Hello all, I haven't posted in a long time, too much wrenching on my Trans AM apparently, but to the point:

I have a very fresh SBC 383 stroker I just finished putting in last week, eagle rotating assy, -12cc dished pistons, factory Vortec heads (rebuilt not modified or ported) in a one piece rear main seal old Goodwrench block. New factory pressure oil pump, Edelbrock performer RPM air gap, and a new Edelbrock 1405 (600CFM manual choke) with factory jetting, no mods. My Camshaft is an older (but never used) "Ultradyne" 272H, which is a great mild cam, .217 single pattern at and .454 lift at 50, which every one told me is the max safe lift for stock Vortec heads. I also had new "Rhodes" anti pump up lifters that i utilized, which are supposed to be a bit noisy but reportedly lower the duration of a given cam at lower RPM's.

Problem is engine noise, and it is bugging me, it produces a very noticable tapping/knocking noise at idle. It's not much of a thump or deep knock, but it seems around the Drivers side #7 cyl and can be heard under the car while it is idling on the hoist, and above, and at the stoplight everyone looks at you like your car might explode (I don't know what's worse hahaha).

Obviously I haven't driven it much due to this issue, I am very concerned for engine assembly issues, but changing the oil and filter twice after break in (with pre-oiling of course) has shown no metal or anything of concern, it runs like a barn stormer, and all the plugs read really well. I have double checked the cyl 5 and 7 ignition wiring and they don't seem to be crossing over, but I don't know where to go from here.

My Static compression is supposed to be around 9.8 according to what Eagle's parts list and my humble calculations, fuel in it is just regular pump Gas (whatever octane) from last fall when I parked it, the tank is full, but before I go about draining it and trying Some Ultra 94, is that reasonable that it would be just an octane issue?

I have been reading about "Dynamic" compression ratio vs static, so I'm concerned my cam may be too small causing a spike in the Dynamic ratio..

Worst case is I pull the motor and send it to the guy who assembled it, but that's the last resort. I thought I'd try here first and see what input you guys have for me.

I have been searching this site and the web for days now and want your input boys and girls!

Thanks!

 

9.8:1 SCR + small cam = You need to use premium fuel. Dont expect to be able to run regular unleaded.

However, you say it just sits around pinging at idle... Thats not exactly the typical place that turns up. It usually shows up under load.

Could just be old gas.

Put some good stuff in there, check the timing (set it conservative... 10 base timing, maybe 30 all in at 3000 RPMs to start with) and make sure you read the plugs after a WOT run to see if its getting enough fuel.

 

I dont think this is knock/detonation. Sounds more like bad lifter or possibly bearing problems, or exhaust leak. If its only around 1 cylinder I'd bet lifter or exhaust leak first.

 

Well, it is under load in drive at idle and makes noise at that point. My timing is at 10 or therabots, not so much noise in park at idle, starts to make more noise as it gets up around 1500-2500 rpm. I could pull the valve covers and double check lifter adjustment on the fly, and try to drain the fuel, Id hate to spend money on a tank of Sunoco 94 as a guess at the price of fuel these days! Gezz.. If those two don't work or produce any results I'm pretty much screwed with pulling the motor and checking it out right? probably not a good idea to drive it too much, I assume if it's a bottom end thing and I don't see anything in the oil yet it is still salvageable?

 

9.8 is not too high with conservative timing on decent pump gas on iron heads. Its up there and should use premium 91-93 oct but it shouldnt detonate at idle IMO.

The noise varying with rpm still sounds like an exhaust leak or lifter.

Also check your torque converter bolts just to be sure. loose bolts in the flexplate can cause loud tapping/knocking sounds that sound like its coming from the rear of the block.

 

If it's valvetrain it should be very steady if it's only one lifter or rocker arm out of adjustment. Tap... tap... tap... tap... and the noise should happen ... for example, if your motor is idling at 600 RPMs, the noise should happen around 300 times a minute, or half the bottom end RPM's. Count how many times the noise happens at idle in 10 seconsd, and compare that to RPMs. Chances are your RPM gauge is inaccurate, but it should be close enough for you to estimate. A bottom end knock happens much faster than valvetrain tap. It happens at the same speed as the RPMs if it's steady.

