1999 Longhorn Nautique Restoration Thread

Thread is blowing up today! Going to have to adjust my notifications to something different besides instant. Had to scroll through my emails to find something else besides this thread.

What is your next big mile marker your expecting to hit?


This thread is giving me the itch to get my 79SN going again with a 408!

Correct. Lower was port matched to the heads, upper was opened up and the throttle body inlet. We will see how it works out.

rosconole wrote: The lower is only part you can port on GT40 intake 9.2 deck lower...in he tubular upper really, you can tootsie roll the throttle body inlet some thats about it... some have tried to cut open and weld the side and change the runner some but not with alot of luck, not like the cast like Cobra or Explorer intake where you can extrude hone or port to your hearts desire. Hopefully its got an accufab throttle body and not the idle hunter BBK. GT40 intake should be fine for what your doing , Might benefit slightly from a Holley system max intake but is it worth another 800...maybe later.

Only (some of?) the 1995 gt40 intakes are tubular. The rest (including his 99) are cast.

It’ll be close but I suspect you’ll be right there.

Prop selection is always a bit of trial and error but I bet you’d be darn close in the 1490-1492 range.

rosconole wrote: Sorry I thought it was staying more OEM But with those heads can't go wrong.   it will probably make 330-340hp., 52mph.

You’re 100hp shy on what it’d take to push that Sport hull 52... but I’d say the speed estimate is probably close.

Which side of the intake is ported? A quick search shows that the 351w lower GT40 intake is pretty decent but the upper (same as the 302 Explorer?) is a bit more restrictive. 70mm TB will help.

Sorry I thought it was staying more OEM But with those heads can't go wrong.   it will probably make 330-340hp., 52mph.

Try to read it all Ross... he’s using AFR heads (185’s IIRC).

The intake may indeed be a restriction since this is a 351 stroker rather than a 302 more commonly seen in Mustangs. I’d do some more reading. There are aftermarket options that don’t look wildly different.

WOW not only a prop expert !

TRBenj wrote: It’s going to make more power than that I suspect... unless there’s a massive bottleneck somewhere that you haven’t mentioned. Even breathing through stock exh manifolds, that cam and head combo with 408ci behind it should pull well past 5k. I’d guess 425 at 5400 if not more.

The only bottleneck could be the intake. Exhaust manifolds are now 4” manifolds. The engine that came out of the boat was a gt40. I am trying to reuse the gt40 intake for aesthetic purposes to keep the originality. If it doesn’t work out, I’ll go another route. I would be willing to sacrifice a little bit of power to keep the engine looking oem but if the power loss is too great, I’ll make a change.

TRBenj wrote: Not sure I quite buy that... no numbers?

Expected is 380-400 hp and 460-480 ft lbs on 93 according to simulation. Can’t speculate any further until it’s dynoed..

I see numbers

Max HP 5000 rpm
Max TQ 3200-3400 rpm

TRBenj wrote: Smh. Cam choice seems reasonable. Did the builder have a hp @ rpm prediction?

Just trying to save you from tearing it back down when it looks like may run into problems! I've made over 1000 hp with a small block ford so I have seen alot before the internet was invented.

Don’t worry about Ross... he talks a big game but is clearly out of his element. If he knew his ass from his elbow he’d recognize your roller block by the machined threads in the valley. I don’t recall seeing your cam specs posted, but assume you’ll be going roller since parts are readily available for this lefty. Whether you use the factory roller provisions (spider retainer and dog bones plus factory style lifters) or aftermarket tie bar lifters is just a matter of money. None of the Ford marine engines came roller from ford even if the block was capable.

In regards to our disagreement on compression ratio, I don’t imagine that an argument over FACTS can last very long. Presumably he will type those magic words into google (“how to calculate compression ratio”) and come to the quick conclusion that since a longer stroke increases swept piston volume (ie increases displacement), that a correspondingly larger combustion volume must accompany it to keep the CR in check. You can do that by increasing chamber volume in the head or increasing piston dish (for a ford Windsor- other makes you can decrease the dome). All looks normal here and don’t doubt the calculated 9.5, which seem appropriate.

I'm just happy they are fussin' at each other rather than you!

Amazing changes to the boat and trailer. Very thorough. Thanks for sharing.