Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Weird, I'm not sure what the second port is used for on yours.

Last night I installed my first starter. Got it lined up and done. Was a tight fit and lesson in patience trying to do it all on jack stands.

Fired up first try. https://youtu.be/J5CxfMAJR5U

To do:
1) check for vacuum leaks.
2) determine why distributor is unreliable to deliver spark to each plug. Potentially replace distributor or at least, distributor cap.
3) figure out why brakes are so weak. This has been an issue since the 350-->402 swap. It may be the vacuum is too low, or another reasons.
4) install converter lock up wire + switch to 700R4. The vacuum line does not seem to engage the lock up, currently.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Well good to hear you got back up and running , yes I would think with your lower vacuum, is giving your braking issues , is it possible for dizzy to be out one cog? if it dropped right into place after you changed out intake then I would think not

The ports believed by one fellow board member is one for gage the other for temp light as different gage packages used either side for sensor ,7 hole gage package drivers side , 3 hole gage package idiot light passenger side

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Check your rotor to see if it has a burn through. This is common with the HEI. If you have a badly worn plug or high resistance wire, the spark has to go somewhere. It can actually burn a hole through the rotor. Put a couple of drops of gas in the well below the center electrode and look for a wet spot, if the hole isn't obvious. The scorching of the plastic of the rotor can also make ready paths to other spark plug terminals in the distributor cap. It is possible that there is carbon tracking in the cap, from a worn button. You may not be able to see them with a black cap, but they would show up well on a red or brown cap. To be honest, the truck didn't sound that bad. One thing I did notice was a bog when you blipped the throttle. I see in this thread that there is provision from Holley for progressive linkage. I would use it, personally.

As for "weak" brakes, do you mean a hard pedal? If so, that's going to be a vacuum leak, I'll bet.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I think he said it only has 6" of vacuum. That's not enough for power brakes. Either that is a real radical cam or there is a leak. It could even be the power brake booster leaking. I once had a spring in a booster break and the broken end of the spring wore a hole in the diaphragm which began to leak. It finally got bad enough I could hear the leak when I leaned up near the booster. The truck also idled like it had a large cam in it too but it was bone stock. :lol:

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Ekliptix, I have one of these progressive linkage parts Holley part number 20-54, if you want to try your more than welcome to, the sniper tuner allows for it thru my reading but Holley doesn't recommend at this time using it , some say it works others say it doesn't

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I get that he has low vacuum now, but was curious what it was like before the FI went on. I don't think that the FI is at fault for the weak brakes, if it was that way before.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I spent some time with the distributor yesterday. I'm back at square 1. Won't start.

Trouble shooting:
1) inspected the cap and rotor. Looks fine. (pics below).
2) turned the dist 1 tooth (clockwise), as suggested by some ppl as I had the cap way advanced to get the truck to run. Result: Won't start.
2) took my spare distributor, installed the spare dist cap on the current base. Result: Won't start.
3) installed the spare dist base + spare dist cap. Result: Won't start.
4) returned to the previous tooth position (counterclockwise) with the spare dist + spare cap. Result: Won't start.

Then I gave up for the day. I still suspect something is up with the spark. I had the timing light setup while trying to turn the engine over and it'd only flash some revolutions, not all.

I also checked a few vacuum things. I used my lungs to provide some vacuum. To the vacuum gauge, I was able to see ~9inches using my lungs. That was my baseline to compare with how much vacuum I could yield with other lines.
- The brake vacuum line, I could get ~4inches until it felt like a valve opened. Blowing (applying pressure), brake vacuum line was 100% sealed and would not take any air going in.
- The dist advance line took ~5inches of vacuum until it sounded like a diagram engaged.

https://i.imgur.com/T62lo3Fh.jpg
https://i.imgur.com/KDJTTwmh.jpg
https://i.imgur.com/gYKaGH8h.jpg
https://i.imgur.com/4k8cuMeh.jpg

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Sorry to jump in near the end without reading all 100 posts first, but I wanted to throw out one thing:

The Holley EFI will not work well at all on a manifold with a split plenum (where it's divided right up to the carb). You have to open up that separator if you have one.

