250 ..... INJECECTION 290HP. BUT LOST POWER AFTER 5600

[DYNOED250]

JUST THOUGHT ID LET YAS KNOW ABOUT MY 250 WHICH HAS JUST BEENM FINISHED ONLY PROBLEM IS THE CAM SHOULD HAVE BEEN STRONG TO 6500 BUT PEAKED EARLYER AND LOST HP FAST AFTER 5600 HAVE HEARD CAM CAN B 2 BIG, FOR THE 250.
ENGINE SPECKS :
200 RODS
ACL RACE SERIES PISTIONS
0-DECK HEIGHT
DECOMP PLATE 2 HEAD GASKETS . STILL HAS 11.2 COMP
CLEVO INTAKE VALVES, STURNED DOWN TO 1.98
LARGE EXHAUSTS NOT SURE ON SIZE
HEAD FLOWED
C2 HEAD COMBUSTION CHAMBERS RELIVED, DECOMP PLATE WAS REQUIRED AS HEAD HAS HAD 140 THO , COMBUSTION CHAMBER WAS 32 CC. LUCKY WE CHECKED THIS BEFORE WE ASSEMBLED
STREET TERRER ADJUSTABLE ROLLERS
SOLID LIFTERS
DOUBLE SPRINGS / CROMOOLY RETAINERS
ARP BOLTS, RE-SIZED RODS
FULLY BALLANCED ENGINE.
CAM IS A WADE 262 @0.50 NOT SEAT 2 SEAT. AND 565 LIFT.



INTAKE- I MADE A ED/XF HYDBRID MANIFOLD. I USED THE STANDARD XF FUEL RAIL AND INJECTOR BLOCK, THEN GOT AN ED INJECTION MANIFOLD, CUT 2 INCHES OF THE RUNNERS THIS LEFT 6 STRAIGHT PIPES, THEN TURNED IT SO THE PLENIN WAS HIGHER THEN THE MOTOR, THE TROTLE BODY FACES THE FIRE WALL.THEN HAD IT TIGED UP TO THE XF INJECTOR BLOCK, THIS WAY I COULD BOLT THE ED MANIFOLD UP TO THE XF HEAD. I PUT IT UP THIS WAY AS I DIDNT HAVE THE ROOM IN THE TE TO RUN IT DOWNWARDS. PHOTOS ARE AVALIABLE
INJECTORS ARE 400 CC , AND RUNNING 450 HP BOSCH FUEL PUMP
COMPUTER IS AN OLD INJECT FUEL ONLY MANIFOLD WAS FLOWED SDHOWED UP GOOD, ENGINE IS RAN OF TPS SIGNAL ONLY DUE TO ENGINE VACUME BEING TO IRADIC FOR MAP SENSOR OPERATION

DISY IS XF, WITH SHORTEND CURVE AND THE MANIDOTORY CROW GEAR
SUMP- HIGH ENERGY
BALANCER- ROMAC ALLOY
EXHAUSTS- PACEMAKER

* THE AIM WAS 300 HORSES WE GOT 430 NM OF TORQUE WHICH WAS SURPRISING, COULD HAVE BEEN THE LONG RUNNERS. BUT MISSED OUT ON 300 FALLING
10 SHORT. ENGINE WAS RUNNING ON BP ULTIMATE AND 32 DEG TOTAL ADVANCE. NOW IT CAN EASLY REV TO OVER 7 BUT THATS EASY TO DO, BUT WHATS THE POINT IF PEAK POWER WAS AT 5600, THE CAM BEING THAT BIG SHOULDNT HAVE PEAKED THAT EARLY HAS ANY ONE RAN INTO SUCH PROBLEMS WITH THE 250'S RUNNING THIS MUCH OVERLAP. HAVE HEARD A FEW STORIES BUT NOT SURE WHICH WAY 2GO. HEY ITS OK THAT IT PEAKED AAT 5600 BUT BY 5700 IT LOST 10 HP, THEN 5800 30 HP , WAS VERY WEIRD. AM CONSIDERING USING SMALLER DURATION CAM, BUT KEEPING THE LIFT, ANY IDEAS WOULD BE GOOD. THE ENGINE SHOP WHERE WE BUILD MY MOTOR AT, HAD ANOTHER 250 WITH THE SAME PROBLEM AND WITH A SIMILAR SIZED CAM, BUT IT WAS A METHANOL 250 RUNNING A 350 HOLEY.

ENGINE IS GOING INTO TE :> LOTS OF FUN
COST OF ENGINE----- PLEASE DONT ASK I DONT WANA KNOW

 

[addo]

What parameters was the cam designed from? The flow numbers of the head alone, or with the manifold taken into consideration?

What was happening to the AF ratio around the maximum output level?

I'm not really able to suggest any answers, but curious as to what was going on around the point of maximum power.

Adam.

