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View Full Version : whats needed to go from ford to gm swap


DooSPX
10-01-2008, 11:29 PM
I know people are going to tell me to stick with the ford, but I want to swap my ford 351 for a 350 when something happens to the 351. I also cannot get a 94 or 93 with a gm. I have a personal attachment to this bout. I have wanted this ecact boat from a friend since it was new.

what do I need for the swap? linkage, motor mounts.

JimN
10-01-2008, 11:40 PM
"I also cannot get a 94 or 93 with a gm"

'94 was GM, '93 was the last year for the Ford motors. If the motor goes and you change to a GM, you'll need different motor mounts and an adaptor for the transmission.

Unless you actually try to blow up your motor, it's unlikely that you'll knock holes in the original one and if it goes, that would be the perfect opportunity to build a nice little lumpy-idling, nasty 351. You can't swing a dead cat without hitting performance parts for that motor.

Same goes for the 350 GM. They have been making it since 1954 and ALL of the bugs have been worked out.

east tx skier
10-02-2008, 12:19 AM
What Jim said. You can rebuild it. You have the technology. Love the 351 in the boat!

JimN
10-02-2008, 12:25 AM
My motto is "I can do it, I'm mechanical!"

DooSPX
10-02-2008, 11:40 AM
"I also cannot get a 94 or 93 with a gm"

'94 was GM, '93 was the last year for the Ford motors. If the motor goes and you change to a GM, you'll need different motor mounts and an adaptor for the transmission.

Unless you actually try to blow up your motor, it's unlikely that you'll knock holes in the original one and if it goes, that would be the perfect opportunity to build a nice little lumpy-idling, nasty 351. You can't swing a dead cat without hitting performance parts for that motor.

Same goes for the 350 GM. They have been making it since 1954 and ALL of the bugs have been worked out.

93 had the intro of the first EFI and GM motor. the LT1.

I am aware that the 351 is a GREAT motor. Im not a ford guy, but the 351 is one of the best SB's they built. In fact, I am helping my better halfs father build a 351 for his 67 mustang. I love the 240hp in mine. but I wanted something different, and I can build a SBC with my eyes closed. i have built 305's, 350's, 383's, 2 400's, and also built LS motors. LS1's, LS2's
If I can figure out how to get a LT1 with the computer in my boat I would. I have LT1's pass by my hands by dozens a year.
Besides, I have a 350long block in my garage and a 400 short block right now and nothing to put them in. *hint*

also, why we are on the subject of LT1's. How did Indmar get the rating of 330HP or 350HP for some of there LT1's. Because Auto spec LT1's were 275/285/305 HP rated. the LT4 is rated at 330HP because of better heads/intake and slightly bigger cam.

flipper
10-02-2008, 11:48 AM
When I replaced my motor, I wanted to do the same thing, but didn't have the coin to do it.

DooSPX
10-02-2008, 11:53 AM
the only this expensive to me is the items needed to swap. motor mounts, trans adapter, other items.

flipper
10-02-2008, 11:54 AM
the only this expensive to me is the items needed to swap. motor mounts, trans adapter, other items.

That's the one that kills ya:D

DooSPX
10-02-2008, 11:55 AM
yea... so what other items is needed to swap?

flipper
10-02-2008, 11:57 AM
I saw that you said that you can get 350's all day long, but are they marine? If so, you'll still need exhaust manifolds, water pump, raw water pump....

DooSPX
10-02-2008, 11:59 AM
those I knew, I also know about the brass freez plugs.

flipper
10-02-2008, 12:04 PM
Then pretty much all you have to do is make it fit. On mine, I had to move the computer from the front of the engine, to the back to make it fit under the engine cover, so had to cut, and splice the whole loom of wires. Not that hard, but took a while.

DooSPX
10-02-2008, 12:06 PM
your 302 is injected?

JimN
10-02-2008, 12:38 PM
93 had the intro of the first EFI and GM motor. the LT1.

I am aware that the 351 is a GREAT motor. Im not a ford guy, but the 351 is one of the best SB's they built. In fact, I am helping my better halfs father build a 351 for his 67 mustang. I love the 240hp in mine. but I wanted something different, and I can build a SBC with my eyes closed. i have built 305's, 350's, 383's, 2 400's, and also built LS motors. LS1's, LS2's
If I can figure out how to get a LT1 with the computer in my boat I would. I have LT1's pass by my hands by dozens a year.
Besides, I have a 350long block in my garage and a 400 short block right now and nothing to put them in. *hint*

If you can get an LT-1, look around for a marine salvage company that may have an engine harness for a '97-'99 MC. That way, all you need is the MEFI III ECM. The CEFI controller (used for one year) may work, too.

