Ant's 65 Comet Build

[ants875]

Sounds like you are in the ball park on the dist advance. Maybe hitting max advance just a little too soon at 2500. How many deg is that mechanical and what is your intitial timing set at.

When I set mine up I used the two lightest springs in the set I have which gave me a max of 21* mechanical advance. Used the 13* notch on the advance piece. Set my timing at 14*. I have 21 * mechanical advance so with the 14 * intial max advance comes in at 35* advance at 2800 rpm.

I'm also running lean at cruise so I need to up the pri jet sizes one size or two to get it off of dead lean.

I wouldn't go any higher than a 6.5" on the power valve. 10 sounds to high as it will be opening way too soon, i think. If yours is wet on the back side either the diaphragm is leaking or the gasket is leaking fuel by. Should be completely dry on the back side.

Looks like you are getting it dialed in.
Ron

I have a medium and a light spring in mine, not sure why yours is coming in at a higher rpm then mine one thing I heard from the guy at AED was that they have seen some issues running two light springs said that they had a few that would hang up and not return to base timing properly so if you have any strange things you might keep that in mind.

My initial is 16 with a total of 36 starts great and seems to be pretty snappy but I need dry roads to know for sure.

thanks
Ant

[CALIFORNIA CALIENTE]

Anthony;power valve should be dry on the back as should the well! You NEED to go up at least two jet sizes at a time on the primaries until you are happy with the AF ratio! Stay with a 6.5,no higher than an 8.5 on the power valve.If it smoothes out when the secondaries are coming in then it is too lean on the primaries!That 650 [428CJs and BOSS 429s only used a 735] will be fine,if you had big heads,big cam,big headers,a lot of compression,a lot of rear gear and were drag racing it all the time,you may need a 750 or larger!! I suggest you get the combo you have now to run the way you are happy with it!! JMO , ROY.

[Comechero65]

I have a medium and a light spring in mine, not sure why yours is coming in at a higher rpm then mine one thing I heard from the guy at AED was that they have seen some issues running two light springs said that they had a few that would hang up and not return to base timing properly so if you have any strange things you might keep that in mind.

My initial is 16 with a total of 36 starts great and seems to be pretty snappy but I need dry roads to know for sure.
thanks
Ant

I used the two lightest springs and adjusted the spring anchor points for about a 1 mm stretch of the springs when I hook them up. I use spring sets for a GM dist. I tried one heavier spring but it raised the max rpm point even higher. I'll keep that in mind if I see any weird things going on.

Sounds like you have yours set pretty good.

I haven't messed with carb jets just yet but will be trying some larger jets to try and get mine off of the leanest reading on the 02 monitor. Need to pull the plugs as I go to see how they look. Mine goes from rich at idle to lean at cruise. Have some other things I need to do to get the idle out of rich. Stinks pretty good at idle.

Haven't really ran it though its' paces yet to know where ideal should be. but it runs and drives good as it is. Takes time to get it all right.
Ron

[ants875]

I got a couple more things done, first the car was stalling when I came to a stop as well as the lean stumble. I mentioned this to the builder today and he said the stalling is usually to high of a float level, that was the first thing I did when I put the carb on was to set the floats and the back one was high so I lowered but since he mentioned that I said i'd go ahead and double check it again and sure enough it was to high again. so I adjusted it and that helped get rid of a bunch of issues, but it still has a weird spot just off idle. I did hear some valve ping so I changed the springs in the distributor from a med and light to both med, I figure that 36 total is still what I want for timing but maybe I need it to come in a little latter. its now all in by around 2800, still need some more drive time to see if that is going to be right.

one thing I know for sure is I HATE this vacuum secondary carb! I know I can change the spring to make them come in sooner but I'm still thinking I want a double pumper. I'm going to get a few more miles on it and then decide what i'm going to do, I hate to spend a bunch of time on this carb to just change it and have to start over again.

ant

[Rocket989]

I 2nd the mechanical secondary carb!!! And you want the biggest carb you can run that'll still give good low rpm drivability!