 

[DYNOED250]

we found that the engine required the most fuel at peak torque. the duty cycle for the injectors was the same from peak torque till peak power, then after peak power they had to be leaned out it main taian .8 lamba. this was in the rev range where the power fell in a hole
we tried heavier valve springs because we thought it was valve floatin, but we only gained a few hp and it still wanted to be leanned out.


I was thinking the runner length in the manifold might b to long for higher eveing but this other engine had the same problem this was a short runner manifold with carby.

the cam was chosen before i decided to go injection but it shouldnt make a difference. i dont know why it peaked so early, could the cam of required more air at these reves , but either the port or the manifold couldnt suply it and thats why it needed to have the duty cycle droped off and so the power droped off to suit.

 

[addo]

Is it possible that the .8 value was too rich for peak power? I remember seeing it commented that an engine made the most hp when it was within a whisker of fatally lean - obviously you can't walk the wire like this in reality. If the cam was designed for carb, then maybe they factored in underfuelling...

 

[xctasy]

My qualifications on this are.....none. But I do have a good idea on what stratagies people have taken when presented with engines which don't yield the power they expect. And I've been around bookes and 6-cylcars since I was 6 years old, and am 33 now.

HEY ITS OK THAT IT PEAKED AT 5600 BUT BY 5700 IT LOST 10 HP, THEN 5800 30 HP , WAS VERY WEIRD. AM CONSIDERING USING SMALLER DURATION CAM, BUT KEEPING THE LIFT, ANY IDEAS WOULD BE GOOD.

There is an optimum size for intake runners volume and length. Volume should be, according to TheFrenchtownFlyer, about 40 to 50% of the engine capacity, and the length is covered by the forumla tunnel rams are based on. The XE/XF intake was a torquer. All the other cammer ones were torque optimised, not power rams.

Ford designed the intakes for no more than 5900 rpm, with power at 5000 rpm or so. Simply, it's too much to ask the air, which is flowing at a huge speed at maximum torque, to allow maximum power to follow suit. Even a dual runner item.

THE ENGINE SHOP WHERE WE BUILT MY MOTOR AT, HAD ANOTHER 250 WITH THE SAME PROBLEM AND WITH A SIMILAR SIZED CAM, BUT IT WAS A METHANOL 250 RUNNING A 350 HOLEY.

A 350 Holley on a 250? Well, there's only 155 hp max on petrol for a start. And the intake has to have proper mixture distribution. A 2-bbl 500 Holley on an Ultraflow with 62.5 thou bored venturis and throttles would hit the 290 hp mark, no danger.

Okay, enough with the dirty details.

1) Firstly, I'd expect, with a set of valves and compression like that that there would be 1.39 lb-ft per cube. That's, if its a +30 engine, 353 lb-ft or 479 Nm maximum. Your as close to that as all get out, so no worries there.

2) Secondly, the specific hp factor I use to determine peak power would be 4500. So if you did 5600 rpm, I'd expect a 254*5600 rpm all divided by 4500, or 316 hp. So the power is close to the theory too.

3) My question is what was the revs that that maximum 430 Nm was reached at? If its between 4000 and 4400 rpm, I'd say you're suffering intake issues. If it is at a higher level, I'd be looking at exhast sizes.

4) If you are still using the stock 33 mm internal diameter intake ports, then that is the issue. You should increase the the diameters and look at the peak flow figures from 400 to 565 thou lift. The tail-off is prety savage, telling me its head flow, not intake runner.

5) Don't, whatever you do, drop the cam specification. Get the gas flow sorted, and then look at how Ferrari TestaRossa's have there V12 Weber~Marrelli injection systems set up. There is no way a well developed six with a 1.6:1 rod ratio and and a 262@50 thou cam, even with a long stroke, can't do well over 340 hp at 6000 rpm.

6) An EFI engine will received fuel and air just like a Triple Webered Six pack Charger. They never did much less than 295 hp net blue printed with the ~ 230 deg at 50thou cam they had. Somehow, the pulse windows and timing of the fuel delievery curve must be getting screwed up.


The Jag 4.2 DOHC guys must have had this problem. Big six, long stroke, nice long rods, high-flow head and limited space for a racy intake manifold. I dunno if Ivan Tigue is still alive, but he's certain to have seen this problem.

 

[addo]

XE, would it not be interesting to put a metered supply of oxygen into the inlet, to vary the AF that way? Never heard of it being done, but this might show up/confirm flow issues.

 

[xctasy]

Ya know Adam, the air speed at maximum power needs to be 200 to 250 feet per second, and I'd be guessing that at about 6000 rpm, their would be a need for 440 cfm into the engine. The pulse length for what should be a 40 mm diameter hole should be straight in, with none of the archemdian spiral sh*t that Ford placed as a torque building excercise to gain runner length.

What I'd like to do is grab his intake manifold, shove it on a flow bench, and do some velocity probing with a pitot tube. Somewhere, there could be a problem. Turbulent flow is fine, as long as it doesn't go 'supercritical', where standing waves set up nasty reverse pulses. This is what used to happen in old non GT40 225 5.0 engines when hotted up, or GT40 engines which were pumped up to 400+ hp.

