Pelican Parts Forums - Newbie '73T 2.4 MFI Engine Rebuild

Pelican Parts Forums (http://forums.pelicanparts.com/)

- 911 Engine Rebuilding Forum (http://forums.pelicanparts.com/911-engine-rebuilding-forum/)

- - Newbie '73T 2.4 MFI Engine Rebuild (http://forums.pelicanparts.com/911-engine-rebuilding-forum/969543-newbie-73t-2-4-mfi-engine-rebuild.html)

Having fun? That's what it's all about.

I'm all for the S spec, cams etc etc, but not really wanting to start another value discussion I see you have matching #'s and what seems to be a survivor. I would recommend rebuilding to spec and enjoying it. A really well done MFI T motor is fun on the street with the lower end torque. It's easy (a little expensive) to go the S route but harder to go back for originality. Not that visually there is much of a difference.

Can always do what I did and after you've had fun with the T you can moth ball it a build a 3.0L MFI:D That's really fun.

I'm sure your doing your homework, Wayne's book only touches on it but it's a must to have your case line-bored if split.

Enjoy

Thanks all for the great feedback. Some responses:

Quote:

Originally Posted by Trackrash (Post 9735600)

Your heat exchangers look to be in good condition. You could have them cleaned and coated for protection. I had mine Aluminum Plasma metal sprayed. Hot jet ceramic coating is another option.
http://forums.pelicanparts.com/uploa...1505250971.jpg

Yours look great! How did you have them cleaned? standard media-blast?

Quote:

Originally Posted by MST0118 (Post 9735581)

If you decide to run S cams, then you'll need to give Gus a heads up to put in the right space cam for your pump.

Also, you may want to consider opening the ports to "S" specs (think 36-35 for intake/exhaust?). If you increase ports, then throttle bodies and stacks should also be bored for that accordingly. If you'll be doing your MFI stacks/TBs, a good place to have this done is Eurometrix or Supertec.

This is in addition to getting pistons with deeper valve pockets for the S cams.

Yeah- understood re. MFI space cam. I'm pretty sure Gus is still fairly backlogged, so I've got some time before I need to commit.

Increasing the intake port size makes a ton of sense from a performance perspective, but definitely starts getting me into that slippery slope territory of stock vs hotrod :) But I'm certainly considering it. Thanks for the shop recommendations.

Quote:

Originally Posted by Trackrash (Post 9735591)

If the tensioner's plungers were firm, they are OK to reuse.

Good to know!

- Jake

Quote:

Originally Posted by Sway Bar (Post 9735642)

Absolutely having fun. Often wish I didn't have to do anything else :)

I love the idea of a 2nd motor. My budget doesn't! I'm definitely guilty of looking around for a rebuildable core somewhere out there that could one day serve as the base for a legit hotrod build... but I need to keep the focus on the task at hand. Your 3.0L MFI must be a monster! What case did you start w? Someday, maybe someday...

Yep, was planning on having my case line-bored, along with the other set of typical machining tasks.

Thanks,

Jake

There is a place in San Diego where I used to live that specializes in coatings. They sandblasted and plasma metal sprayed an aluminum coating on my exhaust.

Ok, let's see how those p's and c's are looking!

Heads off- dirty, but no obvious problems:

1-2-3

http://forums.pelicanparts.com/uploa...1505397915.jpg

4-5-6

http://forums.pelicanparts.com/uploa...1505397915.jpg

1-2-3

http://forums.pelicanparts.com/uploa...1505398199.jpg

4-5-6 Cylinder 4 decided to pull off with the head, a few mallet taps and no problem.

http://forums.pelicanparts.com/uploa...1505398199.jpg

No surprises, which is a good thing.
http://forums.pelicanparts.com/uploa...1505398426.jpg

1-2-3

http://forums.pelicanparts.com/uploa...1505398426.jpg

4-5-6

http://forums.pelicanparts.com/uploa...1505398426.jpg

Everything looks pretty good, at least to my untrained eye. Lots of carbon buildup, and some fairly worn-looking rings, but nothing's broken. Each cylinder looks pretty clean inside, no major scoring or obvious cause for concern.

Next up- head studs :)

-Jake

Ok now time to remove the head studs... after reading Wayne's book (and lots of posts here) I was a little apprehensive about this part of the job. Maybe I got lucky, but it wasn't too bad at all.

