Guys In about 4 hours I am about to pull the plug on my honeymoon on the hotrod power tour. I have built a brand new L98 (gm L31 shortblock) and have a lifter type rattle in the motor. It has been in the motor since I fired it. It runs great, good power, idle, decent mileage, BUT it rattles. It sounds like a badly adjusted solid camshaft. Its a stock L98 roller cam from the first motor with brand new GM roller lifters. New roller rockers, pushrods, tall valve covers etc. I've had the top end apart and everything is mint. I've taken the 1.6 rr's off and installed the stock steel 1.5's...no change. Its got great oil pressure and all sorts of oil at the rockers. I installed a new tpis bigmouth and the four pads that the fuel rails bolt onto are a machined surface. Except for one. Bad casting that is to low. Not alot, but low. Now I cannot remember if the injector body bottoms out on the intake. When I screw the rails down the injectors are pushed right down onto the intake so that the body of the injector is right in the intake. I am wondering if the injector pulse is resonating through the now aluminum heads (were steel before) and thats what I'm hearing. are the injectors on you L98's pushed right up to the body of the injector? Also I installed a holley afpr and I can feel the ticking sound through the body of the afpr. Has anyone else installed one of these and had it tick loudly. I took the car on a 6 hour round trip Saturday and it ran fine. But I am not taking the chance of leaving my new wife on the side of an interstate 1500 miles from home on our honeymoon. Help me out here guys. I've got $7000 and 4 1/2 months of my time in this to go on the power tour and I'm hours from pulling the plug. Please look at your injector locations or let me know about your afpr (mines a holley) Sorry for the long post.

 

i can hear the injectors in every thirdgen V6, 305, or 350 i have ever run across, all pretty clearly. they tick pretty loud, and it sounds a bit like a rattle when the hood is down and it's muffled a bit.

stick a long screwdriver on the motor and listen with your ear pushed up to the handle until you find the area where the noise is the loudest, if its the injectors i'd drive it.

 

Thats the thing....the injectors and rails are the same injectors from the first motor that made no noise. The only new piece in the fuel system in the Holley afpr. The screw driver gives me the loudest noise at the regulator and the pass two rear injectors which are closest to the reg. I'm trying to do a search right now but not finding any issues with a really loud afpr.

 

A fuel pressure regulator has a low chance of making a noise like that. It does have a large spring in it but its not likely that the spring could recieve enough force to cause it to surge that way. Loud high pitch tick? Put a stethescope on the valve covers check em out. anything that moves on the front of the motor can tick to. Make sure your fans are off the radiator fins and no trans lines are bouncing off harmonic balancer grooves, etc.
If power tour is comi9ng through, take it out there and see if someone will lend a hand. You might not b able to figure it out but someone out there surely can.
Good luck to you sir. I hope you find that tickin grimlin.

 

My car makes the same noise. does it have hyperutetic pistions? if it does i've taken mine to a ASE certified tech that specializes in engine noises, he told me it was a little piston skirt noise an nothing to worry about. I've put about 5,000 miles on it and no problems thus far. good luck i hope you don't have to cancel your honeymoon.

 

Yep...I looked into the piston slap issue also. The noise should change as the motor heats up though. This doesn't. I can actually feel it in the regulator. I was thinking the same thing about the afpr. There is only a diaphram, spring, cup/washer and screw. The only moving parts are the flat steel piece on the diaphram with that spring and ball. This is a heavier sound then I thought an afpr could make, but when you put the screw driver up to it, its right there. Just like a lifter only in the center of the valley right in front of the dizz. I still have my stock regulator but I don't have another set of high flow gaskets for the runners to pull the plenum. Anyone got a way of changing the afpr without pulling the plenum?

 

Thanks for the help guys....Heres what I found. After six weeks of chasing this noise (motor apart twice) I have pinpointed it to this. The Big mouth intake, when I pulled it from the box has for mounting points for the fuel rails. Three are machined, one is not. This tells me its a bad casting that is low. As I tighten the rails down it pushes the body of the injectors right up against the intake. I believe these injectors are suppose to float, yes? Therefore if the injectors are solid up against the intake any injector noise, and they are bosch's, would be transfered through the intake into the aluminum heads (new to this motor, steel on the old motor) which is amplifying the injector pulse. Add to that I am now running an afpr (when the old motor was stock) with 45 psi and the old motor had 41 psi. Also being a batch fire injection system it makes matters worse. The old....stock intake, steel heads, these bosch injectors, stock steel 1.5 rockers, 41 psi......the new motor.......tpis intake, aluminum heads, same bosch injectors, afpr w/ 45 psi, 1.6 rr's. So bury the injectors which are louder due to more fuel pressure and then let all the new aluminum amplify the noise and you have a bad lifter noise. I did a search on this last night and found three posts (1 exactly the same problem) with the same issues. I am going to loosen the rails and slide some washers in (easier said then done with the plenum on!) untill the injectors are clear of the intake. Thanks for your suggestions. Power Tour here we come!