When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Just one question from inquiring minds does it really have 78 and 86 jets in what looks like to me a 750 demon carb? My manual doesn't give the factory jetting. Does it have drilled primary throttle blades to get the 4 corner mix screws out to about 1 1/2 turns? If so what are the hole sizes?
Lars, excellent work as always. Can you explain what these statements mean?
"with .015” differences between cylinder strokes and position. Crank was offset index ground and polished to correct all the bad workmanship, and ended up at .030/.030"
The crankshaft journals for each cylinder are supposed to be exactly 90 degrees from each other, and the stroke of each journal (on a 327) is supposed to be 3.250". When crank grinders do sloppy work, they don't get the journals 90 degrees apart, and they can alter the actual stroke of the engine. In this case, the stroke from one journal to another varied from 3.235 to 3.265 (up to .015" off in either direction). In order to correct the stroke and positions, the journals had to be "dialed in" (aka, "indexed"), and each journal was ground to correct the faulty offset to create new, correct journal centerlines. This takes quite a bit more effort and skill on the part of the crank grinder.
Originally Posted by gkull
Just one question from inquiring minds does it really have 78 and 86 jets in what looks like to me a 750 demon carb? My manual doesn't give the factory jetting. Does it have drilled primary throttle blades to get the 4 corner mix screws out to about 1 1/2 turns? If so what are the hole sizes? I think it is time for a single malt Scotch!
I started out with the 78/86 jetting combo because that's the combo that has proven to provide best numbers on the engines I have dyno tested with the same Demon 750 carb. During road testing, the WOT numbers were rich, so jetting was dropped to 76/83. This resulted in perfect numbers throughout the power range, including idle and cruise.
I haven't had to drill throttle plates on any of the street engines I have been building - proper setup of the secondary idle speed allows the throttle plates to be closed far enough to expose less than .020" of the transition slots on both ends of the carb. This produces good idle mixture screw response with the screws at about 1 turn out producing 14.7:1 idle mixture.
Loved reading this........good old meat and potatoes rebuild with no bells and whistles......should run great!!!! Nice and strong!!!!
I am jealous of your chain fall and the fact that folks just ship their Corvettes for you to work on......
Well....more like hand delivered 1350 miles, but Lars' meticulous attention to detail made it worth every mile !!
My apologies.....look like a trip well spent.
I had a 66’ 327/350 4 years ago and it hurts! 😂😂
Yes the car in my Avatar.....
Nice solid build on that, that will represent the breed well.....L-79’s are some of my faves.....
What oil do you typically use for cam break-in?
Appreciate your writeup.
Thanks!
I use Rotella (the non-synthetic version) in either straight 30W or 15W-40 with the CompCams break-in additive part number 159. Additionally, I coat the cam with the 35000 Moly Cam Lube. Before these oil additives and lubes were available or commonly used, I simply fired the engine and got the rpm up. I believe that instant engine start, and instantly getting the rpm up into the 2000-range, is the real key to successful cam break-in.
Lars, excellent work as always. Can you explain what these statements mean?
I keep seeing excellent work by several posters. I can't get over the 1/2 pickup clearance off the bottom of the pan, this is not right. Hopefully the pickup was heli arced to the pump. Blok Shop-Excellent work! Sarno racing heads, no problem there. Dave at mile high crankshaft........well heres my story.
Several years ago before having a crankshaft operation in my shop Dave (Mile High crankshaft) ground cranks for me, I dropped off a std virgin 454 crank to be ground, got it balanced and put in the block, started putting in the even bank of pistons and noticed I had .080 rod side clearance on the first set, got to looking at the crank and noticed the fillet had been ground off right up to the counter weight, crank destroyed, drove back up to Daves shop in the morning 80 mile one way, showed him the crank, and this is what he said...........your crank was like that before we ground it. And this is the problem: I use only VIRGIN unmachined crank cores, this crank came out of a friend of mines boat that had never been touched. A friend of mine drove up there with me when the crank was dropped off, and I told him what happened........this what he said " you know I noticed his wife or girlfriend was over there grinding cranks when we walked in there. People make mistakes, I make mistakes, BUT when you double down and lie right to customers face and don't take responsibility that where the problem is. Having a women in your shop learning to grind MY cranks is a bad idea. The guys a POS.
I can't get over the 1/2 pickup clearance off the bottom of the pan, this is not right.
What do you think is wrong with a 1/2" clearance on a street car with a 5-quart sheet metal oil pan? It's a safe, reliable way to assure good oiling, even after the pan takes a hit on a railroad crossing.
Imagine if the pickup had been set at 1/4" clearance in this typical pan. Oil flow would be blocked off. You can tighten up the pickup clearance in a racecar, but for the street, it's a bad idea:
For street engines, Moroso recommends "just under 1/2" clearance" (they have a You-Tube video showing them setting the pump up with .420" clearance). Melling recommends 1/2" to 3/8", stating that the clearance should never be less than 3/8". Not that they know anything about oil pans and oil pickup systems, but they agree with the 1/2" spec being in the recommended range.
Originally Posted by Vortecpro
Having a women in your shop learning to grind MY cranks is a bad idea. The guys a POS.
Obviously, there is no excuse for bad workmanship and poor quality from any company, and I don't know what actually happened to your crank. I have found that the workmanship you get in this business is dependent on the relationships and contacts you develop, and understanding who to use for what work. I am aware that Dave uses his wife for some of the shop operations, and I always talk to him when I drop off my cranks and specifically request that he personally do my work. Especially when it comes to an offset index grind that requires a bit of skill and setup understanding. I have been building engines and getting machine work done in the Denver area now for 40 years, and through relationships with suppliers, I can take enough preemptive action to assure that I get the best work done.
