How to build a track suitable 4.1

[MADXF]

I've just done the john bowe high performance course at calder on monday, and now I want more!

With the current lpg setup (no petrol), impco mixer and all EFI ECU controlled, it really leaned out at high RPM (zorst tip was very white). I was amazed how well the engine coped with the days events, oil pressure never dropped below half (approx 50psi), temp was stable, and my new DBA slotted rotors and bendix ultimate pads did the trick beautifully

What I noticed on this day was the car had nothing really to give over 3500rpm. I'd really like to have an engine that will happily rev out to 5500rpm all day with strong power all the way up the rev range.

I've got a gas research carby here waiting to go on after I get an EF/L airbox to put in. I've also got an XF carby distributor (mech and vac adv) to be recurved to go along with the new gas carby.


I figure my options are:

1. Buy an EF/L engine and T5 combo, and spend some money getting new lines/hoses made for aircon/power steering. Use the XF dizzy and GRA carby to run it dedicated LPG

or

2. Rebuild the 4.1 I've got and buy a T5 for it.
This is where the real question is....what would need to be added/done to this engine, apart from gra carby and recurved dizzy, to achieve my goal of an engine that will supply decent power all the way to 5500rpm?

Both situations will include a 3.45:1 LSD out back (currently stock 2.77 LSD) I've already got extractors and 2 1/4" exhaust with super turbo muffler (that made a great improvement over the stock crap, lights em up real easy now )


Thanks for any help or suggestions
Paul.

 

[xctasy]

First option 1: is to spend big. Get an OHC engine, and attempt to get the T5 or Supra 5/6 speed to go with it. Then fit the later (smaller intake) manifold with a GRA mixer. Redo the head, head bolts, and get the thing really well blue-printed.

Then find a cam which suits your needs. A set of screamer diff gears from a Pintara, Cortina 4, or Skyline should get the old girl launching hard.


Any lpg engine that attempts to use the stock long runner intake manifold from the EFI will expire at constant high revs because of awfull cylinder to cylinder gas distribution. Any L-series converter will freeze up after a minute of delivering over 250 hp, and 325 for about 10 seconds while the Impco E will handle 325 for ever.


Option 2:The ohv six is just fine, but if you are reving it, then a sound base is needed. Get a set of 6 inch rods and ACL race pistons. I've tried a mock up using two CA 300 mixers on two Ford cross-flow carby manifolds. The front manifold is moved forward one cylinder, the other manifold back one, and the two are TIG welded together, and a 39.37 mm frost plug expoxied in. There is space for two progreesive ADM 34 throttle bodies and two CA 300 a1 mixers on an ABER adaptor is very easy, and you can get a 432 hp potential with your current set up, as it with flow 696 cfm (2 times 348 cfm). With twin Impco L converters, this will solve any gas supply problems. Find a 280 degree cam, better hi-volume sump with windage tray, better rocker studs and a good set of adjustable roller rockers and hang on tight.