1970 Lt1 carb. settings
 

Looking for some feed back... I have a 1970 LT1 M21 4:10 ratio 1970 in a nova. all stock including, air cleaner, exhaust manifolds full exhaust,11 to 1 compression, solid cam with a longer ratio rocker arm, and a smog pump spinning around but not pumping.With a 780 holley carb. My car seems like it could use more fuel. The 202 heads have been ported by machine shop,and bowls have been cleaned up.this is the only wild card. I have the timing set to 8 degrees.Engine has 14 inches of vac. at idle. The primary jets are:78 high flow Power value is 5.0 front and rear. The rear jets are 80 high flow I have a 35 squirter in the primary. Thats whats funny i have been up to 42 and makes no difference, whats going on.... Looking for feed back from z28 guys and deuce owners with similar engine internals to what makes the best torque and horse power. Please help. Thanks todd.

Re: 1970 Lt1 carb. settings
 

What do you mean by you think it needs more fuel?

Is it running out of RPM?

I run a lot more initial timing that that (more than twice) but you need to know what your total advance is and when it is acheived.

I found the FACTORY jets to be WAYYYYYY to rich for my 1970 Z28 M22 with 3.73's for the street. But if you are only going to run it down the drag strip, your cylinder wall washing richness is ok there, but WAY too fat for the street IMHO and experience.

I took my stock primaries (70) and moved them to the secondaries (that WERE 76) and went to 68's for the primaries, lots more response, crisper and only on severe upper acceleration was it any different than the jets that kept on fouling my plugs during everyday street driving

you could take it to a dyno and get it dyno tuned, that's what they did back in the day

Re: 1970 Lt1 carb. settings
 

Thanks for the input. i had more timing but went back to stock and had to start some where. How do i figure total advance What size squirter do you use. Never have fouled a plug yet in 2000 miles, yes feels like the car could have more off the line. it pulls ok , wont break tires loose unless you drop clutch. car pulls ok and then kinda goes flat, stops pulling but keeps aclerating.

Re: 1970 Lt1 carb. settings
 

sounds like your timing is one of your issues

I have the stock carb, 4555 780 cfm, stock accel pump

Re: 1970 Lt1 carb. settings
 

the power valve should be 8.5:

http://www.mopar1.us/carbs.html

Re: 1970 Lt1 carb. settings
 

Yes that is the one thing i m going to do is change power value to 8.5 How do i set timing up like you have done with total advance. what is the stock squirter size?? Thanks todd

Re: 1970 Lt1 carb. settings
 

I can't believe it calls for a 8.5 Power valve! On a decent-sized duration camshaft, that PV would be opening early and fouling plugs. I think I'd go with a 6.5 PV. Get Eric's (Vintage Musclecar) advice on this.

Re: 1970 Lt1 carb. settings
 

Any idea what i could advance timing up to?? And from there i will get a vac. reading and split in half and pic power value.

Re: 1970 Lt1 carb. settings
 

How do I contact eric (vintage muscle car) any one.

Re: 1970 Lt1 carb. settings
 

I'll do my best to verbally explain this since no one else has stepped up. I'll assume that there's no timing tape on the balancer. Take a measurement on your timing tab from the O-TDC hash mark down to the 12 degree hash mark. Multiply that measurement X 3 to come up with the distance where 36 degrees should be on your balancer. Mark this position with some white paint/chalk on your balancer, while revving the motor up to 3000 RPM, check where your timing mark is on the timing tab. That's the total degrees. I use a very simple Timing Light (without the dial) and make sure the Vacuum Advance is dis-connected. 36 Degrees total is a great starting point and motors are usually very happy righ there.

Re: 1970 Lt1 carb. settings
 

amen!

Re: 1970 Lt1 carb. settings
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: todd micheal</div><div class="ubbcode-body">How do I contact eric (vintage muscle car) any one. </div></div>

Here...

https://www.yenko.net/ubbthreads/ubbt...&amp;User=1124

Re: 1970 Lt1 carb. settings
 

Just saw this post, had the exact same issue with my Deuce Todd. The jetting, total timing, and timing curve is critical to these engines. The fact that you can't break the tires loose without a clutch dump is dismal. (You will soon be able to break them loose from a 15mph+ roll, and get 2 ft+ out of the second gear hit!).

