky.  Mine made best power by stagger jetting, up on the driver side front and rear 2 sizes bigger than the passenger side of the carb.   I also get better idle quality by staggering the idle mixture screws slightly.  Driver side front barrel feeds #2 and #3 primarily and I could blacken those plugs with too much idle mixture.   Mine is much like yours, my idle mixture screws are out between 1/4 to maybe 3/8 of a turn, which gives me a nice 14:1 AFR while idling where the engine seems to be happy.  If I go out much more than a 1/2 turn the AFR goes pig rich.   My mixture screws are very active, which is good.

I do all my final tuning with a wide band.   Up here at 5,000 ft elevation I find the stock 68 front jetting to be "okay" on AFR readings when running the stock manifolds and original exhaust system.   I eventually switched to headers, and a better flowing 2 1/2" mandrel bent transverse exhaust system.   My car responds best to a 70 jet front passenger side, 72 jet front driver side, and 76 rear passenger side, 78 rear driver side.   It also likes the 6.5 PV's front and rear.   It cruises with an AFR of about 13:1, which works nicely at 5,000 feet, so when driven to sea level it's not going dangerously lean.  Runs closer to 14:1 cruising near sea level, and with a steady cruise of 65 mph, knocks down 17 mpg.

Up here at 5,000 ft my engine is making between 9 and 10 inches of vacuum idling at 1,000 rpm.  So those power valves work fine for me.  If I take more power valve out of it, say 4.5's, it just creates an aggravating stumble off idle that won't go away even with hours of squirter and pump cam changes.   It just likes 6.5's and I have no need to go higher.   Also works fine when I drive the car down to sea level, where the engine makes just over 13" of vacuum.

Keep in mind that if your running todays 10% ethanol pump gas (which I do) stoich is no longer 14.7:1.   Stoich for 10% ethanol is .7 richer at 14:1

[aaronz28]

Im at sealevel. 

Will try staggering some

[Stingr69]

Aaron,
the lash would be better set at .026"/.026" with stock stamped rockers.  You will be off the clearance ramps (more clatter and wear) if you use the .030"/.030" setting. 

-Mark.

[bcmiller]

Aaron,
the lash would be better set at .026"/.026" with stock stamped rockers.  You will be off the clearance ramps (more clatter and wear) if you use the .030"/.030" setting. 

-Mark.

An EXCELLENT article on that topic (thank you John) is here...
http://www.camaros.org/302valves.shtml

The “old school” way I was taught - with the 30/30 cam and others was to set them hot and running. But there are better ways than that.

[aaronz28]

Guys, ive tried the 26/26 setting

Just more overlap, and less bottom end for an already wimpy 302

The 30/30 setting is not noisy by any means.

[z28z11]

Aaron,
the lash would be better set at .026"/.026" with stock stamped rockers.  You will be off the clearance ramps (more clatter and wear) if you use the .030"/.030" setting. 

-Mark.

An EXCELLENT article on that topic (thank you John) is here...
http://www.camaros.org/302valves.shtml

The “old school” way I was taught - with the 30/30 cam and others was to set them hot and running. But there are better ways than that.

Excellent suggestion. I wonder if the (aftermarket) reproduction camshaft I used in my '68 MO engine will respond to this. Supposedly a dead nuts ringer for the OE grind. I am using long slot 1.5 stamped rockers -

Regards,
Steve

[BobH11]

Aaronz28,  you might want to check the accelerator cam and squirter nozzle size. I had kind of the same problem, the car never revved cleanly from idle. I found the accelerator cam was the flatist one. The kit I got had 5 cams so I changed to the middle one and also changed the squirter from 28 to 32.
This made a big difference with the off idle problem.

[aaronz28]

Hi bob,  yes i had been playing with that too.  I get it to rev clean, just very lazy.  Its just ho-hum on the way up from 2500 rpm to 7k.  I have 2-3 things to sort out tomorrow - and will do a compression test.  I think its more than my carb adjustment.

I noted that while the motor hasnt overheated,  it seems to continually get warmer with prolonged cruises at a constant rpm - and no pressure in the coolant system afger cool down - which is odd.  I have a feeling there might be a head gasket leak or something causing low
Compression somewhere - or a crack in the carb body that is making it go lean at constant rpm once t heats up.

I know stock 302s are very lazy unless you put headers on, but this thing is a dog at the moment.

Will report more when i get some results tomorrow

[X33RS]

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. 

[JohnF]

This probably won't help but if you look at the old Holley tech manual the 4053 carb actually takes a 8.5 PV in the secondary circuit.

[aaronz28]

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.

[X33RS]

I haven't forgotten, the last place I haven't looked is the mezzanine so I'm thinking it's up there with the spare parts.  Hang tight, I'll send you a PM through here.

Larry

[X33RS]

PM sent.