basic timing-250 pre xflow



hey all,

having a few probs with my '74 pre xflow 250. lost some power and runs a bit warm. Back to basics - :roll: how do i set the timing for this motor using a timing light?

ie: disconnect vac advance line, and plug it? what revs, how many degres? The motor was really badly tuned when i picked it up, I've tuned it by ear and test drive, not the most accurate! Is the timing set the same as the falcons-weight issues?....

Next question, the breather line on the rocker cover to carb. A friend told me these can cause probs (long time ago, can't remember) something to do with the valve... Do people mod these, block or remove? Don't know heaps about engines, but if this is restrictive the top end will pressure up and run bad?

Last Q: The motor got pretty warm the other day, so i turned the heater on to help cool it. The air was hot for a min, then went coldish. Toggled the lever again and the same.. I've check the heater valve, seems fine. Can an airlock or similar form in the heater core?

Very last q: My carb aint great, any hints on basic upgrades: ie holly? or places to get a reco stocky? Live near Canberra.

As always thanks in advance for your help, Tom...
For your carbie, if it is a stromberg, you can probably overhal it yourself with no problems. Just pick up a manual, or get someone to scan a few pages out of thier manaul for you, and folow the steps. Those ond single barels are easy as. IF after overhaling it, it still runs like a dog, or you still want to upgrade, holleys rule. How big depends what sort of fuel economy you want, If it were my car, i'd be very happy with a 350.

Tuning, I am the wost engine tuner around, and because of this I NEVER tune my own engine, and if I do, I have to get it Someone will know what the idle timing should be and whatnot. How to use a timing light:
1) Conect power leads to battery, and signal lead to spark plug lead #1.
2) Mark out the notch in your main pulley with chalk
3) Start engine
4) point gun at pulley
5) Line up notch that is made visible with each flash with the right number on your timing chain cover.
6) Even though it sounds like fun, don't try and get that leaf stuck between your radiator and fan while the engine is still running.

Your positive crank house ventelation (PCV), never block it, it is actually importaint....once again someone will elaborate.....basically traped gases/pressure build up.......sorry not much

Sorry I have to cut this short, but I gotta run.

Better yet, mark the notch on the crank with idiot ink. Sounds like its running fairly retarded if it likes to warm up on you.. I believe its fairly standard practice to set base timing at 10 degrees. You'll probably see it fit to use LRP, Ultimate 98, Optimax, or a mix of LRP and higher octane unleaded. Anything between 8-10 degrees is acceptable. Yes, you should disconnect the vacuum advance, and plug it.

Its a '74, yeah? If so, it'll have to comply with ADR27, so no removing and blocking, unless you like the thought of a defect notice. Basically, the way to tell if its on the way out, is you pull it out of the engine, and shake it. If it rattles, its in working order.

With your heater... has it stopped blowing hot air entirely, or is it just random? It might be an idea to try a radiator flush with the heater running. It might not be such a good idea if the heater core is old, it could be rotting away..

Good luck on the tune-up!
lol, remember my old radiator core maggo? That thing was as soft as a sponge.
haha, it was good of you to donate it to SeaWorld to they could use it to clean the barnacles off the whales!
Thanks for the advice, greatly appreciated... I'm off to tune up now, so block vac advance line, 8-10 d setting....

Q: engine revs for setting timing? trying to think, with vac disconnected and blocked does it matter? is there a centrifical advance aswell in the dizzy?

Its a '74, yeah? If so, it'll have to comply with ADR27, so no removing and blocking, unless you like the thought of a defect notice. Basically, the way to tell if its on the way out, is you pull it out of the engine, and shake it. If it rattles, its in working order.

Not worried about adr too much, RTA don't seem to like the corties too much anyways : ) .... I think someone once said to belt the bearing up with a hammer? I'm used to mini's, they have no valve- blow all the time, have seem some connected to a oil catch bottle instead of carb.. If anything like this helps, I'm willing to give it ago....Being '74 I should be outside the 25 year age, ie- rules open up, don't they?

With the heater, fan is fine.. turn it on (even if hot is selected, air can be cold) switch hot/cold/hot/cold then hot = hot air for a minute or so, then it goes cold, almost like some hot water is let in during the toggle stage then cools down, no real flow... Have flushed the entire system - that's how I checked the valve too - some crud came out, but flowed fine.... I may take the valve switch out- straight through = heater hot allways..

What are the signs of a dead water pump? Makes some noise at idle after long drives, but if it was dead then the motor would be toast by now...

Anyways thanks again.... It's great to have decent sites on the net.

Later, Tom...(off to the shed!)
Go to Howarth's (Carburettor Service Co) in Sydney, for a carb overhaul. Think you've likely got a Strommie BOV, or similar. Consider an adaptor and a progressive carb off an XE.

It's not a 2V, is it? (The engine.)

Water pump - get the type with pressed impeller, alloy housing. Harder to find, but worth it.

Your ignition is dual advance. Timing is set with no vacuum applied. The PCV valve should rattle when shaken hard. If not, clean it with Prepsol or fuel until it does.

Cheers, Adam.
Stock head, no 2v :( , yet.. Just has the stock stromberg, will look into the xe carb. Thanks.
The webber ADM, that came of the XE/XF's are nice, but they do have thier limitations (finding parts for them is realy hard). If you get one from a wrecker for under 100, and it works pretty good, that'll work out. However the holley 350 is a much better option, and will probably give you a bit of a performance boost, they are not that expencive second hand. Well that's just what I want, you can have my
tuned up, runs abit better, timing was at about 6deg. I've put a kit through the carb and new mix screw, the old one had been cranked at one stage and was bent! not sure if this has affected the housing in the carb body - doesn't adjust gradually..... I may go and see a machanic..

Car runs ok, potters round happily, hesitates under middle load, ok flat out but doesn't pick up quick as it should.. almost like it's running lean, but plugs and exhaust seem right colour......

I feel it's the carb, I'll go and find out about carbs and adapters in the morning... So under $100 for good carb is the right price, what's the average for an adapter?

Just about to move back up the coast and want the motor running 100% for the trip, 1600km round trip, need 2 trips... but thats why i bought another corty, solid car, solid motor....

Thanks, Tom
Probably around $30 for an adapter. I passed on a NOS in box XE carb at a swap meet a few months ago... $40. Give the carb place I mentioned a call. They are pretty good if you need an honest opinion.

Valve train wear can cause sluggishness in response, too. If you can borrow a vacuum tester, maybe report the manifold vacuum at idle.

Regards, Adam.
heh, managed to sell my spare webber for $75.

This may sound stupid, but have you tried a bottle of total fuel system cleaner? You may find that the fuel jet in the carbie is a bit blocked up. Also if ou put oyur hand over the carbie and then give the engine a few revs, that can mild cases.
hey, full kit and clean in carby, evil carb!!! Don't have or know anyone with vac test... Will do compression test when I make the trip to coffs, This will show valve/ring probs?

See how i go.. If not I'll poter around, probs the best idea on a uni budget!! see what happens, I just like to have things 110% if poss. Can't expect too much from a 25+yr old motor...