Any chance you have a split plenum like that? Because an intake like this will NOT work well at all:

https://www.jegs.com/images/photos/5...555-513002.jpg

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Mine has an open gap between the left and right, so there's no risk of that.
https://i.imgur.com/eYDjBlTh.jpg?1

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

If your wiring isn’t good go the tach signal the EFI will never fire off. Also check connections on battery. Ask me how I know hahaha. On the Nova I did last Sniper install on it would randomly shut off or not start. Battery connections from efi directly to battery from efi had high resistance just in the terminals. Very strange. Replaced them all problems went away.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Great news. I managed to get the gentleman over who did the 350-->402 engine swap in my truck. We did the same timing check of #1 cylinder TDC, check the rotor direction, etc. The distributor appeared 1 tooth out so we pulled the distributor and rotated it 1 tooth. It started up. He adjusted the timing to 14 degrees advanced on the balancer. Done. It took 20 minutes. I'd tried this all before, alone, but I'll notch the 1-tooth-off on the distributor gear due to my inexperience.

I drove the truck for the first time in ~8 months, now with the EFI working. I made a drive to a classic drive in burger joint in town. I can't say how happy I am having this thing back on the road and with the EFI working as it should, after fixing my error with the timing.

It's definitely making more power, it idles 'too good' can barely hear the cam now. I did have to adjust the throttle cable/kickdown bracket to allow for 100% WOT from the floor peddle. It is really sensitive to throttle at low RPM so I may have to buy that part people have mentioned to solve this.

Next: drive 3 hrs to the drag strip and do some passes with drag radials. If I can dip into the 13's I will have met my 1/4 mi goal.

Maiden voyage with EFI. So happy.
https://i.imgur.com/tMVI12xh.jpg

A little wood prep for winter after I got home.
https://i.imgur.com/j2ruaDCh.jpg
https://i.imgur.com/Kx0Svg6h.jpg

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Good to hear you’ve got your issues sorted now.
Though it has for others, the progressive throttle didn’t work well for me. I just made up a small extension for the throttle and that helped the over sensitivity.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

That's great, that you got the bugs worked out. What cam are you running, if you don't mind me asking?

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Glad you got it worked out. How do you like the 3.73’s with the bbc & 700r4? How does it feel at highway speeds? I’m doing something similar & need to decide 3.42 or 3.73.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Here it is
https://i.imgur.com/RLFIO8Xh.jpg


I'm seeing 2500rpm at 60mph. But, the converter is not locking up via vacuum. I plan to wire a ground to the manual lock up via a button in the cab. That may drop the RPM a little.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Good to hear you got sorted and running good , great shot at Peters Drivein

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

what are you running for exhaust?

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Hooker headers, 3" dual exhaust, x pipe, Spintech mufflers. It's great at idle. A little 'glasspack' sounding under WOT. Not mellow at all. I may look into some magnaflows or something else, later.

All packed up and headed to the drag strip tonight.
https://i.imgur.com/aB77k2Ch.jpg
https://i.imgur.com/OJRZt3qh.jpg

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

That thing looks nice!!

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Well, what did it run?

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I think it's a surpise......lol

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

A sluggish 14.5 at 90mph. Something needs some adjusting.

If I left it in Drive, it'd do 14.7 at 88, shifting really early around 4000rpm. I tried tightening the TV cable to the 700R4. It didn't seem to make a difference.
Manually shifting from 1-2-3, I was able to make it shift around 5500rpm which netted the 14.5 at 90mph.

Traction was not an issue. I left as hard as I could which was at the 2,400rpm the converter would let me. 2.0 60' every time.

Possible reasons:
- engine is not making the claimed 430hp so some adjustments need to be made.
- trans is robbing the power somehow.

A fellow at the track said his friend has a TCI 700R4 and they had to change the 'module' to a corvette module and it solve the low rpm shift points. I'll look into it.

In case y'all think I need a 'driver mod', I've been drag racing for 20 years and am used to cutting 1.7# 60' times with manual transmission cars trapping 125mph.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Dyno should help you in that area, how did the sniper feel compared to your old carb setup, better response all around or is it still learning

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

Does installing the Holly system solve the fume issue from having the tank in the cab? Was it an issue for you before the install? Are you glad you left the tank in the cab, or would you recommend moving it to the rear? Thanks for any feedback you can provide.

Re: Install thread- Holley EFI Sniper on '72 402 big block
 

I didn't have any fume issues with the in-cab tank while using a carb. There is still no fume issue now with the EFI. So far (500miles driving) I have had no issues using the in-cab tank with the EFI system. When I turn the key on and hear the pump prime, I can hear a little fuel coming from the return line into the tank, but it doesn't bother me and I can't hear it when the truck is running.