What to do next on carby 250 crossflow?

F

fordmuscle83

Well-known member
Just wanting peoples opinions on where i should go from here.
My car:
85 spac sedan, manual
Rebuilt engine 30000 ago.
Balanced, rebuilt head, pacemakers, 2.5inch exhaust, ULP seat, larger valves, machined exhaust, new lifters springs, so called 1 1/2 cam, re-jetted weber, dyno'd tuned for PULP. New clutch system start or year and carby reco kit too.

As ive jus bought this car the work im quoting is all from recepts i got with sale.

It currently has a 4 speed manual and 2.77 rear end. Can i up the diff to 2.9 odd? If so, what revs would it be doing at 110 with 225's/14? Its around the 3000 mark as is.

I think im wanting to go redline manifold and a 4bbl which offers good power and ok economy on the highway. Should i go for a bigger cam and Yella Terra rollers?

So many questions.

Pete
 
The stock EFI 4.1, 4.9 and 5.8 XE's got 2.92:1 diffs with four-speeders, and would do 40.3 km/h per 1000 rpm. So at 110 km/h, thats 2750 rpm. It is frankly the better ratio. The reason they bailed on it was Australian Standard economy test figuers. There was a slight increase in thirst, as loss of 0.5 l/100 km. I doubt its cost effective to change it, but it depends on what you ask for, what you get.

These diffs are around, but there were changes in pinion crush ring on some. A 78 BW diff is a Salisbury type, needs care when swopping ring and pinions. Backlash and A7M have suggested a straight diff swop, or go see a specialist to do it. If I was doing it, I'd go for a demon 3.23 to 3.9:1 crown wheel and pinion (from Falcon 3.3 5-speed's to Nissan Skylines 3.0 autos) , and get a Japper Toyta Supra gearbox with a long overdrive. When you cam and carb a six, you are looking for performance. Few six cylinder guys ever get into there engine. There are many very tough XR6's and V8's hauling almost 1.6 to 1.8 tonnes around, and a well worked, lighter XE or XF would put up a great fight when pressed, and cruise in a very relaxed manner.


My belief is that a 500 2-bbl Holley on a stock 2-bbl intake modified to fit will allow upwards of 196 hp to flow with the right cam. I've done this with my LPG Falcon, and its been really good. A few 12 mm bits of alloy to space the manifold out enough to fit the carb on, a Redline adaptor, a little die grinding to clean up the casting slag, and your away.

Enough for, on a cammed petrol engine, a 15.4 second quarter at 89 mph with a 3.9:1 diff, and an over driven ratio of 0.79:1 or so to make it cruise at 2850 rpm at 110 km/h. Stock XR6's have run 3.45:1 diff ratios for years, with long over driven 5th gears, and very wide intermediate ratios. (1st to 4 th).

A 465 cfm Holley can run to over 280 hp, so there may be a 13.7 sec, 100 mph quarter horse in there if you spend enough. It could rev to 5500 rpm for power, 6000 rpm for maximum revs with 7/16 stud mounted roller rockers, and would need a screamer 4.4:1 custom diff to fight off a strip challenger. Then you'd need an auto with a long 0.68-0.67:1 over drive to drive it on the street and still have it cruise. THM 2004R, 700 R4's and AOD's spring to mind, but the cost is massive.

Very few people understand that when you cam an engine up, you must widen the spread of ratios, or you end up with a staggering dog on the street which will rev its ring out on the road. Days of just wacking a C4 in it, and cruising interstate for a drag racing face -off are gone if you don't have 500 cubes of big block. A heavy XE/XF six is more in need of an over drive than a V8 or a lightweight early Falcon or Cortina will ever be.

Get a copy of this tread with peoples responses, and go see an engine builder or post it to a cam expert, and sort out a combination. They want your bussiness, and are keen to help someone whos prepared to gear it right for the application.
 
XECUTE, i have an xe efi s pack wagon also and its 4 speed with 2.77 diff. I thought they all were?
My speedo must be out in the car i have now as it does 2950 at 110 with the 2.77 diff and you say that a 2.92 would lower rpm than this which isnt possible.

Also, as you seem to be "the man" to talk to on this forum, could you please explain whats needed to make an ultraflow sprint manifold and 500 holley to be a bolt on 40 rwhp and PLUS.

I read one of your posts about being excited about a quote from someone into historic racing on the hardcore thread. What was this about?

Cheers,
Pete
 
Blast, I lost my post.

Any way, it was long.

Just use a good cam, good intake, got exhast header, and 500 2-bbl PN 4412 carb, and you'll get 143 rwhp by my predictions. A stock 98 kW 250 will have about 103 rwhp.