I have my setup in my glove box, I'll dig it out tonight and respond then. Special thanks to COPO Pete for my setup - it's right off his car! You might do a search here on the site for the thread where I went through this, my issue initially was an off-idle stumble - tracked it down the idle cam, got to use the white one, second hole..... stumble was gone, instantly!

13.50 @ 105mph, stock and on the skinnies! [img]<<GRAEMLIN_URL>>/biggthumpup.gif[/img]

Re: 1970 Lt1 carb. settings
 

Marlin, You are my hero... I tried to send you a pm but mail box is full? Wow you have same prob. Yes it is depressing, all that compression and internals and 4:10 gears and car is nothing special to write in about. Im not looking to make a rocket ship out of it, but i knew there had to be more some where.Thank you for responding. Todd

Re: 1970 Lt1 carb. settings
 

As mentioned before, I am rebuilding/restoring the original owner's (Roofs) dual point, mechanical-advance-only Mallory YC-465HP distributor for my Deuce. Any recommendations on setting this up? Dwell? All advance in by.....? Earl Roof told me that Mallory dual point really woke his car up.

Good thread. Thanks!

Re: 1970 Lt1 carb. settings
 

Ok, the complete setup was not in my glovebox - but in a box in the basement [img]<<GRAEMLIN_URL>>/rolleyes.gif[/img] Can't do me much good there, but....

My Carb setup:

Accelerator pump cam = white one, installed via hole #1
Accelerator gap at w.o.t. = .015
Accelerator gap at rest = 0
Accelerator spring = old style, no nylok nut

Secondary Vacuum Spring color = Yellow

Primary Power Valve = 6.5
Primary Jets = 72

Secondary Power Valve = Blocked
Secondary Jets = 82

Squirter = 31


Timing = ~36 degrees total, all in by 2000 rpm. Personally, I like the dial type timing lights.

Spark plugs = use the NGK's!!!!


Suspension setup:

Front tire pressure = 44psi
Rear tire pressure = 40psi

Front &amp; Rear shocks = good, basic gas shocks - can use 50/50's

Rear springs = 2 spring clamps on each side, both clamps in front of the rear wheels but on different leaf stacks

This setup should get you started, let us know how you make out.

Re: 1970 Lt1 carb. settings
 

OEM stock were 72 primary and 76 secondary, they were way to rich for the 1100 feet elevation here in Phoenix ...

the above may work ok for a drag car but will be &quot;phat&quot; for the street

again, IMHO, YMMV, etc

Re: 1970 Lt1 carb. settings
 

Very helpfull information.

Thanks to Marlin and Peter for this heads-up. [img]<<GRAEMLIN_URL>>/biggthumpup.gif[/img]

Re: 1970 Lt1 carb. settings
 

For what it's worth Eric Jackson restored and rebuilt my carb for my 70Z about a year ago using all the stock type parts...jets, power valves,ect. and my car never ran so good! You would be surprised at what a difference it makes to have someone who really knows what he's doing rebuild your carb and use the correct parts, makes. I rebuilt the carb about a year or so before I sent it to Eric and my car runs absolutely perfect now. I do however agree with Marlin and I also use the NGK XR5 plugs...they seem to be a little hotter plug than the R43 and they don't foul.

Re: 1970 Lt1 carb. settings
 

Marlin, forgive me but how do i set accelerator pump a w.o.t. ( hold open and should have .015 gap) What does old stlye spring look like for accelerator pump? with no lock nut. And what is the best way to block off p.v. in secondary? What number ngk's And i do have a dial in timing light. thank you for all the help. TODD

Re: 1970 Lt1 carb. settings
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: al8apex</div><div class="ubbcode-body">OEM stock were 72 primary and 76 secondary, they were way to rich for the 1100 feet elevation here in Phoenix ...

the above may work ok for a drag car but will be &quot;phat&quot; for the street

again, IMHO, YMMV, etc </div></div>

Jim...according to Eric the stock jet size is 70 primary and 76 secondary...power valve is 6.5. I have the 4489 carb for NA9 Calf emissions and I don't know if they used different jet sizes than a non NA9 carb. A friend of mine has a 69Z and his non NA9 carb is also jetted 70 and 76 with 6.5 power valves.

