LS7 head fix. TSP vs AHS
09-05-2018, 11:57 PM
#1
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LS7 head fix. TSP vs AHS I have a 2007 Z06 with 29,000 miles which had its heads "fixed" about 7,500 miles ago. Bronze guides and solid exhaust valves were installed as was what appears to be a roller trunion kit. Stock rockers. I had a slight tick that quickly developed into a tap that eventually ended up being a collapsed lifter that bent a push rod up into the head and wedged into the rocker. My warranty company paid for a bank of LS7 lifters, the pushrod and rocker. I picked up the car and it still had the "tick" and it seemed to be getting worse..
I readjusted the rockers and found that I was at 2 1/4+ turns to get to 22 ft/lbs so upon AHP's suggestion, I ordered shorter push rods. While I was installing the push rods I checked the trunions and all is good but the swipe on the intake rockers indicate some of them are swiping near the edge of the valve cap. I levered the valve springs with a large screwdriver and could see the valve stems have a lot of movement in them so I am pretty sure the guides are shot. I also noticed some of the newly replaced lifters would compress easily. I put it together and it was dead quiet initially but the tick returned as soon as the car warmed up.
Bottom line, I think I have two problems. 1) I think I need to get the LS7 lifters out of there. All LS7s make a lot of noise and you know what 95% of them have in common? LS7 lifters. I think I need to bite the bullet and update to the Johnson 2110. 2) The valve guides are likely shot which brings me to where I need some advice. I am not really looking for any performance increase. Just reliability without ticking.
AHP has been great with their advice and to work with. They will work with my warranty company. On CF, everyone seems to be a fan of AHP. That said, the bottom line is they are pretty expensive for what is essentially guide replacement and a valve job. I assume they drill out the old guides and press in new guides along the path of the drilled out guide so whatever geometry you had, you will still have.
Texas Speed has been posting that they CNC the guide out. This allows them to place the guide at the correct angle and possibly re-position it as well (which may fix the issue with LS7 heads where the guide is located the incorrect distance from the rocker mount). In addition, they do a CNC port job and get it all done for a few hundred less than AHP. TSP says they will work with you on things like PM guides and hollow stem exhaust valves. https://www.texas-speed.com/p-1413-p...d-porting.aspx
So How is one to choose? AHP has the reputation but TSP seems to be addressing all of the known LS7 issues for less money and giving you some additional airflow to boot. I invite your thoughts.
I readjusted the rockers and found that I was at 2 1/4+ turns to get to 22 ft/lbs so upon AHP's suggestion, I ordered shorter push rods. While I was installing the push rods I checked the trunions and all is good but the swipe on the intake rockers indicate some of them are swiping near the edge of the valve cap. I levered the valve springs with a large screwdriver and could see the valve stems have a lot of movement in them so I am pretty sure the guides are shot. I also noticed some of the newly replaced lifters would compress easily. I put it together and it was dead quiet initially but the tick returned as soon as the car warmed up.
Bottom line, I think I have two problems. 1) I think I need to get the LS7 lifters out of there. All LS7s make a lot of noise and you know what 95% of them have in common? LS7 lifters. I think I need to bite the bullet and update to the Johnson 2110. 2) The valve guides are likely shot which brings me to where I need some advice. I am not really looking for any performance increase. Just reliability without ticking.
AHP has been great with their advice and to work with. They will work with my warranty company. On CF, everyone seems to be a fan of AHP. That said, the bottom line is they are pretty expensive for what is essentially guide replacement and a valve job. I assume they drill out the old guides and press in new guides along the path of the drilled out guide so whatever geometry you had, you will still have.
Texas Speed has been posting that they CNC the guide out. This allows them to place the guide at the correct angle and possibly re-position it as well (which may fix the issue with LS7 heads where the guide is located the incorrect distance from the rocker mount). In addition, they do a CNC port job and get it all done for a few hundred less than AHP. TSP says they will work with you on things like PM guides and hollow stem exhaust valves. https://www.texas-speed.com/p-1413-p...d-porting.aspx
So How is one to choose? AHP has the reputation but TSP seems to be addressing all of the known LS7 issues for less money and giving you some additional airflow to boot. I invite your thoughts.
Last edited by Formula8; 09-06-2018 at 07:15 AM. Reason: Non Sponsor Link Removed
09-06-2018, 07:13 AM
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One thing I would consider is Lance at Pantera EFI has cast steel valve guides. They should last a lot longer. When mine are up for repair, that is my plan. I would consider using roller rockers so that you can properly shim them to get a better wipe pattern, which should also help with longevity. As to lifters, I like the Johnsons (insert 'Big Johnson' T shirt slogan here).
