Help me plan my build

[vanwyk4257]

I'm going to be picking up a '74 2.7 longblock in a couple weeks that will eventually replace the motor currently in my '75.
It will get torn down for inspection. At present I intend to install case savers in the 7R case, possibly do the oil bypass mod.
I am planning on building a strong motor for the street that will see some track duty for DE's as well. I'm not too worried about torque, I like to rev my motor!

If I do this build I will probably do new Mahle Nikasil cylinders with JE pistons, and probably convert from CIS to webers or EFI.
I will probably have the heads machined for twin plugs, but will likely only run a single plug setup for a while until I can afford to upgrade to a twinplug setup.

The car is relatively stock weight, but will get some lightening in the future via fiberglass panels as it becomes more and more of a track car. I will also be running bursch 1 5/8" headers and an M&K 2-in 2-out sport muffler.

What compression and cams would you guys recommend.
What other case modifications or parts would you recommend upgrading "while I'm in there"?

Thanks!

[magic930]

If you do the EFI you might as well finish the twin plug, at that point all you need is a 60/2 pulley, crank sensor, two coil packs instead of one, 6 more wires and 6 more plugs.

[vanwyk4257]

Good point. What is the most cost-effective EFI system out there that would be compatible with a twin-plug setup?

[ChrisBennet]

Hope I'm not stating the obvious...
You can't split a 2.7 case, look at the guts and bolt it back together. Invariably, 2.7 cases requires some machine work - if you want the crank to spin when you bolt it back together.
-Chris

[vanwyk4257]

I have read Wayne's book and others cover to cover a couple of times, I just wanted to seek out the sage advice of others here who know far more than I do, but thanks for asking.

[kenikh]

If you want twin plugs, do it now. It will save you heartache later. Go with a 2.7 liter set up. Install case savers and use top notch studs and bolts. Use 10.5:1 pistons, DC44 cams and EFI on individual throttle bodies. Do the oil pump mod. Have the rotating assembly zero balanced and REV that sucker. Built correctly, this spec wil make a comfortable margin over 250HP at peak.

[vanwyk4257]

I think I need to decide my budget limitations first!
I was looking at the Tbitz setup, which seems very cost effective at first glance, I know it would limit me to single plugs, but I'm thinking even with single plugs, with the right compression 9.8:1 JE's, the right cams, and headers with a 2-out muffler I should be able to get 220hp? Am I right or is it folly to think of 220hp without higher compression and a twin plug setup? I really don't want to sink $10K into my build, my wife would make me sleep in the car if I did...

[kenikh]

WRONG; TBitz does not limit you to single plugs. It is MegaSquirt based. Minor mods allow easy twin plugging. EASY. Here's a nice thread to read:

http://www.msefi.com/viewtopic.php?t=11099&highlight=distributor+trigger+edis

What using the TBitz kit will limit is cam choice if you use the CIS runners, since they are a common plenum. No big cams for you!

[davidppp]

Hello, Kenik.

Not sure that the plenum need limit cam choice here..there are no issues of reversion or stabel vacuum with megasquirt...in the unlikey event that a satisfactory vacuumme signal cannot be obtained with damping etc, it can also run in TPS mode (Alpha-N) at higher loads..or blended vacuum and tps..

I agree that the cost of twin-plug is small in relation to the total rebuild and hottening cost...go for it...

Twin EDIS is simple and reliable and cheap..

Kind regards
David

[kenikh]

I thought reversion was the issue in a common plenum? TPS is probably the easiest solution, regardless.

[vanwyk4257]

Thank you both for your honest input. I'll read up on the TBitz some more!

[davidppp]

Hello, Kenik.

You are right of course...

Reversion really upsets the CIS system badly.

And, BTW, carbs too!

But with the megasquirt, surprisingly perhaps, few folk have any difficulty running exclusively using manifold pressure, albeit maybe with something like a MIG tip plus a small fule filter in the line to the baro sensor.

And as you say, Alpha-N is always available for the odd red-hot nasty cams!

Kind regards
David

[al lkosmal]

My understanding of using hotter cams with the CIS system is they result in reversion causing the airflow sensor plate to cavitate and screw up the fuel distribution/AF mixture. I don't think it's a common plenum issue. From what I've read and am experiencing, the Tbitz/Megasquirt CIS to EFI works great with the common plenum of the CIS. This system removes the restrictive airflow sensor plate and the also unnecessary fuel distributor. I've installed this kit, but I'm using a 3.2 intake on my 2.7. I've also read that Independent Throttle bodies do not work as well using the individual MAP signals and need to be run into a common plenum for this to work well.

[vanwyk4257]

I was just reading through the TBitz thread and that seems to be the consensus. There was a car cited that was running Evo2 cams with TBitz and not experiencing any problems with reversion, although I don't know if it was running in Alpha-N mode or not.

[kenikh]

If it is signal problems, using TPS instead of MAP solves the problem. Go for it!