2.4 T w/ E cams or NOT?

[GotaT]

Some of you guys may be following a thread I have about my broken T cam. Anyhow... I have built my T motor all the way up to the Cam Towers and am in need of a set of cams bc one broke.

I have a 2.4 MFI engine with T pistons and had the Heads resurfaced with .010 taken off on all 6. Im using a .25 base gasket. Im also running with WEBERS.

The car had 2.4 MFI T cams in it.

Anyone have experience or know if I can use MFI E cams? I say MFI E because the Non MFI E cams have a much larger Valve Overlap. Whereas the MFI E cams are Very close to the same as my Stock MFI T cams.

According to Waynes book

..........................................Intake Exhaust Lift

2.4 MFI T cam.. 2.6 valve overlap 36.25 35.51

2.4 MFI E cam.. 2.9 valve overlap 36.58 36.25

2.2 E cam........ 3.15 valve overlap 36.58 36.25

As you can see the differences in the Valve overlap, Can any of you shed some light on this? Now too, One other thing not mentioned is when the Intake and Exaust Open.. not sure if this plays so much into effect.

[dtw]

I am not sure what non-MFI E cam means? you mean the 2.2 cam (also injected)? 'E' stands for something in German like 'Einspritzung' or 'Injection' in English. BTW, as best anyone can tell, the 2.2E and 2.4E cams are identical. Try a search - been plenty of debate on this.

If I'm not mistaken, what you need to be concerned with is valve lift, not just overlap/duration. You are getting approximately 0.75mm more lift on the exhaust valve with the E cam. Combined with the more aggressive overlap and the shaved heads you are running, you run the risk of piston/valve contact or at best insufficient clearance.

The bigger picture though, is that you are not necessarily going to see any benefit by taking this opportunity to upgrade just the cams. Top end upgrades need to work together as a system - changing individual components does not guarantee results. Your 2.4T pistons are very low compression (some people have even turbocharged this setup without changing pistons) and a higher lift, longer duration cam is not likely to improve the performance of the engine. You could start with higher compression pistons, match them with more aggressive cams, open up your ports, and retune your carbs as necessary.

If you don't want to open this can of worms, and it doesn't sound like you do, I'd just try to find a set of good used T cams.

[GotaT]

With so many posts saying "i dont think it will work..." Im going to unfortunatley have to go w/ the Stock T cams.

Now a look at the T cams.

2.4 T cam for MFI 2.6 valve overlap 36.25 35.51 intake and exhaust Lift respectively

2.2 T cam 2.5 valve overlap 36.25 35.51

What would happen if I would run these 2.2 T cams in my 2.4?

Would there be Any loss in power?

And, what about the other mentionables like intake opens/closes exhaust opens/closes ABDC BTDC ... and so on...

Bottom line.. What would be different in Driving the car w/ the 2.2 T cam VS the 2.4 MFI T (what I had)

THANKS FOR ALL the KNOWLEDGE GUYS! BEEN A VERY BIG HELP!

[Roger 911]

I did exactly what you are proposing. I put E cams into a otherwise stock 2.4T MFI motor w/Webers. The engine pulls MUCH stronger above 5K. I use my car for DE events, namely at Road America. The T cams were just running out of breath on the long straights. The motor has been running great for years.

All E cams are indeed the same. The key with these motors is the low 7.5:1 CR. This leaves enough clearance for the increased duration and lift. You will want to check everything very carefully. There is also a lot of confusion regarding head specs. 2.4 T and E MFI heads are the same, same port sizes. So you will realize top end benefits from the cams. I can't really say what the difference on the bottom end was of the cams alone, as I changed over to Webers at the same time. I would probably agree that the throttle response off idle was better with my stock MFI and cams, but that may also be attributable to less than stellar carb tuning for the bottom end. Again, this is primarily a track car, so all I care about is 3500 to 6500.

[tom1394racing]

I think the 2.2T heads are the same as the 2.2/2.4 E heads with the exception of the injector bung.

The 2.4T heads had different port sizes.

I always used this table as a reference:

http://www.carquip.com/parts/911/engines/cyltbl/index.asp

[dtw]

Just measure 'em. Mine were 29mm intake - had to bore 'em out to 34.

[Roger 911]

I don't have Bruce's book in fron of me, but I'm pretty sure that his reference table shows the 2.4T MFI ports at 32mm, same as the 2.4 E. I'll check it when I get home. The T throttle bodies may have a different bore at the base (29 or 30mm), which would effectively eliminate any advantage the larger ports would have with the T bodies.

[Bobboloo]

Bruce's book list the 2.4T MFI ports as 32mm and that is incorrect. The intake ports are 29mm. I don't know however if the Euro 2.4T (carbed) intake is 29mm or 32mm but since were talking MFI then his ports are 29mm on intake.

One problem when you use a cam with more overlap is the effective compression is reduced. So the 7.5:1 ratio pistons would feel less punchy in the low end.

If you go with another set of T cams you can port your heads for more top end but that will cost you some low end punch.

A good alternative is if you can find some E cams and some 2.2E pistons. That would be a great combo in the 2.4. The 2.2E pistons are 9.1:1 CR and when combined with the 2.4 70.4mm stroke will give you something like 9.6:1. The increase in compression will offset some of the loss of low end torque from porting and adding the E cams.

[Roger 911]

I did my swap about 5 years ago. I thought I measured my intake ports at 32mm, but I won't swear to it now. However, in the end it is immaterial. I can personally attest to the dramatic improvement of the E cams and Webers on an otherwise stock 2.4T MFI longblock. I did not do a complete rebuild, as I didn't need one. All I wanted was a cost effective means of getting more top end. To that end, I believe I paid $300 for the reground E cams and $800 for a complete Weber set up. So for roughly $1100 I took a motor that was wheezing above 5K to one that pulls noticeably stronger to over 6K.

The only caveat I would add is that my car is used almost exclusively for DEs, most frequently at Road America (4 mile track). I needed more top end than a stock T could provide. If top end is not important, you may want to stick with T cams. If you want the best street drive-ability, you should probably also keep the MFI, although getting the pump and t-bodies rebuilt to E specs may cost more than buying a complete used Weber setup. I wanted the ability to upgrade to S specs when I have to do a full rebuild, so the carbs were most cost effective for me (I don't want to turn this into another Weber vs MFI debate). One more suggestion, add an auxiliary oil cooler, especially if you track the car. You will make a lot more heat pushing the motor past 6K.

Changing cams is not necessarily easy, but it's not that difficult either. Worst case, put them in and see how you like it. You can always change them back to Ts if you don't like it.