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Discussion Starter · #1 ·
Hi all,

Some details first, since those seem pretty important:
I've got a new 545 I finished building about a month ago in a 79 f250. It's a full forged 2-bolt bottom end in a D1VE block, SR-71 heads, big mutha thumpr hydr roller cam with roller rockers, hv oil pump & 12qt pan, weiand stealth intake, double roller timing chain, Cometic MLS head gaskets, edelbrock 110 gph mech fuel pump, stock Duraspark II dist with new gear, cap, and rotor, and an edelbrock 1913 800cfm carb.
I'm new to engine building so not completely ruling out and stupid mistakes, but a friend of mine who has a shop building engines helped me find the pushrod length and install the heads, rockers, cam, and timing chain, so I'm pretty sure thats all correct. I also had a shop recommended by him with lots of bbf experience assemble the short block, so also pretty confident in that. It runs about 170°, pulls 10" of vacuum at idle and has loads of power. No idea what the timing specs are as I need to take the alternator off to do that and haven't had time or weather to do so. It

Upon initial setup I had the plug wires on the dist set up 1, 2, 3, 4, 5 6, 7, 8 which I know isn't good but it only ran like that for maybe 10 minutes total?

The problems are:
1. It diesels when turned off. Messing with the distributor seems to affect it some, but it's gradually gotten worse to the point where it'll do it for 30+ seconds and I have to put it in gear and push the brake to make it stop.
2. It backfires through the carb when revved up too many times rapidly. Not every rev, but it's not hard to make it do it.
3. It starts backfiring at sustained high rpm. Anything over 4k, give or take a little depending on what gear you're in or if in nuetral, it'll start doing rapid small backfires out the exhaust. But if you rev it quick, you can hit 5,500 no problem. It's only sustained stuff it doesn't like. At least I think it's backfiring. I don't think it's knocking, at least.
4. It smells very rich and when you let off the gas it takes time for the rpms to drop. Idk if that's a timing problem or if the carb just needs tuned.
5. It hesitates a bit when stomping the gas, but replacing the vacuum advance module seemed to help some with that. It's not fully adjusted yet though.

Any suggestions/ideas?
 

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Did you set you’re timing pointer in reference to zero on the balancer while at TDC during assembly of the engine?

I would not run the engine any more until you are ready to set the timing. I’m not super familiar with the SR71 heads but they probably won’t need more than 32 deg or so of total timing.
 

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Discussion Starter · #3 ·
Did you set you’re timing pointer in reference to zero on the balancer while at TDC during assembly of the engine?

I would not run the engine any more until you are ready to set the timing. I’m not super familiar with the SR71 heads but they probably won’t need more than 32 deg or so of total timing.
I did, yes. I had that slightly wrong at first as well. Any idea what a good initial timing spec would be, or how to find what it needs? Seems to be a little different for everyone.
 

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HI,??????"
You say a lot of stuff that Does not make any since????
"No idea what the timing specs are as I need to take the alternator off to do that and haven't had time or weather to do so. It "
What does pulling the alternator have to do with the timing spec's???
"Upon initial setup I had the plug wires on the dist set up 1, 2, 3, 4, 5 6, 7, 8 which I know isn't good but it only ran like that for maybe 10 minutes total? "
I don't think it would even run set up like that.... Maybe this well help,, you sound VERY confused...
Rectangle Font Art Graphics Visual arts


good luck take care be safe
tim
 

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Discussion Starter · #5 ·
HI,??????"
You say a lot of stuff that Does not make any since????
"No idea what the timing specs are as I need to take the alternator off to do that and haven't had time or weather to do so. It "
What does pulling the alternator have to do with the timing spec's???
"Upon initial setup I had the plug wires on the dist set up 1, 2, 3, 4, 5 6, 7, 8 which I know isn't good but it only ran like that for maybe 10 minutes total? "
I don't think it would even run set up like that.... Maybe this well help,, you sound VERY confused...
View attachment 95098

good luck take care be safe
tim
To clarify:
On my motor the alternator is blocking a view of the timing pointer so I need to pull it off to use a timing light.
Yes, I have the wires hooked up properly now. It actually will run connected like I had it, but it needed starting fluid to start and shook like crazy and would die if you tried to let it idle. I was also very surprised.
 

