Intake cam timing

[Silverbullitt]

There is an article in the April 2007 Muscle Mustangs mag. I think it is the under pressure column. They claim that they have sampled 4 valve mod motors from the 96 cobra to the GT500 and found intake cam timing out of sync between banks by as much as 9 degrees. This includes the GT motors. They claim that the horsepower deficit could be as much as 25 hp. Doing a compression test on both banks and looking for a diffference between them will indicate if your motor is on the wrong end of the sample.

Now the big question. If this is true would you be willing to have your motor pulled and have the top end disassembled for 25hp? I will wait for another reason to have my motor pulled and have the timing checked while it is out.

 

[fjpikul]

You read too much. Get out and drive since you have nice weather.

 

[427Aggie]

Chris,

There was a post on this some time ago. From what we heard at the ralley they were not allowed to degree in the cams on our cars....the thought is thats the reason you anywhere from 490-525 on cars from teh factory.

To me its not going to be worth pulling the motor to get that 25HP.

matt

 

[analogdesigner]

What ever happened to tolerances?

Chris,

There was a post on this some time ago. From what we heard at the ralley they were not allowed to degree in the cams on our cars....the thought is thats the reason you anywhere from 490-525 on cars from teh factory.

To me its not going to be worth pulling the motor to get that 25HP.

matt

Yes, I think that Accufab had known about this over a year ago.

With modern day machinery and SPC, it's hard to believe that something is being produced with such wide tolerances. Can you imagine a company such as Honda or Toyota producing something so sloppy? :ack

 

[californiacuda]

It will be interesting to see if any aftermarket cams come along that might provide a big hp difference. What ever hp or tq increase from a new cam would probably be also applicable to the GT500, same heads.

 

[californiacuda]

Isn't the issue of degreeing in the cams, one of a choice in the assembly process? To take the time with a degree wheel and a piston top of stroke instrument, checking each of the 4 cams so that they are exactly as specified. Then making small, minute adjustments on the cam gear to insure their exact location?

I don't know what tolerances are allowed in other engines by other companies, but as more performance is required of an engine, more precision is necessary.

 

[Silverbullitt]

You read too much. Get out and drive since you have nice weather.

I put a few on it yesterday. Hopefully a lot next weekend-Texas Cobra rally. Come on down Frank. I'll get you a weekend Texas pass.

 

[Silverbullitt]

Isn't the issue of degreeing in the cams, one of a choice in the assembly process? To take the time with a degree wheel and a piston top of stroke instrument, checking each of the 4 cams so that they are exactly as specified. Then making small, minute adjustments on the cam gear to insure their exact location?

I don't know what tolerances are allowed in other engines by other companies, but as more performance is required of an engine, more precision is necessary.

I would have thought that they would have some kind of template. Set #1 at TDC and line up the cams. That should be repeatable.

 

[BlackICE]

I don't know much about modular Ford engines, but on others engines I have looked at, the adjustments for the cam timing are are +- one tooth on the cam spocket. Which isn't as exact as you can be. After market cam spocket have different keyways that allow for much finer adjustments. That takes more time and money. I don't know of any production engines in the US that uses adjustable keyways, but it is standard build procedure for made to order high performance engines.

 

[analogdesigner]

I would have thought that they would have some kind of template. Set #1 at TDC and line up the cams. That should be repeatable.

Exactly! I am sure that some method could of been developed. Timing gears can be designed with adjustability to +/2 degrees, without resorting to Mickey Mouse techniques.

 

[californiacuda]

Its a question of how much time/money the manufacturer wants to spend during production or all the little detail,

 

[Silverbullitt]

Its a question of how much time/money the manufacturer wants to spend during production or all the little detail,

That was one of the points of the article. They also mentioned that they were suprised that even the GT engine has this problem. Is there any other $40,000 engine that had a cost of assembly compromise? How much Q/A time would be needed to see the intake bump on #1, go 90 deg for the next bump and so on. Since the cams are sprocketed I'm sure they have a dot on them indicating alignment. Maybe the dots are in different positions on each bank. Swap the left and right and you are 9 deg out?

 

[barondw]

Its a question of how much time/money the manufacturer wants to spend during production or all the little detail,

Go back to a previous comment would Toyota do this? I don't think so. It clearly illustrates the difference in corporate policy between the ebst and the rest.

