1972 Maverick Sprint - Phase 2

[oldvettedad]

I think those tailights are cool. I hope you get to use them.

[VeeDub]

This was at pullapart in Akron Oh.




Cell phone picks. Its 1977 I think, 6cyl. Auto, Red Vinyl w/plaid bench seat. Thats a small car to be having all that power that you have put in yours. I bet its a hoot to drive!

[Maverick]

Thanks for posting that. It looks pretty well picked over but maybe some good sheet metal left.

Planning to get a chassis tune on Thursday. I'm not pushing it too much till the tune is right. It does feel stronger than with the 5.0.

[Maverick]

WXO and I visited some nearby and new to us auto shops on Monday. Piedmont Custom Motorsports, www.piedmontcustommotorsports.com specializes in '79-2012 Mustangs. They'll do a dyno tune on the 347 tomorrow. Nice to see someone doing FORDs. Most of the shops have a strong GM bias, of course.

WXO asked PCM about a dyno run for the TB and they referred him to a shop just across the road that specializes in GM tuning. So, we dropped in on them too. No plan for the TB dyno pull yet but maybe someday. I didn't get their name. Maybe WXO will post some things on that in the future.

Then we stopped in at B-Mac's Auto Restoration in the same area. No web site listed on their card. They had three good sized buildings full of cars in all states of restoration. Some were finished cars just being stored there or for sale. We talked with the owner, Bill McDonald Sr for a good long time as he gave us the full tour. We got lots of nice comments as they checked out the Maverick. Owner claimed to be busy with nine (I think) employees but I didn't notice any cars being actively worked on iwth tools laying around. A lot of vehicles there but its hard to tell how much activity is really going on.

Back to the dyno tune. The car is not running as well as it did on the way home from the last Charlotte trip. It's dropping a cyl on idle and not smooth on light throttle. Now I'm not sure its hitting on all eight under heavy throttle. This is REALLY getting frustrating. Never had this much trouble with any of the 8 or so engines I've rebuilt and/or modified. Its never been this difficult.

I did notice one thing this morning that may be the problem. The rotor on the MSD distributor must be flying too low -- under the contacts on the distributor cap. There's some crusty buildup just on the very bottom edge of the cap contacts -- not part way up the contact where the arc should be occuring. New MSD cap and rotor are ordered and will be picked up and installed tomorrow morning before the dyno pull. I'm taking a new set of MSD plug wires too just in case they become suspects. IF they're not needed, they'll be returned.

The currently installed cap is not an MSD cap. When the engine builder installed the MSD distributor he gave me a choice of the red cap that came with the MSD distributor or a black one. I chose the black one which might not be right for the MSD distributor. Sure hope its something that simple.

[Maverick]

WXO and I took the Maverick to Piedmont Custom Motorsports for the dyno tune today. Good place!! They worked on it for 4 hours and billed me less than the quote. Its better but still not right.

They checked the plugs and compression. Compression was 140-155 which I think is OK. Two or three of the plugs were carboned up some and one was wet with fuel. The tuner checked on the recommended plugs for the Dart heads and found the installed plugs to be too cold and gapped too small at .035". He replaced them with hotter plugs and gapped them at .045". I'm a little skeptical about a gap that wide with the coil that's on it. Will check on that on the next visit.

The peak rear wheel HP was 273 @ about 4850 RPM and peak torque was 317 @ about 4300 RPM. That's right in the middle of the 250-300 range I was expecting. Long tube headers would probably get it up around 300 RWHP but I don't want to drag them on speed bumps.



The charts show the hesitation when first opening the throttle. Tuner's first solution is to replace the 30 cc accelerator pump with a 50 cc pump. Part is on order. If it still hesitates, it'll probably get more aggressive acc pump cam and/or bigger nozzles.

Air fuel ratio looks good thru the run after the initial bog where I suppose unburned fuel is getting to the exhaust.

They'll call when they have the larger accelerator pump.

[Fred32v]

Looks like the right direction. Pictures, videos???

[Maverick]

Neither WXO or I thought to bring a camera.

