ok check this idea out - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bigd65 · 02-01-2003, 06:09 PM

well the clatter problem aint totally fixed, yes i am pissed. but, i got an idea what it could be. he other day when i had the top of the carb off, i noticed the fuel level was below the slosh plates. you know the plates the keep the fuel so the secondaries are fed. well i raised the float level and it fixed it a bit but the clatter is still there at WOT. well today i was at a buddy of mines and we check the total timing. its 28 total at 3,000 rpms. (8*btdc +20*centrifigal) ok thats text book. well as i was reving the engine, i noticed the fuel filter was not filling up, in fact there was very little fuel retaining in the filter and this was after i let it back to idle. so, here i go again, we checked the fuel pressure and it was about 6.5 psi. right thats about normal. well here is my question. is it possible the fuel pump can be weak and not be able to keep up with the demands of the motor drawing the fuel at WOT. i am thinking about changing the fuel pump, but was wondering what yall thought about ths therory.

PRAYERS for THE PASSENGERS AND PILOTS OF THE COLUMBIA

bigd65 · 02-01-2003, 11:07 PM

^^^^^^^^^^^^^^

**swervin ervin** · 02-02-2003, 12:26 AM

I guess anythings possible. If you have 6.5 psi at idle, I doubt you are running out of gas at WOT. It if was, you would sure be able to tell it by the way it ran.

79Silv4x4 · 02-02-2003, 12:50 AM

Actually, yes. Hotrod handbook indicates that you should have fuel pressure of 7 psi @ WOT-any less and you could be losing performance. BTW, carb, not efi.

gchemist · 02-02-2003, 02:28 AM

Change the pump. No major problem and good assurance than having an old pump.

79BIG10 · 02-02-2003, 06:21 PM

I agree. Chenge the pump and look to see if it makes a difference.

**swervin ervin** · 02-02-2003, 07:27 PM

I think changing the pump is a waste of time and money, unless it's falling on it's face at WOT. Although, it is pretty cheap and would be one more thing off the list.

AJII · 02-02-2003, 09:44 PM

In my RX7 I had the same problem. Whenever I hit the gas it wouldn't accelerate and would chatter real bad. Replaced the pump and the problem went away.

AJ

bigd65 · 02-03-2003, 09:37 AM

i replaced the pump yesterday. i will see if that fixed it today, i other thigs to do yesterday. i am thinking this may have been the problem, yea how many times have i said that LOL. anyway, im thinking it wasabout to go south, i could smell fuel in the oil where the pump mouts but i may have been smelling what leaked out. anyway, it was time to change that because it was off the old tired 305 with 180,000 miles that i took out about 5 years ago. i know this cause i didnt replace it and the 87 BURB this motor came from was fuel injected and didnt have a mechanical pump.. it seems better and the fuel filter is about 3/4 full all the time. i'll keep yall posted . i will be excited to be able to set my timing at 12* initial, it runs fantstic at off idle and part throttle at 12*.

**swervin ervin** · 02-03-2003, 01:09 PM

Good luck with it Jeff. I didn't realize the pump was this old. You done good by changing it then. One things for sure, it won't hurt nothing.

bigd65 · 02-04-2003, 03:56 PM

well it didnt help what i wanted, well sorta. it did get rid of some of the clatter but the timing is still set at 8*. my next step is to put another distributor in it. the guy that has the wrecking yard is gonna give me one. i did notice while looking at another one the difference in the center shafts. this one i was looking at had ears that came off the advance plate and the slots did seem smaller. now this could be my mind playing tricks, but if the slots are smaller then that would limit my total advance and thus FIXING MY PROBLEM and then be able to set timing at 10-12* oh well back to the drawing board. just think how good its gonna run when i do get it right, i have been through everything else

*Zilverado* · 02-04-2003, 04:03 PM

Sorry to hear the bad news, Jeff. I don't have any advice, but have been following your saga for interest sake.

Hope things turn around soon.

**swervin ervin** · 02-04-2003, 04:44 PM

Never give up. You will get it one day for sure. I just can't understand it myself. I bet when you do finally fix it, it will be something fairly simple.

Good luck.

bigd65 · 02-05-2003, 09:10 AM

yea and it will help out another. this other guy has been having the same problem but in a van.

