Ford X-Flow Rev Limit
Discussion
As a new owner of an old Westfield, I'm after some Gospel according to PH.
It's a 1700 X-flow 711 block with no rev limiter. The engine was rebuilt '2 years ago' (according to the previous owner) with a piper fast road cam and high pressure oil pump, but I don't think it's got any other high spec parts inside.
I'm putting in a rev limiter - what's a reasonable limit to set? I'm not wanting to rev the nuts off it and don't want to expect to have to rebuild it every year... Would 6,500 be 'safe'? I'm not going to be bouncing off the limiter in every gear... is 7,000 occasionally okay?
Or am I way off the mark?
It's a 1700 X-flow 711 block with no rev limiter. The engine was rebuilt '2 years ago' (according to the previous owner) with a piper fast road cam and high pressure oil pump, but I don't think it's got any other high spec parts inside.
I'm putting in a rev limiter - what's a reasonable limit to set? I'm not wanting to rev the nuts off it and don't want to expect to have to rebuild it every year... Would 6,500 be 'safe'? I'm not going to be bouncing off the limiter in every gear... is 7,000 occasionally okay?
Or am I way off the mark?
I run a 1660cc x-flow with a BCF2 cam and high-pressure oil pump - very similar spec to yours. The only difference is that I rebuilt it myself, so I know what went into it! 
I've set my megajolt ignition system's rev limit to 6300rpm, which I consider to be a safe limit. I rarely get that high anyway as everything's getting quite exciting at that point... and LOUD!
6500 may well be safe - but I'm chicken as I would prefer to have steel main bearing caps & top-quality conrod bolts before I explore the higher realms.
I've set my megajolt ignition system's rev limit to 6300rpm, which I consider to be a safe limit. I rarely get that high anyway as everything's getting quite exciting at that point... and LOUD!
6500 may well be safe - but I'm chicken as I would prefer to have steel main bearing caps & top-quality conrod bolts before I explore the higher realms.
I have an old Westfield with the same engine. I rev mine to 6500 and no higher, i do not have a rev limiter but you'll find one really useful, especially if you have the old 4spd ford gearbox with useless ratios in. I would set my limiter to 6250 so if you bounce up into 6500 everything should be ok.
I would set 6.5k as the safe maximum(power will be tailing off already)ahh all my X Flow tuning years just came flooding back 
one of my early builds was 1660 spec 711m block with 1300GT cast pistons Kent 244 cam and that lasted 35k + before updating and that was limited to 6.5 k and made 114 RWHP at 6.9k for the Dyno out of interest 
very tough bottom end unless you take the piss even with those heavy slugs 
one of my early builds was 1660 spec 711m block with 1300GT cast pistons Kent 244 cam and that lasted 35k + before updating and that was limited to 6.5 k and made 114 RWHP at 6.9k for the Dyno out of interest very tough bottom end unless you take the piss even with those heavy slugs Edited by Simon Says on Thursday 3rd December 19:43
From your spec, I would think the rev limit is determined by the valve springs, Stock cranks are strong, and if you use the 711 block I dont think steel caps are needed, if you have the smaller caps from the pre711 engine, they are still pretty strong, just with sensible mods, all the engines can be made to work at high revs,
Example,
1600 691 small cap block, bored to 1750ish, Lotus 125e rods, beam polished, and cosworth bolts, Lotus/hepolite forged pistons, crank stock, apart ftom de burring, Arp cap bolts, I think we machined about 5mm off the deck to get the comp height!!!!, so in theory the block is well beyond its limits of stability with a thin deck, fitted with a GOOD pre X flow head on 45s, so its really quite limited on flow, made 153hp on the engine dyno, this is not a race engine but a daily driven 105e Anglia. It would be even better if we could talk my mate into doing away with the clockwork dissy and went mapped ign, I think theres a bit more torque to be found low down
Now for Rev limits, 8000, as a basic, 8250 when playing hard, and its seen nearly 8800 on missed shifts,
OK dont expect this engine to do 50k miles before a rebuild, but its been built 3 years now and arpart from the odd broken valve spring, [offy springs for small blocks are not designed to hit nearly 9k] and regular tune ups, its been great,
Theres a new long rod tall deck engine in the wings, still built around the 691 cortina block, knife edged crank and silly compression, cant wait to see how this one runs,
The other thing about this engine, other than the decking of the block, and general machining the engine was built in my mates spare bedroom and shed, is he a pro engine builder, NO, pedantic, OH YES, but its the attention details that make things like this work!!!!
Example,
1600 691 small cap block, bored to 1750ish, Lotus 125e rods, beam polished, and cosworth bolts, Lotus/hepolite forged pistons, crank stock, apart ftom de burring, Arp cap bolts, I think we machined about 5mm off the deck to get the comp height!!!!, so in theory the block is well beyond its limits of stability with a thin deck, fitted with a GOOD pre X flow head on 45s, so its really quite limited on flow, made 153hp on the engine dyno, this is not a race engine but a daily driven 105e Anglia. It would be even better if we could talk my mate into doing away with the clockwork dissy and went mapped ign, I think theres a bit more torque to be found low down
Now for Rev limits, 8000, as a basic, 8250 when playing hard, and its seen nearly 8800 on missed shifts,
OK dont expect this engine to do 50k miles before a rebuild, but its been built 3 years now and arpart from the odd broken valve spring, [offy springs for small blocks are not designed to hit nearly 9k] and regular tune ups, its been great,
Theres a new long rod tall deck engine in the wings, still built around the 691 cortina block, knife edged crank and silly compression, cant wait to see how this one runs,
The other thing about this engine, other than the decking of the block, and general machining the engine was built in my mates spare bedroom and shed, is he a pro engine builder, NO, pedantic, OH YES, but its the attention details that make things like this work!!!!
