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Just Some Dude in Jersey
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I had a high comp '70 engine that was worn, but okay compression-wise, and all I could afford at the time was a big valve head. It made a HUGE difference. A year or two later I put a block with 2.0 pistons under it and it only made a little bit of difference. In one respect, it's all about getting air into the engine, which a big valve head will do. Side drafts are racing carburetors. Yeah, a few cars came with side drafts from the factory, but mainly go fast guys go for them. They are generally not made for daily driving, although if tuned down for local speeds and economy they aren't too bad. Generally they throw gas and air at the engine and you accelerate very quickly at low rpms. Just driving around town, this can get annoying. Racers like to run at 5000rpm+ and side draft carbs are best at that and most people who put them on don't give a fig about fuel economy.

I disagree with post #13 assertion that the engine is the most important thing. That's the way young guys and motorheads think. The only reason to buy a GT is because of the body, therefore, the body is the most important thing. You can put a V8 in a GT or any other car with a crappy body and all you have is a fast piece of crapp. But, you can have a really nice looking GT and nobody will give a fig about how fast it goes. Engines can always be acquired, but good bodies that you're not ashamed to drive are as rare as hen's teeth. Send OGTS $2500 and you've got yourself a big valve 2.0 that is perfectly capable of getting off the line faster than most cars on the road and with a humble 32/36 you could floor it all day and still get 25mpg.

Yeah, Holley Sniper FI "carbs" are the current hot item amongst us at the moment, but they have their drawbacks. The air cleaner situation can be a problem with our low hoods. They are in a downdraft configuration using the oem manifold, which HAS to be less efficient and more restrictive than an FI system that's configured more like a side draft. The oem manifolds are vacuum leak-prone, the single and dual side draft manifolds are less so. As far as whether a Sniper or some other carb-look-alike system is faster, yes, no one has compared them on the exact same engine. Remember that for the first 20 or so years of fuel injection, carbs were faster that FI. The FI systems weren't very tunable for power. They only cared about 2 things: Low emissions and fuel economy. That's still primarily how passenger car FI systems are designed. Muscle and performance cars, plus some normal vehicles, now give you various options for "Sport-mode-like" performance. push a button on your dash and some cars will change their engine behavior to favor power. Holley Snipers were not designed for power, they were made to fit carb manifolds as a way to adapt older cars to run FI and to self-tune themselves to start and run well and efficiently. Can they be tweaked to favor power? I'm sure they can, but no one has given us the results of such a comparison test.

Just some thoughts.....
 

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I disagree with post #13 assertion that the engine is the most important thing. That's the way young guys and motorheads think. The only reason to buy a GT is because of the body, therefore, the body is the most important thing. You can put a V8 in a GT or any other car with a crappy body and all you have is a fast piece of crapp. But, you can have a really nice looking GT and nobody will give a fig about how fast it goes
THAT'S RIGHT tell em Gordon LOL
 

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Pedal Smasher
1973 Opel GT
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2,889 Posts
I disagree with post #13 assertion that the engine is the most important thing. That's the way young guys and motorheads think.
Did I say that the engine is the most important thing? No. I said...
If you want to restore a GT, wise advice I keep finding is to do all the mechanical improvements first. Then worry about all the pretty stuff.
The reason being, if you focus on making the car all pretty first, there is a good chance you will damage the paint when doing all the mechanical improvements later. So, it’s a good idea to sort out engine and chassis upgrades first. That is very different from saying the engine is the most important thing. I even started out my post by questioning the importance of doing power adders on a tired engine and finished that post by saying he could focus on handling instead.

Also, there is something to be said about pulling the engine out once, worry about everything you want to do to it all at one time, then put it back in. You can avoid a lot of headaches that can come up when you incrementally try to improve an engine, and have to troubleshoot various issues that likely won't be there on a freshly rebuilt engine. For example, having problems with idle because there is a vacuum leak somewhere and it's hard as hell to work on the engine inside the GT's anorexic engine bay. Pulling a carb off the engine in the car is a lot harder than removing it on an engine run stand that cost a few hundred bucks to make. I'm a fan of getting it all done at the same time and if the car was driven prior to all that work, then it will be very obvious how much different all the improvements made on the vehicle. 5% increments over time have less of a noticeable impact than a 30% improvement from your last experience. Doesn't make the engine the most important thing, but not everyone wants to endlessly chase issues as you improve an engine.
 