"also, why we are on the subject of LT1's. How did Indmar get the rating of 330HP or 350HP for some of there LT1's. Because Auto spec LT1's were 275/285/305 HP rated. the LT4 is rated at 330HP because of better heads/intake and slightly bigger cam."

don't know, I wasn't there. Fuel mapping, timing at 10BTDC, no exhaust back pressure to speak of, whether it was connected to a transmission at the time, etc all influence the power specs. OTOH, it's still all about torque.

JimN
10-02-2008, 12:41 PM
[QUOTE=DooSPX;546043]93 had the intro of the first EFI and GM motor. the LT1.

I know, but when most people talk about putting a GM motor in their boat, it's not usually an LT-1.

That said, the LTR is possibly a more marine-friendly package because it doesn't have aluminum heads.

TRBenj
10-02-2008, 12:41 PM
Im not a die-hard Ford guy, but that happens to be all I own. My dad and several friends have Chevies in their boats, several 310/330hp LT1's, and several Excaliburs (330hp). Ive driven the 409hp PCM 6.0L in a CC 196 (new for 2009). I havent found anything yet that can keep up with a ~310hp Ford 351w out of the hole. Im pushing a bit more hp than that, but the PCM GT40 hangs tight with me. The one thing I will concede is that the Chevies breath very well, and have an advantage on the top end (3500+ RPM).

Regardless, if you use the boat for skiing, the Fords are tough to beat. Add a little hp to them to get into the 300-350hp range, and they will put a smile on your face like no Chevy Ive encountered so far.

flipper
10-02-2008, 12:42 PM
your 302 is injected?

yes..........

JimN
10-02-2008, 12:44 PM
Im not a die-hard Ford guy, but that happens to be all I own. My dad and several friends have Chevies in their boats, several 310/330hp LT1's, and several Excaliburs (330hp). Ive driven the 409hp PCM 6.0L in a CC 196 (new for 2009). I havent found anything yet that can keep up with a ~310hp Ford 351w out of the hole. Im pushing a bit more hp than that, but the PCM GT40 hangs tight with me. The one thing I will concede is that the Chevies breath very well, and have an advantage on the top end (3500+ RPM).

Regardless, if you use the boat for skiing, the Fords are tough to beat. Add a little hp to them to get into the 300-350hp range, and they will put a smile on your face like no Chevy Ive encountered so far.

300-350 HP is 300-350 HP, regardless of who made it. Torque curve is another thing and the LTR is a good motor.

DooSPX
10-02-2008, 12:49 PM
all very good points. what is the trq rating of a LT1?
I heard that the LT1 with the PowerSlot has the quickest 0-36 even beyond the 285 with the slot, is that true?
TR, I followed your threads to the T. what makes the new 310HP GT40 PCM have more power than the 285HP carb'ed GT40?

300-350 HP is 300-350 HP, regardless of who made it. Torque curve is another thing and the LTR is a good motor.
Jim, what are the spec's of the LTR, and do you know the trq curve?

JimN
10-02-2008, 01:09 PM
"all very good points. what is the trq rating of a LT1?"

Nobody will say. At the MKE boat show in early '99, the 'Bu dealer was saying that their Mercruiser engine was more powerful, yada, yada, yada. I called Merc, Indmar, MC, Alan and my friend who was working at the Desert Proving Grounds in V8 Powertrain Development. Nobody would, or could, tell me. I made the point about torque being more important and the debate ended after being reminded of this by Alan.

"I heard that the LT1 with the PowerSlot has the quickest 0-36 even beyond the 285 with the slot, is that true?"

The motor is more powerful and the Powerslot multiplies the torque, so it probably is true. You also need to think about the HP:weight ratio.

DooSPX
10-02-2008, 01:31 PM
I understand all about hp/weight factor. racing for years.
my boat is a Powerslot, so if I were to swap to chevy lets say, what would YOU get? the LTR, Vortec MX or the LT1. BTW, my boat is FW ONLY.
also, I know about torque as well. I build mostly torque motors and let the HP fall where it may. I also know that in a ski boat, when you hit it, you get about 3000 rpm +/- a few. So, you need to have peak torque at 3000, but have a smooth almost table top curve.

TRBenj
10-02-2008, 02:40 PM
300-350 HP is 300-350 HP, regardless of who made it. Torque curve is another thing and the LTR is a good motor.
Ive got no experience with the LTR, but Ill take your word for it.

