New to me 78 Tique

I have some videos of the holeshot stutter but am having a time getting them up on YouTube. Ran the boat out of a cup (didn't have enough fuel line to go in the can). Same thing. No pressure registered but it did spew if you loosen a hose clamp. The guage goes to 100psi. Maybe it just couldn't get a reading that low or maybe the guage is junk. Anyway. Drove the boat for another half an hr and same stuff. Get fuel. Just not at holeshot. Sometimes it quits and sometimes it stutters. Frustrated to say the least but it is a learning project. Think next is either new fuel pump or get rid of the carb wedge.

I know some here joke about Autozone, but my local store is actually very good. I borrowed a fuel pressure gauge last fall for more than a month, free. You leave a hefty deposit on it but get a full refund if you bring it back by the deadline. It was a full kit with a variety of connectors.

Yes, you need a gauge with a 15 psi range, or maybe 30 psi max, to get decent readings on your fuel pump. Having said that, if the needle didn't even move on the 100 psi gauge then I think your pump is suspect.

Believe me, I know this stuff can get really frustrating. Hopefully we are getting close to a solution.

I'm telling Pete.

backfoot100 wrote: KENO wrote: . From here I think the stumble sounds carburetor related. How's the accelerator pump and it's adjustment. Agreed. You need to make sure that the idle mixture screws are set to the highest vacuum or highest RPM while loaded. That means you need to be on the water in gear and idling. Then adjust to the final idle RPM setting. If you still have a bog when throttling up, then look at the accelerator pump shot.

The video sure makes these statements seem pertinent,

Your Edelbrock manual should be helpful on the accelerator pump adjustment and off idle tuning

Getting all of my parts ready for a weekend of testing and my list of items to check/adjust. Shadow, if you are around and would like to take a look, I would welcome that and could come to you if need be! I will be at the lake Fri evening-Tues.

I got the new fuel pump gauge so I will put that inline for testing. Also bought some new Mr Gasket carb gaskets so I can remove wedge and make sure it isn't an issue at the seals.       

My bog mainly happens in gear. In neutral I can move up the RPM fine. Is that bc it needs more fuel under load (seems obvious but nothing is for an engine newby)?

One of my friends threw out the PCV as a potential culprit...I plan to check that it has suction. Could it be related to this issue? Should I grab a PCV before heading down? Advance Auto doesn't show having one for a 78 302 (I am looking under F-100). Are they fairly standard?

Does anyone have an Edelbrock and know how their floats are set (let me know if you have a wedge or not). We set ours as per the rebuild manual: FLOAT LEVEL (7/16"); FLOAT DROP (15/16" TO 1").

Thanks for all of the help. I love learning about this stuff and really want to whip these issues.

Think at this point that ship has sailed from a delivery standpoint. If fuel pressure is bad I will order asap and have one in hand for the following weekend!

samudj01 wrote: Does anyone have an Edelbrock and know how their floats are set (let me know if you have a wedge or not). We set ours as per the rebuild manual: FLOAT LEVEL (7/16"); FLOAT DROP (15/16" TO 1").

I set mine per the specs and it seems to do OK.

I have and have always had a wedge. I am not a motorhead and am no expert, but I have heard many time through the years that the Edelbrocks like and perform better with a wedge, so I would be hesitant to remove it. Without reading the whole thread again, I think I recall you starting out without the wedge, correct? Did operation/performance change or worsen when you added it that would lead you to want to remove it?

Interesting yours has the PCV valve set up. Mine does not. I have two vents from the valve covers up to the arrestor, but no PCV valve and that port on the carb is plugged off.

Riley. Would be great to get a part number.

Larry. I like the wedge and think in the long run it is needed. Just trying to cross of potential issues. One being that there could be a vacuum leak due to the wedge. We had to bend the studs to get all three parts on, pcv spacer, wedge and carb. Seated ok but not great. First will be fuel pump.

2072

I don't believe our issue with 427 is carb related, may find out how a Holley runs at some point.

Sounds good Cable adjustment and synchronization with each other can be a little tricky.

Now you have a vacuum gauge to play around with too, along with verifying fuel pressure

I think I'd leave that wedge alone if it was me

5.5 psi is right where your Edelbrock manual wants it too

Is there a way to test vacuum on the edelbrock. I am under the impression that there are no vacuum ports on the marinized 1409? If so, what are we looking for on the guage? Hoping to also have an external tach and dwell meter for this weekend to do some final tuning.

Or just plug the gauge into whatever vacuum source the pcv valve is using... it will be ok to go without it for a while.

samudj01 wrote: Perfect! What vacuum am I looking for at idle and load? When we got the boat there was a vacuum plug in a hole on the bow side of the carb. Looking in it looks like a solid cast. Any chance this is a small vacuum hole of sorts. I just need to put my finger over it to see.

A lot of people aren't gonna want to believe what I'm about to say, but if that's the case they can verify some readings for themselves.

You always hear that boats run under constant load and then when a power valve discussion pops up, somebody will say that when you punch it from a dead stop, vacuum goes to zero and quickly recovers.

It don't happen that way though

If you give it full throttle vacuum drops to zero and stays there till you back off the throttle.

If you run the boat at a steady 4000 rpm's vacuum stays steady, it never recovers to a higher vacuum till you back off the throttle.

Same thing at any RPM in a boat that's operating under a constant load.

Here are some representative numbers on a good running 351 that I wrote down a couple of years ago and verified again with a quick boat ride tonight

Full throttle     zero ish

4000 rpm        2.5 inches vacuum

3000 rpm        7 inches

2000 rpm        9.5 inches

1000 rpm in gear   13 inches

idling in neutral 20 inches

This particular boat has a 6.5 power valve so it's open whenever the boat is going over about 3300 rpm

All these numbers can vary some from what I have depending on engine loading, hull efficiency etc but they'll be steady at whatever reading you have till you move the throttle. It's the concept we're after here. And remember it ain't a car.

Hook your gauge up my way or Tim's with enough tubing to run it outside the engine box so you or a passenger can read it and you might be surprised at the results.

You don't have to worry about power valves ...........till you find your Holley.

Like I said, it's bound to lead to some discussion, but you can check it for yourself easily enough.

You want a vacuum source that's below the throttle plates and not all carb vacuum fittings are below the plates so you have to watch out for that.

A few updates:

Checked vacuum. At neutral 13 in. Running up the rpm in neutral was 20 in. Learned that you can't remove the pcv line or the engine will die.

Checked dwell. 28.8-29 degrees. The very high end of what the manual calls for. We ok?

The actron 7677 that we were using was reading double on rpm. We are looking into that with tech support. We connected as per the manual. Set on 8 cyl. The connections for dwell were the same and that seemed to work fine. Sure it is something easy that we are missing.

Overall the boat is running pretty well since we have worked a few of the items out. Just have to warm it up for some time before it will idle. Idling around 800 and topping out around 4400rpm

samudj01 wrote: We will have to come up with a solution for a plate of some sort to get the pylon attached to the floor. We think the cup is ok.

Same thing happened to my Promo up at Tim's with 5 or 6 guys on trick skis. I ended up cutting out the entire section between the stringers and bedding in a new piece of Doug Fir.

Might have to sacrifice the carpet but it's well worth the time/work in rebuilding.