A cam by Sam at C.O.M.E, or Ray at Crow, could be made to breed up to 230 rwhp from the 500 2-bbl. This has been done on larger V8's which are stuck with 2-bbl Holleys.

Jimbo65 posted a link to it. Check his last posts on his Mustang 200 2V, and it's there. It's a Hot Rod article on a 289 with 352 hp from a stock 500 Holley 4412. I'm sceptical, but I do belive the article after checking the figures.

I'm less sceptical about hi-po Henries with dual throaters than ever. I think they have a great future if the valve gear studs, crank splash (windage), and rods bolts are fixed. The Falcon engine is dirt cheap, and as tough as an axe.
 
hey xecute is it possible to change ratios in the ford gearboxes?
 
Yes, if its a single rail, anything goes. The gearshift is in different positions on the Cortina 6, while Centuras, P76's and Valiants also got 'em as options.

351/5.8 close ratio with a set of 2.46, 1.78 and 1.26:1 intermediates.

302/4.9 or XE EFI with 3.06, 1.93, 1.31,
or the wide ratio 250/4.1 with 3.47, 2.00, 1.43 gears. It's all possible. I suspect most 4.1 Cortinas ran this box, as apposed to the wide ratio one used in the Falcon 4.1's.

Even a set of E49 Charger gears with the 302/4.9 ratios but with a tall 2.83:1 first is a goer....if you can find one!

Best for a six with a cam is the 4.9 / XE EFI version. Ratios are friendly to a hard worked six. The wide ratio is going to leave you with a poor gear choice, while the 5.8 number is good for a race car, but possibly too savage for the street unless you run a really good drag racing diff. The E49 set is similarly rather to tall in first.

Depends if your cruising or pulling boats, or drag or circuit racing.

Good rebuild kits are still around, but you need to be quick. The single rail is one of Fords best Borg Warner transmissions, a second to the T10 and Super T10, and pretty soon some bean counter will stop stocking gears for it. Thankfully, its very strong, accomodating up to 350 hp and 350 lb-ft without dying.
 
Can you easily explain the relatinship between power deliverly and gearbox/diff ratios?
Today i raced a 88 skyline manual with pod filter 2.5 inch system, extractors and 5 speed.

Off the line in second we were together and into second he was infront by half a car length. once we hit third and he changed to forth i was so far back its not funny.

Rolling start in 1st at about 30km/h i had him and even pulled away from him in second. Hit third again and he took off, darn!

Another note....at 4000 the car seemed to loose power like there wasnt enough fuel from the rejetted weber (cant wait for 500 holley!!!!!).

Im still shocked that it was so close upto about 100/kmh!

So back to my question....what gear ratio would be perfect for the crossflow......is factory nearly as bad as you can get being such a slow rever or the oposite as it takes advantage of that nice fat torque curve???

Pete
 
Can you easily explain the relatinship between power deliverly and gearbox/diff ratios?
Click to expand...

Glad you asked!

Basically, there is a sweet spot to hit for that reduces your 0-100 km/h time. Lower the diff (go for bigger number), and use a stump puller 1 st. You only gain a few tenths. All the rest is pure power. That's why he caned you. Falcon sixes allways win the first 60 foot of a race. Ricers with hi-po engines cane us after that because of a better hi rev power to weight ratio. We win becasue our sixes have a better low rev power to weight ratio.

Examples:-

EB XR6 Falcon 15.2 sec i/4 mile, 0-100 km/h in about 6.8 sec's

The best ratio for a manual street six is the same ones XR6 Falcon's ran. 3.47, 2:1, 1.29, 1:1, 0.79:1 or something, with a set of 3.45:1 diff gears.

That's an overall 1st gear of 3.47*3.45, or almost 12:1. The bigger the number, the more torque multiplication, the more turning force the wheels see, the better the inital urge off line. But if you go for anything lower geared, then you have to do more gear changes, and you loose a bit on each gearchange before 100 km/h.

XC GXL 5.8 Fairmont 15.9 sec 1/4 mile, 0-100 km/h in about 8.3 seconds.

This had 3.00:1 diff, 2.46, 1.78, 1.26, 1:1, or something. Overall first gear was 7.38:1. This still romped off line, but was 1.5 seconds slower off line to 100 km/h than the XR6, but only 0.7 secs slower over 402 meters.

Summary: Any gearbox which allows you to get between 12 and 9:1 for the first gear overall ratio, but try to get close to 12:1, not 9:1. 3,47 ist, 3.45:1 gears, or down to 3.06 1st with 2.92:1 gears (XE EFI/XA to XE 4.9 V8).
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