Also agree on peak HP vs. Torque curve. Perhaps I should have noted my assumption that the people putting these powertrain packages together (everyone from the original manufacturer of the longblocks to the engine marinizer to the boat manufacturer who selects the tranny and prop) would be optimizing them for their intended application. I maintain that a stock HO 351 will pull harder than a similarly rated stock Chevy (LT1, Excal, etc) out of the hole. It is also very easy to build a base 351w up to the 300-350hp level and make it even stronger than the aforementioned bowties. The parts to do so are commonly available and cheap (GT40/GT40p heads, etc). Like I said, I only own Fords, so I have no idea how easily a similar-performing Chevy would be to build. I just know that the ones Ive driven and lined up against (stock-ish) werent as strong from the factory, despite their similar hp ratings- so my train of thought is that the Fords have an inherent advantage for our application. Again, this comparison is of holeshot and midrange- the GM's seem to have an advantage on the top.

Doo, I suspect there is very little that seperates the 285 and 310hp Fords. I believe the longblocks were the same, as the ratings on the carb'd HO ranged from 285hp to "300+" depending on whose literature you read. The induction system on the EFI GT40 (rated at 310) could have easily accounted for a few hp.

JimN
10-02-2008, 03:49 PM
I understand all about hp/weight factor. racing for years.
my boat is a Powerslot, so if I were to swap to chevy lets say, what would YOU get? the LTR, Vortec MX or the LT1. BTW, my boat is FW ONLY.
also, I know about torque as well. I build mostly torque motors and let the HP fall where it may. I also know that in a ski boat, when you hit it, you get about 3000 rpm +/- a few. So, you need to have peak torque at 3000, but have a smooth almost table top curve.

The LT-1 torque curve is about as smooth as they come but in a boat, unless the prop is really aggressive, incredible torque doesn't work because of cavitation. If we were trying to hook it up to a street or strip, it's a different story. As much as I like the LT-1, I would hate to cook it just because I picked up some weeds or a plastic bag, so either the LTR or MCX. The TBI has a bump in the low end, which is great for trick and 'boarders but they have high end turbulence issues. Still, it has been a really good motor.

DooSPX
10-02-2008, 06:06 PM
The LT-1 torque curve is about as smooth as they come but in a boat, unless the prop is really aggressive, incredible torque doesn't work because of cavitation. If we were trying to hook it up to a street or strip, it's a different story. As much as I like the LT-1, I would hate to cook it just because I picked up some weeds or a plastic bag, so either the LTR or MCX. The TBI has a bump in the low end, which is great for trick and 'boarders but they have high end turbulence issues. Still, it has been a really good motor.

I understand about the cavitation. but how to the ProTour boats and the other boats that have the LT1 w/ the slot hook up on a 14x18?? (which mine is) (powerslot) and are you saying the LT1 has cooling issues using the thru-hull pickup?

JimN
10-02-2008, 07:55 PM
The only cooling issues I have seen were due to people not changing their impeller when it needs it or clearing out the oil cooler when the water has weeds and debris.

IIRC, the 14x18 has more cup and the standard drive came with a 14x17 no cup prop.

DooSPX
10-02-2008, 09:40 PM
know where I can get the FI and pcm for the LTR?

JimN
10-02-2008, 09:58 PM
I would think Indmar or an MC dealer, if you can't find a blown up motor or a salvage boat. Delphi MEFI 4 is what they came with.

rcnjson
10-02-2008, 11:46 PM
I'd stick with the ford. I just stuffed a fresh one in my boat last week. Its a 351 based roller motor aluminum heads fuel injected some other stuff...

JimN
10-03-2008, 12:11 AM
"some other stuff".

Such as,.....?

east tx skier
10-03-2008, 01:06 AM
If you can get an LT-1, look around for a marine salvage company that may have an engine harness for a '97-'99 MC. That way, all you need is the MEFI III ECM. The CEFI controller (used for one year) may work, too.

"also, why we are on the subject of LT1's. How did Indmar get the rating of 330HP or 350HP for some of there LT1's. Because Auto spec LT1's were 275/285/305 HP rated. the LT4 is rated at 330HP because of better heads/intake and slightly bigger cam."

don't know, I wasn't there. Fuel mapping, timing at 10BTDC, no exhaust back pressure to speak of, whether it was connected to a transmission at the time, etc all influence the power specs. OTOH, it's still all about torque.

They got to 350 hp with a more aggressive cam in the 98 Anniversary boat per Engine Nut many posts ago. No idea on the rest.

