need help asap engine problems - The 1947 - Present Chevrolet & GMC Truck Message Board Network

special70gmc · 02-09-2004, 08:09 PM

okay, i made a deal with my autobldy teacher that wile my truck was in his shop (im painting it now) he could drive it in and out of the shop to make room, BUT the f***ing truck never wants to start. it fouls the plugs every two days at least(acdelco r45's) hes getting really aggitated about this whole thing. all i know is the choke IS working correctly,the primary float setting is about an 1/8 inck down from the sight plug and the seccondary float over flows a little out the sight plug. mortec says i have a holley 4160 the # is 80508 and its jetts are (F)72 (R)plate 134-21 6.5
im nt sure how big the accelerater pump is either.

is this carb too bug for my combo? do i need a 650? please help thanks alot -kyle

355cid LT-1
10.3-1 compression
total seal rings
comp xe274-h cam w/comp roller rockers
vette ''492'' castings w/bowl port
2.08/160 manly ss valves
forged + balenced rotating assembly
1 5/8 headers 2 1/2 exaust w/flows +h-pipe
rpm airgap intake
holley 750
regular gm hei
tci street fighter trans w/2400stall
4:10 posi rear

tom hand · 02-09-2004, 08:29 PM

Looking at this page :
http://www.compcams.com/Technical/Dy...74H-10_001.asp
that cam doesn't have very much vacuum, so at idle your power valve is staying open all the time if you are still using the stock one. Use this page to determine how to get the correct one

http://www.holley.com/HiOctn/TechSer...fo/CI-121.html

special70gmc · 02-09-2004, 08:42 PM

it says i have a 6.5'' triggerd power valve so is that really the problem?

cableguy0 · 02-09-2004, 09:10 PM

very well could be the power valve is stuck wide open because that cam is pretty big go down a size or two and see what happens. if everything else is working properly than thats the likely suspect. im willing to bet your gets are actually too small front and rear

tom hand · 02-09-2004, 09:15 PM

Hook up a vacuum gauge and see what it holds in gear. It doesn't say you have a 6.5...it says that is a good all around one. Holley power vales go up to 10.5 I think and the first page says that cam idles at between 11 and 14 inches. I bet the power valve is opening as soon as you drop it in gear...fouling your plugs

*rage'nrat638* · 02-09-2004, 09:18 PM

THAT IS A LOT OF CARB....
YOU DID CHANGE THE RESISTOR WIRE POWERING THE HEI RIGHT?

HOTTER PLUGS....
GAP SIZE????

Short-Fuse 72' · 02-09-2004, 09:28 PM

Damn, you must have your body scraping the ground judging by how high your wheels come into the engine compartment.

special70gmc · 02-09-2004, 10:43 PM

i actually have an hei modified harness so its all been done for me as well as the int regulated alt, i just threw the puugs in i probly could widen the gap some right?

its not that low i really would like bags tho.....................

just remembered that pic was with 31'' tires before i swaped for 26'' ers lol

02-09-2004, 08:09 PM	#1
special70gmc Registered User Join Date: Sep 2002 Location: long island, new york Posts: 1,333	need help asap engine problems okay, i made a deal with my autobldy teacher that wile my truck was in his shop (im painting it now) he could drive it in and out of the shop to make room, BUT the f***ing truck never wants to start. it fouls the plugs every two days at least(acdelco r45's) hes getting really aggitated about this whole thing. all i know is the choke IS working correctly,the primary float setting is about an 1/8 inck down from the sight plug and the seccondary float over flows a little out the sight plug. mortec says i have a holley 4160 the # is 80508 and its jetts are (F)72 (R)plate 134-21 6.5 im nt sure how big the accelerater pump is either. is this carb too bug for my combo? do i need a 650? please help thanks alot -kyle 355cid LT-1 10.3-1 compression total seal rings comp xe274-h cam w/comp roller rockers vette ''492'' castings w/bowl port 2.08/160 manly ss valves forged + balenced rotating assembly 1 5/8 headers 2 1/2 exaust w/flows +h-pipe rpm airgap intake holley 750 regular gm hei tci street fighter trans w/2400stall 4:10 posi rear Attached Images __________________ 1986 c-10 swb 5/7 drop 20'' coys 1958 belair 2door

02-09-2004, 08:29 PM	#2
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	Looking at this page : http://www.compcams.com/Technical/Dy...74H-10_001.asp that cam doesn't have very much vacuum, so at idle your power valve is staying open all the time if you are still using the stock one. Use this page to determine how to get the correct one http://www.holley.com/HiOctn/TechSer...fo/CI-121.html __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS Last edited by tom hand; 02-09-2004 at 08:35 PM.

02-09-2004, 08:42 PM	#3
special70gmc Registered User Join Date: Sep 2002 Location: long island, new york Posts: 1,333	it says i have a 6.5'' triggerd power valve so is that really the problem? __________________ 1986 c-10 swb 5/7 drop 20'' coys 1958 belair 2door

02-09-2004, 09:10 PM	#4
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,948	very well could be the power valve is stuck wide open because that cam is pretty big go down a size or two and see what happens. if everything else is working properly than thats the likely suspect. im willing to bet your gets are actually too small front and rear __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

02-09-2004, 09:15 PM	#5
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	Hook up a vacuum gauge and see what it holds in gear. It doesn't say you have a 6.5...it says that is a good all around one. Holley power vales go up to 10.5 I think and the first page says that cam idles at between 11 and 14 inches. I bet the power valve is opening as soon as you drop it in gear...fouling your plugs __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS

02-09-2004, 09:18 PM	#6
rage'nrat638 Account Suspended Join Date: Mar 2003 Location: THE FALL GUY CHICAGO IL Posts: 5,883	THAT IS A LOT OF CARB.... YOU DID CHANGE THE RESISTOR WIRE POWERING THE HEI RIGHT? HOTTER PLUGS.... GAP SIZE????

02-09-2004, 09:28 PM	#7
Short-Fuse 72' Registered User Join Date: Jan 2004 Location: Austin, Tx Posts: 51	How low can you go Damn, you must have your body scraping the ground judging by how high your wheels come into the engine compartment. __________________ Ya'll hear that? We's usin' codenames.

02-09-2004, 10:43 PM	#8
special70gmc Registered User Join Date: Sep 2002 Location: long island, new york Posts: 1,333	i actually have an hei modified harness so its all been done for me as well as the int regulated alt, i just threw the puugs in i probly could widen the gap some right? its not that low i really would like bags tho..................... just remembered that pic was with 31'' tires before i swaped for 26'' ers lol Attached Images __________________ 1986 c-10 swb 5/7 drop 20'' coys 1958 belair 2door

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