first here's my combo-
-350
-600 cfm edel carb
-rpm intake
-afr 195 heads
-9.9 compression
-comp cams 268xe
-crane full roller rockers 1.5 ratio

i've got a bunch of tuning problems...

-first the engine has a tick to it. my mechanic friend says it's a lifter to loose. i've set them twice now trying to feel for zero lash and then going a half turn more.... am i doing this right? how do i tell zero lash? the first time i tryed playin with the rocker to get it, the 2nd time i was movin the pushrod to try and get zero.... any suggestions?

-second i've got a back fire through the carb at less than 3000rpm. if i give around say half throttle it stammers and/or POW! POW! thru the carb. i tryed a jet that richened it 8 percent for power, but kept the fuel the same for cruising and it got alot worse!! does jetting really cause a backfire through the carb? or am i just multiplying another larger problem... possibly with the valves and or rocker arms?

also does timing play a part in this? i have it set at 12 degrees at about 500 idle with the vacuum line off

any help is really appreciated. i'm hopin to get it running decent by tomorrow afternoon... got somewhere i'd like to take it. http://www.camaros.net/forum/cool.gif

thanks
-Andy

Andy, first I think your idle is a tad low. Bring it up to about 650-700 RPM. Next, I adjust the rockers with the engine running. It's a little messy but it the most accurate method. Pull one valve cover at a time. With the engine running, back off one rocker till it starts tapping. Slowly tighten it till the tapping just stops, then turn 1/4-1/2 turn. Do each rocker this way and you know the valves are adjusted right. Your timing sounds ok at 12 initial but don't be afraid to advance it a little more. Double check your plug wire routing and check for any vacuum leaks. I'm not familiar with Edelbrock carbs so I can't help you there. But I'd set the carb back to stock specs and start over from there. Good luck

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409SB, TH350, 12bolt 4.10
7.18 @ 95 on premium pump gas

andy i have a 268xe in a 76' vette with a 350, and we've set the rockers many many times, my brother, a local mechanic, along with a friend of the family who drag races a blown 80' vette, and we still have alot of tapping.
The reason i've heard it to be is the fast valve ramps of the xe cams.

I'm wondering if you have an intake valve sticking and not closing fast enough?
Is this a new engine?
David

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Check my web page for First Gen Camaro suspension info:
David's Motorsports page (http://ourworld.compuserve.com/homepages/David_Pozzi/)
First Gen Suspension Page (http://ourworld.compuserve.com/homepages/David_Pozzi/first_gen_suspension.htm)
67 RS 327 original owner. 69 Camaro Vintage Racer, 65 Lola T-70 Chev SB Can-Am Vintage Racer

yea everything is brand new... at most i've ran one tank of gas through the new engine rebuild before it started acting up. i put the orgininal jets and rod back in the carb... no difference... advanced the timing, retarted the timing... still no difference... made sure all the spark boots were on good, and changed to another coil... still sputtering hacking and backfiring like mad. starting to think i flattened part of the cam or broke a valve spring.

o yea and i even tryed backing off the rockers from 1/2 to 1/4 turn to make sure they were seating all the way... made no difference.

Aaahh! #@$%& %&*$#!!!!

I'd do a compression test and verify cam lift at each rocker to see if the cam is wiped out.
Check for a broken valve spring.

Watch out for number 5 and 7 spark plug wires. they need to be separated as much as possible, or the juice from #5 firing will jump to #7 and make it fire too early causing problems.

Is there any time it runs right?
David

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Check my web page for First Gen Camaro suspension info:
David's Motorsports page (http://ourworld.compuserve.com/homepages/David_Pozzi/)
First Gen Suspension Page (http://ourworld.compuserve.com/homepages/David_Pozzi/first_gen_suspension.htm)
67 RS 327 original owner. 69 Camaro Vintage Racer, 65 Lola T-70 Chev SB Can-Am Vintage Racer

Cam went flat on one or more lobes is my vote. That "ran good for one tank of gas and then sounds like "pow, pow, pow" backfiring through the intake is a good clue. That is exactly how it sounds. Do some more checking before you tear it all down to be sure.

-Mark.

Backfiring thru the carb is most commonly either bad timing or running the carb too rich. Your timing sounds reasonable but you may try playing with it some.

Pull out the plugs. If they have a black soot covering them, then indeed you are too rich. Check your bowl levels first. Then jet down until your plugs look normal.

Dave

I'm with Mark on this one! Being un-sure of rocker adjustment, less than 1 tank of gas... What cam break-in procedure did you follow? Did you run the carb on anything before the new engine?

Here's some good valve adjustment info, www.camaros.net/techref/ftecref17.html (http://www.camaros.net/techref/ftecref17.html) there's no reason to do it running and get that new engine and everything under the hood messy.

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...Dennis
"The '69 (http://chevelles.com/showroom/ww.jpg), the '96 (http://www.camaroslimited.com/graphics/memcars/96ss.jpg) & the club (http://camaroslimited.com/)"

[This message has been edited by DjD (edited 07-07-2002).]

I keep seeing y'all mention how messy it is to adjust hydraulic lifters with the engine running. I used to use cardboard beer case flats as a shield. Stick the bottom down in the head and maybe some duct tape to keep it in place. It catches most all of the oil and drains it back to the head. Done this a lot of time on straight 6. Should work on V8.

<BLOCKQUOTE>quote:</font><HR>Originally posted by Winch:
I keep seeing y'all mention how messy it is to adjust hydraulic lifters with the engine running. I used to use cardboard beer case flats as a shield. Stick the bottom down in the head and maybe some duct tape to keep it in place. It catches most all of the oil and drains it back to the head. Done this a lot of time on straight 6. Should work on V8. <HR></BLOCKQUOTE>

The real question is why? You can set (espically hyd) them once not running and be done with it forever!!

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...Dennis
"The '69 (http://chevelles.com/showroom/ww.jpg), the '96 (http://www.camaroslimited.com/graphics/memcars/96ss.jpg) & the club (http://camaroslimited.com/)"

I'll jump on David's bandwagon. Do the compression check. There have been two friends of mine that have sticky valve problems on their AFR heads.

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The Red Beast http://www.geocities.com/casanoc

Yeah. I also agree. Start with a compression check and post the results.

Oh, I do my lash adjustments with the motor running too. Not messy at all. You can buy clips that deflect the oil at any parts stop and it really does the trick.

Dave