Don Terrill’s Speed-Talk

Did the guys that started FST come from Quickfuel?

Yes same people. They had plans for a 800vs which I was waiting on for my 400 street engine but Covid slowed everyone down and they are quoting me 2 1/2 weeks for the 750 carb which I'm thinking will be fine

JMHO - Black and never look back! Easier to clean, always looks good. Heat does not seem to be an issue. We have two sets of QF black and two sets FST black.
For info... Phil @ FST is from QF, he does the design work for FST.

HQM383 wrote: ↑Fri Oct 15, 2021 10:25 pm

steve cowan wrote: ↑Fri Oct 15, 2021 1:58 amsince you have bought several this year i suspect you like them ,what do you recommend for a SBC 383 that makes 550 ish

Apologies for jumping in on this question but what is the intended use of the 550hp 383?

I ask because I have tested on my 383 a 650, 750, 825, 850, 850AN, and 975 (that I would actually put inbetween 825 and 850 due to venturi/throttle sizes) cfm carbs. All mechanical secondaries. Every one of them worked great when tuned but the way they drove was different and it was in a way most people don’t contemplate when choosing cfm size. All would break traction @ 100kp/h when foot mashed to the floor, as one method of comparison but when driving was primaries only as 95% of cruising the streets would be that’s where the biggest difference was. And it’s backwards to widely accepted theory.

Good question that most people don't talk about. In my race applications, I use 1:1 linkage since I want the carb to work correctly and not have to switch calibrations between primary/secondary. I also don't think there is too much carb or TB except when dealing with electronic trans that use TPS for control. The engine takes what it wants, it's up to you to control the fuel curve, EFI or Carb.

I think a small fuel return line can work wonders compared to a dead-headed system. It can keep the fuel going into the carb quite a bit cooler than letting things percolate under the hood. Maybe not so effective if the fuel tank is being heated up by the track surface radiation.

Another case where a few measurement experiments some times make my best theories go down in flames.

The thermal emissivity of paint etc of different colors does not always behave as expected.
https://www.thermoworks.com/emissivity-table

https://www.europhysicsnews.org/article ... n07102.pdf

https://www.transmetra.ch/component/jif ... -table-pdf\

Differences in emissivity is Something to consider when using an infrared thermometer to compare a painted engine block to an aluminum radiator or header tube or rusty iron manifold etc, and etc.

HQM383 wrote: ↑Fri Oct 15, 2021 10:12 pm What’s everyone’s thoughts on aluminum being able to dissipate heat so much better than zinc color should not matter?

That depends on how hot the air around it is or the fuel running thru it.

Nothing to do with the air temp or fuel in the carb. The substance just sees it as a temperature difference, whether it be a liquid or a gas coming in contact with the substance. Every substance has a thermal conductivity quotient. Alum is about twice that of Zinc.

So if the air or fuel is hotter than the carb, alum will absorb heat faster than zinc

BOOT wrote: ↑Sat Oct 16, 2021 8:54 pm So if the air or fuel is hotter than the carb, alum will absorb heat faster than zinc

it also means it will dissipate it faster.

lefty o wrote: ↑Sat Oct 16, 2021 9:27 pm

BOOT wrote: ↑Sat Oct 16, 2021 8:54 pm So if the air or fuel is hotter than the carb, alum will absorb heat faster than zinc

it also means it will dissipate it faster.

Agree lefty o. Simply, it’s harder to get heat into aluminum because it loses it so easy. Very apparent when welding stainless and carbon steels v aluminum.

I think it's been covered earlier that alum dissipates heat better already

But if it's hotter around the carb, then it absorbs heat soooo that means it's not dissipating!

BOOT wrote: ↑Sat Oct 16, 2021 10:00 pm I think it's been covered earlier that alum dissipates heat better already

But if it's hotter around the carb, then it absorbs heat soooo that means it's not dissipating!

Let’s look at another part of an engine with constant heat input.

Why does an aluminum cylinder head allow for higher compression ratios than iron?

The head is always being given heat by combustion but the aluminum takes on and loses that heat better than iron heads. Same with alum v zinc carb. Same reason heat sinks are made from aluminum. Heat passes through easier.