They did shoot a video that they said they'd post on You Tube. I'll bug them about it when I go back.

[Maverick]

Made another small change today that might help some. One of the forums suggested its not a good idea to put the PCV hose to a port on a single intake runner. The only vacuum port on the Air Gap intake is on the #8 runner. Not thinking about the single cyl issue, I had the PCV hose connected at the *8 runner.

Sounds right that the extra air and crank case fumes should be spread across all cylinders rather than just going to one. Moved the PCV hose to the port on the back of the carb where it belongs. Now, if I can find my vacuum gauge i'll re-adjust the idle mixture screws.

Another thing to consider: is it best to have an filter cap or a closed cap on the valve cover that doesn't have the pCV valve? Better to have air flowing thru the crankcase or a vacuum on the crank case? Right now my oil filler cap is a filtered one that allows air in. Seems like the stock systems are closed either with two PCV valves or one and a solid oil filler cap. Seems like it might help the idle if less air was getting in from the PCV valve but its hard to notice any differenc with the opposite valve cover vented or not.

[Maverick]

Just went back and compared the 347 dyno chart to the 5.0 chart. 347 provides 78 more RWHP (274 vs 196) and 72 more ft lbs of torque (317 vs 245).

Differences:

347 vs 302 CI
Edelbrock Performer RPM Air Gap intake vs Edelbrock Performer 289
Quick Fuel 650 CFM carb vs Holley 600
Dart Pro 1 170 CC heads vs lightly ported E7 heads
Custom hydraulic roller cam vs (I think) stock HO cam
Roller rocker arms vs stock E7 rockers
Electric fan vs belt driven
AC compressor belt missing vs installed
MSD e-Curve distributor and MSD Blaster II coil vs HEI distributor
235/60/15 tires vs 205/70/14s
Cragar SS 15" wheels vs factory 14" wheels (Cragars are noticeably heavier)

The same:

Approx 9.0:1 compression for both
Built C4 and stock converter
3.00 Traction Loc
Exhaust system (Doug Thorley shortie headers, 2.5" exhaust pipes, Thrush Turbo muflers, 2.25" tail pipes.)

When the drag strips open again and WXO has the TBSS ready, we'll see what effect there is at the strip.

[MostMint]

The PCV and breather should be on opposite sides of the engine. The idea is to flow the air through the crankcase. At least this is how it has been on every GM car I have ever worked on. No breather in the PCV valve cover.

[Maverick]

The PCV and breather should be on opposite sides of the engine. The idea is to flow the air through the crankcase. At least this is how it has been on every GM car I have ever worked on. No breather in the PCV valve cover.

Yes, PCV on one valvecover; breather on the other.

[MostMint]

So are you considering if not having a breather would reduce the airflow through the PCV hose and help the idle?

[Maverick]

So are you considering if not having a breather would reduce the airflow through the PCV hose and help the idle?

Yes. I think some or most of the factory PCV systems put a vacuum on the crankcase either by using PCV valves on both valve covers or by using an unvented oil filler cap on one valve cover and a PCV valve on the other. Either would allow less air into the intake and presumably provide a more uniform air/fuel charge. Seems like a PCV connection to the intake is similar to a vacuum leak.

[MostMint]

The objective is to get a set air/fuel ratio at idle. My opinion is that it does not matter if some of it comes in through the PCV and the rest comes in through the carb and is metered in with fuel. The part coming though the carb should be a little rich so that when it mixes with the air through the PCV you get the right amount. Every Chevy I have ever owned was like this and the opposite valve cover had a breather. Even the 265 CID Chevy put up with the 3/8" line and open breather and it idled fine.

Now maybe there is something different about your carb that is not conducive to that extra flow of air.

[Maverick]

Think you're right. Now I'm remembering that the tube on the valve cover that DIDN'T have a PCV valve went to the air cleaner so it could draw clean air into the crank case. A breather cap is an alternative to the tube to the air cleaner and should be used.

Thanks for help in thinking this thru. I'm trying to eliminate things that might be causing the idle and off-idle roughness.