Junkyard 360 performance build questions

[rumpfox]

most after market cams are ground on chevy blanks. smaller than chy. blanks. so you have to run longer pushrods which changes the hole lift, centerline mojoe of things.plus the blanks were softer steel and the lifter load was greater which screwed them up faster

 

[Bart]

OK folks, I rebuilt the engine a few months ago. I have around 2500 miles on it, with no problems. I ended up with about 8.8:1 compression, and went with the Performer intake. It has 2.25 dual exhaust with H pipe, and a higher stall converter. I re-curved the distributor (single points) to 11 degrees at the cam, or 22 at the crank. I have tuned it about as far as it will go. It runs with no ping at 28 all-in on 87 octane, where I am getting really close to 95mph in the 1/4 mile. It takes off very well with no hesitation anywhere. I can turn it up to 32 degrees, and it REALLY takes off there, but it pings on low grade gas. My new challenge is that it will not run over 4000 rpm. I just replaced the distributor tonight (reman single point), as I was having trouble keeping a steady time with the old one. It cleared up the variance in timing, with no change to max rpm. I want to slowly but surely upgrade so I can run up to 5200-5500 if I want to. Should I be looking at a performance coil and bigger wires, with or without a Pertronix conversion, or do you think I am starving for fuel, and need to move up into the 650cfm-700cfm range? It runs smoothly all the way up, by the way. No hesitation, no stumbling, and I am well over 100 mph on the speedometer.

 

[The Horvaths]

OK folks, I rebuilt the engine a few months ago. I have around 2500 miles on it, with no problems. I ended up with about 8.8:1 compression, and went with the Performer intake. It has 2.25 dual exhaust with H pipe, and a higher stall converter. I re-curved the distributor (single points) to 11 degrees at the cam, or 22 at the crank. I have tuned it about as far as it will go. It runs with no ping at 28 all-in on 87 octane, where I am getting really close to 95mph in the 1/4 mile. It takes off very well with no hesitation anywhere. I can turn it up to 32 degrees, and it REALLY takes off there, but it pings on low grade gas. My new challenge is that it will not run over 4000 rpm. I just replaced the distributor tonight (reman single point), as I was having trouble keeping a steady time with the old one. It cleared up the variance in timing, with no change to max rpm. I want to slowly but surely upgrade so I can run up to 5200-5500 if I want to. Should I be looking at a performance coil and bigger wires, with or without a Pertronix conversion, or do you think I am starving for fuel, and need to move up into the 650cfm-700cfm range? It runs smoothly all the way up, by the way. No hesitation, no stumbling, and I am well over 100 mph on the speedometer.

First thing I would do is check your condensor. Has it been replaced? Then check your plugs and wires for any obvious damage. If none of that pans out, check your engine for a vacuum leak causing a lean condition. If all else fails, double check your cam timing.

 

[Bart]

You know, now that you bring vacuum up, the idle mixture adjustment screw gasket is fairly loose on my Holley. I found it on the manifold the other day, and just pushed it back in. It was moist. I will order a couple of cork ones to see if it helps. Thanks!

 

[moper]

:laughing4::laughing4::laughing4::laughing4::laughing4::laughing4:

Priceless. Who has not done that.:busted:

From about age 19 to 22 one of the many nicknames I was assigned was "King 180". It was earned by having the carb blast remove most of the hair on my left arm trying to start an engine I put a cam in. Lucky for me the Twister pose I was in trying to jump the ballast with my right hand, and turn the distributer with my left, kept my face away from the blast zone. It was one of the reasons I started only doing first starts without friends around. It's not that I stopped doing stupid things, but I removed the creative witnesses...

 

[moper]

In regard to the rpm issue - if it did it, then the distributor was replaced, and it still did it, logic dictates the dist. was not contributing to the issue. However - do you own a dwell meter? Setting points by gap is really not the best way to see what the points are doing. You should use a dwell meter, and I would adjust the points to give you 28° of dwell, and test the coil and condenser for resistance. Single points should be good up to 6K give or take, if they are set up right. I'm also curious about your timing curve. It seems odd that it would ping that bad anywhere near 32°.. It should take 38-42, then be good with the vacuum advance hooked up. When you say "11 degrees at the cam", what do you mean by that exactly? Also - what carb exactly do you have?

