TPiS Big Mouth Fuel Rail Shims
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From: Norwich, CT
Car: '89 Trans AM/'88 GTA
Engine: (2) Tuned Port L98's
TPiS Big Mouth Fuel Rail Shims
Hey friends,
I thought I was going crazy with a collapsed lifter, thankfully.. I’m not crazy. I’ve searched thoroughly, after reading the Big Mouth requires shimming of the rail so the injectors don’t bottom out hard, causing excess noise and poor injector performance.
My L98 does indeed have these exact symptoms after the install with AS&M runners and new valve guide seals.
Ive read multiple threads, however... none gave me specific guidance on what I should use and/or what TPiS provides in their instructions.
Any help would be fantastic.
I thought I was going crazy with a collapsed lifter, thankfully.. I’m not crazy. I’ve searched thoroughly, after reading the Big Mouth requires shimming of the rail so the injectors don’t bottom out hard, causing excess noise and poor injector performance.
My L98 does indeed have these exact symptoms after the install with AS&M runners and new valve guide seals.
Ive read multiple threads, however... none gave me specific guidance on what I should use and/or what TPiS provides in their instructions.
Any help would be fantastic.
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From: Norwich, CT
Car: '89 Trans AM/'88 GTA
Engine: (2) Tuned Port L98's
Re: TPiS Big Mouth Fuel Rail Shims
I’m awaiting confirmation from another member on a Corvette forum but, 1/4” washer shims on the fuel rail towers should provide relief. I’ve noticed loud ticking and decreased performance, (ie running very rich) since the install.
Ive used a stethoscope in numerous locations, valvetrain sounds completely normal, the ticking protrudes mostly from the driver side injector banks.
Ive used a stethoscope in numerous locations, valvetrain sounds completely normal, the ticking protrudes mostly from the driver side injector banks.
Re: TPiS Big Mouth Fuel Rail Shims
Been on here since 1997, never heard of anyone needing shims under the fuel rail.. Seems weird that you'd need to shim the fuel rail when the TPIS intake is the same basic casting as the Edelbrock. Tons of them are out there, you'd think it'd be common knowledge if it was really an issue. By default, the injector O-rings should insulate the noise of the injector bodies from the intake. Further, most aftermarket injectors are shorter than stock, which generally requires leaving the injector keeper clips off, and installing the injectors into the intake base first then into the fuel rail.
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From: Norwich, CT
Car: '89 Trans AM/'88 GTA
Engine: (2) Tuned Port L98's
Re: TPiS Big Mouth Fuel Rail Shims
I’ve been around quite awhile myself, and while most posts and research suggest it is normal for TPI engines to tick that loud... however, I do not agree. If you search enough, you will find quite a few with the same concern. TPiS included washer shims in the package and instructions, not sure why Edelbrock omitted them. I can assure you, it is obvious and loud.
Nevertheless, I’m tracking on it and it will be resolved.
Nevertheless, I’m tracking on it and it will be resolved.
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From: Norwich, CT
Car: '89 Trans AM/'88 GTA
Engine: (2) Tuned Port L98's
Re: TPiS Big Mouth Fuel Rail Shims
Circa 2006:
https://www.corvetteforum.com/forums...gine-what.html
Another:
https://www.thirdgen.org/forums/tpi/...r-problem.html
The complaint is few and far between, but it does exist.
https://www.corvetteforum.com/forums...gine-what.html
Another:
https://www.thirdgen.org/forums/tpi/...r-problem.html
The complaint is few and far between, but it does exist.
Last edited by TPI; Sep 2, 2018 at 11:34 PM.
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From: Pittsburgh PA
Car: 89 Iroc-z
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Re: TPiS Big Mouth Fuel Rail Shims
I agree with drew. Never heard of this problem before.
Injectors do make noise. Some brands are louder than others for whatever reason. Injector sitting in rails at different heights will not do anything for the noise. That just doesn’t make sense.
Second, as said previously, most aftermarket injectors are shorter by a tiny bit which would require you to double o ring the base OR grind down the fuel rail posts on the intake
my last install of a tpis base i had to do this. Did not shim up anything and with southbay injectors there was no excessive noise.
also had to cut down the posts on my stock tpi base to install bosch 36 lb injectors
Injectors do make noise. Some brands are louder than others for whatever reason. Injector sitting in rails at different heights will not do anything for the noise. That just doesn’t make sense.
