170 head flow

[Anonymous]

Hi guys,
I have a 71 Maverick with a stock 170 with 75,000 miles. I am planing on doing some modding of the motor. I was wondering if putting on a latter model head off a 200 or 250 would benefit me. Either way I'm planing on porting and a 2 bbl carb. My goal is not to build a race car but to just liven up the motor a bit. I'm planning on running a 260 ish cam, upgraded ignition, header, 2bbl card (either adapter or milling of the log) and maybe some roller rockers. Also some better gears and this is an auto car.
Thanks In advance

 

[wallaka]

Welcome to the forum. Sounds like you've got it planned pretty well. The later heads have larger valves, intake logs and combustion chambers. The first two are advantageous, the last isn't. It will probably balance out but for best performance a little needs to be milled off of the head to raise the compression ratio.

 

[Anonymous]

OK
I've got a 250 head located for free . I going to have it magnafluxed tomarrow. On a mild setup like I'm planning would I benefit from milling the log for the 2bbl carb or will the adapter be sufficient?

 

[CZLN6]

Howdy IBH:

Welcome to The Forum. Please note the "Profile" section available to all participants. It's not that we're being nosey. It's that the more details you provide the more specific we can be in trying to help you get the most out of your situation. It is optional, so it's up to you.

It would be most helpful to have a little more information on your car/engine. A '71 Maverick 170 will likely have the same head as used on 200/250 of that year. After the '69 "M" head, all engine sizes used the same head castings. Compression was altered with piston type, dished or flat-topped, and deck height. Chamber size can be surprising during the years '69 to '73. Prior to this change CR were consistently 9:1. During this time chamber sizes were increased from a typical 52 cc to 62 cc. These were the years FoMoCo was backing down compression ratio to comply with EPA standards. FoMoCo's "empty Bin" policy added to the variations.

Given all that, what is the casting number on your '71 head? It is located on the top of the intake log behind the carb. It will likely read D0DZ, or D0DE. Also note the suffix after the 4 digit part reference.

The only downside of the D0xx castings is that they had a 1.69" intake valves and no hardened valve seats. D7xx and later castings have a 1.76" intake and hardened valve seats. The D0xx head can be upgraded by adding larger valves and hardened valve seats, but it adds to the $$$.

Does your engine have the Dura-Spark, small cap distributor, electonic ignition? or the points distributor?

What is the rear gear ratio?

Be sure to read the Sticky at the top of this forum on Head Swapping. Make special note of the differences in head gasket thicknesses and how to compensate.

Adios, David

 

[Anonymous]

I'll check the casting #'s on the head and get the gear ratio. I'm guessing its somewhere around 2.70. The car does have the 7.5" diff. It also has points so I was thinking about the Petronix upgrade. I see you stated that the 200/250 head in 71 would be the same as my 170 but when I read the sticky I thought that it was stated the the 250's had bigger logs and runners?

I will update my profile I just didn't have much time yesterday

Thanks
Bob

 

[addo]

What about the 1970-ish Mavy head Leroy Poll mentioned? Small chambers, but otherwise like a 200/250 head from the same year.

 

[CZLN6]

Howdy back Bob and All:

Bob- The large log, large chamber head is the "M" suffix castings which 1st appeared in 1969. That is when the Changes began. Other known large log, flat-topped castings are the D0DE, with an "A" suffix. These will be the larger 62 cc chambers with a squarer cornered chamber shape. Your head could be a 52cc chamber hold-over. I'm hopeful the casting number will shed light on it.

More than likely your rear is a 7.25" type. I don't think the 7.5" was ever used in a leaf sprung Maverick(?). Check the ID code on the drivers side door. Is it a 4 bolt wheel flange?

The Petronix Ignitor is a good upgrade with this distributor. It has both centrifugal and vacuum advance built in. Try adding a additional 5 degrees of initial advance over stock settings.

You could also upgrade to a Carter YF one barrel from a 200 Maverick for a nice increase in CFM. Up from 150 to 187 CFM. It should be a direct bolt on.

Adam- The C9xx (non-M) castings had many iteration, most with 52 cc chambers and various log configurations. D0xx castings also lacked consistancy of features. All will share a common carb bore diameter of 1.75", 1.69" intakes and 1.38" exhaust valves. None had hardened seats, OEM and most chambers were the smaller 52 ccs. These years have been very difficult to nail down the details, and as always, the devil is in the details.

Adios, David

 

[LEROY POLL]

HEY ADAM


.....I DO HAVE A 1970 MAV. HEAD FROM A 170. THE CAST # READS DODE 6090 A.

.....THAT IS THE SMALL CHAMBER. IT DOES MAKE A BIG DIFFERENCE IN THE TORQUE. I'D SAY IT'S ABOUT A 10-12 HORSE POWER DIFF. THAT'S ON THE SAME MOTOR WITH NO OTHER CHANGES. LOW END STARTUP IS VERY STRONG. MOTOR WILL JUMP WITH JUST A LITTLE TOUCH OF THE PEDAL. IT IS HARD TO KILL THE MOTOR, BUT EASY TO KILL THE CLUTCH. IT MAKES EVERYTHING MOVE FORWARD.

.....GOOD MEMORY....!!!!

LIVE IN GRACE

LEROY POLL