how to get the most from your motor...

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monzaz
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how to get the most from your motor...

Postby monzaz » Tue Jan 29, 2008 9:17 am

The best way to get the absolute most from your motor is timing and carburetion.

Timing : Making sure the optimum amount of timing for your engine combo will give the most an engine can. Usually more inital advance(balancer reading at idle) will produce quicker and more low end torque. But it also must stay with in the total advance recommended specs. Total Advance(spark advance when the distributor is fully advanced usually after 3000-3500 rpms stock cars)

Total advance should be brought in as quickly as possible for maximum performance also. before 2500 is recommended. (Usually can be controlled with aftermarket distributor)

A multi spark box and matching distributor if you can afford it is the way to go for performance.

Carburetor: If you have a aftermarket carburetor bought new...You should probably leave it along. esspecially if you aree still learning about the systems and how they work. A carburetor is one of the BIGGEST culprets to BAD motor performance. Someone has bought a use carb and they try to make it work or fiddle with it so much that it is so out of wack you will never get your car in tune. AGAIN if you have the money start FRESH buy it new. To understand how your car reacts to different ingintion timing you will NEED this component TRUE and uninhibitated. The only thing that should be turned on a carb that is new for now is the throttle and maybe a 1/4-1/2 turn on a idle screw. As long as your car is not a 1000 horse 300 advertised duration motor that carb should run on your motor.

What I am getting at here is that you need to make certain that the motor is running correctly before blaming other parts of your car to make up for what you think is loss of power from gear ratio, or a torque conveter etc.

ANY CAR WITH ANY SBC V-8 RUNNING CORRECTLY WILL HAVE THE POWER TO DO A BURN OUT WITH A SMALL AMOUNT OF BREAK TORQUE. If it can not there is probably a problem with the motor...be it compression and old, valves in the head worn, ignition/timing off, carbuertor not correct, vaccum leak...and on.

All the info is if your motor is in good mechenical condition long block.

One last comment. A bad compression and carb combo will be hard to over come also which is the second most mistakes I see in customers cars and loss of low end power.

Great fun performance starts with tons of lowend torque. and most of the time that comes with lower duration cams 280 and less advertised duration. Unless your keeping your foot to the floor from light to light choose the smaller cam for the street. Take the 300fot bls. of torque at 2000-2500 than the 400foot lbs. of torque at 4500-5000. YOU will be much happier...trust me. Good luck and lets here your comments. Jim
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67cat
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Re: how to get the most from your motor...

Postby 67cat » Tue May 01, 2018 7:31 am

Hi Jim,

I have a 1967 Catalina fastback with a stock rebuilt Pontiac 400 and it has 10.5 compression heads that have been rebuilt stock also. According to the service manual it weighs in at 3860. I chose the Summit racing 2801 cam, 288/298 duration and 444/466 lift. I also replaced the points and condenser with a Petronix electronic ignitor with a msd coil. Initial timing set at 14 degrees. I have an edelbrock performer manifold and a new 650 edelbrock carb that has been tuned with a vacuum gauge. Running the stock exhaust manifolds with 2.5 downpipes into 3.0 crossover exhaust. 400 turbo trans with a stock converter and as I said in my other post it has a 2.56 gears open carrier. 275/40/18 tires in the rear. It gets around 14-16mpg on the highway with this combo and it has pretty good pep off the line. I shouldn't complain but i would like for it to leave a little faster off the line. Do you think a 2000-2200 stall would do the trick? Gears in the rear? Timing too low/high? A combination of all that? Not looking for a drag car just something a little quicker off line. :lol:
Thanks, Eric

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Re: how to get the most from your motor...

Postby monzaz » Wed May 02, 2018 7:44 am

cam seems to be right in the wheel house of working with your combo. 1800 - 5000 so if you stall in the 2000-2500 range it will pep up nicely

So I definitely start with a easy swap of a stall converter which will make a great difference out of the hole with that camshaft.

Timing should always be figured on a full advance in - so you should disconnect the vacuum post advance to the carb...plug it - then find a full advance timing light so you can take a reading on the balance with the engine running at 3000-3500 RPM . See what your advance is should be from 32-40 degrees FULL ADVANCE. If the engine does not get all its advance in by 3500 you really need to get the distributor checked out ...weight springs too stiff or fly weight advance arms are stuck, not letting the dist advance in full or quick enough.

So before spending a ton of money on the gears and hard to find expensive parts try the simple things first as it might be enough to give you the tire burning fun you desire with out loosing your freeway driving. :) Jim

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Re: how to get the most from your motor...

Postby 67cat » Wed May 02, 2018 12:19 pm

Thanks Jim,
I will definitely try the stall converter first.
This one has 2700-3000 stall, do you think that's too high? I was thinking 10" vs 12" weight difference.
JEGS Performance Products 60401

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Re: how to get the most from your motor...

Postby monzaz » Wed May 02, 2018 5:24 pm

do not go too high as the freeway will over heat your trans as it will not fully lock ... 2000- 2500 that is it. with 2.56 or 2.93 gearing Jim
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Re: how to get the most from your motor...

Postby 67cat » Wed May 02, 2018 7:06 pm

Gotcha!
Will a converter advertised as Chevy turbo 400 work as long as its 11.5 bolt circle or a dual pattern or does it have to be specifically a BOP converter?

Thanks, Eric

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Re: how to get the most from your motor...

Postby monzaz » Thu May 03, 2018 7:40 pm

GM 350 AND 400 SHOULD BE THE SAME UNLESS YOU HAVE THE REALLY SMALL 153 TOOTH VEGA MONZA FLYWHEEL
MOST GM FLEX PLATES ARE DUAL DRILLED FOR SMALL AND LARGE CONVERTER PATTERNS. 6 HOLES 3 LARGE 3 SMALL DIAMETER.



bop CHEVY SHOULD NOT MAKE A DIFFERENCE.
BEFORE YOU MESS UP THE CONVERTER MEASURE THE BOLT CIRCLE. THAT IS THE SAFE WAY.

oH geez I have the caps on... sorry
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Re: how to get the most from your motor...

Postby 67cat » Fri May 04, 2018 9:14 am

Ok, I should have changed the converter when I had the engine out! I'll pull the inspection cover and figure out what the bolt pattern is.
I checked the timing advance with the vacuum hose off and plugged, it was fully advanced at 32 deg around 3000rpm.
Also it's running 2200 at 65 on the highway, so I'm looking for a 2200 stall. Albeit, I never run 65 on the highway! :lol:

Thanks for all the info and knowledge,
Eric

PS Happy Cinco de Mayo

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Re: how to get the most from your motor...

Postby monzaz » Fri May 04, 2018 1:12 pm

Yes, but also think about if you do find a 2.93 the RPMs will move up some too.

That is your call but yes 2200 with 2.56 and freeway driving will be fine.
If you ever want to upgrade do a tranny cooler it helps too especially if your switch your mind and do the 2400-2500 stall. :)

Just measure diagonally from one triangle to the other point triangle. then measure the converter the same way.

View the attached picture
converter will normally only have 3 connecting spots unless you get a original corvette gm one which had 6.
your starter flywheel will usually have 2 different triangle bolt pattern lengths... measure the orange or the green and see which one fits your converter. You only need to measure one length of each as they will all be equally spaced on each triangle pattern.
Jim
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