Heartthrob exhaust not sealing to manifolds - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Orion88 · 04-21-2016, 08:32 AM

I installed a manifold-back system from Heartthrob (the same kit available from JC WHitney or LMC). Had to put a dent in the passenger downpipe to get around the bellhousing. Then after I had all my pipes routed, clamped, and hung, I went to tighten my stud nuts/springs. After they bottomed out I got up and looked in the engine bay, and there were gaps where the donut seals the downpipe and the manifolds. I used the same length studs that I had on the truck initially, and the springs are even a little taller because they aren't compressed down from years of use. Has anyone else had this problem? Is it the donut seals Heartthrob sent me or is the angle wrong on my downpipes?

Orion88 · 04-21-2016, 08:43 AM

Drivers side

Pine Bark Auto · 04-22-2016, 08:04 PM

Looks like mismatched parts to me. Are you sure that manifold uses a "donut" seal? Manifolds that use those usually don't have that material that looks to be about 3/4 to 1 inch thick below the flat surface where your studs screw in. Many later manifolds have a rounded flange such that the pipe seals directly to the manifold without using the seals. If that manifold was meant to use the seals, it would be beveled where the seal fits. The picture looks like the seal is against a flat surface with nowhere to "seat" to. Chip.

crewcabshorty · 04-22-2016, 08:40 PM

oem should have the coil springs to lenghen the the area between the flange and the stud

El Dorado Jim · 04-21-2016, 03:08 PM

use shorter studs

Orion88 · 04-21-2016, 03:17 PM

Thought about that but since I used the same length studs as what I removed and given what a royal pain it would be to pull the manifolds to swap out studs, I wanted to see if there was something else causing my problems. Seeing how heartthrobs kit is an OEM style replacement exhaust system and tons of people on here have used them with no real problems, I'd find it rather unusual that OEM studs would be too long.

TrailerTrash · 04-21-2016, 07:20 PM

im with El Dorado Jim. if you ran out of threads on the studs then that is the problem. you could probably jerry rig it by using spacers or stacking washers or even get a cheap tap and die set and make more threads on the studs.

but ideally new studs are the answer

**MikeB** · 04-24-2016, 11:32 AM

Some donuts are thicker than others. For example, the ones that came with my aftermarket Dorman manifolds are thicker and beefier than the ones included with my HeartThrob kit. I'd stop by a muffler shop to see if they have any that are thicker than yours.

Pontiac1976 · 04-24-2016, 02:13 PM

Get a tap die set make the stud treads a little long so you can tighten a bit more. And maybe replace the center stud it may not take tapping.

04-21-2016, 08:32 AM	#1
Orion88 Registered User Join Date: Feb 2014 Location: Bloomington, IN Posts: 164	Heartthrob exhaust not sealing to manifolds I installed a manifold-back system from Heartthrob (the same kit available from JC WHitney or LMC). Had to put a dent in the passenger downpipe to get around the bellhousing. Then after I had all my pipes routed, clamped, and hung, I went to tighten my stud nuts/springs. After they bottomed out I got up and looked in the engine bay, and there were gaps where the donut seals the downpipe and the manifolds. I used the same length studs that I had on the truck initially, and the springs are even a little taller because they aren't compressed down from years of use. Has anyone else had this problem? Is it the donut seals Heartthrob sent me or is the angle wrong on my downpipes? __________________ You gotta have fun while you're little!!

04-21-2016, 08:43 AM	#2
Orion88 Registered User Join Date: Feb 2014 Location: Bloomington, IN Posts: 164	Re: Heartthrob exhaust not sealing to manifolds Drivers side Attached Images __________________ You gotta have fun while you're little!!

04-22-2016, 08:04 PM	#3
Pine Bark Auto Registered User Join Date: Dec 2008 Location: Clover, SC Posts: 55	Re: Heartthrob exhaust not sealing to manifolds Looks like mismatched parts to me. Are you sure that manifold uses a "donut" seal? Manifolds that use those usually don't have that material that looks to be about 3/4 to 1 inch thick below the flat surface where your studs screw in. Many later manifolds have a rounded flange such that the pipe seals directly to the manifold without using the seals. If that manifold was meant to use the seals, it would be beveled where the seal fits. The picture looks like the seal is against a flat surface with nowhere to "seat" to. Chip.

04-22-2016, 08:40 PM	#4
crewcabshorty Registered User Join Date: Jan 2012 Location: greenville pa 16125 Posts: 283	Re: Heartthrob exhaust not sealing to manifolds oem should have the coil springs to lenghen the the area between the flange and the stud

04-21-2016, 03:08 PM	#5
El Dorado Jim Registered User Join Date: Dec 2009 Location: El Dorado Ca Posts: 3,374	Re: Heartthrob exhaust not sealing to manifolds use shorter studs

04-21-2016, 03:17 PM	#6
Orion88 Registered User Join Date: Feb 2014 Location: Bloomington, IN Posts: 164	Re: Heartthrob exhaust not sealing to manifolds Thought about that but since I used the same length studs as what I removed and given what a royal pain it would be to pull the manifolds to swap out studs, I wanted to see if there was something else causing my problems. Seeing how heartthrobs kit is an OEM style replacement exhaust system and tons of people on here have used them with no real problems, I'd find it rather unusual that OEM studs would be too long. __________________ You gotta have fun while you're little!!

04-21-2016, 07:20 PM	#7
TrailerTrash Registered User Join Date: Jun 2015 Location: PA Posts: 441	Re: Heartthrob exhaust not sealing to manifolds im with El Dorado Jim. if you ran out of threads on the studs then that is the problem. you could probably jerry rig it by using spacers or stacking washers or even get a cheap tap and die set and make more threads on the studs. but ideally new studs are the answer

04-24-2016, 11:32 AM	#8
MikeB Senior Member Join Date: Jul 2000 Location: North Texas Posts: 3,599	Re: Heartthrob exhaust not sealing to manifolds Some donuts are thicker than others. For example, the ones that came with my aftermarket Dorman manifolds are thicker and beefier than the ones included with my HeartThrob kit. I'd stop by a muffler shop to see if they have any that are thicker than yours. __________________ Mike 1969 C10 LWB -- owned for 35 years. 350/TH350, 3.08 posi, 1st Gen Vintage Air, recent AAW wiring harness, 5-lug conversion, 1985 spindles and brakes. 1982 C10 SWB -- sold 1981 C10 Silverado LWB -- sold, but wish I still had it! 1969 C10 (not the current one) that I bought in the early 1980s. Paid $1200; sold for $1500 a few years later. Just a hint at the appreciation that was coming. Retired as a factory automation products salesman. Worked part-time over the years for an engine builder and a classic car repair shop. Member here for 24 years! This is the very first car/truck Internet forum I joined. I still used a dial-up modem back then!

04-24-2016, 02:13 PM	#9
Pontiac1976 Registered User Join Date: Oct 2015 Location: Ottawa, Ontario, Canada Posts: 769	Re: Heartthrob exhaust not sealing to manifolds Get a tap die set make the stud treads a little long so you can tighten a bit more. And maybe replace the center stud it may not take tapping. __________________ 1977 REG cab Long Bed with a 1984 Front Clip, 82 305 .60 over 9.0.1 flat top pistons, 4bbl, TH350, w/84 SS-intake & cam , w/ 1977 big block rad, 1975 gear box, 1984 master w/ metric fittings top & SAE fitting @ portion block, 1975 3.42 gear open diff. Duel 77-87 Factory air cleaner, duel inlet from rad support . Down sized 9' to new 8' Steel flat bed Was a 77 454 w/308 gear. Taken out 550 lbs. up front with motor clip change.



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