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Although the whole scenario of converting to EFI on my 64 was pricey, well, oh well. Holley HP EFI. I am now installing their plug and play dist, to run sequential injection along with ecu controlling timing. Drivability and response from my right foot is phenomenal.
I have the same unit on my 65. Working with a good tuner is essential.
The reward is a great running car. Good throttle response, great drive-ability. It brings it into the modern era. 21 mpg highway w/TKO 600.
Very nice upgrade. However, it is pricey.
I would also recommend an in tank fuel pump. I had external fuel pumps and they are loud and unreliable.
Last edited by woodsdesign; 09-02-2017 at 08:50 AM.
Ok this is where it gets tricky. For starters, my camshaft is of very radical design and therefore there is a very fine line of settings that make this car either a lot of fun to drive verses a pain to drive. All 3 carbs have great performance at WOT but not on the idle circuit. I will add that the 1st Qjet that I installed (not one of the 3) was an Autozone rebuilt, straight out of the box, no adjustments, and was on the car for over 20 yrs / 90,000+ miles before its issues began. The cam was designed for fuel mileage and that carb produced a consistent 24-25 MPG. With the 6 speed and the 3:08s it has a final drive of 1:54. This is where the problem lies since under most driving conditions I am barely off the idle circuit.
To answer your question specifically about the 3 carbs: Qjet #1 - loads up at idle; engine stalls when braking (rebuild by a local Qjet "expert")
Qjet #2 - Autozone - installed last week; accelerator pump not working properly - this carb replaced another Autozone carb that was defective and warrantied
Carter AFB Competition Series carb - 17 and 18 MPG max - not acceptable
There are some things here that don't add up:
First underlined quote contradicts the second. Which is it? As an example of a "radical" cam, the idle vacuum @ 800 RPM with my 327 is about 8 in-hg. What is your idle vacuum @ a given and stated RPM? That will give us an idea of just how "radical" your cam is.
Second and third highlighted quotes tell me that your final drive ratio is too low. Modern cars using a six speed double overdrive transmissions use higher numerical axle ratios (3.42:1) to end up with a higher final drive ratio than your 1.54:1. You are lugging your engine unless you cruise at very high speeds! You probably don't shift into high gear until 75 MPH.
Last 2 underlined quotes. First of all, the Q-Jet is not known for adjustability, and obviously the 2 that you bought were defective. It sounds like the Carter(Edelbrock) was improperly jetted.
Just as a comparison: my 327 runs a fairly big cam and makes close to 500 horsepower, yet is very drivable around town. It has a 3.70:1 axle with 5th gear of .67:1 for a final drive ratio of 2.47:1. I get a consistent 22-23 MPG at a steady 80 MPH cruise (about 2500 RPM). If you are chasing MPG, it seems to me that you are trying to economize and the money you spend on an expensive and complicated EFI system will probably never be recovered by fuel savings in your lifetime.
This is all a waste of breath because you are determined to install EFI. Good luck to you, but I wouldn't do it before changing your axle ratio to 3.55:1 and tweaking that Carter.
Last edited by 65tripleblack; 09-02-2017 at 11:19 AM.
I agree here, you can purchase a good quality carburetor and tune it for mileage. The Holley style modular carburetors are good for tuning and you can work on the idle and main circuit for good results.
What are these radical camshaft specs you refer too.
Gross valve lift .628 IN/ .585 EX
Duration at .006 281 IN/ 291 EX
Duration at .050 230 IN/ 235 EX
Lobe Lift .3650 IN/ .3443 EX
I have more numbers if those mean anything to you. They don't to me. All I know is if idle speed is too high and timing is too fast, it slams (for lack of a better word) the drive train every time you touch the throttle from idle (while driving) or let off throttle. When I first drove the car with this cam, I hated it. I still hate that it has to be dialed in so precisely to minimize this problem. Have over 30K miles on this cam now.