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Discussion Starter · #8 ·
HI,??????"
You say a lot of stuff that Does not make any since????
"No idea what the timing specs are as I need to take the alternator off to do that and haven't had time or weather to do so. It "
What does pulling the alternator have to do with the timing spec's???
"Upon initial setup I had the plug wires on the dist set up 1, 2, 3, 4, 5 6, 7, 8 which I know isn't good but it only ran like that for maybe 10 minutes total? "
I don't think it would even run set up like that.... Maybe this well help,, you sound VERY confused...
View attachment 95098

good luck take care be safe
tim
It also shot fire 3+ feet out the exhaust and sounded like a machine gun from the backfiring. We had to turn it off to talk, even shouting didn't work.
 

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That family of cylinder heads. SCJ, P-51 and SR 71 rarely need more than 28 or 29* TT.

Those thumper cams require a bunch of initial timing for idle quality which is purposefully lopey.

16 to 18 initial and 28 to 29 total. All in by say 3000 rpm.

If your distributor is not properly set up and sorted out DO IT.








Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Parkland Auto Machine
 

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Discussion Starter · #11 ·
I was able to get a good angle on the pointer and actually hit it with the light. Initial was 26 degrees, yes with vac advance disconnected and plugged. I turned it to 10 initial and it no longer smells like raw fuel behind it, but it has the same high rpm problem. Total timing, at 3k rpm with vac advance connected, seems stuck at 34 degrees no matter how I turn the Allen key.
Scotty, just saw that post. I'll go try that.
 

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Just to confirm, this is on the BTC side of the balancer, correct? Not the ATC side?

Total timing is checked with NO vac advance. BTDC of damper.

Check dizzy advance mechanism to see if it is locked out.






Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Parkland Auto Machine
 

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Discussion Starter · #14 ·
Total timing is checked with NO vac advance. BTDC of damper.

Check dizzy advance mechanism to see if it is locked out.






Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Parkland Auto Machine
Oh. Huh. I assumed total included vacuum advance.
It reaaally liked 17 initial at 800rpm, but as soon as I connect the vac advance it jumps to 36 degrees and nothing except lowering the idle will adjust that. The more I retard the distributor the higher it'll rev before it starts acting up...is it just advancing too much??
I'll check to see if it's locked out or not.
 

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Discussion Starter · #15 ·
My hood magically locked itself shut so I couldn't check if the distributor is locked out, but I did check total timing properly and it was...weird. Initial was 17 degrees at 800 rpm, revved it to 3k and checked and it went down to 14 degrees. How...?? With the vac advance disconnected and timing set like mentioned it'll hit 5k--5500 before having issues.
 

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Hopefully, when installing the timing set, it was degreed in. It is all too easy to have a 460's valve timing out of whack if an aftermarket off the shelf timing set is simply installed "dot to "dot". Omitting the degreeing process, I my opinion, gives you less than 50/50 shot to have a successful outcome.
 

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Discussion Starter · #18 ·
My dizzy is not locked out as total timing does change to 28*/30* at 3900 and somewhere past 40 at 5k, which is where it starts pinging.I've tried initial timing everywhere from 5* to 18* and 17* is what it likes while driving but 14* helps with the dieseling. Octane booster also helped a lot with it, but did not eliminate it.
I did not degree the cam as I did not have access to a wheel or feel it necessary.
Can I just leave the vac advance disconnected? It seems to drive fine other than being a little less snappy and starts pinging at 5k instead of 4k. I'd like to have it, but just wondering if I can while I try to solve the problem.
 

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HI,
I've never degreeed a cam ether and mine all run fine..
What kind of idle are you at.. should be like 650 with a manual transmission and 750 with an automatic.. To fast of an idle can cause dieseling as well as to rich a choke.. or fuel mixture lean would make it run hot and cylinder heat.

good luck take care be safe
tim
 

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Discussion Starter · #20 ·
HI,
I've never degreeed a cam ether and mine all run fine..
What kind of idle are you at.. should be like 650 with a manual transmission and 750 with an automatic.. To fast of an idle can cause dieseling as well as to rich a choke..

good luck take care be safe
tim
It's set at about 1000 right now; I need to set the high idle and lower the normal one. I think I had it set at 800 earlier and it diesled less, maybe.
 
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