Skipper
10-03-2008, 08:39 AM
...You can't swing a dead cat without hitting performance parts for that motor...

That's funny. :D

Ben
10-03-2008, 09:58 AM
The only cooling issues I have seen were due to people not changing their impeller when it needs it or clearing out the oil cooler when the water has weeds and debris.

IIRC, the 14x18 has more cup and the standard drive came with a 14x17 no cup prop.

LT1 is a great engine. I check the tranny cooler / screen every so often (adding raw water strainer this winter for extra precaution as we are getting more lakeweed), and pull my impeller in the fall & replace every 2 yrs. Would not eliminate from the pool.

JimN
10-03-2008, 10:38 AM
I don't have a problem with that engine but my perspective is from the side of having repaired boats that weren't properly maintained. The point is- some people need the most bulletproof stuff imaginable because they won't be doing anything before going out, other than turning the key.

Ben
10-03-2008, 11:02 AM
I don't have a problem with that engine but my perspective is from the side of having repaired boats that weren't properly maintained. The point is- some people need the most bulletproof stuff imaginable because they won't be doing anything before going out, other than turning the key.

Agree, potential probably exists for more $$ damage if not maintained.

I just hate that a good engine frequently gets a bad rap because it has two thermostats and prefers not to be overheated.

JimN
10-03-2008, 11:47 AM
IMO, the people who give it a bad rap are the ones who A) don't know much about it, B) melted their heads (See A), and C) had to work on them without any foreknowledge of the way it's set up.

An intern at the shop in Indiana, where MC training was done, put an LT-1 in his Jeep CJ-5/7 (not sure which) and he was in high school at the time.

Dam- that's the kind of job I would like to have had then.

TMCNo1
10-03-2008, 12:24 PM
An intern at the shop in Indiana, where MC training was done, put an LT-1 in his Jeep CJ-5/7 (not sure which) and he was in high school at the time.


How was the wake?http://smileys.smileycentral.com/cat/4/4_12_12.gif

DooSPX
10-03-2008, 12:28 PM
my routine checks would kill some.... takes 20 minutes to do before each outting. and a 20 minute check after its back at home, including being flushed even though its only used in fw. I do the same for my Doo too.
I will keep my eyes peeled for some parts.

JimN
10-03-2008, 05:26 PM
5 minutes kills some people, apparently. "I just want to ski!" is fine if they have someone there full time, to do this kind of thing. Even doing things that take 10 minutes at first will take less with repetition.

DooSPX
10-03-2008, 08:32 PM
I know what you mean jim. if I can get a 350 to make the same or more low end torque like a 351 HO I will do it. I like the ram jet, but there is NO way that will fit under my motor box.

JimN
10-03-2008, 09:07 PM
You mean the 350 Ramjet crate motor? Why won't that fit? The throttle body is at the front, just like an LT-1. and I really don't think it's that much taller. Alan has one on his S-10 pickup and there was no problem getting it in there.

This motor?

http://www.technicalservicesin.com/popup.php?image=images/testfleet_gallery/2002%20S10%20Ramjet%20350/100_0028.JPG&w=638&h=478

http://www.technicalservicesin.com/popup.php?image=images/testfleet_gallery/2002%20S10%20Ramjet%20350/100_0025.JPG&w=638&h=478

THe Jeep in teh middle is the one with the LT-1

http://www.technicalservicesin.com/popup.php?image=images/testfleet_gallery/Truck%20group/73BH5799.jpg&w=638&h=478

DooSPX
10-03-2008, 09:17 PM
Jim, when I look at the pics of the Ramjet, It looks like the runners on the intake manifold are much taller. The LT1 manifold is much lower, just a little about the valve covers.
Of course, when you look at the risers on the exhaust manifold, they are normally taller than the intake. Do you think that the risers will be taller than the manifold on the Ramjet?
also, you know that the torque curve of the LT1 is like a table top... do you think that the Ramjet is going to have the same curve? See, I have never had experience with the crate motors. I have always built all mine. but sense the crates come with the ECM on the bracket, that is the best option in a case like this IMO.
better yet, a 383 Ramjet... OH YEAH!!! 8p:cool:;)

JimN
10-03-2008, 09:39 PM
See if you can look at a TBI motor. The throttle body is the usual Rochester and the intake manifold is pretty tall. It's also a really good intake. I would actually like to put one in my truck but I know that won't fit unless I pound some bumps in it or install a scoop (or something)

