trouble tuning mild 351c with holley 3310

[mustbrad]

Get The MR Gasket Spring Kit 925D change them in to get mechanical advance in earlier.

 

[87fox72mach]

Thats where im headed next. I bumped back initial timing a bit to 10 deg. And turned back my vacuum advance. Noise is less prominent and may even not be there. Hard to hear over motor. But definitley and inprovement. But has a harder time idling when started. Thinking base is to retarded

 

[87fox72mach]

ok I got my mr gasket 925d spring kit. do I install 1 spring or both?

 

[TommyK]

IMO you start by keeping the one heavy factory spring and installing one light spring from the kit. You then map the curve to see what you have and then drive the car aggressively to see how it reacts.

 

[Don C]

I agree with Tommy, one step at a time, it may take longer but it's the only way to assess the effects of changes.

How are you on timing, now? Did you ever change to ported vacuum?

 

[87fox72mach]

Good point. Want to get this thing dialed in right

 

[87fox72mach]

Took down some numbers today. This is all mechanical advance vacuum was plugged. Increments of 500 rpm starting at 1000 rpm. At 1000 10 deg. 1500. 12. 2000 16. 2500 18. 3000 22. 3500 26. 4000. 30. 4500. 34. This is the stock springs of the dizzy. No new springs. Do i swap out the prmary spring or second spring first?

 

[Stanglover]

I'm no where  near an expert on this, but from what I'm reading, you're having much the same issues I did on my 71 351C 4V, manual trans.  My cam is a little different , but not that much. I believe you said you had a stock distributor. What size is the slot for the stop pin? I'm guessing it is an L15. If it is I think you'll find it is too big as it gives you 30* on the crank and why you only have 10* initial. If it is an L13, I think you can tune it with a small plastic sleeve on the pin and that will cut down the mechanical advance. Mine runs great on an L10 slot, 20* on the crank with 14* initial for a total of 34* mechanical. I also cut my vacuum advance down to 3-4* and I run it from the timed port on the carb. Another 'tweak' I might try is to add a sleeve to the pin and bump the initial up to 16*. Should still be about 34* total, but I'm hoping a bit better response, we'll see I guess. I recently posted a similar write-up the other day, perhaps you've already read it.

From what you posted above, my feeling is that the timing is not all in soon enough. I also am running 1 factory heavy spring and 1 Mr. Gasket 925d, but I want to play with tension to fine tune it. It gets to be fun when things start coming together, for me anyways.

Good luck, keeps us posted.

Geoff.

 

[SR71 BLACKBIRD]

My experience on the way I had my closed chamber 4V Cleveland set up was: no vacuum advance, I think it was abt. 12 degrees initial, went to 38 degrees total advance, and I hit total advance by 2200 RPM. This was on 11.5 compression, 3310 vac. secondary 750, 2400 stall C4, headers, 2.25 exhaust. Flat tappet cam with Rhoads Lifters, MSD, .565 lift, 225 degrees duration @.050, Torker intake. I think a big early shot of accelerator pump takes care of a lot. I used the orange pump cam where it would hit the accelerator pump right off idle. can't remember if it was position 1 or 2 on the pump cam. Always adjust pump lever for .015" overtravel. Always use vacuum gauge to maximize idle vacuum with the mixture screws after you've established idle speed. Idle mix should be your last adjustment before messing with accelerator pump.

 

[87fox72mach]

Thanks for the replies. Im gonna open up the dizzy and see what i can find. We did have carb idle screws adjusted to best i performance spot. Changing the pump cam may be another option. My vac advnace is about 6 deg .

 

[87fox72mach]

Just wondering if i need the 925 d spring on the primary moving weight or secondary

 

[TommyK]

Just wondering if i need the 925 d spring on the primary moving weight or secondary

Put the new spring on the primary and test.

 If you like the first part of the curve with the new spring but it is taking to long to achieve full advance, sometimes you can tweak the tab the secondary spring attaches to which reduces the spring tension and makes the timing come in quicker. If that doesn't work you will have to use a lighter spring on the secondary side as well. Sometimes one of the factory springs is lighter than the other. Use the lighter one on the secondary side.

Without  a distributor machine this can take some time to get right. Alternatively, you could send the distributor out to be recurved.

In my opinion you want as much initial timing as the engine will tolerate and full advance of 36 degrees +/- all in by 3000 rpm.