Gross valve lift .628 IN/ .585 EX
Duration at .006 281 IN/ 291 EX
Duration at .050 230 IN/ 235 EX
Lobe Lift .3650 IN/ .3443 EX
I have more numbers if those mean anything to you. They don't to me. All I know is if idle speed is too high and timing is too fast, it slams (for lack of a better word) the drive train every time you touch the throttle from idle (while driving) or let off throttle. When I first drove the car with this cam, I hated it. I still hate that it has to be dialed in so precisely to minimize this problem. Have over 30K miles on this cam now.
That's a fairly mild cam for a 454. With those lobe lifts at relatively short durations, it's probably a roller. I'll bet your idle vacuum at 700 RPM is more than 15 in-hg.
You should get some help from a mechanic and have your u- joints/differential/axles checked for slop, and while you're at it change the ratio to 2.55. Worse, there might be something loose in the driveline mounts.
Save money, reinstall the Carter and have it jetted properly.
Last edited by 65tripleblack; 09-03-2017 at 12:07 PM.
That's a fairly mild cam for a 454. With those lobe lifts at relatively short durations, it's probably a roller. I'll bet your idle vacuum at 700 RPM is more than 15 in-hg.
You should get some help from a mechanic and have your u- joints/differential/axles checked for slop, and while you're at it change the ratio to 2.55. Worse, there might be something loose in the driveline mounts.
Save money, reinstall the Carter and have it jetted properly.
Your cam knowledge is impressive. You are correct. It is a roller and idle vacuum is very close to what you said. Funny you mention changing ratios (I'm sure you meant 3.55s). That is what I had until a bearing went south right before a long trip we had planned so I just threw the 3:08s in since I knew they were good. Was also a good time to inspect all U joints since I was at the 100K mile point on those. One out of 6 was "barely bad". Only have app. 35K miles since then and there is no slop. I agree. I need the 3:55s back in. Too much to do. Not enough time.
Since you have hit the numbers on the cam, what kind of numbers do you predict I can get with fuel mileage out of the Carter? When I had this cam built, I made it real clear to Chris Straub of Straub Technologies that MPG was priority #1. Horsepower #2.
I'm with 65tripleblack...for the first part but I will go farther...
Agree, at a minimum you need to change gears and retune the carb...I bet that thing comes to life...however, I would go with a 3:73 in anticipation of the next step...
Going farther, (and I have often beed accused of trying to spend people's money), once you get the gearing and carb sorted, take your EFI money and buy the TKO600 5 speed...the TKO600 combined with a 3:73 or 4:11 will make that 454 and your car so much more enjoyable...
I'm with 65tripleblack...for the first part but I will go farther...
Agree, at a minimum you need to change gears and retune the carb...I bet that thing comes to life...however, I would go with a 3:73 in anticipation of the next step...
Going farther, (and I have often beed accused of trying to spend people's money), once you get the gearing and carb sorted, take your EFI money and buy the TKO600 5 speed...the TKO600 combined with a 3:73 or 4:11 will make that 454 and your car so much more enjoyable...
The T-56 has been extremely well liked, reliable, smooth and it now has 135K miles since 1994 installation. Pre '94 and pre fuel mileage/ cross country driving setup, this engine performed quite nicely with the 292 Comp cam/ 4:11 gears/ M-21. 11.95 in the 1/4 on 8"slicks.
I'm with 65tripleblack...for the first part but I will go farther...
Agree, at a minimum you need to change gears and retune the carb...I bet that thing comes to life...however, I would go with a 3:73 in anticipation of the next step...
Going farther, (and I have often beed accused of trying to spend people's money), once you get the gearing and carb sorted, take your EFI money and buy the TKO600 5 speed...the TKO600 combined with a 3:73 or 4:11 will make that 454 and your car so much more enjoyable...
In post #9 rahaul states that he has a 6 speed, which I assumed was a T56............double overdrive. The reason I recommended a 3.55 was because later model Corvettes with 6 speed trans use a 3.41 axle and 3.55 is closest to that. The 3.55 will give him a good cruise speed where he can shift into top gear at a reasonable speed and excellent fuel economy.
Another reason I suggest the 3.55 and not a 3.73 is because rahaul made it clear early on that he wants high fuel economy.