It lookes like DYNOED250 has the right approach here with his intakes design. Adding something like an air pump of an old ADR 27A engine couldn't reduce the air speed if its way over 300 ft/sec. Extra intake volume and a shorter runner is the next option, if this isn't a head flow problem.

The evils of being supercritical...

 

[Anonymous]

Dont know what your air flow figures are for the head and intake. My guess would be you are runnig out of air. Post some figures.

 

[DYNOED250]

ill get the figures of the guy that done the head people, i remember it was 128 not horse power might have been cfm or inches not sure which scale it works on not sure what that means to any one. il find out for sure . it would have to be running out of air the more that i think bout it. but i juist dont know. ill get back 2 u all soon

 

[xctasy]

Good on you. Take it easy.


We'll try not to hen peck you half to death. We all want what you've got. You're yet another inspiration, a Ford guy whos crankin it!

 

[Anonymous]

Execute. I remmember you saying that with 200 rod it may be possible to get another 500 rpm. If that Ford Engineers figure of 4800rpm (no matter what cam was used ???) is to be taken as a bit of a guide (and maybe even the BA at around 4750 rpm) then another 500 on 4800 brings it to around 5300.
Its probably got nothing to do with it at this level, just thought Id throw it in anyway. I know its only a limiting "factor" as you have suggested, its not critical.

DYNOED 250 . Is it for a trip down to the store for groceries or just for fun? Hope you get it all sorted. Cheers?

 

[xctasy]

There is another thing to look at. Valve lash. If Wade suggest say, 24 thou on the intakes and perhaps 20thou on the exhast, you should go onto this next phase of checking.

Going below spec on valve lash should increase the duration, increasing the lash should drop it. If your peak power goes up with a 6 thou reduction in valve lash (eg 18 thou intake/14 thou exhast), then the cam isn't big enough for the head/block/manifold combo. And look at the head first, then the manifold.

If the peak power goes up with an increase in lash (eg 30 thou intake/26 thou exhast), the cam is too big for the head/block/manifold combo. Again, look at raising the rest of the engine to the challenge, not backing off. Sam Blumstein from COME says there are only bad engine/head/manifolds, no such thing as a bad cam choice.

Geeze, 383 cube engines kick out 700 hp with little 280 degree @ 50 thou cams, yourse should hit the 350 hp level with vim and vigor with this cam.

 

[Anonymous]

With air flow figures for the intake and exhaust lift at .1, .2, .3, ect. I can tell what the HP and torq should be and what RPM for each.

 

[aussie7mains]

Sounds like the diameter of the intake runner is too small, id estimate that to get power at those rpm, youd be needing something around 40-50mm, which the fei system isnt anywhere near. The crosshead port is designed for good mid rpm power and will become restrictive above 5000-6000rpm, and you wont be able to port it out big enough to get much above say 6000rpm.
So overall, unless your willing to do MAJOR reworking of the intake port, id stick with power to 5600rpm but sort out that, so a bit less CR, and cam may help. Get yourself a computor programme like "engine analyser" find all the data that is reqired and fiddle about till you get the result your after.
A7M

 

[Anonymous]

Quote from Execute
"To answer your question,Tim, 33 to 35 mm (1.300-1.375") for the HF-5 alloy cross-flows I've got.
'76-'79 Cast iron cross-flows had 40 mm ports (1.575")."

This is interesting and what I suspected (heard rumour that this is the head the racers use). If the Iron head crossflow has 40mm inlet ports (bigger than alloy crossflow) and better exhaust ports that the 2V head then wouldnt it be the pick of the bunch if real power above 5000 rpm was sought after.
Biggers ports like the 2V at 42mm make it boggy down low in rpm but with better exhaust ports maybe just the thing in a crossflow for high rpm.

 

[Anonymous]

Spoke to Raymond at Brough Race Engines (crossflows). He has a secondhand re-ground roller cam for a crossflow (about 250 deg at 50) for sale.
Interesting he says this was a bit mild for the crossflow it was in and has gone as much as 270 deg at 50 (ported head) in crossflow before.
Can get ph number if anyones interested.

 

[Anonymous]

How does one get a roller cam into a crossflow block without cutting it up?

 

[xctasy]

Cross-flow roller cams? Not a problem!

Five nice big 70 by 35 mm windows which allow the tied in lifters to sit side by side. You only have to get them in. Unlike the non-crossflow, which has buttresses between each group of five lifters, and very little room.

The cross flow doesn't need a bore bar passed through these buttresses, it doesn't have any asside from a few flanges. The extra strength comes from the extra 15 mm of metal added on both sides of the cross-flow block.

 

[DYNOED250]

making a new manifold, using short runners and 6 45 mm throtle bodies, like triple webbers but with injection