More MidRange for Pre Crossflow

[Roath]

Hi Guys

Been working hard on the boat.. the motor will be next winter, but still trying to work out what I will do with it. The engine bay is REALLY narrow and just fits the XA 250. This limits my re power options cause most engines are allot wider. (on the inlet side)

Currently WOT is just on 3000 rpm.. which is fair moving.. I would estimate I wouldn't want more than 3500 rpm otherwise I will be into suicide speeds. ( yes I know.. sounds good!)

Spent a few minutes this morning looking at motors

Now I have been told that for best performance WOT should be half way between max torque and max HP. Interestingly that's where mine is.

Now I see my options are:

*Do a good rebuild of the non cross-flow.. but what should I do to get the grunt up. I guessing I want a sort of 'towing' cam?

*Go for XF EFI - looks the best match power wise.. lighter and no changes to engine mounts (not sure of the bolting to the Gearbox) but I guess the Injector will be too wide for the engine bay?

*Go for a late model motor that AUII LPG motor looks like perfect power and running on LPG would be awesome. But I guess nothing would fit.. would need to redo mounts , new adapter and probably too wide anyway.

I guess I have answered my own questions.. the only real option left is to rebuild the donkey. I have a spare in the garage with no lip at all. What should I do to it for max power at about 3500 RPM ( without going wider.. so no grafting on side Weber's [/img]

 

[lyonsy]

hey
id go a crossflow bolts straght in and will make heaps of grunt.
tight on speace use a redline/cain inlet manifold.
you will have to change the exhaust to a crossflow type.
how much power you want?
a cam swap can give you up to around 150flykw
also your xa engine unless built up doesent have that power when they done the power figures back then they dident run alternators/waterpumps/fans and there actully power is around 90kw.
does this have a closed cooling system if not only put a steel head in due to corrsion that will happen with the alloy.
for a full rebuild what do you want to do?
drift

 

[Roath]

the power figures back then they dident run alternators/waterpumps/fans and there actully power is around 90kw.
does this have a closed cooling system if not only put a steel head in due to corrsion that will happen with the alloy.
for a full rebuild what do you want to do?
drift

Ahh didn't know that. Thanks, I was wondering how a non cross flow with what looks to be very restricted breathing could compare so well. As you should be able to see in the picture.. Header tank and Exchanger, so closed. Anyone got some measurements of the width of the cross-flows.. centre line to widest part of the intake side? I'll start hunting for the redline/cain inlet manifold... what carbs go on these and anyone got measurements?

Cheers

 

[lyonsy]

hey
carby anything you want 350/500 holley, falcon webber, any 2bbl but the only bolt holes are for 350/500 holley
ill try and get some measurements for ya today.
drift

 

[L6]

Hi Guys

Been working hard on the boat.. the motor will be next winter, but still trying to work out what I will do with it. The engine bay is REALLY narrow and just fits the XA 250. This limits my re power options cause most engines are allot wider. (on the inlet side)

Currently WOT is just on 3000 rpm.. which is fair moving.. I would estimate I wouldn't want more than 3500 rpm otherwise I will be into suicide speeds. ( yes I know.. sounds good!)

The existing unit looks like a rear drive with fresh water cooling. That is a good reliable arrangement and you should try to retain it.

Conversion to a cross flow will be very expensive because your existing manifold will not fit. This will mean a new inlet manifold –not a big deal, but a new water-cooled exhaust manifold will be pricey.

To set up a full fresh water cooling system on a replacement Xflow, will cost more than the replacement engine unless you can find a used cross flow already marinised. Raw water cooling is cheaper but you will lose power.

If in spite of this you go ahead with a Xflow and pick up an EFI engine, convert it to carb. High-pressure fuel lines and electronics are not a good marine arrangement; also drum fuel plays havoc with injectors and EFI filters.

I have been out of the marine business since Flipper was in nappies; so do not even know if manifolds are available for the OHC. The gearbox certainly will not bolt up and there is a bit of a fiddle changing it to carb so my belief is that it should be the last choice.

So far as engine revs are concerned. Operating close to max torque will give best economy, and max power is just that -the point where you will achieve max grunt. A replacement or repitched prop will be another expense if you deviate too far from your existing operating conditions.

Others here can give you more reliable advice on mods for power gains than I ever could, but remember you can run a much more aggressive cam in a boat because the prop acts as a fluid coupling and allows the engine to spool up when the throttle is opened at low boat speed. My guess is that larger valves would have little benefit with such a poor flowing manifold.