Your cam knowledge is impressive. You are correct. It is a roller and idle vacuum is very close to what you said. Funny you mention changing ratios (I'm sure you meant 3.55s). That is what I had until a bearing went south right before a long trip we had planned so I just threw the 3:08s in since I knew they were good. Was also a good time to inspect all U joints since I was at the 100K mile point on those. One out of 6 was "barely bad". Only have app. 35K miles since then and there is no slop. I agree. I need the 3:55s back in. Too much to do. Not enough time.
Since you have hit the numbers on the cam, what kind of numbers do you predict I can get with fuel mileage out of the Carter? When I had this cam built, I made it real clear to Chris Straub of Straub Technologies that MPG was priority #1. Horsepower #2.
That's harder for me to estimate. Based on the fact that the Quadrajunk produced a consistent 24-25 MPG with the 6 speed and the 3:08s, and assuming that you were somehow cruising in top gear, I see no reason that if the Carter is properly set up wouldn't deliver the same. If you put the 3.55s back in you'll give up a couple but the car will be much more fun to drive and you won't be lugging and damaging your engine while cruising.
I don't like the clunk you get in your driveline. You should look into it further.
That's harder for me to estimate. Based on the fact that the Quadrajunk produced a consistent 24-25 MPG with the 6 speed and the 3:08s, and assuming that you were somehow cruising in top gear, I see no reason that if the Carter is properly set up wouldn't deliver the same. If you put the 3.55s back in you'll give up a couple but the car will be much more fun to drive and you won't be lugging and damaging your engine while cruising.
I don't like the clunk you get in your driveline. You should look into it further.
The clunk or slam only occurs when the idle speed is too high or ignition timing too much advance. Idle has been all over the place only recently and that is the only time that it occurs. The 3.55s were giving me very close to the same MPG as the 3:08 so changing back is not a problem. As far as lugging the engine, that's what is rather amazing with this cam. I can shift into 6th at 40 MPH/ 800 RPM (not something I normally do) and throttle up w/o any hesitation or any lugging. Another 800 RPMs and I'm at 80. Oil pressure never goes below 35 lbs.
The clunk or slam only occurs when the idle speed is too high or ignition timing too much advance. Idle has been all over the place only recently and that is the only time that it occurs. The 3.55s were giving me very close to the same MPG as the 3:08 so changing back is not a problem. As far as lugging the engine, that's what is rather amazing with this cam. I can shift into 6th at 40 MPH/ 800 RPM (not something I normally do) and throttle up w/o any hesitation or any lugging. Another 800 RPMs and I'm at 80. Oil pressure never goes below 35 lbs.
If you had a vacuum gauge in the car you'd see that every time you do that, vacuum will drop and very likely the power enrichment diaphragm is moving the stepped rods inside the orifices, enriching your fuel mixture just like a power valve does in a Holley.
Likely the reason the Carter gets poor economy is because the power enrichment is set to come in quicker that that of the Quadrajunk. If you change to 3.55s, I'll bet that the mileage increases because you'll be "out of" the power enrichment zone.
I have a vacuum gauge in my car. My Holley's power valve begins to open at 4.5 in-hg. I keep an eye on the vacuum, and whenever the gauge starts to dip close to 5 in-hg, I downshift. That's one good reason I get mid twenties MPG with a 750 CFM race Holley carb with no choke horn feeding a 480 horsepower 327.
The carb MUST be tuned/setup properly to match your engine and driving style. I'm not an Edelbrock expert but I'm sure that plenty of great instructions can be found online or lots of people here can help you with that.
Last edited by 65tripleblack; 09-05-2017 at 09:54 AM.
If you had a vacuum gauge in the car you'd see that every time you do that, vacuum will drop and very likely the power enrichment diaphragm is moving the stepped rods inside the orifices, enriching your fuel mixture just like a power valve does in a Holley.
Likely the reason the Carter gets poor economy is because the power enrichment is set to come in quicker that that of the Quadrajunk. If you change to 3.55s, I'll bet that the mileage increases because you'll be "out of" the power enrichment zone.