I started by trying the "2 nut" approach, which worked ok on the first stud. On the 2nd stud, the 2 nuts kept spinning together, independent of the stud, no matter how hard I tightened the nuts together. I cranked the nuts against each other as hard as I could, and ended up stripping the threads out of one of them before I got any movement from the stud itself :(

http://forums.pelicanparts.com/uploa...1505536160.jpg

Though Wayne's book recommends a collet-style stud removal tool, I just couldn't swallow the price tag. I picked up one of these locking stud-remover tools for much cheaper, and it worked like a champ:

http://forums.pelicanparts.com/uploa...1505536160.jpg

Only issue I could see is that it does bite into the stud, leaving noticeable marks. I'll be replacing the studs anyway, so no worries.

http://forums.pelicanparts.com/uploa...1505536160.jpg

Done!

http://forums.pelicanparts.com/uploa...1505536160.jpg

- Jake

Almost ready to pull this thing apart!

Flywheel and pulley off:

http://forums.pelicanparts.com/uploa...1505537283.jpg

Case studs:

http://forums.pelicanparts.com/uploa...1505537283.jpg

Ready to split:

http://forums.pelicanparts.com/uploa...1505537283.jpg

One case-half off and away:

http://forums.pelicanparts.com/uploa...1505537283.jpg

And the moment of truth!

http://forums.pelicanparts.com/uploa...1505537283.jpg

Very cool. Like Wayne's book says, it's a great little moment when you get to see inside the case for the first time.

- Jake

... and the oil pump.

http://forums.pelicanparts.com/uploa...1505623409.jpg

http://forums.pelicanparts.com/uploa...1505623409.jpg

Any opinions on rebuild vs. replace here? There's nothing obviously wrong with the pump, but I'm assuming doing something to help increase oil flow couldn't hurt.

- Jake

Might be a good time to upgrade pump for not too much $$.

BTW. Also, saw what appeared to be a nice set of 2.2 S pistons for sale on used parts forum for $700. Those may work well with your cylinders if you want more power or to run S cams.

Quote:

Originally Posted by MST0118 (Post 9740916)

Thanks! I'm all over those pistons. Now just need some S cams to pop up, though I gather E cams would work as well, if a bit milder.

- Jake

Awesome thread Jake... thanks for sharing the link....
I'm really interested to see how you go about getting all those parts cleaned...
Keep us updated with those pics.
You are definitely inspiring me to get my 3.2 rebuilt.

Quote:

Originally Posted by Trakrat (Post 9744196)

Thanks!

I don't plan on fully cleaning everything myself. I'll do what I can, but most bits will end up getting media blasted and painted/coated/plated as appropriate. I figure I should at least do a preliminary cleaning so that I'm not embarrassed to send any of the parts to a real professional :)

- Jake

Now that the case is apart and the crank and rods are out, it's time to go back and take apart the head assemblies.

Here's the left-side cam carrier and heads 1-2-3:

http://forums.pelicanparts.com/uploa...1506055989.jpg

First rocker arm parts out:

http://forums.pelicanparts.com/uploa...1506055989.jpg

More rocker arms.

http://forums.pelicanparts.com/uploa...1506055989.jpg

Notice how cloggy the journals in the rocker arm pin are:

http://forums.pelicanparts.com/uploa...1506055989.jpg

With camshafts:

http://forums.pelicanparts.com/uploa...1506055989.jpg

Ready to remove the heads now!

http://forums.pelicanparts.com/uploa...1506055989.jpg

- Jake

Pulling the cam towers:

http://forums.pelicanparts.com/uploa...1506817764.jpg

Wow- lots of blue silicon on the right side. Records show a top end rebuild back in '82; if nothing else, that stuff holds its color!

http://forums.pelicanparts.com/uploa...1506817764.jpg

Compressing the valve springs:

http://forums.pelicanparts.com/uploa...1506817764.jpg

Exhaust valves are pretty cruddy, but no obvious damage. Getting those shims out from under the springs was one of the most annoying jobs yet! My magnet was too big to fit right in the gap, and there was just enough surface oil to kinda stick 'em all together. I was to afraid to forcefully pry them out with a pick, so the only thing that worked was to float some WD-40 in there to try to break up the stickiness, and then jiggle everything just enough that my magnet would eventually pull up a shim. Took forever!

http://forums.pelicanparts.com/uploa...1506817764.jpg

http://forums.pelicanparts.com/uploa...1506817764.jpg

Valve seats look pretty good.

http://forums.pelicanparts.com/uploa...1506817764.jpg

That's pretty much all there is to a teardown. Now it's time to clean everything, and to figure out what to send out for repair (most of it), repair myself, and what to replace.

Stay tuned-

Jake

Post a shot of valves sitting in head? No need to re-install springs.

Be interesting to see how much valve recession over the years.

As I mentioned early in the thread, I would like to give this old lump a little extra kick. I'll keep things relatively tame, but it seems like a shame to me to do all of this work without taking the opportunity to improve a few things. So, after many, many hours of searching through the wealth of info in this forum (including the helpful replies in this thread), as well as talking with some local experts, I've decided to:

- Increase the compression, ideally to 9.8:1, but could go a bit higher
- Replace the camshafts to something that will take better advantage of the increased compression
- Replace the MFI space cam to match

According to everything I've read so far, the compression gain is easily achieved by swapping in pistons from an older 2.2. This seems like a straight-forward affair; the 2.2 pistons are 84mm just like the stock 2.4T's. With some tips from you guys here, I grabbed some 2.2S pistons from another Pelican.