*rayville body* · 02-05-2003, 09:44 AM

put a pickup coil and advance weight kit in your distributor. they dont cost but $7 at the most, much cheaper than new one. i had a 305 i just rebuilt ,had 2000mi on a rebuild and it started rattling. it sounded like weak mains but it wasnt. i got in it one day, it fired up and went dead, that was it! i towed it home, put a pickup coil in it and weight kit and it ran like a new one. just my 2cents

GMC Jim · 02-05-2003, 02:01 PM

Not as simple as just putting in a advance weight kit....Every engine has specs for the advance curve ( amount of degrees advance per specific RPM.). Only a shop that has a distributor machine ; enabling the installation of the proper weights and springs combination to achieve desired specs.....Also the vacuum advance must operate in the appropiate RPM range....

For example; GMC Shop manual for my '71 402 BB is (degrees) ---- 0 @ 930 RPM; 2 @ 1260 RPM; 16 @ 2400 RPM and 30 @ 4400 RPM. The vacuum advance should be 0 @ 8" h.g and 20 @ 17 h.g

Another GM manual shows the the total ( centrifugal and vacumm) advance should be 28 to 35 @ 2000 RPM... So, when installing the calibrated HEI distributor; I set the timing lite at 33 degrees, engine@ 2000..... and have been quite satisfied with engine performance andf fuel mileage......
I don't pretend to be an expert in all this but the distributor shop did stress the importance of maintaining factory specs ...
..........Made sense to me............

02-01-2003, 06:09 PM	#1
bigd65 Registered User Join Date: Mar 2000 Location: Clute, TX. Posts: 1,935	ok check this idea out well the clatter problem aint totally fixed, yes i am pissed. but, i got an idea what it could be. he other day when i had the top of the carb off, i noticed the fuel level was below the slosh plates. you know the plates the keep the fuel so the secondaries are fed. well i raised the float level and it fixed it a bit but the clatter is still there at WOT. well today i was at a buddy of mines and we check the total timing. its 28 total at 3,000 rpms. (8btdc +20centrifigal) ok thats text book. well as i was reving the engine, i noticed the fuel filter was not filling up, in fact there was very little fuel retaining in the filter and this was after i let it back to idle. so, here i go again, we checked the fuel pressure and it was about 6.5 psi. right thats about normal. well here is my question. is it possible the fuel pump can be weak and not be able to keep up with the demands of the motor drawing the fuel at WOT. i am thinking about changing the fuel pump, but was wondering what yall thought about ths therory. PRAYERS for THE PASSENGERS AND PILOTS OF THE COLUMBIA __________________ 2004 Silverado Crewcab 1972 Chevy Monte Carlo 2017 Chevy Tahoe

02-01-2003, 11:07 PM	#2
bigd65 Registered User Join Date: Mar 2000 Location: Clute, TX. Posts: 1,935	^^^^^^^^^^^^^^ __________________ 2004 Silverado Crewcab 1972 Chevy Monte Carlo 2017 Chevy Tahoe

02-02-2003, 12:26 AM	#3
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	I guess anythings possible. If you have 6.5 psi at idle, I doubt you are running out of gas at WOT. It if was, you would sure be able to tell it by the way it ran. __________________ Mike 1985 Chevy C-10

02-02-2003, 12:50 AM	#4
79Silv4x4 Workaholic Join Date: Oct 2002 Location: Katy, TX Posts: 1,589	Actually, yes. Hotrod handbook indicates that you should have fuel pressure of 7 psi @ WOT-any less and you could be losing performance. BTW, carb, not efi. __________________ 1979 K-10 Silverado (work in progress) 1991 V1500 Subruban 1999 Suburban LT 4x4 2006 Suburban LTZ (daily driver)

02-02-2003, 02:28 AM	#5
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	Change the pump. No major problem and good assurance than having an old pump. __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos

02-02-2003, 06:21 PM	#6
79BIG10 I'm back with 2nd truck! Join Date: Feb 2002 Location: Texas Posts: 3,774	I agree. Chenge the pump and look to see if it makes a difference. __________________ 1979 Chevrolet Bonanza Big10 "Tootsie Roll" 1985 Chevrolet Silverado (wife's) Member of the Southern Bowties Club "Don't underestimate how sexy a fat man who drinks to excess can be." Homer Simpson

02-02-2003, 07:27 PM	#7
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	I think changing the pump is a waste of time and money, unless it's falling on it's face at WOT. Although, it is pretty cheap and would be one more thing off the list.

