2x4 1850 holleys Jetting?

[Michael C Henry]

last summer I thought my carbs were the problem with fouling plugs and had the carbs redone .Turned out to be the Mallory HyFire VI was giving up .New box ,things got better. Still fouling plugs but more gradually. You can hear it start under certain conditions gear and load( this time on the right side)Carbs came back from being redone with 73 jets in primaries. I feel that is a little fat. Carbs came in car from Reno with 64s. In Washington, the emmission statiton said I had a lean missfire. Carbs were originally produced from factory with 67s . I think they were redone as if I were racing and changeing plugs was an every other run thing. Changing plugs in an FE with alluminum heads is not verry quick or convenient.I seriously beleive I've spent verry little time if any with the secondaries open. I'd like to be able to drive it around and not have to worry how far I can get before the plugs start causing missing and poping out exhaust and wondering if I'll be able to get it home if I don't head home now.. It realy detracts from the cars impression. I really hate those foam elements in the two Stellinig and Helling air strainers.

[Excaliber]

I'm running two fours on my 427 FE side oiler also. 600 cfm vacuum secondaries. I forget the exact jet size now but I know it's low 60's or under and TO lean! I was running 660 Holley center squirters (drag race only, no power valve and mechanical secondaries). THOSE had 73's all around (8 jets total). I dropped them to 68's and it was MUCH better. I think I'll pull the 68's out and put them in my 600's.

BUT, I been playing with the power valve and what a difference THAT makes!!!! My old PV's (on the newer 600's) were 3.5" when I bought them, which was fine when my radical roller cam (which pulled almost NO vacuum). With my new "streetable" flat tappet cam and lower compression (from 12.5 down to 9.8) those 3.5" PV's NEVER opened! Talk about running lean and missing big time at cruise rpm.

Now I know YOUR running rich, but don't rule out the POWER VAVLES as a cause. All though, 73's still sound to big to me. If your PV's are rated at a vacuum higher than your cruise or idle vacuum signal they will be OPEN and thus will richen the mixture big time! I rigged up a vacuum gauge with a long hose and set the gauge on the windshield held in place with the wiper arm. Then I could read IDLE vacuum AND cruise vacuum. Idle and cruise were (surprise) about the same, 11 inches or so. SO, I installed 10" PV's. MAN what a difference!!!! Cruise was smooth, throttle response was WAY better. Transition from idle to "rev up" was instant and no more "back fire" and hestitation. WORLD of difference.

Now cruising at 75 or 80 I feel that kind of "jerky" uneven hit and miss thing, subtle, but it's there. Just a "touch" more gas and the PV opens and everything smooths right out. BUT I'm thinking I shouldn't have to "open the PV" at cruise rpm to get "smooth", thus an increase in jet size is now warranted. One thing at a time you see, PV or jets till you nail the problem.

In your case I would do two things.
1. Check my PV rating against my idle/cruise vacuum signal.
2. Decrease the jet size into the 60's.

Every cam, compression ratio, engine specs are different. YOUR carb has to match YOUR engine. There is no easy answer here. Set your PV size (vacuum rating) JUST under your idle/cruise vacuum by a point or two. Idle at 11, go with 10 or 9.5 PV's. Any vacuum signal ABOVE 10 or 9.5 will keep the PV "closed". A touch more throttle, vac drops below 10 and the PV opens and introduces more fuel, think of it as a "third main jet". You DON'T want it to open unless you NEED it to. Open at cruise rpm/vacuum will cause big time "rich" to occur, passing or going up a hill then it SHOULD open due to slightly lower vacuum signal!

Hope this helps.

[Seaman]

I have two 1850-1 and feel that I have just gotten a handle on them.

1. Main jets - 60.
2. PV - 6.5 for a Comp Cams 282S have about 11"/hg
3. Curb idle screws at about 1/2 to 5/8 turn.
4. Vacuum secondaries are tied together

Idles at about 850 or so and gets about 14mpg without hesitation or black smoke at idle. The PV may be a little low as the pedal travel is a bit more than I would like to get a small increase in speed on the highway.


The biggest issue to determine is: are the carbs reacting to the adjustments. Does the curb idle fall when you crank the screws, etc?

Dave

[Michael C Henry]

I went through my sets of jets (two sets).I'm missing the 68s out of both sets .I went up to the local Baxter auto parts. They give me one set of 67s as 68s. that is all they have I stopped at a Schucks auto parts store ,no jets at all..I call the local main Lakewood wharehouse store Schucks .Wait twenty minutes on a hard line,call on cell ,bam I'm talking to a person.They have one ,oops that was a mistake they have none.They can restock if I come in and prepay. Twenty minutes and two tripps .That is crapp. Local parts stores wonder why bussiness sucks.I called Summit and will pay the shipping and save the sky high state sales tax. Sales person ask how is it going .Not good .

[Excaliber]

Update!!! I just pulled the 58's from my two fours and replaced them with what I had on hand, four 68's.