I have a vacuum gauge in my car. My Holley's power valve begins to open at 4.5 in-hg. I keep an eye on the vacuum, and whenever the gauge starts to dip close to 5 in-hg, I downshift. That's one good reason I get mid twenties MPG with a 750 CFM race Holley carb with no choke horn feeding a 480 horsepower 327.
The carb MUST be tuned/setup properly to match your engine and driving style. I'm not an Edelbrock expert but I'm sure that plenty of great instructions can be found online or lots of people here can help you with that.
Appreciate the help here. I will say that is impressive mileage for a Holley especially on your engine. Makes sense what you are saying using a vacuum gauge. I'm using an air/ fuel ratio gauge. Last light goes out at 16:1 and that's where it always is except at idle. I normally just stay in the tallest gear and shift down when it goes richer than 16:1.
Appreciate the help here. I will say that is impressive mileage for a Holley especially on your engine. Makes sense what you are saying using a vacuum gauge. I'm using an air/ fuel ratio gauge. Last light goes out at 16:1 and that's where it always is except at idle. I normally just stay in the tallest gear and shift down when it goes richer than 16:1.
street demon 650 cfm.......they also make a 750 cfm, i have a 383 sbc
in my 37 ford and when i went to the street demon 650 it never ever ran like that before......turbo 350 trans, now it burns rubber in all three gears
while in the drive mode........and very smooth idle and transition to normal cruising.......5 stars from me.....Bill..
First I want to thank all those who chimed in on my impossible vacuum leak problem and wanted to explain if anyone is interested. To start with I was dealing with multiple issues which is never good - HEI bad modules (more than one), intake gasket vacuum leak but only from the lifter galley, carburetor issues. After a solid year of trying everything I could think of including swapping out 3 HEIs and 4 different carbs in various combinations, I had reached the end of my rope. I can now teach a course on the number of different possibilities for erratic idle.
With all that said and after spending over $700, I still do not have a carb that I am happy with. My friend Matt who helped me find all my issues has been telling me I may want to look into EFI. I know they are 1K and up but I'm also looking at what I've already spent and I'm still not happy. I read an article that said the most common problem with the EFI systems is wiring, either poor positive or poor ground or both. I would welcome any recommendations and anyone's 1st hand experience with a newer EFI system. I read that they have come a long way since introduced years ago.
Thanks, Vic in Arkansas
I put FITech efi on my ZZ383 in my 66 convert and I love it! I did it myself and I went with the in tank fuel pump solution. That solves all of the problems people had with EFI surge tank in the engine compartment. Very good instructions included. Installing the unit is easy, setup is easy and then it learns and keeps improving as you drive. The modifications to the fuel tank I did could have been avoided by buying an efi ready tank from Tanks,Inc. Must use the right fuel gauge sender for Corvettes. No need for a long return line if you get the combo pressure regulator and fuel pump. You mount this at the fuel tank and your return line is 18 to 24" long. All of the work is done with common tools and some mechanical skill.
Bottom line: quick starts, equal or better torque & horsepower, better fuel mileage, NO fuel smell in the garage and great throttle response. No problems with it so far and I have been running it since late Jan 2017.
I installed a Sniper on my 65 327 a few weeks ago and so far am very pleased with it. The most difficult part for me was installing the gas tank while correctly bending the new straps. Otherwise a pretty simple installation. Here's a pic of it before I installed the throttle linkage.
I'm in the process of installing Holley Sniper EFI. Fairly simple - lots of wires but good instructions -- just make sure all wiring is NEW to avoid problems - don't tap into old wiring. I rewired/replace all relays, sensors and wiring for cooling fans. ECU can control 2 fans at different temps.
I'm also changing lots of other stuff and already had gas tank with pump inside and O2 sensor bung. If you were just changing to EFI I think you could do it over the week end assume you didn't have to go the FLAPS for stuff.
I would rule out upper intake / carb gasket vacuum leak than replace the intake gasket.
Thanks, I am guessing its a vacuum leak, when I try to smother the carb it will not cut out keeps running so it's getting air from somewhere
What else can cause such horrible gas mileage?
09-02-2017, 08:49 AM