Interesting reading, ta.
If anyone is interested, here's a dyno run I had done at Exeter kit car show.
Nowt special I know, but it's pretty torquey all the way through. It's running a bit rich at the moment so perhaps I'll get over 100 when it's tuned.
Oh, I'm not really sure the engine speed on the dyno graph is quite calibrated right, I don't think it got quite as high as 7,000 on the run.
If anyone is interested, here's a dyno run I had done at Exeter kit car show.
Nowt special I know, but it's pretty torquey all the way through. It's running a bit rich at the moment so perhaps I'll get over 100 when it's tuned.
Oh, I'm not really sure the engine speed on the dyno graph is quite calibrated right, I don't think it got quite as high as 7,000 on the run.
Although the torque curve is flat it actually isn't very torquey. In fact it's pretty crap. With only 88 ft lbs which is under 52 ft lbs per litre from a 1.7 that's way under what even a standard engine ought to produce. 60 plus ft lbs per litre would be a more realistic target. I've seen plenty of other curves like this where the engine produces no torque but wants to keep revving and revving to try and produce some power. The usual causes are either or both of the following.
1) Not enough compression ratio to make the cam work properly.
2) An exhaust manifold issue which is preventing the engine pulse tuning properly.
Clearly an inlet side restriction or the incorrect mixture could also be factors.
The cam doesn't appear to be all that hot because it's still pulling down to just over 2k rpm but even so it probably wants about 10:1 CR or even a tad more to make it work. If the bottom end is bog standard then this won't be happening. What exhaust issues might be present I obviously can't say.
With a good BV head, cam, exhaust, appropriate CR and twin carbs an easy target is 130 bhp and 125 ft lbs which would blow your socks off compared to what you currently have.
You might want to read the Crossflow tuning article on my website. If you don't know who I am or can't find my website then your Google skills need a tune up too. I ain't that hard to find.
1) Not enough compression ratio to make the cam work properly.
2) An exhaust manifold issue which is preventing the engine pulse tuning properly.
Clearly an inlet side restriction or the incorrect mixture could also be factors.
The cam doesn't appear to be all that hot because it's still pulling down to just over 2k rpm but even so it probably wants about 10:1 CR or even a tad more to make it work. If the bottom end is bog standard then this won't be happening. What exhaust issues might be present I obviously can't say.
With a good BV head, cam, exhaust, appropriate CR and twin carbs an easy target is 130 bhp and 125 ft lbs which would blow your socks off compared to what you currently have.
You might want to read the Crossflow tuning article on my website. If you don't know who I am or can't find my website then your Google skills need a tune up too. I ain't that hard to find.
I must admit that my x-flow gives only around 100BHP (with luck and a following wind ). However, in a 7-style car it still means that I can fly along at a good speed and have a blast - I don't feel the need to go faster just at the moment (shock - horror!).
If I did feel the need for more power I wouldn't invest any more cash in the x-flow, much as I like that engine. Simply replacing it with a stock Toyota 4-AGE will give me 130BHP (with minor tweaks) and a lot more power if I make changes to it. In fact I can fit a £50 Zetec that will, if in reasonable condition, exceed my current engine's output by quite a few BHPs - with scope for a lot of improvement.
And, of course, I could always fit a 2-litre Duratec!
). However, in a 7-style car it still means that I can fly along at a good speed and have a blast - I don't feel the need to go faster just at the moment (shock - horror!).If I did feel the need for more power I wouldn't invest any more cash in the x-flow, much as I like that engine. Simply replacing it with a stock Toyota 4-AGE will give me 130BHP (with minor tweaks) and a lot more power if I make changes to it. In fact I can fit a £50 Zetec that will, if in reasonable condition, exceed my current engine's output by quite a few BHPs - with scope for a lot of improvement.
And, of course, I could always fit a 2-litre Duratec!
I quite agree. As my tuning article states, the Crossflow isn't the easiest or cheapest engine to extract decent power from and getting a head ported really well is a rarity. Much better to fit just about anything else from a CVH upwards. A Stock 2 litre solid lifter Zetec with a decent manifold and system will give nearly 145 bhp and with a pair of TBs more like 170. It'll also be completely reliable, fuel efficient and totally untemperamental.
Spending thousands on tuning antique 2 valve cast iron engines is a waste of time when modern 4 valve ones do a better job straight out of the box.
Spending thousands on tuning antique 2 valve cast iron engines is a waste of time when modern 4 valve ones do a better job straight out of the box.
I 100% understand and agree with the above. I'm not going to spend a lot of money on this engine.
Having said that, I like the old fashioned nature of the engine. It suits the car well and it goes well enough for me to have fun. I don't mind spending a little bit now to get it running as sweet as reasonably possible.
Having said that, I like the old fashioned nature of the engine. It suits the car well and it goes well enough for me to have fun. I don't mind spending a little bit now to get it running as sweet as reasonably possible.
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