Archive for December, 2005

Wrong head gasket!!!

OK — I have always been the type of person that double checks things that I’m unfamiliar about (you would think head gaskets would be one of ‘em). Well, in all the excitement of ordering the AFR heads and the ARP head studs from Brother Performance Warehouse¬† back in June I never double checked the head gaskets that they sent. Well, as luck would have it (and I’m a very unlucky person) I decided to double check them yesterday and found out they sent me gaskets with the wrong bore. The head gaskets they sent are Cometic #C5511-040 which are for 302-351w production blocks with a bore of 4.030″ and a compressed thickness of 0.040″ (that is the stock thickness). I called Cometic to verify the bore and sure enough, since I have a block which is boared to 4.030″ Im supposed to be using a gasket of 4.080″ bore. If I used the ones I have installed now the metal gaskets would create hot spots in the combustion chamber which would cause pre-ignition resulting in detonation. Not to mention Im assuming it would severly decrease the lifespan of the gaskets.

Now — what really sucks is that I installed the heads a few months ago including all the valvetrain components along with lower intake manifold. So yesterday I spent a few hours tearing it down. Below are a few pics:

I called Anthony at Brothers yesterday and he seemed OK with letting me send back the old ones. He said they would need to inspect the set I have now to give me store credit. The correct Cometic head gasket is part #: C5513-040. Brothers didnt have it in stock so I ended up calling Bill at RPM Machine in Utah It should be here next week sometime.

Rocker stud issues

A few days ago I was reading through the documention that came with the AFR 185′s and saw something that I didnt catch my first time through. The rocker studs that come with the heads from the factory are suitable for all stud mount rocker arms — EXCEPT the Comp Cams Pro Magnum Rocker Arms. Guess which type of rocker arms I own?! You guessed it – the Pro Magnums!! So while I sat to wallow in my self pity I began recalling how difficult it was to install the rockers arms. The problem I had was the studs didnt seem to have near enough threads which had me worrying if and when they would break. After reading a little further I found out that I need to order a longer stud from AFR to keep the valvetrain geometry correct. I immediately called AFR and 1 week and $50 later I had the new ones in hand. Below is a picture of one of the new studs (left) next to the old one (right):

You can clearly see the difference in length. Plus what you may not see is the new studs have a wider base just below the hex shaped portion which make it easier to adjust the guideplates by limiting the amount of play. This makes it much easier to adjust the valves (in my opinion).

Going distributorless

As I write this Im contemplating starting a whole new page just on the distributorless dilema. The topic of going distributorless can get very confusing, especially given all the many different combinations of ignitions setups there are. Therefore I will try to keep it simple, as I am still trying to understand it myself and learning new information all the time. Here is what Ive learned so far (please keep in mind, that while I KNOW there are other alternatives, I am trying to stay focused on a setup specific to my own car with a few constraints; keep the AEM for sole ignition control and keep it inexpensive while still looking good):

A distributorless ignition requires a few specific pieces to operate. The first thing is a crank trigger wheel and pickup. Simply put, the wheel is just a round metal plate with devices on it that indicate the location of the crank as its rotating in the block. The pickup reads the teeth and sends that information to the ignition controller. There are alot of different wheels out there, all with a varying number of teeth. Im going to try and keep it simple and talk about two approaches I believe optimal for my setup. The first one is a custom piece by Mike Sitar, who unfortunately doesnt make them anymore.

It involves a magnetic pickup mounted on the timing cover which generates a signal when a tooth passes the end of it. I’ve heard pros and cons for this setup but it seems to work very well for a few of the Mustang guys on the AEM forums: The second one is the MSD “flying magnet” setup.

With this system the magnets are embedded into the wheel so when they pass the pickup, it triggers a pulse. Personally I’mleaning more towards the MSD setup but its very pricey. Not to mention its red. I’d have to have the anondizing stripped and redone in black to make it look pretty in the engine bay :)

Now turn your attention topside. With the distributor gone there is nothing now turning the oil pump. Therefore the next part which is essential to operation is the cam plug. This item serves the main purpose of keeping the oil pump shaft connected to the rotation of the camshaft which in turn rotates the oil pump to obviously provide oil pressure. As an added bonus the MSD part I bought provides an additional signal to the computer to indicate position of camshaft relative to the crank. I knew I would need this part without a doubt so it was the first one in the system that
I bought (below).

Now that the old way of providing engine position has been removed and replaced with the electronic version its time to look at the way it provides spark to the plugs. This is the part that is the most confusing to me. Because Im using the AEM I need to figure out how to sync up the cam plug and crank trigger events to fire the plugs. This shouldn’t be too bad because I can always call AEM’s tech line. My concern is what to fire them with. Before the AEM the stock setup used a single coil which fired 8 times for every 1 complete engine cycle. (EDIT: Dont forget — the camshaft which drives the distributor turns once for every 8 spark firing events, the crankshaft turns twice because of the timing chain crank gear being half the size of the cam gear! Turning the crank over once is not a complete cycle!) Now that the coil and distributor are gone I need a replacement coil to supply the voltage. As I see it, there are two options for my setup; either coil packs with ignition drivers OR coil-on-plug. An example of coil packs is a wasted spark configuration, like the Electromotive coil packs (which would only work with my setup if I wired in coil drivers ahead of the coil packs):

An example of the coil-on-plug setup is on ’96-’98 Cobra 4.6L engines and uses two coil packs (which technically aren’t full output coils like the ones above, they are more like mini step-up coils) with four posts on each pack that fire another mini-coil inside the spark plug wire – like these performance parts from Performance Distributors:

Now – See how this could get kind of confusing for a first timer? I’ve yet to figure out which one to go with. And currently I’m waiting for some advice from a few people online on the best route to go. Hopefully I’ll know in the next few months or so as Im getting very close to firing the engine for the first time.

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