stevo1988

I drive a 1985 Oldsmobile Cutlass Salon which originally came with a Chevy 305. Over summer of 2012 I just built a 350 30-over to put in the car. So far it has about 3,000km on it since i put it in. I had this problem since day one and I believe it is timing related since i drive the car every day and it hasnt blown up yet.

The motor is a 4-bolt 2-pc rear seal 350, the only parts I carried over were the block, crank and connecting rods, everything else was put in brand new.

I sent the block, crank and rods to a machine shop and they punched out and honed the bores and turned the crank, aligned the rods, honed the lifter bores and gave me a new oil pump (stock volume/pressure) and new pistons from speed-pro. digital diamond series hypereuretic flat top pistons with 4 valve reliefs. I believe they add about 6-7cc to the combustion volume. they installed the crank, rod and cam bearings for me.

The cam i am using is hydraulic flat-tappet comp cams hi-energy 268 (adv. dur.) with the lifters and springs to match it with a Milodon double-roller taiming chain set. Up top is a set of World Products S/R Torquer cast iron heads with 2.02"/1.60" Manley valves. I got the heads machined 0.125" on the rocker stud base to install guide plates and removed the pushrod guide holes to make clearance for 1.6 ratio rockers i got from JEGS. they are the 50-series aluminum full rollers. The heads have an advertised chamber volume of 67cc so combined with the rest of the motor i should be just above 9:1 compression, nothing that could cause octane to knock. The intake I am using is the JEGS 331 dual plane aluminum intake topped with an Edelbrock 600cfm performer carb #1406. The rest of the ignition is the stock HEI unit that came with the car aside from a set of 8mm plug wires and AC Delco R43 spark plugs.

Right know I am running without vacuum advance hooked up because it caused alot of pinging to happen around 2000 rpm. I backed off the timing to about 8 degrees which solved the problem except when im in 1st or 2nd gear at light throttle it pings around 2000 rpm. If I am heavy on the throttle it doesnt ping nor does it ping while in 3rd gear. I am thinking that maybe my mechanical advance is too lazy causing the timing to advance too much at cruising speed. But then I think maybe my carb is too lean at part throttle with my combination because in 3rd gear my secondaries may be opening enough to richen the mixture thus not pinging like at lower speeds.

Can anyone help me to trouble shoot what could be the problem? I am willing to re-jet/rod the carb or re-curve my distributor (or both) if needed.

Ask me anything
Thanks

kevinkpk

Try a 700 or so cfm. Valve size is okish for a 600, but the cam may be the issue with that small of carb. What fuel?

stevo1988

Been running it on 89 octane, trying lots of octane boosters. its warming up where i am and it pings a little tiny bit more than usual. All the motor has seen so far is winter and the whole winter at that.

The Edelbrock 1406 carb i bought was geared toward the 305 that i retired so its considered a "Mileage-over-Performance" 600cfm model. Are main jets referring to the primary off-idle system? Or do i need to change any jets to my secondaries if the problem begins around 2000 rpm?

Its for light throttling only, at WOT it does not ever ping like marbles in a tin can. It isnt loud but when i had vacuum advanced hooked up it seemed to make it worse.

I am using the manual charts to choose what rods or rods+jets to improve my situation:
Stock: Main Jet #1427 (.098") Metering Rod #1459 (.075" x .046")
Change: Main Jet #1426 (.095") Metering Rod #1446 (.068" x .042")

would this configuration be a good change? Using the chart it puts me into a richer cruise mode and toward Power Mode: Low Vacuum / High Power - Rod up 2 stages rich (8% over stock)

Cam Specs:
Single Pattern
Hydraulic Flat-tappet
218* Duration @ .050"
0.302" Lobe lift
0.484" Valve lift (w/ 1.6)
110* Lobe separation
106* Intake centerline

kevinkpk

Not real familiar with edelbrock, but with quadrajet. The primary rods are what is used without wot, with wot that kicks in the secondary. You might increase the metering rod (primary) a little since you only have this issue at lower rpms.

stevo1988

I ordered the rods and jets. I'll try one at a time to see how they work. I also ordered a re-curve kit for my HEI and an adjustable vacuum advance kit both from accel. I also ordered timing tape from msd so i can properly set the timing since i dont have a dial-back light

kevinkpk

To me it is a little fuel starvation at lower rpm due to the larger intake valve size. Anyway, post back. I'd be interested in the metering rod increase before doing anything else if that alone cures the problem.

stevo1988

That is an interesting idea about the intake valves affecting the A\F mixture. It probably doesnt help that I increased the valve lift too by using 1.6 ratio rockers. But thats why I decided to go 2 stages rich on the primary side and not only 1. I will post back with my results

Camaro 69

Are you using anything different timing related (harmonic dampener, timing cover and/or timing tab) than what was on the old engine? If you're using an aftermarket timing cover and tab, you want to make sure the marks are in the same position as the stock ones that were matched with with the dampener you're using. Not all dampeners have the timing notch in the same clocking position, depending on application. It's possible TDC may not be where you think it is. Since you're going to use timing tape, it would be a good idea to pick up a TDC tool and find your true TDC before you stick the tape on.

stevo1988

My timing tab (which is part of the timing cover) is an after-market piece, yes. The balancer also is after-market and no the timing marks did not match up when i put it together. But at the time i hadnt installed the heads yet so using a dial indicator i found true TDC and put a center punch on the balancer. The problem was that i was limited by the amount of degrees from the tab which is not enough to check total timing. I will order a TDC tool for sure though

kevinkpk

Seems to me you matched a cam with valve porting, however I feel the weak link is the 600 cfm carb.