Have had mine for about 5 years now and never hot soaked. Will follow.
Summit 600cfm carb, 800 mile test drive.
I was heading to Michigan this weekend to visit some friends and could not resist the temptation to replace my trusty Holley 1850 with a Summit M2008. I had a few days to tune it to idle (not easy to get off high idle) and get the vacuum secondary spring changed out. The car ran well with one exception. As per the following video, my carb too appears to be susceptible to the idle leaning out under heat soak conditions. This happened to me when stuck in Chicago stop & go traffic. While I have a stock temp gauge, I doubt temps ever got above about 220. It ran fine off idle, but a couple times when pushing in the clutch and breaking the car would just flat die. Pretty hair raising. Twice I had to pull between cones in the construction zone to get it started. I don't have my AFR gauge installed yet, but it acted like no fuel (lean). If I could heal toe it to keep the RPM up it would not stall, so no vapor lock or low float bowl issue.
The jury is out still. This carb has taken WAY more messing with to get to run than my old 1850. It does get better mileage and throttle response does seem smoother. I have the idle feed restricter kit so I hope upping the size will cure the stalling "hot" stalling issue. Worst case the 1850 goes back on.
The jury is out still. This carb has taken WAY more messing with to get to run than my old 1850. It does get better mileage and throttle response does seem smoother. I have the idle feed restricter kit so I hope upping the size will cure the stalling "hot" stalling issue. Worst case the 1850 goes back on.
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you need a phenolic spacer - these carbs suffer from fuel percolation much like the edelbrocks - curious why you would take a perfectly good 1850 off to put an autolite clone on?
I've been running 2 Summit carbs here in TX with no heat issues.
Went from Holley to Edelbrock to Demon to Summit. Love the Summits, they ran fine right out of the box. I recommend them to everyone.
Went from Holley to Edelbrock to Demon to Summit. Love the Summits, they ran fine right out of the box. I recommend them to everyone.
I have no room for the 1/4" gasket they provide let alone a thicker phenolic spacer unless I swap out my 3" air filter for a standard Hipo filter. My understanding was that the thick gasket was due to interference problems on some intakes. I did double the gasket for a little more insulation.you need a phenolic spacer - these carbs suffer from fuel percolation much like the edelbrocks - curious why you would take a perfectly good 1850 off to put an autolite clone on?
Why? I thought I would try something with annular boosters.
One of the reasons I asked for pix was to see how you supplied your fuel from the pump to the carb. You should have no rubber hose and a metal in-line filter or fuel pump with integral canister filter only. Also, check your float levels... HALF WAY up the sight glass seems to work best.
I will have to take some. Pretty standard 289, standard RPM intake, braided lines, PCV to the back, manifold vacuum to dizzy.Pix of your installation?
You need to look at why annular boosters are sometimes used in a performance application....Typically, it is when a large carb is used (to meet upper rpm airflow demands) along with a high duration camshaft.....the larger booster helps velocity at lower RPMs.....on a little street motor that is done making power by 5k this bigger venturi/bigger booster combo is not needed.....undoubtably the carb needs adjustments to the air bleeds and primary jets to compensate for the extra fuel the annular boosters are delivering too.....I know its "cool" to used a "ford" based carb on your mustang to be like everyone else here, but the 1850 is likely a better starting place for your combo - and if it makes you feel better, it was derived/descended from carbs holley developed for 1957 Ford-Lincoln-Mercury vehiclesWhy? I thought I would try something with annular boosters.
Floats are 1/2 way up. Filter is Earls aluminum with AN fittings.One of the reasons I asked for pix was to see how you supplied your fuel from the pump to the carb. You should have no rubber hose and a metal in-line filter or fuel pump with integral canister filter only. Also, check your float levels... HALF WAY up the sight glass seems to work best.
In 40 years I have never had all steel lines. I have driven through the Mojave desert to Vegas in 113 degrees with my Holley and zero issues.
75-80 degrees in Chicago should not be an issue.
I have seen you comment that a steel line helps cool the fuel, but I question that. Fuel coming from the tank is largely at ambient temps. A diaphragm pump pumping at 6psi is not likely to add much heat. I would think fuel would be cooler in an insulated line by protection from higher underhood temps, especially close to the engine.
With my cam and heads my engine only pulls 12-13" of vacuum, so it could be a leaner at idle with factory settings than something that pulls 19".
Pulling only 12-13" of vacuum I thought the annulars would be of benefit. Agreed, when retrofitting a standard straight or down leg carb the air bleeds need to be adjusted. These carbs seem to control the mixture by restricting fuel vs air.You need to look at why annular boosters are sometimes used in a performance application....Typically, it is when a large carb is used (to meet upper rpm airflow demands) along with a high duration camshaft.....the larger booster helps velocity at lower RPMs.....on a little street motor that is done making power by 5k this bigger venturi/bigger booster combo is not needed.....undoubtably the carb needs adjustments to the air bleeds and primary jets to compensate for the extra fuel the annular boosters are delivering too.....I know its "cool" to used a "ford" based carb on your mustang to be like everyone else here, but the 1850 is likely a better starting place for your combo - and if it makes you feel better, it was derived/descended from carbs holley developed for 1957 Ford-Lincoln-Mercury vehicles
The issue with rubber line is that it's not bad at absorbing heat but terrible at radiating heat. So, what happens is that when it passes an area where the rubber is cooler than the air around it, it picks up heat and, consequently, warms the fuel inside, and then when it gets to an area where the heat is lower than the line it doesn't readily SHED the heat... Today's fuel doesn't like to get hot and vaporizes easily. Steel line is pretty equal at absorbing and then radiating heat.