If this were mine I would do up the pre-X engine, fit an appropriate cam to raise the power band slightly, and ensure the ignition timing is spot on. The engine will then run a few hundred revs higher giving a higher boat speed with the same prop.

Resist the temptation to really soup up the engine. Remember a boat motor will frequently operate at high power for long periods without a rest at the traffic lights.

 

[lyonsy]

hey
will bolt in as the bellhouseing and crank are the same as pre xflow.
but everything else he said is right.
if you decided to keep the log motor then i recomend getting a pffy tripple carby setup.
as for durabillty keep a ford 6 below 5500rpm and dont go over 40thou on an over bore it will last forever.
drift

 

[Roath]

If this were mine I would do up the pre-X engine, fit an appropriate cam to raise the power band slightly, and ensure the ignition timing is spot on. The engine will then run a few hundred revs higher giving a higher boat speed with the same prop.

Resist the temptation to really soup up the engine. Remember a boat motor will frequently operate at high power for long periods without a rest at the traffic lights.

Thanks L6 She's a stage 3 Hamilton Jet with fresh water cooling. I need to replace the exhaust manifold at some stage(They are aluminium so they only last 5 - 7 years). I will be replacing it regardless of a new cross-flow or rebuilt non cross-flow. Both manifolds are available from Australia and the cross flow is actually cheaper! ( about $200 cheaper). Being a hammy jet there is no water pump.. so pretty easy to swap out to a different motor. As Drift said, same bellhousing too.

I know rebuilding an XA motor is likely to be cheaper as I won't have to buy an aftermarket inlet manifold and carbs etc. The XF is still tempting though...lighter and the power in about the right place!

I will try and get the measurements of an XF with that aftermarket inlet and see if it will fit in the current engine cover. Height of the carb maybe as well. If it fits I will see if I can get a motor to rebuild.

I see there are 4 different models of XF, all with different compressions etc. I will have to work out which ones best and how I can work out which one I'm buying .. oops, better wait till I know if it fits!

 

[lyonsy]

hey
height should be fine as the xflow is actully lower in height then a pre xflow but there width it a bit wider then the pre xflow.
if you measure how wide the sump is this will give you a pretty close indication.
if it will or not
drift

 

[Roath]

hey
height should be fine as the xflow is actully lower in height then a pre xflow but there width it a bit wider then the pre xflow.
if you measure how wide the sump is this will give you a pretty close indication.if it will or not
drift

Cheers for that. I don't think the sump isn't an issue as I have plenty of space there. Or do you mean the sump will tell me the width of the inlet manifold somehow?

I have found one for sale here on Trademe http://www.trademe.co.nz/Browse/Listing.aspx?id=64197158 so I can ask the width of the standard manifold at least

 

[L6]

hey
will bolt in as the bellhouseing and crank are the same as pre xflow.
but everything else he said is right.
drift

I have been out of the marine business since Flipper was in nappies; so do not even know if manifolds are available for the OHC. The gearbox certainly will not bolt up and there is a bit of a fiddle changing it to carb so my belief is that it should be the last choice.

The gear box for the pre X and Xflow will bolt up, but not the OHC. The para above related to the OHC

 

[Roath]

hey
will bolt in as the bellhouseing and crank are the same as pre xflow.
but everything else he said is right.
drift

I have been out of the marine business since Flipper was in nappies; so do not even know if manifolds are available for the OHC. The gearbox certainly will not bolt up and there is a bit of a fiddle changing it to carb so my belief is that it should be the last choice.

The gear box for the pre X and Xflow will bolt up, but not the OHC. The para above related to the OHC

Sorry, my poor reading skills .. worse at the end of the day. Must be old age getting to me.

Thank you for all the good advise. I must remember to read carefully when getting peoples advice

 

[TCSTEVE]

I think you would be better off with a XE motor rather than a XF one.
XE motor was only carby, same size everything, has electronic ignition and an alloy head. Better spark and keep the weight down a little.

Make sure a Xflow will fit. Buy the cheaper marine exhaust for it. Using the $200 you saved buy a mild cam just spend your time chosing one.
Then possibly go look for a redline manifold to suit crossflow/holley and put a dime a dozen 350 holley on it and jet it for low down torque.
Low down torque is what youll need more of to get this thing out of the water and make sure your skiier is left behind
The cam will give you a wider power band so pick one that finishes a little after your 3500RPM so youll have max power around the mark and more torque all the way there. Good luck, Steve

 

[L6]

Just a few random thoughts.

