I need new heads for 351W

Whoa... good point 79. I hadn't considered the need for shorter push rods although it makes perfect sense...

I still don't like the idea of shaving anything. In my mind that's a fix that can't be undone. I will look into pistons though. No hurry here - just thinkin. I gotta get my '66 in the water before I pull down the '68. That's why we have a "back-up" boat right?

Joe, the GT-40Ps were a direct bolt-in on the 289. Very easy. I am running stock Interceptor aluminum manifolds. Absolutly no problem with the spark plug angle.

The only problem I had was selecting the spark plugs. When you walk into Autozone, or anywhere else, the fisrt thing they ask is what type of car you have. I ended up ordering up plugs for a 1998 Explorer, which is what I was told the heads came off. I am not at home right now so before anyone runs off and orders 1998 Explorer plugs for their GT-40Ps check with me first so I can go to my records. Maybe it was a 1996 but who cares right now.

Make no doubt, even with the lower compression the engine is much stronger than prior to the head change. Maybe it was the cam or the carb or the heads - I don't know - it just worked.

I installed a mildly warm SpeedPro marine cam which has a little more lift than stock and a little more duration on the intake but not much.

Pushrods are stock and original. I did not replace them. (I did replace the lifters however.)

At this point, so I can check prices, if you can recommend some possible pistons I would appreciate it. Don't spend time on this. Before I order we can go thru the exercises. This could easily be a next winter project. The boats runs pretty strong as it is. It throws you back in the seat and holds you there when you hit it.

Jim,
    What kind of Exhaust logs are you running with those GT-40Ps, have you had any spark plug angle issues. Additionally, you would have had to change the push rods to make this happen correct? Disclaimer..I am making some assumptions here, most of this applys to autos and I am assuming marine as well..   Early 289 heads had a combustion chamber of 54.5 ccs and the resulting compression was about 9.3 to 1. The gt-40p has a combustion chamber of 59-61 ccs dropping your compression to about 8.7 to 1, but they are much better flowing heads with a more efficient plug location than stock I would say a net gain in most set ups. To get that compression back you could deck the head or cylinder a combination of about .030 to .040. Or per your preference change the pistons, a piston that would have been called "10 to 1" with your stock heads would yield you about 9.4. I think it would be pretty easy to find the correct pistons, if your serious we can talk actual measurements and compute out what you would need. Enough of this talk and I will be thinking of replacing the heads on an engine I swore I wouldn't mess with again for at least 2 years...
-Joe.

Jim, with closed-chamber heads, it might be better to zero-deck the block to boost the CR, you would gain not only better cr but better squish.. (less trapped HC in the areas of the chamber that the flame front can't reach, swirl and burn well...)

A 327 stroker shortblock would boost the CR as well..

Changing CR as well as head airflow increases the density of the A/f mix at wot, increasing the speed of the flame, thus requiring less advance.

So with a reworked engine, the stock ignition timing one used for stock heads could either be set too advanced at wot, or if reset for wot, would be too retarded at low rpms, giving one the sensation that the heads 'killed' the low-end.

Spending quality time with the timing gun, some graph paper and a fully-adjustable distributor is required to see best overall results after changing CR, cam, heads, etc.

The gt40 heads are available with the holes already drilled out for a 351w, and were used by pcm with great success on Ski Nautiques from the 90's until the ford marine blocks dried up in about 2002. Combined with a good marine/rv grind cam they will give you more horsepower, going with anything larger than the valve size on the GT-40 would probably start to have an effect on your low end. I have put junkyard GT-40s off a 1996 explorer 302 on a friends 351w in a full size bronco mud bogger it was a huge improvement (we drilled out the holes for the headbolts and had to change the push rods because it was a seventies bronco but other than that it bolted up) You might need updated PCM manifolds if you went with the GT-40s. Compression will of course have a huge impact on engine performance so make sure your piston/head combination gives you the compression you are looking for, or the best heads on the planet won't save you.
-Joe.

When I rebuilt the engine for my '79 I reused the stock D80E (casting number) heads. I had them machined for slightly bigger valves and gave them a mild port job. I increased the compression ratio slightly with the pistons. I couldn't be happier with the results, she pulls hard.

Be careful that you don't get too much head for your applications. As has been said already boats don't get much above 4500rpm and probably run mostly in the 2500-3500 range. A lot of high end heads are probably mean to flow a lot of air in the 5-7k range.

See this site for more information:

http://www.allfordmustangs.com/Detailed/630.shtml

I am looking for the best(new)heads for our family '81 SN. Rebuilding engine stock ,maybe mild cam. Who likes what and why??? Considering GT40s cast iron..Roush 180s. Valve size? combustion chamber size?
Thank for your intrest
David Wilkins
262.719.5522
2canucks@core.com