 

[Stanglover]

Just wondering if i need the 925 d spring on the primary moving weight or secondary

Looking down on the guts, I have my heavy spring on the left side which I believe is primary and the 925 d on the right. Spring tension also counts and can be adjusted by bending the pegs in small increments to get the all-in rpm where you want them. Don't be afraid to play with other springs as well, but changing the tension. It's a PITA for sure but worth it in the end.

Like I said, I'm no expert, but have learned a lot in the last year or so, thanks to all the great guys and help on this site.

Geoff.

EDIT: I missed TommyK's reply before adding my 2 cents worth. It comes down to 'trial-and-error' without a distributor machine for sure. If I remember correctly, the original factory distributor had the heavy spring on the left, that' is why I put that one on that side. If I'm wrong, it is easily changed, but as said before, the engine is running strong with 20* + 14* all in at about 2800. Still could be improved I'm sure though.

 

[Stanglover]

This might help. I got these pictures from Cardone when they sent me a set of weights and springs to try after I complained about their generic attempt at a rebuilt 351C distributor. They are a bit generic, but I think answers the question of there to put the heavy spring. NOTE: when I got theses parts, they were labeled, but I think you can tell the light is on the right.

Hope this helps.

 

[87fox72mach]

Thabks guys. I opened up dizzy today. Looks like the peg is in the 13l slot. Heavier spring appears on my left. Looser tensiin one on right

 

[Stanglover]

Thabks guys.  I opened up dizzy today.  Looks like the peg is in the 13l slot.    Heavier spring appears on my left.   Looser tensiin one on right

Ok, good. the L13 equates to 26* on the crank. You can cut this back by simply adding a small plastic sleeve to the pin/peg. I got one from a DuraSpark dizzy I happen to have as it's made for the job. If you look, there is a sleeve on the same side on the one shown.The heavier spring, according to the picture, is the same side as the rotor slot. I'm really not sure about the weights though, as mine are the same.

 

[Don C]

The instructions for the Crane kit should give you some insight on the stock configuration:

http://www.cranecams.com/uploads/instructions/272e_(1).pdf

The discussion on the stock springs begins with #11.

I used the yellow/yellow on mine. with the short slot (don't remember what it was, now I'll have to look).

 

[87fox72mach]

ok today I was back on the car. I put the 925d spring in place of the heavy spring all timing seems to be in by 3200 rpm. I dialed back the vacuum advance a bit after hearing the pinging again. took the car out a second time after dialing back vacuum and car ran phenomenal no noise, good power! finally seem to have it dialed in right at idle I'm at 12 deg wiith a total of about 36 38 by 3200.

 

[Stanglover]

ok today I was back on the car.   I put the 925d spring in place of the heavy spring   all timing seems to be in by 3200 rpm.   I dialed back the vacuum advance a bit after hearing the pinging again.   took the car out a second time after dialing back vacuum and car ran phenomenal   no noise, good power! finally seem to have it dialed in right    at idle I'm at 12 deg wiith a total of about 36 38 by 3200.

 That's awesome news!! Clearly you are getting the hang of it now, as I did a year or so ago. Frustrating as hell, but once we get the idea straight in our heads, it turns into fun............ well sort of!

So it looks like you have 26* crank (L13) + 12* initial for a total of 38 mechanical? How much vacuum advance do you have on top of that, or is that total with vacuum @3200? Vacuum should be on the timed port off the carb imo. I mentioned before about using a sleeve on the peg, as seen in one of the pictures I posted. It might be worth a try, simple to do and easily removed, to cut your crank advance down a bit and then add to you initial as much as it will tolerate, but no more than 16*. I'm still playing with mine in this manner hoping for a bit more 'snap'. Just need some time to do it!!

Once you get it running better, take it out and drive it hardish for several miles, then pull the #1 plug and see what color you have. Hopefully it will be a light tan to brown. Plug choice and gap are very important I found. I run Autolite 24 with .040" gap but that's with a Pertronix II and coil on a 351 C M code and a Holley Street Avenger 670 that has been slightly altered and tuned.

It all works together, timing and tuning, so with a bit of patience, you'll have a car you can have fun with, not frustration.

Geoff.

 

[87fox72mach]

38 total with vacuum. I only have 2 deg vacuum advance. 10 deg initial base. Anything more than that seems to ping when driving. There seems like there was a plastoc sleeve on the peg already in the 13l slot