Backfire/loss of power

KennyB_
Jun 25, 2021

Rank 0

Jun 25, 2021

Looking for advice! Been experiencing alot of power loss with my 351w. Thinking about converting my 2bbl to a 4- probably a 600 eldelblock. Then updating my distributer(not sure what the best route would be) some time after that, if there's still some back fire. (Backfire only happens when engine is cold)
What other modifications/tweaks could I make on my 351w? I dont have the experience to jump in and rebuild it, it is also my daily so I'm looking for quick fix projects, if possible.

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TK1215
Last edited by a moderator: Jun 25, 2021
Moderator

Life is a Highway

Jun 25, 2021

#1
Looking for advice! Been experiencing alot of power loss with my 351w. Thinking about converting my 2bbl to a 4- probably a 600 eldelblock. Then updating my distributer(not sure what the best route would be) some time after that, if there's still some back fire. (Backfire only happens when engine is cold)
What other modifications/tweaks could I make on my 351w? I dont have the experience to jump in and rebuild it, it is also my daily so I'm looking for quick fix projects, if possible.
Have you checked your timing? Sorry I know it’s obvious so please forgive me. I would possibly switch to an MSD system. Otherwise points , plugs, wires, coil, check it all, tune it up and time that bad boy
KennyB_

Rank 0

Jun 25, 2021

#2
TK1215,

Yes! Definitely will get my timing adjusted, just thought I'd do that after the carb swap. And I never actually thought about switching to MSD, I will for sure look into that! Thanks for the input!

Rank I

Jun 25, 2021

#3
Definitely verify timing. A quick fix could be to replace the distributor points. Those old distributors eat them. Make sure you don't have a plug wire arcing too. And yes, new 4bbl 600 cfm carb and MSD ignition, coil, and distributor would be a great upgrade for performance and reliability.
KennyB_

Rank VI

Jun 25, 2021

#4
Back firing through the
Carb or after firing out the exhaust?
If it pops through the carb, only when cold. Your choke plate is opening too fast. Adjust the choke toward the rich direction. And check your timing.
KennyB_, TK1215

Rank VI

Jun 25, 2021

#5
If it’s out the exhaust, make sure the choke plat is opened fully and check your timing.
TK1215

Rank 0

Jul 03, 2021

#6
Back firing through the
Carb or after firing out the exhaust?
If it pops through the carb, only when cold. Your choke plate is opening too fast. Adjust the choke toward the rich direction. And check your timing.
It is starting to backfire more and more when accelerating, and climbing up hills. Im idling pretty high, so I do know timing is off

Rank 0

Jul 03, 2021

#7
Definitely verify timing. A quick fix could be to replace the distributor points. Those old distributors eat them. Make sure you don't have a plug wire arcing too. And yes, new 4bbl 600 cfm carb and MSD ignition, coil, and distributor would be a great upgrade for performance and reliability.
Thanks for the advice!

Rank VI

Jul 03, 2021

#8
All your symptoms scream carb issues. Clogged jet or ruptured accelerator pump. Stuck power valve or all the above. I send my carbs out. The pros are so much better rebuilding.
KennyB_

Rank VI

Jul 03, 2021

#9
This one’s 30 years old 1625348629342.jpeg
Deano Bronc

Rank 0

Jul 03, 2021

#10
This one’s 30 years old View attachment 15144
She's a beaut! Yeah I would love to rebuild it, but I've been wanting to do a 4 bbl swap for a while... I'll definitely think on it. Im in no rush, got all summer to think about it while I'm fighting fires!

Rank VI

Jul 03, 2021

#11
Check the pvc valve , could be a huge vacuum leak. Too. Check cheap stuff first. Once you start changing parts troubleshooting gets list in the sauce.

Rank 0

Jul 03, 2021

#12
Absolutely, will start small and see what I can't figure out! I'll do some more research to find out more things to check out too.

Rank VI

Jul 03, 2021

#13
Just remember older carb parts are incompatible with methanol in gas. Seals and rubber parts shed particles and clogg passages in the carb. All your symptoms seem to point at leaning mixture. Acceleration,heavy loads. I’d go to the carb. Rebuild replace whatever you can afford. Good luck and stay safe.
Deano Bronc

Rank 0

Jul 03, 2021

#14
I will keep that in mind, thank you for your knowledge!

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