Second, as said previously, most aftermarket injectors are shorter by a tiny bit which would require you to double o ring the base OR grind down the fuel rail posts on the intake
my last install of a tpis base i had to do this. Did not shim up anything and with southbay injectors there was no excessive noise.
also had to cut down the posts on my stock tpi base to install bosch 36 lb injectors
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Car: '89 Trans AM/'88 GTA
Engine: (2) Tuned Port L98's
Re: TPiS Big Mouth Fuel Rail Shims
The injectors are OEM, I cannot emphasize enough that I’m not making this up. The injectors are bottomed out at the intake base bungs (more or less) and I know for a fact after 12 years of playing with these cars that something is not right. I’ve driven myself crazy pulling valve covers and adjusting lash. I can go on and link others with the same symptoms with the same intake... but, I guess nobody would believe me heheh.
Last edited by TPI; Sep 2, 2018 at 11:51 PM.
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From: Norwich, CT
Car: '89 Trans AM/'88 GTA
Engine: (2) Tuned Port L98's
Re: TPiS Big Mouth Fuel Rail Shims
Update:
Shimmed the fuel rail with 2 standard washers a piece on the fuel rail towers.. no clearance issues with the plenum, obscenely loud ticking symptom is gone, just your standard injector ticking actuation is present, idle quality improved, as well as the rich exhaust fumes.
The injector bodies are not slammed down into the injector bungs like it was.
Shimmed the fuel rail with 2 standard washers a piece on the fuel rail towers.. no clearance issues with the plenum, obscenely loud ticking symptom is gone, just your standard injector ticking actuation is present, idle quality improved, as well as the rich exhaust fumes.
The injector bodies are not slammed down into the injector bungs like it was.
Re: TPiS Big Mouth Fuel Rail Shims
Weird. Now I'm tempted to dig out the parts and try to recreate a clearance issue on the bench.
It's not so much that no one believes you, it's just odd to hear something like this that you would think would come up a lot more often than an occasional post about noisy injectors, and an obscure mention of shims supplied by TPIS and mentioned in their instructions. If it is in the instructions, I'm sure someone could find the instructions in their files and post a copy here.
If it is true that the aftermarket intakes reduce the injector clearance, that'd be good news for those that don't want to run OEM injectors. LT1 injectors, Bosch 3 injectors, even a lot of the parts store injectors and those offered by the aftermarket as stock replacements are 1/8-1/4" shorter than stock.
It's not so much that no one believes you, it's just odd to hear something like this that you would think would come up a lot more often than an occasional post about noisy injectors, and an obscure mention of shims supplied by TPIS and mentioned in their instructions. If it is in the instructions, I'm sure someone could find the instructions in their files and post a copy here.
If it is true that the aftermarket intakes reduce the injector clearance, that'd be good news for those that don't want to run OEM injectors. LT1 injectors, Bosch 3 injectors, even a lot of the parts store injectors and those offered by the aftermarket as stock replacements are 1/8-1/4" shorter than stock.
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From: Norwich, CT
Car: '89 Trans AM/'88 GTA
Engine: (2) Tuned Port L98's
Re: TPiS Big Mouth Fuel Rail Shims
Weird. Now I'm tempted to dig out the parts and try to recreate a clearance issue on the bench.
It's not so much that no one believes you, it's just odd to hear something like this that you would think would come up a lot more often than an occasional post about noisy injectors, and an obscure mention of shims supplied by TPIS and mentioned in their instructions. If it is in the instructions, I'm sure someone could find the instructions in their files and post a copy here.
If it is true that the aftermarket intakes reduce the injector clearance, that'd be good news for those that don't want to run OEM injectors. LT1 injectors, Bosch 3 injectors, even a lot of the parts store injectors and those offered by the aftermarket as stock replacements are 1/8-1/4" shorter than stock.
It's not so much that no one believes you, it's just odd to hear something like this that you would think would come up a lot more often than an occasional post about noisy injectors, and an obscure mention of shims supplied by TPIS and mentioned in their instructions. If it is in the instructions, I'm sure someone could find the instructions in their files and post a copy here.