02-02-2003, 09:44 PM	#8
AJII Registered User Join Date: Jan 2003 Location: Guntown,MS Posts: 172	In my RX7 I had the same problem. Whenever I hit the gas it wouldn't accelerate and would chatter real bad. Replaced the pump and the problem went away. AJ

02-03-2003, 09:37 AM	#9
bigd65 Registered User Join Date: Mar 2000 Location: Clute, TX. Posts: 1,935	i replaced the pump yesterday. i will see if that fixed it today, i other thigs to do yesterday. i am thinking this may have been the problem, yea how many times have i said that LOL. anyway, im thinking it wasabout to go south, i could smell fuel in the oil where the pump mouts but i may have been smelling what leaked out. anyway, it was time to change that because it was off the old tired 305 with 180,000 miles that i took out about 5 years ago. i know this cause i didnt replace it and the 87 BURB this motor came from was fuel injected and didnt have a mechanical pump.. it seems better and the fuel filter is about 3/4 full all the time. i'll keep yall posted . i will be excited to be able to set my timing at 12* initial, it runs fantstic at off idle and part throttle at 12*. __________________ 2004 Silverado Crewcab 1972 Chevy Monte Carlo 2017 Chevy Tahoe

02-03-2003, 01:09 PM	#10
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	Good luck with it Jeff. I didn't realize the pump was this old. You done good by changing it then. One things for sure, it won't hurt nothing. __________________ Mike 1985 Chevy C-10

02-04-2003, 03:56 PM	#11
bigd65 Registered User Join Date: Mar 2000 Location: Clute, TX. Posts: 1,935	well it didnt help what i wanted, well sorta. it did get rid of some of the clatter but the timing is still set at 8. my next step is to put another distributor in it. the guy that has the wrecking yard is gonna give me one. i did notice while looking at another one the difference in the center shafts. this one i was looking at had ears that came off the advance plate and the slots did seem smaller. now this could be my mind playing tricks, but if the slots are smaller then that would limit my total advance and thus FIXING MY PROBLEM and then be able to set timing at 10-12 oh well back to the drawing board. just think how good its gonna run when i do get it right, i have been through everything else __________________ 2004 Silverado Crewcab 1972 Chevy Monte Carlo 2017 Chevy Tahoe

02-04-2003, 04:03 PM	#12
Zilverado Account Suspended Join Date: Nov 2002 Location: Winnipeg, Manitoba, Canada Posts: 798	Sorry to hear the bad news, Jeff. I don't have any advice, but have been following your saga for interest sake. Hope things turn around soon.

02-04-2003, 04:44 PM	#13
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	Never give up. You will get it one day for sure. I just can't understand it myself. I bet when you do finally fix it, it will be something fairly simple. Good luck. __________________ Mike 1985 Chevy C-10

02-05-2003, 09:10 AM	#14
bigd65 Registered User Join Date: Mar 2000 Location: Clute, TX. Posts: 1,935	yea and it will help out another. this other guy has been having the same problem but in a van. __________________ 2004 Silverado Crewcab 1972 Chevy Monte Carlo 2017 Chevy Tahoe

02-05-2003, 09:44 AM	#15
rayville body Account Suspended Join Date: Nov 2002 Location: rayville,LA Posts: 226	put a pickup coil and advance weight kit in your distributor. they dont cost but $7 at the most, much cheaper than new one. i had a 305 i just rebuilt ,had 2000mi on a rebuild and it started rattling. it sounded like weak mains but it wasnt. i got in it one day, it fired up and went dead, that was it! i towed it home, put a pickup coil in it and weight kit and it ran like a new one. just my 2cents



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02-05-2003, 02:01 PM	#16
GMC Jim Senior Member Join Date: Dec 2002 Location: Portland, Oregon Posts: 901	Not as simple as just putting in a advance weight kit....Every engine has specs for the advance curve ( amount of degrees advance per specific RPM.). Only a shop that has a distributor machine ; enabling the installation of the proper weights and springs combination to achieve desired specs.....Also the vacuum advance must operate in the appropiate RPM range.... For example; GMC Shop manual for my '71 402 BB is (degrees) ---- 0 @ 930 RPM; 2 @ 1260 RPM; 16 @ 2400 RPM and 30 @ 4400 RPM. The vacuum advance should be 0 @ 8" h.g and 20 @ 17 h.g Another GM manual shows the the total ( centrifugal and vacumm) advance should be 28 to 35 @ 2000 RPM... So, when installing the calibrated HEI distributor; I set the timing lite at 33 degrees, engine@ 2000..... and have been quite satisfied with engine performance andf fuel mileage...... I don't pretend to be an expert in all this but the distributor shop did stress the importance of maintaining factory specs ... ..........Made sense to me............ __________________ '71 GMC;fleetside;PB/PS/AC/CC/402 Eng./Custom Paint/110,000act miles/3 fuel tanks(52gal).

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