What do you think is wrong with a 1/2" clearance on a street car with a 5-quart sheet metal oil pan? It's a safe, reliable way to assure good oiling, even after the pan takes a hit on a railroad crossing.
Imagine if the pickup had been set at 1/4" clearance in this typical pan. Oil flow would be blocked off. You can tighten up the pickup clearance in a racecar, but for the street, it's a bad idea:
For street engines, Moroso recommends "just under 1/2" clearance" (they have a You-Tube video showing them setting the pump up with .420" clearance). Melling recommends 1/2" to 3/8", stating that the clearance should never be less than 3/8". Not that they know anything about oil pans and oil pickup systems, but they agree with the 1/2" spec being in the recommended range.
Obviously, there is no excuse for bad workmanship and poor quality from any company, and I don't know what actually happened to your crank. I have found that the workmanship you get in this business is dependent on the relationships and contacts you develop, and understanding who to use for what work. I am aware that Dave uses his wife for some of the shop operations, and I always talk to him when I drop off my cranks and specifically request that he personally do my work. Especially when it comes to an offset index grind that requires a bit of skill and setup understanding. I have been building engines and getting machine work done in the Denver area now for 40 years, and through relationships with suppliers, I can take enough preemptive action to assure that I get the best work done.
Lars
I shoot for .320 for clearance myself. The thing is I had no idea Dave had this women grinding cranks, its how the problem was handled is my problem.
Regarding the straight up timing mark, what setup is it that the mark would go at the 12 o'clock position?
The timing marks always go straight up at the 12:00 o'clock position on all GM engines. If you put the marks "together" with the crankshaft at 12:00 and the cam dot at 6:00, you are at TDC on the exhaust stroke. That works fine for cam timing, but you cannot drop the distributor into the block in the #1 firing position if you align the cam that way - you will be lined up on #6 cylinder instead of #1, and the engine will never start. The "Chilton's" and "Haynes" manuals state to put the dots "together," and you'd be amazed how many people can't get their engines started after doing this.
Originally Posted by Vortecpro
I shoot for .320 for clearance myself.
That's much tighter than any of the pump, pan, and oiling system manufacturers recommend... If it works for you, that's great. I wouldn't do it on a street engine that I'm putting my name on and delivering to the other side of the country.
Lars
You said that if this build was for Ultimate Performance, that would have installed JE custom pistons. Would you explain the reason you upgrade the pistons. And any other changes for Ultimate Performance. I’m interested, in the pistons possibly for my build a 1970 L46.
Bob
The timing marks always go straight up at the 12:00 o'clock position on all GM engines. If you put the marks "together" with the crankshaft at 12:00 and the cam dot at 6:00, you are at TDC on the exhaust stroke. That works fine for cam timing, but you cannot drop the distributor into the block in the #1 firing position if you align the cam that way - you will be lined up on #6 cylinder instead of #1, and the engine will never start. The "Chilton's" and "Haynes" manuals state to put the dots "together," and you'd be amazed how many people can't get their engines started after doing this.
Lars
I realized that you had already rotated the assembly to set the lifter pre-load for the cylinders and the timing cover was left to the end.
I realized that you had already rotated the assembly to set the lifter pre-load for the cylinders and the timing cover was left to the end.
No, actually I don't set the lifter pre-load until I have the engine on the run stand. That way, I can use the starter to "bump" the engine over for the lifter adjustment and make my life easy. I install the gears with both dots "straight up", do the cam degree process, and then bring the dots back to "straight up" before installing the cover and balancer. I do the pre-oiling on the run stand using the hand drill, drop the distributor in, and then, finally, use the starter to bump the engine over for the lash adjustment.
Lars, there is one photo conspicuously missing ----- the one of the big smile on the owner's face after his first post-op drive. Good to see another top notch, informative post by one of the true masters, it's been a while, at least for me. I do, however, refer to the Q-Jet papers on a fairly regular basis. Can't thank you enough for that one.
Regarding the pcv valve at the breather tube ----- can those still be had? I ordered what I thought was one reasonable priced but it turned out to be opposite flow direction from original.
Lars, there is one photo conspicuously missing ----- the one of the big smile on the owner's face after his first post-op drive. Good to see another top notch, informative post by one of the true masters, it's been a while, at least for me. I do, however, refer to the Q-Jet papers on a fairly regular basis. Can't thank you enough for that one.
Regarding the pcv valve at the breather tube ----- can those still be had? I ordered what I thought was one reasonable priced but it turned out to be opposite flow direction from original.
The owner is scheduled to arrive this Saturday morning to take it for its first road test... I'll get the camera ready...
The screw-in PCVs are available under Standard Motors part number V100, which also crosses over to NAPA/Echlin part number CRB 29255. Cost for either one is about $7.
The owner just stopped by with his flatbed trailer and picked up the car after going for a test drive and checkout of the new engine setup. Our conversation:
"It feels like a new car..!"
"It is.."
Hopefully the car will continue to deliver lots of smiles and fun - this thing really feels good on the throttle, and is a real kick to drive. Right now, car and trailer should be somewhere eastbound on I-70 headed back to Mississippi:
07-01-2018, 09:45 PM
does it really have 78 and 86 jets in what looks like to me a 750 demon carb? My manual doesn't give the factory jetting. Does it have drilled primary throttle blades to get the 4 corner mix screws out to about 1 1/2 turns? If so what are the hole sizes?