If you need a new exhaust manifold, and the Xflow manifold is cheaper that is starting to throw the pendulum the other way and make the Xflow more attractive.

Did not realise earlier you are using a jet unit (was thrown off by mention of gearbox). The flywheel cover and drive plate for jackshaft will bolt up to the Xflow without mods.

You have fresh water cooling with heat exchanger so it does not matter what head you use, just make sure you keep the green goo fresh. Do not be talked into converting to raw water cooling you will lose too much power.

You would be well advised to steer clear of the EFI engines. There is a bit of work to convert them to carb and conventional distributor, more importantly some variants are very prone to detonation and this will kill a marine motor in one afternoon. A well prepared XE will give you a more modern engine without the hassles of the EF.

Your old motor cannot be too bad if it will pull a 3-stage jet to 3000 rpm. Do not expect a massive increase in rpm after the rebuild, going from 3000rpm to 3500rpm requires a 60% increase in power.

If you go for a different cam seek advice from the manufacturer or draw on the experience here. There is no point in worrying about performance at 4000-5000rpm; the engine will never run that fast with a 3 stage. Similarly loss of low torque is not an issue at all, the jet will allow the engine to spool up even at zero boat speed. I remember one of the mechanics salvaged the cam from a factory built Chrysler HiPo marine engine and put it in his car engine thinking it would give it a kick in performance. The motor had so little torque down low the vehicle was almost undriveable yet in a boat it was fine.

Do not underestimate the punishment a marine motor is exposed to. A car engine burbling along the highway is putting out about 25hp with occasional bursts of power when passing or climbing a hill. A boat motor is running at close to max load most of the time, and is equivalent to towing a 2 tonne tandem trailer up a steep hill with pedal flat to the floor for hours at a time. We had Chev 350s and slant 6 Chryslers that were so worn after two seasons there was hardly a part worth salvaging.

And even though it is stating the obvious, after the new motor has been installed do not be tempted to tune it at WOT with the bucket in the “neutralâ€￾ position.

 

[Roath]

I think you would be better off with a XE motor rather than a XF one.
XE motor was only carby, same size everything, has electronic ignition and an alloy head. Better spark and keep the weight down a little.

Thanks Steve. I have details of XE injection models.. on this page http://www.geocities.com/falconfacts/falcon/xefalcon.html so I'm a bit confused about you saying XE was carby only. Apart from the ignition is there any other differences. You imply that the XE would be lighter.. whys that?

Thanks Heaps

 

[Roath]

Just a few random thoughts.
And even though it is stating the obvious, after the new motor has been installed do not be tempted to tune it at WOT with the bucket in the “neutralâ€￾ position.

Cheers L6.. I wont be doing that!. The non cross flow motor that was in the boat when I got it pulled 3200 rpm.. but it got full of salt water due to a blown exhaust manifold.. so is in my garage. The one that's in the boat now is one straight from a Wrecker.. has done the job for 2 seasons now. Your advice on timing a while back helped out heaps .. thank you.

I'm getting all excited about a cross flow.. been chatting to Chubs about how much better his standard XF ran compared to his 2V.. so must be heaps better than my old log motor.

But I am starting to think the XF wont fit.. so I have started looking into these Offy tripple carbs.

Would look pretty cool, but I'm not sure about getting someone to install the kit. (which isn't too expensive http://store.summitracing.com/partdetail.asp?part=OFY-5970&view=1&N=150+4294840131+0&appfilter=1)

Cheers to all the advice guys :thanks:

 

[TCSTEVE]

I think you would be better off with a XE motor rather than a XF one.
XE motor was only carby, same size everything, has electronic ignition and an alloy head. Better spark and keep the weight down a little.

Thanks Steve. I have details of XE injection models.. on this page http://www.geocities.com/falconfacts/falcon/xefalcon.html so I'm a bit confused about you saying XE was carby only. Apart from the ignition is there any other differences. You imply that the XE would be lighter.. whys that?

Thanks Heaps

Firstly i didnt even realise that XE's ever had efi motors, sorry to confuse you.
The motor would only be light due to the alloy head which should be ok for marine use although they are a little more prone to problems at high temp. Ignition wise the XE/XF engines have elctronic dizzys with modules bolted on the side of them. The EFI ones might have a differnt curve to the carby ones but if you picked out a new cam you might want to have the dizzy recurved to suit it and get max pick up out of the new motor. Also if you stick with the log motor you can still run one of these XE dizzys with a few little mods, might make some difference.
Ive been down the river plenty of times but never seen a boat with a ford six in it. Would love to see those tripples on yours Steve