1999 Longhorn Nautique Restoration Thread

Why did you go with so much of a dished piston? Unless they cut the hell out of the block or milled the heads way down....They must have been on sale...

Which Holley EFI are you going with ? I am doing something similar. Hopefully you know the mapping will need to be the biggest adjustment below 160 degrees.

Their is only a couple of reasons why you would want that much dish in a piston...a cylinder head and/or camshaft profile that would dictate that much clearance which I hope is not the case because it would be entirely too much for the cylinder head flow potential even if they were fully ported and you would never get to that RPM range . The other reason is if their is a positive pressure to raise the compression i.e. turbo or supercharger. I would be interested as to what the final compression number maybe , Because it maybe a loss of performance down in the lower RPM range where you really need it.

In any event you would want a little more compression not less that what it originally had ,

following

rosconole wrote: Its fine that its a 408 doesn't have anything do with math

Oh yeah? Last I checked compression ratio was in fact a ratio. I assume you know what it is a ratio of?

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.

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.

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.

Max HP 5000 rpm
Max TQ 3200-3400 rpm

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

I see numbers

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..

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.

WOW not only a prop expert !

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.

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

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.