CK5
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My old man hotrod/dd
- Thread starter 80' 427
- Start date
So where were we? Oh yes we had just modified the carb and were awaiting the mpg numbers. So it looks like the gain is a solid 1.25 mpg to 14.7 Still at high vac crusing was surging. I let thinking lean but under power it ran hard and it wasn't getting hot. I talked with my machinest who has a lot of experience with these 2bbls because of Imca hobby stock class. He suggested it could be the power valve fluttering open and closed. Sure enough the surge is right at 16-14 in any speed (which happens to be right were it likes to cruise). Clipped another coil of the spring hoping to sneek up up on 8-9 inhg. This could make a big difference in the mpg and I may even go back to 49 jets because this maybe what I thought was a lean surge.
Other things. The carb is definitely too small because at wot the vac gauge goes right too 3inhg and then just makes noise with no more power.
I was getting a slight rattle at different spots in the acceleration. I reevaluated my homemade curve kit made with what springs I had left over from curve kits I have installed. The advance was a 12 degrees intial 38 intial+mech and 14 vac so 52 total. Problem was it was coming in at 2200. Pretty early. I tried a again and still get 38 but now all in by 2800. Not awesome (hoped for 2500). Still no rattles now.
Other things. The carb is definitely too small because at wot the vac gauge goes right too 3inhg and then just makes noise with no more power.
I was getting a slight rattle at different spots in the acceleration. I reevaluated my homemade curve kit made with what springs I had left over from curve kits I have installed. The advance was a 12 degrees intial 38 intial+mech and 14 vac so 52 total. Problem was it was coming in at 2200. Pretty early. I tried a again and still get 38 but now all in by 2800. Not awesome (hoped for 2500). Still no rattles now.
^^^haha right? But I still read it.
All I really got out of it was, more fuel is need to produce a burnout.
I am not that smart, I promise. I spent over an hour this evening trying to figure out the ladder bar geometry for the radio flyer suspension i am building for my daughter's gasser wagon. Now I have to form then quench and temper my own leaf springs for the front.
See, you said it again. Geometry....gross.
And I used trig to figure out the geometry and if there was a curve maybe I could have used calc but who really wants to work that hard on a wagon. I mean figuring out the caster, camber and Ackerman angle was enough.
So, where were we? I yes tuning the car for mpg. So I had just finished the carb mods and was playing with timing. It had this lean surge I couldn't figure out. I thought maybe the power piston was opening a closing so I clipped another coil and it may have been opening a little because it was MUCH WORSE. I finally quit being lazy and installed my wide band. Ya the lean surge was the carb dipping into the 20s in A/F. So I installed my biggest jet and it was better but still WAY lean. Finally I drilled out my 49 to a 55 and now it dips into the 18s under low load crusing. Runs much better but the mpg was no difference. I was racking my brain about why and finally it occured to me that I had retarded the timing. I again bumped up the timing to 52 at crusing the mpg came up to 14.8-15s but it was still pinging on hills. First thing I did was after reading Doug Roes book I found that the thermac keeps the inlet air coming off the exhaust until the inlet temp is at least 126 degrees. Though Marty hates them I tried a open element aircleaner. The pinging was greatly reduced and the crusing vac was much higher. The mpg came up a bit but the pinging was still there at times. I first ran some water through it while it was running, then the next week some sea foam. I also cut the outside of a aircleaner top and put in a tall 80s 305 air cleaner so I could keep all the pvc stuff in place. The best mpg so far is 15.28, still not great but better than 13.5 it was getting.
So on the my winter plans.
For the 350 I have decided to install a performer I got for free, headers, summit 2 1/2 duals and a cam. I wasn't going to do a cam but well, I am crazy. My buddy ordered a 214/224 cam for his crawler engine build and decided to build it more radical for a hot rod instead, so I am getting it for a case of beer.
I think I found a WS6 front sway bar if someone would ever tell me what it costs. My bestest good friend Greg gave me a blazer rear axle so I can steal the rear disks off of and possibly figure out a way to use the sway bar it came with too. I am going to have to buy new rotors and backing plates but the rear disks should help braking as well as a poor mans axle retainer.
On the front Red found me a set of from 12" B body from rotors and spindles so it will have big (for me) brakes all the way around.
I pulled my posi out of my old camaro axle and disassembled it and found the clutches were pretty worn. Replacments were discontinued long ago from GM and aftermarket ones are $200. Luckly I found some nice used one on ebay for $90. I looked at the 3.23s marty gave me and though a little rusty they look good and should be a nice little addition to help it accelerate without killing the mpg.
Finally the Carburetor. I had planned on a Q jet since the beginning. I guess I am learning quite a bit about them along the way.
First there are many variations and the post 1975 have some benefits and some draw backs. The benefit is they have a top adjustable part throttle or (APT). You remove a plug and you can raise or lower the stop on the primary rods and allowing you to lean or richen the cruise. The early ones had this same thing but it is in the base plate behind a steel plug that is hard to reach.
The draw backs. Well as you know about 1975 catalitic converters were being installed. Cats DO NOT like hot lean exhaust or rich exhaust. So because of this lots of modifications were done to keep the a/f near stoch. So for example on the 77 model I am working on it has huge .125 air bleeds.
So about the carbs I have. Local machinests are some of my best friends. They buy engines by the truck load as cores for the local dirt track racing. They had 15+ cores that were laying on the shelf so they made me a deal on 4 of them for $50. So far I have a 77 and 78 chevy 750 and a 77 olds carb. I still have yet to pick up the last carb. The 1975 models share lots of the same parts with the 1976 but some have an adjustable anaroid that works poorly so they are best avoided.