By your logic an aluminum head, and throw manifolds in too, should run hotter because it absorbs heat easier.

HQM383 wrote: ↑Fri Oct 15, 2021 10:10 pm

1980RS wrote: ↑Fri Oct 15, 2021 1:29 amI would say a 750 would work great on the 383, FST's 850 is a little deceptive as it's a 750 main body with an 850 base plate but it worked pretty good on my 358 pump gas engine.

Same as Quickfuel 850. Did the guys that started FST come from Quickfuel?

Good advice to take note of venturi and throttle rather than cfm label.

At first I was like Humm, can this be right but the more I looked at the carb the more I figured that their idea must have been to get a better booster signal from this animal. Must have worked, my little 358 ran pretty sweet with it out of the box , no changes other than tightening up the sec vacuum pod a bit.

HQM383 wrote: ↑Fri Oct 15, 2021 10:25 pm

steve cowan wrote: ↑Fri Oct 15, 2021 1:58 amsince you have bought several this year i suspect you like them ,what do you recommend for a SBC 383 that makes 550 ish

Apologies for jumping in on this question but what is the intended use of the 550hp 383?

I ask because I have tested on my 383 a 650, 750, 825, 850, 850AN, and 975 (that I would actually put inbetween 825 and 850 due to venturi/throttle sizes) cfm carbs. All mechanical secondaries. Every one of them worked great when tuned but the way they drove was different and it was in a way most people don’t contemplate when choosing cfm size. All would break traction @ 100kp/h when foot mashed to the floor, as one method of comparison but when driving was primaries only as 95% of cruising the streets would be that’s where the biggest difference was. And it’s backwards to widely accepted theory.

PM sent

1980RS wrote: ↑Sun Oct 17, 2021 12:14 am

HQM383 wrote: ↑Fri Oct 15, 2021 10:10 pm

1980RS wrote: ↑Fri Oct 15, 2021 1:29 amI would say a 750 would work great on the 383, FST's 850 is a little deceptive as it's a 750 main body with an 850 base plate but it worked pretty good on my 358 pump gas engine.

Same as Quickfuel 850. Did the guys that started FST come from Quickfuel?

Good advice to take note of venturi and throttle rather than cfm label.

At first I was like Humm, can this be right but the more I looked at the carb the more I figured that their idea must have been to get a better booster signal from this animal. Must have worked, my little 358 ran pretty sweet with it out of the box , no changes other than tightening up the sec vacuum pod a bit.

the 950HP carb is the same -750 main 850 base
i just purchased a new 850hp main body i am going to swap out the 750 main body and test.

HQM383 wrote: ↑Sat Oct 16, 2021 11:56 pm Let’s look at another part of an engine with constant heat input.

Why does an aluminum cylinder head allow for higher compression ratios than iron?

The head is always being given heat by combustion but the aluminum takes on and loses that heat better than iron heads. Same with alum v zinc carb. Same reason heat sinks are made from aluminum. Heat passes through easier.

By your logic an aluminum head, and throw manifolds in too, should run hotter because it absorbs heat easier.

This is a very poor comparison for several reasons, the Total Surface Area exposed to a much higher temp is very small, that's like if only the fuel bowl bolt heads were exposed to a higher temp of course the rest of the carb would disperse the heat. The pathway is small! Not to mention the engine coolant system dedicated to disperse the combustion heat!

If you check the temp like I have(open hood venting HOT AIR) most likely your intake is cooler than the heads/block and the carb cooler yet, heck my front fuel bowl is hotter than the rear, wanna guess why? And I've taken several measures to reduce carb temp. Do a search people have recorded pretty HIGH underhood temps in some vehicles.

By your logic an aluminum head, and throw manifolds in too, should run hotter because it absorbs heat easier.

I'm gonna assume you mean hotter than iron because LOL

Have you ever considered header wrap or ceramic coating to reduce underhood temps? Turbo wraps/blankets? This has been discussed over n over in those type threads.

There are also discussions on why iron may be better than alum, heat = power. In control obviously.

I don't even want to get into a compression discussion because it would have noting to do with this thread.