On a warm (don't know your cam specs or CR), good breathing 347 with a manual and 3:73's I'd roll a 750 out of the gate!

Edit: Holley or same type other brand - don't really know much about other carbs!

JH

[ants875]

I 2nd the mechanical secondary carb!!! And you want the biggest carb you can run that'll still give good low rpm drivability!

On a warm (don't know your cam specs or CR), good breathing 347 with a manual and 3:73's I'd roll a 750 out of the gate!

Edit: Holley or same type other brand - don't really know much about other carbs!

JH

Jh

Cam is. 544 lift 226,234 duration at. 050. My builder and also the guys at prosystems agree with you about the 750. The demon I had on it did not seem to be too much it just was very erratic so I think I want to buy something new so know it's not been messed with. As for brand once you get into a decent carb they are all about the same money, the machine shop swears by quick fuel. They like that they are fully adjustable, you can replace the air bleeds, the jets in the emulsion well and even the way the secondaries come in from coming in at 40% to 60% or 1:1, they say you can really dial them in.
We'll see what happens I have yet to decide which way to go.

I did play with the carb I have a little this morning thinking that the accelerator pump was miss adjusted but it looks right so I don't know why I have the stumble that I do, I know I'm tired of chasing my tail on this one.

One thing that the machine shop talked about with regard to carb size was that the boss 302 came with 780 carbs. For that matter so did the Chevy 302s in the early z28 camaros.

Ant

[CALIFORNIA CALIENTE]

The 780 Holley on a BOSS 302 was a vacuum secondary,as were the 735s ! Did you ever fatten up the primary jets? ROY.

[ants875]

Roy,

I have not changed the jets yet, I forgot to check and see which ones were in in when I had the bowl off. the stumble it has is still just off idle when cruising which is why I thought it was the accelerator pump though it seems to be working. I might try moving the pump cam to the other bolt hole and see how that works. if that does not work maybe jets is what I need to try.

Ant

[Rocket989]

Ant - I haven't heard a single bad thing about Quick Fuel carbs either. The local speed shop also said their tech folks are great. I'm going to roll one of their HR series carbs next up! With your combo I'd definitely snag the 750!

JH

[CALIFORNIA CALIENTE]

Anthony;it is your car to do as you wish! I still feel for a street combo a 750,mechanical secondary is too much carburator!! This is just my opinion based on my experience with 347s!! Good Luck , ROY.

[Comechero65]

I agree that the 750 is too much carb for a SBF. Even a 650 cfm is pushing it but does still work for most.
Ron

[Rocket989]

Roy - No way I'm going to argue with your 347 experience(s)! I've just seen bigger carbs consistently make more power! As long as you can get it to run happily at lower RPM's - you're good!

Ron - There are so many considerations… for example, a combo could run from a 4500rpm 302 in a 3800lb. car with an auto and 3:00 gears to a 6800rpm 427 stroker in a 2900lb. car w/ 4:30's and a 5-speed. No way a 650 is going to be enough at the high to higher end!

JH

[CALIFORNIA CALIENTE]

JH;Anthony has his Comet setup as a street car is why I say a 650 should work!! I have seen BOSS 302s with two Dominators,but they were full race setups!! I run a PRO SYSTEMS worked 1050 Holley Dominator on my 418" Windsor,but that thing has all the big parts and RPMs for it to work,it is 'DRIVABLE' at low RPMs,barelly!! I feel Anthony needs to get everything working properly before he starts messing with carb sizes!! JMO , ROY.

[Comechero65]

For the everyday SBF street driven car and not pumped out to the gills I think the 650 is plenty of carb. I know there are many combos'. A 427 is not a SBF, that's a whole different animal.
Ron

[poboyjo65]

I agree with Roy. I have a street driven 347. it ran good with a 600 edelbrock, but I needed the 600 to put on a 302 so I put a 650 edelbrock on the 347 & does good with it too. to me, it seems like mechanical secondary's would drink more gas on the street. Your going to have to fine tune what ever you use,,,so I would dial in what you have for the street ,,,, maybe get a big one for the track later on.