Re: 1970 Lt1 carb. settings
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: todd micheal</div><div class="ubbcode-body">Marlin, forgive me but how do i set accelerator pump a w.o.t. ( hold open and should have .015 gap) What does old stlye spring look like for accelerator pump? with no lock nut. And what is the best way to block off p.v. in secondary? What number ngk's And i do have a dial in timing light. thank you for all the help. TODD </div></div>

Running the 82's on the secondary side with a blocked p/v is indeed on the fat side, but it rocks! The AC plugs will foul (quicker than normal) with this setup, but NGK's will hold out a bit longer. I have 2 sets of NGK's, and just swap out, clean up, swap out, etc... Did I mention that this setup RIPS [img]<<GRAEMLIN_URL>>/grin.gif[/img] especially in 3 gear!!

Todd, the Acc setting for wot would indeed be with the linkage at wot, a feeler guage will do it. I believe (others correct me if I'm wrong) that the 'at rest' gap is more important, as it will help prevent a stumble. The old spring - not sure what a new-age one looks like! Just make sure its not something funky, no funky nuts either (no comments from the midwest gallery!). You need to buy a 'blocked' p/v for the secondary, you don't have to do anything to block one, just install it. You need a set of part number XR5 for the plugs, don't bother with the fancy, higher priced NGK's, just use the basic version = XR5.

Oh, btw = get the timing right, by that I mean, set up the carb per the above, and then set the timing - then test drive it, adjust it - then test it. That is the best way to dial in the timing, I usually take a wrench and the light with me and just pull over in a parking lot, tweak it, and then blast off [img]<<GRAEMLIN_URL>>/wink.gif[/img]

Re: 1970 Lt1 carb. settings
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 70 Forest Green Zee</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: al8apex</div><div class="ubbcode-body">OEM stock were 72 primary and 76 secondary, they were way to rich for the 1100 feet elevation here in Phoenix ...

the above may work ok for a drag car but will be &quot;phat&quot; for the street

again, IMHO, YMMV, etc </div></div>

Jim...according to Eric the stock jet size is 70 primary and 76 secondary...power valve is 6.5. I have the 4489 carb for NA9 Calf emissions and I don't know if they used different jet sizes than a non NA9 carb. A friend of mine has a 69Z and his non NA9 carb is also jetted 70 and 76 with 6.5 power valves. </div></div>

my bad, I had stated it correctly earlier in this thread, 70 &amp; 76 were OEM, according to the link I posted earlier in this thread, sorry.

Re: 1970 Lt1 carb. settings
 

No problem Jim...you're right on 99.9% of the time! [img]<<GRAEMLIN_URL>>/beers.gif[/img]

Re: 1970 Lt1 carb. settings
 

Actually, the 70 or 72 primary jets are too fat for the street here in PA too. In street trim I put 68's in the primary side to help stave off the plug fouling, but I leave the 82's and the blocked p/v in the secondary side. I've got the timing curve and secondary spring synced up to the point that just when the full timing advance is coming in - so is the slam from the blocked p/v and the fat jets. This makes 2nd and 3rd gears a blast to drive! [img]<<GRAEMLIN_URL>>/grin.gif[/img]

Re: 1970 Lt1 carb. settings
 

Marlin, What do you think about a 50cc accerlator pump??Should i give a shot, and down size squirter little??? any one else many chime in. Thanks for all the help out there, Todd

Re: 1970 Lt1 carb. settings
 

a 50cc pump will just drown the engine, he has too much fuel it sounds like and not enough timing

Re: 1970 Lt1 carb. settings
 

No.