WOW, what a difference! Much smoother off idle, better transistion on reving up, cruise rpm perfect, AND idle screw adjustments dialed right in, much better idle. Cool. BUT, the 68's are TO FAT! Loads up at idle if I idle to long, belches black smoke when I nail it (but zero hesitation). I'm onto something. Going with 63's next, I'm almost there!

Dave,
I was tempted to go with your settings, 60's. To paranoid about running lean at high rpm. 63's next, maybe 60's down the road. 60 vs 63 vs 65 may also depend on the "style" of the PV. There are TWO styles. ONE is "big" has a larger orifice and introduces more gas at the same vacuum signal. The other is "standard", less gas at the same vacuum signal. I'm running "standard", I wonder if your running "BIG".... ?

[Michael C Henry]

The powervalve is't the limiter there are small orifices in the mainbody that are the flow limiters.the large window powervalves flow more than the orifices. I'm running 5.5 pv s and at 250ft above sealevel I'd think 67s or 68s should be close. unless internal things have changed .64s ran great but were lean according to emmisions testing station. Will be watching untill I get my Jets from Summit.I have no chokes and starting takes a few pumps but be careful you don't flood it.May end up buying a pair of off the shelf carbs for colder weather.

[Excaliber]

Thanks for the heads up about the main body orifice being the deciding factor on flow rates for the PV. I'm learning all the time!

Yup starting takes a few pumps and it IS kind of "cold blooded" even with the 68's, but nearly as "cold blooded" as with the 58's!

Hmmmm,,,,, I'm sure 68 is to big for me and I'm at about 250' elevation also. But then again, my PV is 9.5, considerably higher than yours. Perhaps thats why 68's are to fat for me? I'm going to try 64 next.

[Michael C Henry]

I'm at or near 250 ft above sealevel also .The number on the powervalve determines when it is closed .If you mormaly carry 11 inches of vacume a 9.5 will start opening pretty quickly when you step into it.as vacume dropes below 9.5.I'm running 5.5 or 6.5 so I have to step into it a little more before they open ( unless diaphram has been ruptured by a backfire) If diaphram is ruptured it wont close and fuel may leak fuel into the vacume passage for the powervalve.If your just nailing the throttle the 9.5 will start sooner than 6.5 but its just a fraction of a second. The problem is the vacume staying just at or below the set threshold and it drouling fuel in when not needed.
I need to take mine to a dyno tune and see if I'm running rich ,is the spark giving up ,or what I know just enough about carbreuters to be dangerous and I'm the first to say I need help.I'm looking for that zip when I crack the throttle and plugs that will last atleast the summer.I do think less fuel will get me closer to what i want.

[Excaliber]

9.5 is working well for me, it all depends on your cam profile and final gear ratio what PV you wind up with. I was surprised to find my vacuum stays above 9.5 even while cruising at 80 mph, 11 while cruising at 60! I can actually feel the PV open with just a slight increase in throttle. This is due largely because I'm currently running some fairly heavy springs on the vacuum secondaries. I didn't want them opening to soon and interfere with my continuing diagnosis of the jets and PV settings.

Bigger jets if your running a lower vac setting on the PV, makes sense to me. You would be relying primarily on the jets to "tack up the slack" before the PV opens. Hmmmmm,,,,,,,, an interesting thought there and may be more fuel efficient.

Crisp accelleration with no hestitation and/or backfire, THAT is the goal. Was real good when I FIRST ran the 68's. Now after a few days, I've got fouled plugs!

63's tomorrow.

Insulated the fire wall today, WOW, no more burned up tennis shoes for me. WAY cooler. On that note: My exhaust temperatures are definitly higher than I had before, which is perplexing. I was running 12.5 to 1 with a radical cam and WAY RICH before. Now I'm at 9.8 to 1, much milder cam and rich or lean, the exhaust IS hotter than before. Could be the "squish" factor I think, I moved the piston UP .030 in the bore at the same time I dropped compression (new custom order blue printed pistons).

[Michael C Henry]

The 1850 Holleys carbs came from the factory with 67s,for Detroit and most of the midwest. I have replacable air bleeds and different accelerator cams (pink) that give a little squirt through the full travel of the primaries.Don't know how that is affecting things.

[Michael C Henry]

Face it it, now it's another engine entirely. you'll have to start testing and settimg peramitters . The lower compression ratio will let you buy and run pump gas which will make it a little more practicle. The hotter exhaust temps maybe what modern emission systems are looking for.Heck! it may be running correctly now.
Took the car out for a ride with my brother last night. Turns out the gas gauge is pretty much correct .When the gas gauge needle is on empty it's allmost empty. Put 23.5 gal in a 25 gal tank. At least the gas in tank is fresh now.
I tried the K&N E-2570 elements 1 15/16" tall and they are about 1/8" to 3/16" too high . They hold the hood up.

[Excaliber]

Went to the strip last night, ran 11.99 at 118 mph.

I was running 62 jets, which seem to be almost perfect in "street trim", air cleaners, side pipes. When I removed the air cleaners and opened the headers I could tell right away I was a little bit lean. Maybe I'll go 64's for all around steet/strip.