Best upgrade for 4 barrel 351? Or do prop?

[Bimmerboyz]

The motor was rebuilt a few years ago and it has a Edlebrock intake manifold.

I was wondering what to do as the engine is out to replace the flywheel?

Should I do a mallory ignition system or points are good?

Get the head port and polished?

I don't want to get too expensive.

Or I could do a prop.

I just want more hole shot when I add wait for wakeboarding.

[Andrew]

RE: Best upgrade for 4 barrel 351? Or do prop?

i'd pick something that requires the engine to be pulled since you already have it out.....

[Rick]

RE: Best upgrade for 4 barrel 351? Or do prop?

I would do electronic ignition for reliability and Prop for the holeshot $125 for the Pertronix ignition and a prop with 2" less pitch for 325.00.

[Bimmerboyz]

I don't know if it has to come all the way out can't I just slide it forward?

Also I want the best bang for the buck upgrade.

[Bimmerboyz]

Re: RE: Best upgrade for 4 barrel 351? Or do prop?

I would do electronic ignition for reliability and Prop for the holeshot $125 for the Pertronix ignition and a prop with 2" less pitch for 325.00.

I have 2 props right now I need to know what is the best pitch to use?
If I do end up buyin one should I get a 4 blade or not needed?

[AirTool]

RE: Re: RE: Best upgrade for 4 barrel 351? Or do prop?

Others can tell you what prop. Here is a link to save you about a hundred bucks.

http://www.planetnautique.com/index....delta+discount

If you work on your engine I'd put a cam in and do some valve/head work. A cam might suffice and you won't have to pull the heads. You could also change to roller rockers so you'll never have to worry about your lobes wearing down.

Without really working over your engine and replacing a bunch or parts that are still in great shape, a low-end performance cam would be the best bang for buck.

Plus, you'd be the only boat in the tie up with a loped idle like a hot-rodded 69 Mach 1.

AirTool

[TRBenj]

RE: Re: RE: Best upgrade for 4 barrel 351? Or do prop?

Ive done every single upgrade mentioned here and I can tell you that the best bang for your buck mod out there is a new prop, hands down.

In my opinion, I wouldnt bother with an electronic ignition conversion kit for any amount of money- especially the Pertronix. Ive found points to be very reliable, start great when tuned properly, and cheap! If you want to modify the motor, get a full electronic ignition system (distributor) instead of a conversion kit. If you absolutely have to go EI for whatever reason, stick with Mallory E-Spark or PCM/Prestolite and avoid the Pertronix.

None of the engine modifications mentioned require pulling the engine out. A head/cam/intake upgrade will really improve overall performance, but I would do it all in one shot. Expect to spend ~$1500 to do it right.

Again, I recommend you just go with a new prop and call it a day. If its for your '78, then an Acme 540 will really wake it up- holehot, midrange acceleration, speed holding and smoothness will all improve. Top end may get a slight boost as well. I wouldnt go with a 4-blade as the modern 3-blades outperform them.

[AirTool]

Re: RE: Re: RE: Best upgrade for 4 barrel 351? Or do prop?

None of the engine modifications mentioned require pulling the engine out. A head/cam/intake upgrade will really improve overall performance, but I would do it all in one shot. Expect to spend ~$1500 to do it right.

Agree on the prop. Also a clarification on head work. If the heads are brought back to new or even better, and the rings are old and worn, the engine will then smoke/burn oil because the old rings won't be able to hold the compression properly and ultimately properly wipe/replace oil.

Usually, if you do one thing on a worn engine, you have to do it all.

Agree you don't have to pull the engine to do that work but you'll save a lot of trips in and out of the boat and won't make such a mess. Assumption was the engine was out to replace the flywheel.

[Andrew]

RE: Re: RE: Re: RE: Best upgrade for 4 barrel 351? Or do pro

the ONLY reason that I would say a prop isn't your best "bang for the buck" is if the current prop is ideal or close to..... it would definitely warrant some research!

[AirTool]

Re: Best upgrade for 4 barrel 351? Or do prop?

Agree with Andrew on the prop. I assumed you had the wrong or old non-cnc prop and improving is possible.

The motor was rebuilt a few years ago and it has a Edlebrock intake manifold.

I read this the first time but then forgot. Sounds like improving inhalation won't cause you ring problems.

I still vote for the cam and roller rockers. Don't mess with the heads. A head job (don't start) would be a little more bang for a lot more buck.

[Bimmerboyz]

Re: RE: Re: RE: Best upgrade for 4 barrel 351? Or do prop?

Again, I recommend you just go with a new prop and call it a day. If its for your '78, then an Acme 540 will really wake it up- holehot, midrange acceleration, speed holding and smoothness will all improve. Top end may get a slight boost as well. I wouldnt go with a 4-blade as the modern 3-blades outperform them.

I have a amce prop box that I believe my spare prop is in 540 rings a bell I will have to check when I get it out of storage. So I hope and I might have a 540 already. Cam and head work might be the route I take if I have the 540.

[bobchris]

Re: RE: Re: RE: Best upgrade for 4 barrel 351? Or do prop?

. If the heads are brought back to new or even better, and the rings are old and worn, the engine will then smoke/burn oil because the old rings won't be able to hold the compression properly and ultimately properly wipe/replace oil.

a standard valve grind will not change the compression so it's not going to burn any more oil than it all ready does, Now if the heads are warped and need decked then yes there is a slight increase in compression but usually not enought to change the comrepssion more than .1 and you still won't burn any more or less oil.

Set of GT-40p's is the best bang for the buck even without a cam change for this application.

[AirTool]

Re: RE: Re: RE: Best upgrade for 4 barrel 351? Or do prop?

. If the heads are brought back to new or even better, and the rings are old and worn, the engine will then smoke/burn oil because the old rings won't be able to hold the compression properly and ultimately properly wipe/replace oil.

a standard valve grind will not change the compression so it's not going to burn any more oil than it all ready does, Now if the heads are warped and need decked then yes there is a slight increase in compression but usually not enought to change the comrepssion more than .1 and you still won't burn any more or less oil.

Set of GT-40p's is the best bang for the buck even without a cam change for this application.

Fixing valve problems will increase compression. Not the theororetical ratio but the actual pressure achieved in compression stroke and during combustion.

It's not about whether the valve grind is special or standard. It is about the condition of the valves, seats, guides, gaskets, and rings prior to fixing said problems with the valves, seats, guides, or gaskets and NOT bringing worn rings back in spec. Compression pressure and combustion pressure are going to increase....especially if some change was made to allow more CFM and fuel to flow into the cylinders on intake stroke. The latter would be the primary reason one would change the cam and work the valves. A secondary reason would be to change valve timing.

Nevertheless, bringing all that pressure back up to or exceeding the spec and having worn out rings is going to be a problem. Fixing head problems without fixing the cylinders and replacing rings or vice versa is a no no. Sure some have done it...but only to sell it. Be sure to watch out for high crankcase pressure and PCV oil entrainment problems.

Besides, he said his rings were good.

[Bimmerboyz]

Re: RE: Re: RE: Best upgrade for 4 barrel 351? Or do prop?

Set of GT-40p's is the best bang for the buck even without a cam change for this application.

That is around 2500 to do and they have to drill and tap for those heads. If it was slightly cheaper I would go that route.

[SNobsessed]

RE: Re: RE: Re: RE: Best upgrade for 4 barrel 351? Or do pro

I think you can get GT40p heads from Clearwater Cylinder for under $700.