So on the my winter plans.
For the 350 I have decided to install a performer I got for free, headers, summit 2 1/2 duals and a cam. I wasn't going to do a cam but well, I am crazy. My buddy ordered a 214/224 cam for his crawler engine build and decided to build it more radical for a hot rod instead, so I am getting it for a case of beer.
I think I found a WS6 front sway bar if someone would ever tell me what it costs. My bestest good friend Greg gave me a blazer rear axle so I can steal the rear disks off of and possibly figure out a way to use the sway bar it came with too. I am going to have to buy new rotors and backing plates but the rear disks should help braking as well as a poor mans axle retainer.
On the front Red found me a set of from 12" B body from rotors and spindles so it will have big (for me) brakes all the way around.
I pulled my posi out of my old camaro axle and disassembled it and found the clutches were pretty worn. Replacments were discontinued long ago from GM and aftermarket ones are $200. Luckly I found some nice used one on ebay for $90. I looked at the 3.23s marty gave me and though a little rusty they look good and should be a nice little addition to help it accelerate without killing the mpg.
Finally the Carburetor. I had planned on a Q jet since the beginning. I guess I am learning quite a bit about them along the way.
First there are many variations and the post 1975 have some benefits and some draw backs. The benefit is they have a top adjustable part throttle or (APT). You remove a plug and you can raise or lower the stop on the primary rods and allowing you to lean or richen the cruise. The early ones had this same thing but it is in the base plate behind a steel plug that is hard to reach.
The draw backs. Well as you know about 1975 catalitic converters were being installed. Cats DO NOT like hot lean exhaust or rich exhaust. So because of this lots of modifications were done to keep the a/f near stoch. So for example on the 77 model I am working on it has huge .125 air bleeds.
So about the carbs I have. Local machinests are some of my best friends. They buy engines by the truck load as cores for the local dirt track racing. They had 15+ cores that were laying on the shelf so they made me a deal on 4 of them for $50. So far I have a 77 and 78 chevy 750 and a 77 olds carb. I still have yet to pick up the last carb. The 1975 models share lots of the same parts with the 1976 but some have an adjustable anaroid that works poorly so they are best avoided.
Finally about 1979 most carbs went to what is called the single air bleed. This causes not only the cruise to be rich but also uses bigger power tips on the rods so it can't get into richers power mixtures typically used under power. All of these carbs can be corrected to allow not only a nice lean mixture at cruise but proper mixture under power.
I have also learned that one of my favorite books is actually wrong in suggesting that the idle tube should be enlarged as the engine becomes more radical. This is actually bad advice. Because the rochester quadrajet idle never stops like a holley does it becomes additional and causes this great economy carb to be fat at cruise. There are also quite a few wild mods I am considering that hopefully I will document but I will provide some links incase I don't.
http://racingfuelsystems.myfunforum.org/viewtopic.php?f=26&t=430
http://racingfuelsystems.myfunforum.org/viewtopic.php?f=26&t=498
That forum has lots of great info if you have time.
I have also learned that one of my favorite books is actually wrong in suggesting that the idle tube should be enlarged as the engine becomes more radical. This is actually bad advice. Because the rochester quadrajet idle never stops like a holley does it becomes additional and causes this great economy carb to be fat at cruise. There are also quite a few wild mods I am considering that hopefully I will document but I will provide some links incase I don't.
http://racingfuelsystems.myfunforum.org/viewtopic.php?f=26&t=430
http://racingfuelsystems.myfunforum.org/viewtopic.php?f=26&t=498
That forum has lots of great info if you have time.
Pics?
Martin
Martin
Looking forward to your Q-jet build up, still a great carb with many attractive features. If you want some 12 inch rotors for those tall B body spindles, get a set of 1990 Camaro 1LE rotors. They bolt right on the spindle, accept the B caliper and have the 4-3/4 bolt pattern your car has now. Difference is the Camaro rotor has metric wheel studs
I personnaly think they are the best "all around" carb. I think edelbrokes are garbage and though I love holleys they aren't always the best application for a streeter. The disadvanges of these carbs are because of emissions not because of poor design. I hope to get as much hp and I would normally get with better mpg because of the super efficient primary system.
I need to find out if the b body disks are drilled for 4 3/4 or I had already planned on 1LE disks to keep my pattern. Problem is they are the spensive.
I need to find out if the b body disks are drilled for 4 3/4 or I had already planned on 1LE disks to keep my pattern. Problem is they are the spensive.
I know a fella with a set of gently used 1LE rotors should you require some
Turn all the letters out.
Looks so good.
Looks so good.
Bump.
Martin
Martin
Letters in...I've been hating on white letters for decades. Do you have a NASCAR sponsorship agreement? If not, why are you running advertising on your tires? Fuvk em, I bought them, I own them, they should have my name on them, not their name...
Clearly I'm in the minority here, but that's my thinking. I don't have any dealer 'tags' on my 2015 GMC for the same reason. When I took delivery they were applying all the stupid window decals etc, and I made a stink. Told them they can remove all of that crap, or we can go back inside a negotiate how much they're willing to pay me to advertise on my truck.
Clearly I'm in the minority here, but that's my thinking. I don't have any dealer 'tags' on my 2015 GMC for the same reason. When I took delivery they were applying all the stupid window decals etc, and I made a stink. Told them they can remove all of that crap, or we can go back inside a negotiate how much they're willing to pay me to advertise on my truck.
I'm with you on both counts, letters in and I remove all dealer tags. I always tell my wife, "I'm not paying them $xxx a month to give them free advertising"