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Opeler
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135 Posts
Gordo's comments about airflow are super valid. I have seen so many cases of folks with various facets of the car hobby that spent a ton of time and money on the bottom end of an engine and then run out of money or didn't focus enough on the cylinder heads and with V8s making sure the cam/head/intake combo works well as a combination. I sadly have laughed when I see folks spend a ton of money building a small block chevy or ford V8 with forged crank/rods/pistons and an aftermarket block only to bolt on a set of box stock aluminum heads and then realize the money the spent on the high horsepower reliability of forged internals and aftermarket block are wasted because the engine will never reach those power levels due to top end restriction.
 
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I added a 75 Fuel injection to the engine, (discussed in My first Manta build), and was extremely disappointed in the throttle response trying to autocross that particular car. Should have stayed with the 32/36 carb.
 

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Opeler
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I had a high comp '70 engine that was worn, but okay compression-wise, and all I could afford at the time was a big valve head. It made a HUGE difference. A year or two later I put a block with 2.0 pistons under it and it only made a little bit of difference. In one respect, it's all about getting air into the engine, which a big valve head will do. Side drafts are racing carburetors. Yeah, a few cars came with side drafts from the factory, but mainly go fast guys go for them. They are generally not made for daily driving, although if tuned down for local speeds and economy they aren't too bad. Generally they throw gas and air at the engine and you accelerate very quickly at low rpms. Just driving around town, this can get annoying. Racers like to run at 5000rpm+ and side draft carbs are best at that and most people who put them on don't give a fig about fuel economy.

I disagree with post #13 assertion that the engine is the most important thing. That's the way young guys and motorheads think. The only reason to buy a GT is because of the body, therefore, the body is the most important thing. You can put a V8 in a GT or any other car with a crappy body and all you have is a fast piece of crapp. But, you can have a really nice looking GT and nobody will give a fig about how fast it goes. Engines can always be acquired, but good bodies that you're not ashamed to drive are as rare as hen's teeth. Send OGTS $2500 and you've got yourself a big valve 2.0 that is perfectly capable of getting off the line faster than most cars on the road and with a humble 32/36 you could floor it all day and still get 25mpg.

Yeah, Holley Sniper FI "carbs" are the current hot item amongst us at the moment, but they have their drawbacks. The air cleaner situation can be a problem with our low hoods. They are in a downdraft configuration using the oem manifold, which HAS to be less efficient and more restrictive than an FI system that's configured more like a side draft. The oem manifolds are vacuum leak-prone, the single and dual side draft manifolds are less so. As far as whether a Sniper or some other carb-look-alike system is faster, yes, no one has compared them on the exact same engine. Remember that for the first 20 or so years of fuel injection, carbs were faster that FI. The FI systems weren't very tunable for power. They only cared about 2 things: Low emissions and fuel economy. That's still primarily how passenger car FI systems are designed. Muscle and performance cars, plus some normal vehicles, now give you various options for "Sport-mode-like" performance. push a button on your dash and some cars will change their engine behavior to favor power. Holley Snipers were not designed for power, they were made to fit carb manifolds as a way to adapt older cars to run FI and to self-tune themselves to start and run well and efficiently. Can they be tweaked to favor power? I'm sure they can, but no one has given us the results of such a comparison test.

Just some thoughts.....
I have a Holley Sniper on my 2.2 in my GT. I can attest, out of the box tuning is a baseline setting which is just geared to learn your engine. You need at drive 250-500 miles to allow it to learn your motor and needs. Then you can start tuning. At the beginning, I felt I didn’t have much off idle oomf, but once at a higher RPM the car would take off when given gas. I contacted the place I bought it from EFI Systems Pro and sent them my data logs from various conditions (idling, off idle gas, cruising, etc). They made changes and the car ran like a completely different version. It had way more get-up-and-go from the jump, and we have continually tuned it, based on my feedback and the data logs.
This EFI is not the old 1975 EFI, nor is it direct port injection, but it offers tremendous ability to tune it to your motor and driving habits or desires.
Eric
 

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Opeler
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681 Posts
So my experience with the Holley Sniper has been hit and miss. I have it bolted up to a highly modified intake manifold using all of RB's tricks. The engine is my 2.6L build which has run fantastic all season. Initial setup was perfect and she started and ran pretty good right from the start. The idle has been the biggest PITA for me though as it seems to change all the time and when coming off throttle say at a stop sign or light it will want to die. Reading the Holley forums this seems to be a VERY common problem. I've tried to tune this better but haven't had much luck.