If it is true that the aftermarket intakes reduce the injector clearance, that'd be good news for those that don't want to run OEM injectors. LT1 injectors, Bosch 3 injectors, even a lot of the parts store injectors and those offered by the aftermarket as stock replacements are 1/8-1/4" shorter than stock.
It threw me through a loop as well, I’ve built 3 TPI based engines, none of which had a Big Mouth intake base, so this has been a first for me as well. According to the TPIS instructions, step 7 in the included install instructions calls for the shims. (Vehicle dependent, injector dependent)
Im willing to bet, because of the thinner tolerances of the Big Mouth, and the fact injectors audibly acuate, the intake is prone to increased resonance of the dreaded “tick” that sounds like a Cold War era Russian beater car.
Id love for you to try and recreate it, and save someone heartache.. keep in mind, this is a ‘88 L98 with factory injectors, and the injector bodies were pretty dog gone deep in the bungs.
Nevertheless, it was abnormally audible, and it ran fairly sloppy considering this car is in fantastic condition. I’m glad I researched it, but it was NOT easy to find any information on it. Maybe 5 or 6 posts in the last 10-12 years with the TPiS Big Mouth and loud ticking.
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Car: '89 Trans AM/'88 GTA
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Re: TPiS Big Mouth Fuel Rail Shims
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From: Norwich, CT
Car: '89 Trans AM/'88 GTA
Engine: (2) Tuned Port L98's
Re: TPiS Big Mouth Fuel Rail Shims
They actually are alittle on the high side, just because I really wanted to isolate the situation. I’ll probably tighten them down a smidge more. No leaks otherwise.
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Car: '89 Trans AM/'88 GTA
Engine: (2) Tuned Port L98's
Re: TPiS Big Mouth Fuel Rail Shims
I can’t find the other post but, he said he scanned the original TPIS instructions, and sent it to the OP; annotating that step 7 calls for the usage of shims.
Last edited by TPI; Sep 3, 2018 at 09:55 PM.
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Re: TPiS Big Mouth Fuel Rail Shims
I would love an explanation how injectors height in the bung holes change fueling characteristics and idle quality
that just does not make any kind of sense
that just does not make any kind of sense
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Re: TPiS Big Mouth Fuel Rail Shims
My car in particular ran pretty dog like in open and even more so closed loop with the nasty click, wish I had some datalog to back it up.
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Re: TPiS Big Mouth Fuel Rail Shims
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Re: TPiS Big Mouth Fuel Rail Shims
I can see how the inj body could hit the lower intake "bung hole" (12 yr old me is laughing) and transmit the noise but how would it reduce performance? You'd have to reeeeally be crushing the inj somehow.
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Re: TPiS Big Mouth Fuel Rail Shims
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Re: TPiS Big Mouth Fuel Rail Shims
The injectors should be able to be rotated easily if not they will cause the issues you had. Just shim up until the can be rotated easily. This does happen from time to time with after market intakes and binds the injector and it my not allow it to close all the way causing the rich condition.
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From: Pittsburgh PA
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Re: TPiS Big Mouth Fuel Rail Shims
The injectors should be able to be rotated easily if not they will cause the issues you had. Just shim up until the can be rotated easily. This does happen from time to time with after market intakes and binds the injector and it my not allow it to close all the way causing the rich condition.
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Re: TPiS Big Mouth Fuel Rail Shims
You call that buried lol? Here is a shot of my injectors in a TPI base, no problem whatsoever. It's possible the bungs in your base cause the injectors to bottom out early (measure the depth so we can compare), and if that is the case, the pressure from the "locked" injectors being held in place by force might be causing internal damage in the injector somehow...
- Rob
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Car: '89 Trans AM/'88 GTA
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Re: TPiS Big Mouth Fuel Rail Shims
Yeah Lethal, I was looking at pictures of my last two motors, and the injectors look like your picture... I think Turtle touched on it, they should be able to rotate freely, regardless of height. Given different intakes and injectors etc etc... the builder should just be cognizant of injector bind.
Im interested in the theory behind having injectors too tight causes a open condition which translates to performance issues...
Im interested in the theory behind having injectors too tight causes a open condition which translates to performance issues...
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