If it's a very fast, unsteady knock I would check teh flexplate bolts. If it's a slower tap, I would check valve lash and the header/exhaust manifold gaskets. Remember the exhaust pulses at the same speed that a lifter would tap, since it's sync'd with the valvetrain. But an exhaust leak should be a relatively steady noise (it may come and go but it should be steady when its there).

If it's spark knock you should be able to pull the plugs and see what they're doing. Go drive around the block and make it do that noise, and then pull the plugs and see if you get a bunch of black pepper-like specks on the porcelain portion of the plug under the electrode.

 

my 383 has the same thing, to me sounds like piston rocking in the bore a little, but mine kinda goes away when warmed up, not completely, may have something to do with the stroke and short skirted pistons....

 

I just spoke to a local engine guy, and he said he was concerned about Possible block clearance issues. Like it was not properly clearanced in the first place and possibly why it may be hitting the block around number 7 cyl in the engine. He was pretty rave about the quality of eagle kits like mine so he thinks it's more of a clearance issue since my oil pressure is good and my oil shows clean still. Any thoughts on that opinion?

Steve

 

I have three videos posted in my youtube channel from when I first started my 383.

http://www.youtube.com/user/wortman72?feature=mhee

It still makes the valvetrain noise a little bit on cold starts and at idle, but after it revs, the lifters fill right or whatever and it sounds good. Its not near as severe as in the videos now, so I assume the issue is components that had to wear together. Now I have a very nice pattern on the valve stem and no excessive wear with almost 2000 miles on the motor.

These videos should at least give you an idea about the difference between valvetrain noise and bottom end noise.

 

Sounds very possible to me.

 

well theres a hundred potential reasons an engine might make a tapping noise but on a newly built 383 Id be thinking the connecting rods to block or the connecting rods to cam , or connecting rods to oil pan,were not clearanced correctly, or the valve train has clearance or valve train adjustment issues, most guys who have not built several 383 engines don,t check oil pan,valve to piston, rod to cam or correctly check valve train clearances, theres a huge difference between building an engine and slapping a few parts together and thinking that clearancing the connecting rods to block so they don,t touch is the only mod required

http://forum.grumpysperformance.com/...p=21369#p21369

http://forum.grumpysperformance.com/....php?f=44&t=38

 

Or even rods hitting a windage sreen, if it has one..

 

when fitting a 383 stroker ,you have to dry build the bottom end and rotate ,as the rods run very,very close to the bottom of the bore, it has to be ground down for clearance... just a suggestion,,, hope some help, ive just spent bout 1.5 months trying to start mine from fitting,grrrr..starter probs

 

383 did you have to cut the block back or grind on the crank for clearence.. I had to on the one i built.. sounds like it needed more room to rotate.....just a thought

 

Here's one that got me - changed dipsticks as an incidental during a cam change, and the new one was slightly wider than the old - rod was flicking it each time it came around, sounded like a lifter tap but from the bottom end. Took me a while to figure it out!

 

hey brian,
you always grind the bottom of the bore/liner for the clearance with a die grinder,,,,never touch the crank as this has to be balanced, cheaper rotating assemblies(whatever make,scat,eagle etc) are externally balanced of which you get them balanced....the dearer ones are internally balanced so you just throw them in, but you still have to dry build for clearance.
DONT FORGET ..whatever clearance you have cold,WILL get smaller when the engine heats up give yourself a good 2-3mm cold clearance to be safe

 

Well everyone, looks like the guy thy built my bottom end didn't put in the wrist pin locks and thought they were press fit.. The noise was piston slap and wrist pin on the cyl walls.. Nasty.. Very sad!

I'm not sure how to upload a picture from my mobile here but I have a few pictures people would appreceate..

Thanks for your input folks! Pm me if you want to see the damage!

Steve