Posted By: Glen440
weird hesitation in my 318, need opinions(UPDATE) - 09/02/09 02:47 AM
I ended up putting a 98 magnum 318 in my Volare. Its carburated with a rpm air gap intake. Stock roller cam. It cranks 165-175 PSI. My timing curve has 15 initial and 32 total and is all in around 2500. I'm using a low gear 904 lockup with a 2500 stall converter and the car has 4.10 gears with 26.5" tire on the back. I did do rings and bearings and ported the heads a bit and they got a fresh valve job. I'm going to be putting my 8 3/4 with 3.23 gears back in the car once its sorted out.
I started playing with it in the spring but got sidetracked and started at it again last weekend.
The engine idles great, you can bring the revs up slowly and everything is fine. Its when you give it a quick snap of the throttle the engine stumbles. When driving its worse, you slow down and go around a corner and it has a stumble from idle to part throttle. Its a 600cfm holley vac secondary. It has 25 squirter and 64 jets in the front.
I'm going to try another carb on it tomorrow. I did have a 750 DP on it that my friend races with and it was better but still there.
What I'm thinking is it has too much vacuum and the power valve is opening way too late. I was thinking about taking the power valve out and jetting up 8 sizes and try it. Maybe its too lean?
Its an out of the box carb, I changed it over to the dual feed bowls. I could play with the distributor and put more initial timing in it if that would help.
Any ideas?
Thanks
Glen
Posted By: 6bblFLASH
Re: weird hesitation in my 318, need opinions - 09/02/09 03:08 AM
Ck float level in both bowls. Make sure you have`nt over exsposed the transfer slot in the primaries .043 max. Yes the power valve on the list also....
Posted By: MR_P_BODY
Re: weird hesitation in my 318, need opinions - 09/02/09 04:04 AM
Could be both carb and timing... I would up the timing
to 18 initial. Put a vac gauge on it and see what its
got in gear at idle... have you checked to see what
PV you have in it
Posted By: formula S
Re: weird hesitation in my 318, need opinions - 09/02/09 08:26 AM
Sounds like an accelerator pump, make sure their is no lash between the pump lever and arm. Then test it to make sure fuel comes out of the squirters the moment you move the throttle, do this with the engine off, and check the float level as stated earlier. With your engine their is no reason that an out of the box carb wouldn't work, your engine is basically stock ie; the cam. If the car has been sitting for a while it just might be varnished a little bit, and need a little cleaning up sometimes the check valves under the squirters get stuck, remove the squirter and spray a little carb cleaner in the hole. Be careful not to blow the check valve out of the hole.
Posted By: Lil Wedge
Re: weird hesitation in my 318, need opinions - 09/02/09 10:49 AM
Sounds like pump is bad or squirter is too small. If you can visually see the pump working, I would go up to a 31 squirter and see how it likes it. tune the squirter size from there. Air gap has a lot more area than stock manifold. I run an air gap, while I have a 360 with a large cam in the heat I run 31 and 37 squirters and when it gets real cool I have to go up to 42 and 45's on a 750 but this is race only.
Posted By: patrick
Re: weird hesitation in my 318, need opinions - 09/02/09 02:18 PM
I've been tuning my engine for a week now, it's essentially the same as yours but with the cam reground by bulletcams with their HR259/316 lobes on both the intake and exhaust. I've got my timing at 23 initial, 36 total, it pulls 21" vaccuum in neutral at 920 RPM, 16" in gear at 700. I had a real bad stumble when snapping the accelerator. I'm borrowing a friend's wideband 02, and it was going wicked lean (like 21:1 momentarily) at the stumble. granted, I'm using an edelbrock 600, but adding more fuel to the acc pump circuit by moving the acc pump link to the closest hole on the arm and bending the link to make sure there is no lost motion to give the biggest shot, and removing the weight over the check ball has eliminated it in all instances except a quick snap from idle, and there it's much better...I might try drilling the nozzles out on my eddie to get more fuel in quicker.
for you holley, work on the fuel enrichment circuit...I don't know holleys so I don't know if that means playing with acc. pump cams that are more aggresive, larger squirters, and/or a stiffer powervalve spring to open it up sooner.
btw, this cam rocks on an otherwise stock bottom end 318...I'd recommend getting yours reground to stock specs (less than $200 round trip to bullet), and use Hughes 1110 springs with their retainers, or chrysler 2.2L retainers (what I'm using)
Posted By: Glen440
Re: weird hesitation in my 318, need opinions - 09/02/09 09:24 PM
I'm starting to plug away at it at the shop. For vacuum it has 20 at 900rpm in park and 18 at 700 in gear. I was inside the distributor and replaced the pickup as one wire looked cracked. I welded the slot a bit and it has 22 initial and 32 total, went too far but that has made no difference. next up is carb. The power valve is a 6.5, this thing may need a 10 in it if there is such a thing. Gonna try a couple things and see what happens.
The accelerater pump is adjusted fine, I have some 31 and 35 squirters I can try.
Posted By: Glen440
Re: weird hesitation in my 318, need opinions - 09/02/09 10:16 PM
I fixed the problem. Its the power valve. I took it out and jetted up 9 sizes and the stumble is gone and driveability is what I would expect, can lug it in 3rd gear with no bog or stumble. Slight hint of detonation so either take timing out or run better gas.
The carb is cranky at idle like this. I will have to find a power valve to stick in it.
I may end up with a bigger cam at some point, I was looking at the comp cams computer controlled cams.
I put some converter in it because I may race it on a pro tree the odd time and its important to get some revs up to nail the tree.
What power valve should I put in it?
Thanks
Glen
Posted By: Glen440
Re: weird hesitation in my 318, need opinions - 09/04/09 01:37 AM
I could only find a 8.5 power valve in stock local so I put that in. I also put in a 35 squirter and a more agressive pump cam. I didn't get much time to play with it today so I drove it around the building once and it seems fine. Has good throttle response.
Something good came out of this, I learned a bit about tuning the holley carb, never had to play with power valves before. I never paid much attention to them.
I'm going to put some miles on it this weekend and try to race it sept 13.
Posted By: formula S
Re: weird hesitation in my 318, need opinions - 09/04/09 08:12 AM
What size jets did you end up with
Posted By: Glen440
Re: weird hesitation in my 318, need opinions - 09/04/09 09:34 AM
out of the box it had 64 in the front. I put 65's in. I have no idea what the plate in the back is equal to jet size.