DooSPX
10-03-2008, 10:07 PM
so, your saying that the ramjet intake is not as tall as it looks and should fit under the motor box on my 91 PS190 Slot?
also, do you think that the ramjet is going to have the same kind of table top curve like the good 'ol LT1?

but, the vortec casting are based off of the LT1 design. (minus the reverse flow) and the few other small things. the curve has more to do with the cam and a little bit of the intake manifold design and runner length in this case.... The ramjet's manifold looks like the intake plenum and runners promote good torque and hopefully are designed not to be so peaky ( I hate peaky motors, no fun to drive)



of course.... I can always get a custom cam by crane or lunati. ;)

JimN
10-04-2008, 12:21 AM
The block is basically the same for the TBI, LT-1, MCX, LTR and Ramjet, with the heads, intake, cam and other differences but I'd bet that if you measured the height from the motor mount top bolt holes on all of them, the TBI will be the tallest, with the Ramjet being either the same or close to it.

As far as specs, the Ramjet is 350HP and 390 ft-lb of torque, so I really don't think it will have any trouble turning the prop. Hot Rod did an article about that and the 502 crate motors and I have a copy, so I'll see if they showed the curves.

DooSPX
10-04-2008, 12:28 AM
The block is basically the same for the TBI, LT-1, MCX, LTR and Ramjet, with the heads, intake, cam and other differences but I'd bet that if you measured the height from the motor mount top bolt holes on all of them, the TBI will be the tallest, with the Ramjet being either the same or close to it.

As far as specs, the Ramjet is 350HP and 390 ft-lb of torque, so I really don't think it will have any trouble turning the prop. Hot Rod did an article about that and the 502 crate motors and I have a copy, so I'll see if they showed the curves.

besides the electric fuel pump and motor mounts and trans adapter, what else would I need to get it hooked up to my boat. will the tach input be the same?
and actually Jim, the new Ramjet 350 has 400lb trq. and the new MEFI4 (apparently designed for the marine motors)

JimN
10-04-2008, 12:41 AM
The crate motors have used the MEFI 4 for quite a while. The Ramjet was just coming out when I was at MC training the last time, in fall of 2000 and Alan (the S-10 photo) had that one for a while before that because it was a validation motor. He was involved in the final calibrations for Delphi and GM.

The spec I saw was 390 but they may have made some changes to increase it.

IIRC, the Ramjet uses the same distributor as the TBI and the tach will get its signal from the ECM.

DooSPX
10-04-2008, 11:47 AM
so the tach needs to be wired into the ecm. ok....
I need new exhaust manifolds too, trans adapter, starter, alt., waterpump, and of course the fuel suppy. is that it?

btw, here is the dyno.... nice curve

JimN
10-04-2008, 11:58 AM
Raw waterpump- I would use the same Johnson pump they have always used with the GM motors. Marine GM starter- you can buy new if you want but the rebuilt ones I have used are still working and they cost far less.

I'm not sure what the fuel pump recommendation is for the crate motor but I would imagine it needs about 40 lb.

DooSPX
10-04-2008, 03:57 PM
Thanks Jim. The info about the crate motor says it needs an O2 so it can run in closed loop. How in the world do you hook up an O2 to a water injected exhaust?
I know what im getting! ;)
Im lovin' the curve

JimN
10-04-2008, 07:31 PM
Look into the current line of motors. They run an 02 and catalytic.

DooSPX
10-04-2008, 10:59 PM
where would I install the O2??

JimN
10-04-2008, 11:13 PM
If you want to do it right, buy the exhaust manifolds they use now, with a port for the 02 sensor in the dry exhaust stream. WHen it was being developed, they used a block between the exhaust manifold and riser, but that was on a dyno stand and they can keep water from hitting the 02 and cat more easily than in a boat. If you search around, you may find someone with a program for that motor that's open loop.

DooSPX
10-04-2008, 11:28 PM
thanks.... any ideas? is it possible to do it on the old manifolds?

JimN
10-04-2008, 11:39 PM
With the old style manifolds, I would consider going open loop. The chance of water hitting the sensor is pretty good with those.

DooSPX
10-05-2008, 11:07 AM
any side affect of going open loop? just economy right?

JimN
10-05-2008, 12:47 PM
Economy, control won't be quite as strict, maybe some power/throttle response, Warranty.

I just remembered something else- GM performance parts specifically states that if a motor is used for marine apps, there's no warranty.

DooSPX
10-05-2008, 07:43 PM
not bothered with warranty. I quess I will get the ETX manifolds too when the time comes. are the ETX 3"??