[1937Austin]

I'm still sorting out my tunnel ram set up, and wondered what things anyone has done to make them perform best on the street?
My setup is a old Holley Pro Dominator, with two new Holley 450's that are designed for a dual carb setup. These carbs have mechanical secondaries, but only have accelerator pumps on the primaries. I changed out the 30cc pumps to 50cc pumps, which made a huge improvement already. My linkage is set up so both carbs open in synch, not progressive.
Just looking for suggestions to further improve things to make the 327 a little quicker and perform a bit better!

 

[406Rich]

I`ve read several threads about tunning Holleys for tunnel rams, I`ve never done but looking into it, they mainly talk of changing idle air bleeds and high speed air bleeds and venturi boosters to match your current set up and from what I`ve read it makes a real differance.

 

[DaveS]

Or, forgot the Holleys and go EFI?????

 

[406Rich]

What jets are you runing, my brother inlaw was running a tunnel ram, he changed out the jets to 57/62 not sure what was in there before though and that was on a big block, helped on the low end response.

 

[bentwings]

I run blowers but the same applies. I would recommend you run a vacuum advance ..about 10 deg. I'd also set your cent adv to be all in by about 2500 rpm. You may have to shorten the curve to get enough initial. I like to run 2-4 deg less than what will kick back against the starter. I think the MSD boxes have a built in retard below 500 rpm so they start easier. Mine hardly ever kicks back. only when very hot and on a quick restart.

I'd start with 34 total.

Once you get the ign set the carbs will probably run right out of the box. Then you can do some fine tuning. This is assuming they haven't been monkeyed with.

I have my adv all in by 2000-2100 and still have 18 deg showing at 750 idle.

I have and AFR gage which make setting this stuff up really easy. Great tool. Innovate Motorsports.

 

[1937Austin]

I run blowers but the same applies. I would recommend you run a vacuum advance ..about 10 deg. I'd also set your cent adv to be all in by about 2500 rpm. You may have to shorten the curve to get enough initial. I like to run 2-4 deg less than what will kick back against the starter. I think the MSD boxes have a built in retard below 500 rpm so they start easier. Mine hardly ever kicks back. only when very hot and on a quick restart.

I'd start with 34 total.

Once you get the ign set the carbs will probably run right out of the box. Then you can do some fine tuning. This is assuming they haven't been monkeyed with.

I have my adv all in by 2000-2100 and still have 18 deg showing at 750 idle.

I have and AFR gage which make setting this stuff up really easy. Great tool. Innovate Motorsports.

Thanks! My carbs are stock out of the box new, with just the accelerator pumps changed per the Holley tech who said they should be changed for a tunnel ram setup. Haven't changed anything else, and don't know what stock jets are, but that's what's in them. I'll check the timing. I have a Pertronix igntion distributor, with the lightest springs on my mechanical advance, so they come full in at around 2,000 rpm's. I am running vacuum advance now. Need to check the total timing to see where I'm at, then I'll try your settings.

 

[Marks63PontiacGasser]

When I had my tunnel ram and twin 600 vac secondary Holleys, I made sure the secondaries on both carbs closed all th eway closed so not air could sneak by. That made sure that all my idle tuning was being made by the front primaries. This allowed me to have the primary throttle blades down far enough to stay out of the main fuel circuit (still in the idle circuit) of the front barrels and a much smoother idle. It helped alot in the transition into the main circuits as well. You might want to get an assortment of squirters so you can use a size just large enough to cover any stumble but allow the accelerator squirt to last long enough the full transition to open throttle. If it sprays in too much fuel it may make it cover the transition nicely at first, but up to a point and then runout of fuel in the spray to cover the whole transition. Creating a delayed stumble that you can't figure out. I also connected the ywo carb secondary vacuum canisters so they operated in sync but you do not have that problem since yours is all mechanical. Just for anyone else running tunnel rams and vac carbs. Just a thought. Mark L

 

[1937Austin]

Thanks for that info Mark. I'm a bit surprised that Holley reccommends these 450's without either a secondary pump, or vacuum secondaries. I personally thought one or the other would make them work better for street use, but maybe they figure it's mostly track use, and don't design them for the street.
I even considered disconnecting the secondaries if it turns out to be too much CFM for my .040" over 327 engine. Don't plan on it, but if it makes the car more responsive for the street it might be an option. Of course then I'd end up under carbureted at around 4,000 rpm's, and that would suck.

 

[bentwings]

Good info from Mark...You may also want to try a 1" spacer to increase the plenum volume. These are not a sure thing but more case by case. I think Holley has an adjustable link that allows you adjust where the secondaries come in. It's kind of a screw link. I've seen them on the DP so I would think it would fit yours.

At least get a vacuum gage with a long enough hose so you can put it where you can read it going down the road. Recored the various load situations and the vac reading so you know where to do your tune up.

The book with the sectioned holley carb on the cover is a great book for learing how these things really work. Lots of no non sense info.