Question.... manual or power brakes? Also don't forget that under deceleration, in gear, vacuum will be high and suddenly depressing the clutch will decrease vacuum. Are you supplying your distributor vacuum advance from manifold or ported?
Question.... manual or power brakes? Also don't forget that under deceleration, in gear, vacuum will be high and suddenly depressing the clutch will decrease vacuum. Are you supplying your distributor vacuum advance from manifold or ported?
Following this. I have the Summit 600 on my 351W. I was having this same issue really bad when it got above 80 here because the previous owner had the idle set at around 5-600. I bumped that up to about 750-800, dialed in a little more timing and adjusted the mixture screws and that helped tremendously but it has died on me a couple times since then. Once restarting after being in a store for 5 minutes it died on take off. Another time just the other day sitting idling in a parking lot waiting for my wife to come out of a store. I do have a spacer that I think is 1/4”. Might 1/2”. I haven’t actually measured it.
Manual brakes. Manifold vacuum.The issue with rubber line is that it's not bad at absorbing heat but terrible at radiating heat. So, what happens is that when it passes an area where the rubber is cooler than the air around it, it picks up heat and, consequently, warms the fuel inside, and then when it gets to an area where the heat is lower than the line it doesn't readily SHED the heat... Today's fuel doesn't like to get hot and vaporizes easily. Steel line is pretty equal at absorbing and then radiating heat.
Question.... manual or power brakes? Also don't forget that under deceleration, in gear, vacuum will be high and suddenly depressing the clutch will decrease vacuum. Are you supplying your distributor vacuum advance from manifold or ported?
I am pretty sure each material has its own thermal conductivity coefficient and that it holds for both rate of heat gain and loss. If it gains it slower, it looses it slower.
Great post - thanks for the feedback as I have the same carb sitting on the shelf for eventual use.
So what kind of fuel mileage were you getting on the highway?
what drivetrain and what speed?
So what kind of fuel mileage were you getting on the highway?
what drivetrain and what speed?
Yup, that would be interesting to know mileage. No mater how you tune a 600 Holley, it's going to be fairly thirsty.
My basically "just set up correctly" 650 double pumper is massively less efficient than a correctly tuned 1.12 Autolite
hipo carburetor. (as in at least 2 mpg if not more..... it's quite noticeable..... the top end rpm is also way, way less spongy
with the Holley)
My basically "just set up correctly" 650 double pumper is massively less efficient than a correctly tuned 1.12 Autolite
hipo carburetor. (as in at least 2 mpg if not more..... it's quite noticeable..... the top end rpm is also way, way less spongy
with the Holley)
Really? an 1850 Holley is FAR different from your 650 Double Pumper (or even a 600 DP for that matter) I assure you, the 1850 can be tuned for the same efficiency as the summit carb......These summit carbs were MAJOR flops when they were introduced by Holley for the reasons posted here and more- Summit buying the tooling and moving the manufacturing to china did not make them any better. Can they be made to work? Sure.Yup, that would be interesting to know mileage. No mater how you tune a 600 Holley, it's going to be fairly thirsty.
My basically "just set up correctly" 650 double pumper is massively less efficient than a correctly tuned 1.12 Autolite
hipo carburetor. (as in at least 2 mpg if not more..... it's quite noticeable..... the top end rpm is also way, way less spongy
with the Holley)
My best was about 21.5. 289 with typical performance goodies. Similar build to a hipo, but with AFR165 heads. Transmission is a T5z and rear end is 3.55. Tires are short, 225/60r-14.Great post - thanks for the feedback as I have the same carb sitting on the shelf for eventual use.
So what kind of fuel mileage were you getting on the highway?
what drivetrain and what speed?
Lots of 80 MPH. Speed limit on 69 and parts of 94 was 75. 80 in Chicago (when not crawling) was to prevent getting run over.
You can “assure me” all you want. Fill me in on how it’s different. I have 50 years experience dealing with Holleys technically and selling them as well at JBA.Really? an 1850 Holley is FAR different from your 650 Double Pumper (or even a 600 DP for that matter) I assure you, the 1850 can be tuned for the same efficiency as the summit carb......These summit carbs were MAJOR flops when they were introduced by Holley for the reasons posted here and more- Summit buying the tooling and moving the manufacturing to china did not make them any better. Can they be made to work? Sure.
I’m all ears……
My recollection with the Holley was 19 mpg on the highway, but that may have been factory heads vs AFR so not totally apples to apples. Also, people reporting that they need to back down the timing makes some sense as better atomization of fuel should burn faster, thus less need to spark it sooner.Yup, that would be interesting to know mileage. No mater how you tune a 600 Holley, it's going to be fairly thirsty.
My basically "just set up correctly" 650 double pumper is massively less efficient than a correctly tuned 1.12 Autolite
hipo carburetor. (as in at least 2 mpg if not more..... it's quite noticeable..... the top end rpm is also way, way less spongy
with the Holley)
I also found the need to lighten up the vacuum secondary spring. With the Holley I was running the yellow spring (2nd to lightest). I put that in the Summit and it seemed to come in late. There was not a smooth transition and it felt like a turbo kicking in as the secondaries opened. I never felt that distinct sensation with the Holley. I put the white spring (lightest) in the Summit and it cured that but the engine now seems to lug at 1,500-1,600 rpm where I could roll along with the Holley at 1,300 rpm without the hint of lugging.
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