What exactly does GT40 mean?

[chris2000proair]

I'm getting some conflicting information here. The engine shroud on my boat says GT40 5.0 however the tag on the block says 5.7L. I did some investigating and found that in fact it is a 350 (5.7L). So, does the GT40 come in the 5.0 and 5.7? I was always under the assumption that a GT40 was a 5.0L engine.

[jedgell]

RE: What exactly does GT40 mean?

The GT-40 is a Ford engine, 351 ci (5.8L). The 5.0 and 5.7 are Chevy engines.

[surroundsound64]

RE: What exactly does GT40 mean?

5.0 is the Ford 302.
Chevy has a 305, but I don't think that was ever put in a CC.

[AuMDLST]

RE: What exactly does GT40 mean?

Nautique has used 351 ford blocks for most of their boats - The GT40 is a ford 351 - The 351 is no longer made therfore the change to the 350 chevy in recent years - -The GT40 designation on the motor is the model of the "heads" that are used

[core-rider]

RE: What exactly does GT40 mean?

5.0 and 5.7 are just the engine's displacement measured in liters. Ford made a big deal in the Mustangs with the 5.0 Liter engines which is 302 cubis inches. The 351 is 5.8 liters. Chevy 350 measures 5.7 liters though. As was mentioned earlier, GT-40 is the "tag" given to the heads and intake setup. I'm not really sure why they came up with that name since there is no relation to them and the old LeMans GT-40 race cars.

On a side note.... I have noticed on different boats in the CC line that the upper intake was changed from time to time. Some of the boats I've seen had the cast aluminum intake commonly refered to as the "Cobra" intake while others came with the "GT-40" intake which was welded pieces of aluminum tubing. They are both basically the same intake, but the GT-40 intake was much more expensive to purchase. I don't knoe if it was just what they had laying around at the time or what.

I'm done...

[pj]

RE: What exactly does GT40 mean?

They did put the GT-40 heads on many 5.0 L fords too. A poor man's way to upgrading is to find an old explorer with the gt40p heads and swap them out. Check over at CCfan, those guys have TONS of info along these lines.

[core-rider]

RE: What exactly does GT40 mean?

You have to watch the "P" heads though because the spark plug hole was repositioned and may cause clearance problems with the exhaust manifolds.

Basically the GT-40 heads and intakes were performance parts made by Ford Motorsport for the older Mustangs or any other small block Ford engines. They came factory on all Cobras and the first generation Lightnings. Great setup for about 40-60 more horsepower.

[DanielC]

RE: What exactly does GT40 mean?

The Le Mans race cars were 40 inches high, thus, the name GT-40. By the way, when Carrol Shelby first made the GT-350 Mustang in 1965, the engine assembly room was about 350 feet from the car assembly line. Not an exact quote, but I heard that when the name for the car was being discussed, Carrol said, "If it is a bad car, a good name will not make it any better, but if it is a good car, it does not matter what we call it"

[TRBenj]

Re: RE: What exactly does GT40 mean?

You have to watch the "P" heads though because the spark plug hole was repositioned and may cause clearance problems with the exhaust manifolds.

Basically the GT-40 heads and intakes were performance parts made by Ford Motorsport for the older Mustangs or any other small block Ford engines. They came factory on all Cobras and the first generation Lightnings. Great setup for about 40-60 more horsepower.

Actually, plug clearance improves with our marine exhaust manifolds.



The P's are actually a better head than the GT40's. They outflow them by a little (even with a smaller exhaust valve) and the smaller combustion chambers are good for a little added compression.

[AuMDLST]

RE: Re: RE: What exactly does GT40 mean?

PCM and SECC both confirm you have a 5.0 liter (302 ford block) with the GT40 heads - typically it was the 5.8 liter 351 ford but the 5.0 was offered at a slight cost savings

[AuMDLST]

RE: Re: RE: What exactly does GT40 mean?

sorry -submitted before complete - that confirmation is based on the engine cover description - the 5.7 motor tag is interesting due to the ford 351 described as a 5.8 liter. Can you upload any pics?

[chris2000proair]

With out a doubt my engine is a Chevy 350. I used the firing order which is stamped on the block to confirm this. So I guess I can only assume that the engine shroud was replaced at some point with the wrong one which reads 5.0. Now that being said, is it normal for a 2000 Nautique to have a Chevy 350 in it? When did PCM switch from the Ford 351 to the Chevy 350?

[bkhallpass]

The Chevy engine was an option for several years. Is it normal, yes. Is it common, not so much. If it is a Chevy, and your boat is a 2000, it is likely a 320 HP, Multi-Port PCM called the APEX. If I remember correctly, 2003 was the first year that Ford's were not available, and Chevy became the only engine choice. BKH

[Mikeski]

This is one time when a picture is worth a thousand words. What is the firing order you see, 18436572 or 27563481? Carb, EFI, Red valve covers, equidistant intake/exhaust ports, bolts through valve covers, side mount throttle body...

Lots of ways to tell chevy vs. ford. By far most 2000 Nautiques had Ford GT-40's but that does not mean you didn't get a special order chevy.

[core-rider]

TRBenj, I agree that marine manifolds don't pose as much of a problem with the P heads. Guess I didn't think about that. The relacatoed spark plug unshouded the intake valve more which ment better scavenging... equals more power. Plus like you said, that added compression.

I thought I remembered basically all SBC having the same firing order until you got the the LS series engines and other newer injected models... I could be wrong though. Definately a pic would help.