Mike
 

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The Young One
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Discussion Starter · #28 ·
Thanks for all the help everybody. I didn’t respond yesterday because I felt really bad and stayed home from school. But Today I am felling much better and will hopefully go back to school tomorrow. It kind of sucks having to stay home from school my my birthday which is today. I turned 15 So I should be hopefully getting my permit this summer and my license next year!
 

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Thanks for all the help everybody. I didn’t respond yesterday because I felt really bad and stayed home from school. But Today I am felling much better and will hopefully go back to school tomorrow. It kind of sucks having to stay home from school my my birthday which is today. I turned 15 So I should be hopefully getting my permit this summer and my license next year!
My youngest (the tinkerer) just got his license today almost a yr to date of when he got his L.P.
Guess who isn't home right now including the Dakota LOL
 

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Opeler
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1,332 Posts
So my experience with the Holley Sniper has been hit and miss. I have it bolted up to a highly modified intake manifold using all of RB's tricks. The engine is my 2.6L build which has run fantastic all season. Initial setup was perfect and she started and ran pretty good right from the start. The idle has been the biggest PITA for me though as it seems to change all the time and when coming off throttle say at a stop sign or light it will want to die. Reading the Holley forums this seems to be a VERY common problem. I've tried to tune this better but haven't had much luck.

Mike
I have talked with the techs about this and from what I have been told from what some have experienced it seems like this can be closely related to an issue with the wiring and electrical interference from the car wiring and the unit. They said most idle issues are due to this, and it becomes more evident once the fuel tuning has been fine tuned and dialed in…then it exposes the electrical interference, which can be “covered up” by improper tuning.
Hope this helps.
Eric
 

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I would be using the stock cam. I won’t port the or mill the head. Do you have like a rough number like around 120hp or would it be less than that.
I used Rally Bob's recipe for SBC valves and a mid range hydraulic lift cam on a 1.9 bore to 2.0 with OGTS hi comp pistons, a 38 Weber, a Rally Bob modified intake, header and Getrag 5 speed and it makes for excellent performance. Don't know why you wouldn't upgrade the cam if you are doing larger valves. Let that engine breathe.
 

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boomerang opeler
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The number 1 best change to driving fast, Brakes.
 

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Can Opeler
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The number 1 best change to driving fast, Brakes.
Stock brakes with DOT 5.1 fluid are more than enough for 105HP on the racetrack and probably double that in the street. No need to spend money on the most over designed part of the GT.

I did catch my rear brakes on fire once on the track but that was because my emergency brake wasn’t completely released lol.
 
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Opeler
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Well not
Stock brakes with DOT 5.1 fluid are more than enough for 105HP on the racetrack and probably double that in the street. No need to spend money on the most over designed part of the GT.

I did catch my rear brakes on fire once on the track but that was because my emergency brake wasn’t completely released lol.
well not on the race track but fine for street if in good shape. Think theres a lot to do on this car before he needs to worry about better brakes
 

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Opeler
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681 Posts
I have talked with the techs about this and from what I have been told from what some have experienced it seems like this can be closely related to an issue with the wiring and electrical interference from the car wiring and the unit. They said most idle issues are due to this, and it becomes more evident once the fuel tuning has been fine tuned and dialed in…then it exposes the electrical interference, which can be “covered up” by improper tuning.
Hope this helps.
Eric
I've read those threads as well plus many others who have similar problems and there doesn't seem to be a one shot clean answer. Trust me my wiring is by the book and I even took extra measures to assure solid voltage supply to the unit. Holley Sniper seems to be much more finicky than it should be and they make a lot of excuses online to cover the design deficiencies. I have the laptop dongle and have been playing with programming but not much success on the idle issue. I'll make a change and it seems to work fine for a while then change again. I've read that Holley used under quality sensors on the unit and many have had to replace sensors. Perhaps that is one of the factors I'm chasing.
 
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