 

[Bart]

I welded the slots in the distributor plate (that control the distance the weights can travel), then filed them out so it limited the travel to 11 degrees advance at the cam, which is 22 degrees at the crank. That normally allows me to set my initial timing around 12-15 degrees at the crank, plus the additional 22 from the mechanical advance from the distributor, giving me the ideal 32-36 degree window for total timing on a mild performance engine. I am using a brand new 4160 Holley 600cfm with electric choke. No modifications or jet changes to it at this point. I have not checked the dwell, yet, because my meter is on loan to a friend, but I did set the points at .017... Your dwell recommendation of 28 is lower than what I am used to doing in the 32-34 range. Am I missing something (always up for learning something!)? BTW, the condenser and coil are new, and I did try a different, working coil just to check, although I did not check resistance on either... I am chalking the ping at lower timing up to the suspected vacuum leak at this point, but open to suggestions!

 

[moper]

Ok. You may try running a vacuum gage taped to the windshield and plumbed to a manifold vacuum port. See what you're pulling for vacuum at idle, light throttle cruise, and light acceleration. Then use that info to match the power valve properly. My impression is you have a much higher vacuum signal which is not working well with the as-supplied 6.5" valve in the carb. It makes things lean, which can make it ping. Once ping starts it will not stop until the conditions that made it start are removed (aka letting off the throttle). Dwell is the time in degrees allowed for the coil primaries to saturate. The more they saturate the higher the output of the secondary will be (the actual spark event). That's one of the reasons I said check the resistance in the coil. It could still be good, as in not shorted, but not performing well. Reducing dwell will give any coil more time to saturate, resulting in a hotter spark.

 

[70bigblockdodge]

Make sure wires are tight on points/condenser, also make sure the condenser is tight mounted/grounded as well. Double check these, sounds like you did not have this problem originally?

 

[Bart]

Sorry for the late reply... I recently installed a tachometer. It has always been stopping right in that RPM range. I replaced the idle mixture screw gasket, and got up to 4500 cleanly. I am still concentrating on the potential vacuum leak. I took the Fury into my buddy's shop last Friday for body work and paint (I am doing a work trade- he is doing the body, I am rebuilding/modding a 225 slant 6 he has in a 1972 Valiant), so I can't get it on the road to test right now. I was there last night, and put a heavy spring back in the distributor ( I was running 2 light springs), and installed a phenolic spacer under the carb. I could see I had a leaking gasket when I removed the carburetor. It seems to run really well in the garage. If that does not fix it, I will start messing with the dwell meter, carburetor, and probably even the dash pot on the distributor, next! Thanks for the advice, I will let you know what happens. The car should be at least in full primer by mid-March, so I will take her for a fun run then.

 

[Bart]

I was able to drive it yesterday, when we pulled it out of the shop to turn it around. I still have the ping, although it is reduced a little. I checked the ohms on the coil- 1.7 and 9,750. My multimeter does not have enough decimals on it, but the condenser is less than 1... I will put a different one on just to see. Next week, I will try to check dwell and vacuum. I will post results!

 

[Bart]

I cannot drive the vehicle, yet, so I can't confirm that this fully took care of my problems, but I replaced the condenser, just to be sure. I also checked the dwell angle. I was hovering around 23 degrees. I always set my points at .017... I must not have been on the peak of the cam, because it was around .021. I reset to .017, and dwell changed to around 29. I am betting this cures all the problems. Thanks for talking me through it, guys. I will let you know in a week or two how she performs now.

 

[Bart]

Ok, for those of you still following; I am moving next month back to MT. I drove the 71 1000 miles and dropped it off in Helena. On the way, I had opportunity to really listen to the motor at sustained higher RPM. My problem is valve springs! I noticed it started missing just a little above 3000, and was stumbling enough to 4000 to keep it from going any faster. Anyway, the heads I used were ones I had laying around. I had them rebuilt 10 years ago, and did a minor port and polish about 3 years ago. I thought they had performance springs in them, but I'm guessing not... Anyway, thanks for all the help!