I read a bunch about the cam choice, and the go-to seems to be an S or mod-S cam, when the goal is maximizing performance at full revs (and assuming proper airflow). As I'll be only driving on the street, I'd prefer something with a flatter torque curve- even if I give up a few HP at the top end. With that in mind, and given some feedback here and from John Dougherty, I've decided to go with a set of E cams. And, luckily, I found some straight away.

Consensus seems to be that the 2.4T is under-compressed (if that's a term) at its stock 7.5:1 ratio, meaning that rest of the motor should have no fundamental issues with a higher compression ratio. The most common concern seems to be valve interference when running a spicy cam, but the collective wisdom suggests that the somewhat conservative E cams should have no problems. Still, I will certainly triple-check the clearance when the engine finally comes together.

The question that seems hardest to answer so far is: what will the compression ratio actually be (assuming 2.2S pistons and everything else stock 2.4)? I can't seem to find a clear answer, despite the significant number of related posts. The message seems to be, "It'll work, you'll like it, many have done it without issue...", which is great- but I am curious as to what the final CR will be.

What really made me question things was a conversation with Ted from German Precision- off the cuff he thought the CR might be as high as 12:1. I tried to tell him that was way too high, but then quickly realized that a total newb like me, despite being armed with (the always infallible) data from the Internets, should NOT be arguing with a guy with 40-something years experience working on P-car engines :)

Needless to say, I started getting a little nervous about my choice in pistons. Obvious next thing to do was calculate the CR myself, but without the actual pistons in-hand yet, nor the proper measurement tools, this would be difficult... but I did find this great table in a older post:

http://forums.pelicanparts.com/uploa...1322793830.jpg

Great! Now I can take the 2.2S dome volume (V4) and swap it into the rest of the stock 2.4T numbers. As I understand it, none of the other values would change; so my values would be:

V1 = 390.14
V2 = 5.54
V3 = 68
V4 = 32 (assuming 2.2S pistons. was 13.5 w stock 2.4T pistons)

and as CR = v1+v2+v3-v4 / v2+v3-v4, I get:
CR = 10.39:1

Ok, math is fun. Good news that it's not the 12:1 Ted was afraid of, but still, 10.4:1 seems a bit higher than I expected! That's racecar territory- should I be concerned?

Possible caveats: My math is wrong, my assumptions about the calc are incorrect, etc.

Possible explanations: There are many, many discussions about "real" CR vs. calculated CR. Even without getting into dynamic CR stuff, many previous posts seem to suggest that the actual CR might be a bit lower than what the calc would provide. In other words, don't worry about it ...

Possible remedy: Use different pistons. Looks like our host sells some 84mm "9.8:1" pistons. Can I take this to mean that they'd have a dome volume V4 of around 29.5 (back-solving for 9.8:1 CR)? I'd prefer to stick with the OE Porsche pistons, if I can.

Anyway, I'm inclined to proceed with the plan, and hoping the CR stuff is much ado about nothing. Thanks in advance for your feedback-

Jake

Quote:

Originally Posted by manbridge 74 (Post 9758232)

Post a shot of valves sitting in head? No need to re-install springs.

Be interesting to see how much valve recession over the years.

Hi Jeff, here's a pic of #2-3 from before I disassembled everything. Probably too dirty to see what you're looking for, but worth a shot.

http://forums.pelicanparts.com/uploa...1506837743.jpg

I've since done a lot of cleaning, so I'll throw one of 'em back together and snap another pic for you tomorrow.

- Jake

Its hard to know exactly what you will end up with until assembly. That is when you do the actual measurements to verify your calculations. There are lots of variables. Then there are adjustments that can be made, like cylinder base gaskets.

First find out if your calculations represent real world results. There are those on this board who have done this mod. Hopefully some will chime in.

Have you done the calculations using 2,2 E pistons. Those might be closer to what you want. Are you seriously going to use OE 2,2 pistons?

What you might want to consider are JE 9,5 to 1 pistons. That is what I used on my recent build. I was able to actually get 9.8 to 1 after I did all the assembly and took my measurements.

EDIT: I just read in Bruce Anderson's book "The change in stroke will increase the compression ratio by about 0.55 above what it would have been in the shorter stroke engine.
Therefore the S in the 2,2 was 9.8 to 1 so in the 2,4 it would be 10.35. Looks to match your calcs.
The E piston from the 2,2 was 9.1 so in a 2,4 would be 9.65, right where you want to be.