But its nothing new, go back to the cam shaft problem on some early cars with the sleeve. Do you literally think that Toyiota would have accepted out of spec cam shafts and used them? And then suggested the sleeve as the solution.

I don't think a supplier would have knowingly shipped out of spec product to Toyota.

This is not an Escort.

Dave

 

[BlackICE]

...Is there any other $40,000 engine that had a cost of assembly compromise? How much Q/A time would be needed to see the intake bump on #1, go 90 deg for the next bump and so on. Since the cams are sprocketed I'm sure they have a dot on them indicating alignment. Maybe the dots are in different positions on each bank. Swap the left and right and you are 9 deg out?

Just because Ford list the fully dressed engine at 35K, doesn't mean it is built any better than a Mustang engine. Yes, with the proper specs to the suppliers and QA test for the parts would made cam timing a simple bolt on procedure to get very close to ideal. I suspect that the parts tolerances are not as good as they need to be for this to happen and Ford does the best they can with the parts they get. That's is why the aftermarket cam sprockets with adjustable keys exist. To get everything to bolt up right on the "tooth" would cost a bunch more money because of the much higher tolerances on the parts.

Do we wish our engines were assembled better? Yes.

Did Ford meet or exceed the publish specs for the engine, 550 SAE HP at the crank? Yes

So why all of the whining? Just think on the positive side, the engine has a lot of unleashed potential!

 

[analogdesigner]

Go back to a previous comment would Toyota do this? I don't think so. It clearly illustrates the difference in corporate policy between the ebst and the rest.

But its nothing new, go back to the cam shaft problem on some early cars with the sleeve. Do you literally think that Toyiota would have accepted out of spec cam shafts and used them? And then suggested the sleeve as the solution.

I don't think a supplier would have knowingly shipped out of spec product to Toyota.

This is not an Escort.

Dave

Dave,

Do you think that my 2000 Acura NSX-T's 3.2L engine has that kind of "loose" manufacturing tolerances? The service manual has several bearing clearances spec'ed to 50 microinches (50 millionths, 0.000050")

Then again, BLACKICE is right, it does meet spec. Perhaps I overreacted to this whole thing and that's why I am not capable of manufacturing cars at a profit...

 

[BlackICE]

Perhaps I overreacted to this whole thing and that's why I am not capable of manufacturing cars at a profit...

Unfortunately, neither can Ford!

 

[Accufab]

I have had the opportunity to work on two of these engines for some upcoming stories we are working on for Muscle Mustangs Magazine. Both engines I degreed in the stock cams to see where they were before disassembly. Both engines the cams were off on the same intake cam several degrees. For sure no manufacturer will take the time to degree in cams exactly because it costs too much. I think that it is reasonable that they could do a better job than this however.

In addition, we ran one of the engines on the engine dyno for several days doing product evaluations on our products as well as the Whipple supercharger and the new Kenne Bell 2.8 supercharger. We also did a first version cam swap. All of the testing went well and we will be going back on to finish the testing again maybe later in the week.

I will do a follow up story when I am done with my testing. It is safe to say though that after several days and at least a hundred dyno pulls to 7500 rpms that the engine is very durable.

Accufab Inc

John

 

[Black2003Cobra]

John - Do you know what the specs are (lift, duration, LSA) on the stock bump sticks? Thanks.

 

[Silverbullitt]

Not whining, but not happy. There had to be a better way. If there were tighter tolerances we could be sitting at 575 advertised hp. Maybe 1+mpg, less guzzler tax. Mods would be a little more responsive. As the boost climbs I bet the hp difference grows at least linear, maybe worse.

 

[BlackICE]

Not whining, but not happy. There had to be a better way. If there were tighter tolerances we could be sitting at 575 advertised hp. Maybe 1+mpg, less guzzler tax. Mods would be a little more responsive. As the boost climbs I bet the hp difference grows at least linear, maybe worse.

There is always a better way, but like I said, it would cost time and money. Ford took a big risk building these cars.Do you really it would have made any difference to how many cars sold if it was speced at 575 hp! Ford's pricings could have been better at launch. Ford could have left off the Mac system at priced the car at $170,000 and sold the entire production, even at 550 hp.