I would have no issue using TSP or AHP. I see your point about AHP, you're at almost triple the money by the time you add the porting and upgraded valve guides. Very likely the "Moldstar90" is a cast steel piece. I think I would use TSP and see if they can source the steel guides myself.
I would have no issue using TSP or AHP. I see your point about AHP, you're at almost triple the money by the time you add the porting and upgraded valve guides. Very likely the "Moldstar90" is a cast steel piece. I think I would use TSP and see if they can source the steel guides myself.
09-06-2018, 09:15 AM
#3
One thing I would consider is Lance at Pantera EFI has cast steel valve guides. They should last a lot longer. When mine are up for repair, that is my plan. I would consider using roller rockers so that you can properly shim them to get a better wipe pattern, which should also help with longevity. As to lifters, I like the Johnsons (insert 'Big Johnson' T shirt slogan here).
I would have no issue using TSP or AHP. I see your point about AHP, you're at almost triple the money by the time you add the porting and upgraded valve guides. Very likely the "Moldstar90" is a cast steel piece. I think I would use TSP and see if they can source the steel guides myself.
I would have no issue using TSP or AHP. I see your point about AHP, you're at almost triple the money by the time you add the porting and upgraded valve guides. Very likely the "Moldstar90" is a cast steel piece. I think I would use TSP and see if they can source the steel guides myself.
09-06-2018, 11:32 AM
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Originally Posted by KCS
Just FYI, Moldstar90 is a safer alternative to berrylium copper. Good heat dissipation properties but still somewhat soft like bronze.
09-06-2018, 11:59 AM
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Are steel guides better than bronze guides? My PRC LS7 heads from TSP came with bronze guides.
09-06-2018, 12:32 PM
#6
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I do know that with bronze guides it is advisable to use roller-tipped rockers to prevent side-loading the valves which will prematurely wear any softer-metal guides, which bronze is.
09-06-2018, 02:04 PM
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IDK better/worse/etc...
I know people lean toward the bronze in general, because the guide will wear before the valve quicker. Stainless valves do well with bronze guides, because they are softer than carbon steel. G is correct, typically with bronze guides roller tips are recommended due to scrubbing. Bronze will transfer heat better also. However, titanium is harder than steel, and I can see the Ti intake valve cutting away at the guide even faster, resulting in broken valves. I do not have direct experience with the steel guides, but I am planning to use them when the guides are done in my heads, so I'm not trying to push something I wouldn't do myself.
So, my opinion is -- if the concentricity issue is fixed on the heads, I believe the steel guides will last longer with the titanium intake valves. If you are running stainless, stick with bronze guides
I know people lean toward the bronze in general, because the guide will wear before the valve quicker. Stainless valves do well with bronze guides, because they are softer than carbon steel. G is correct, typically with bronze guides roller tips are recommended due to scrubbing. Bronze will transfer heat better also. However, titanium is harder than steel, and I can see the Ti intake valve cutting away at the guide even faster, resulting in broken valves. I do not have direct experience with the steel guides, but I am planning to use them when the guides are done in my heads, so I'm not trying to push something I wouldn't do myself.
So, my opinion is -- if the concentricity issue is fixed on the heads, I believe the steel guides will last longer with the titanium intake valves. If you are running stainless, stick with bronze guides
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09-06-2018, 04:38 PM
#8
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This topic goes on for days and days over on CF. I have no answers. Several guys over there send their heads off to be “fixed”, only to get them back and 10k miles later they are back in the same boat.
My opinion, and I have an engine building background, is to just say no to bronze guides on any engine that you expect to last very long. The benefit of bronze along with heat dissipation, and natural lubricity properties, is that it’s easily machined, because it’s soft. Personally I like stainless valves and pm guides. It just works. Titanium valves are lightweight, and full of “cool factor” but they belong in a race engine. Ti doesn’t have a long lifespan. It get hard and brittle. Yes, there are coatings, but coatings never last forever. I’d go with hollow stem stainless intake valves (weighs 98 grams vs. 88 grams Ti), and put a new set of pm guides in the heads. It works on every other GM engine just fine, for hundreds of thousands of miles. That’s what I have in my LS7 heads, and I expect a long life out of it. Stainless or inconel for the exhaust as well.
My opinion, and I have an engine building background, is to just say no to bronze guides on any engine that you expect to last very long. The benefit of bronze along with heat dissipation, and natural lubricity properties, is that it’s easily machined, because it’s soft. Personally I like stainless valves and pm guides. It just works. Titanium valves are lightweight, and full of “cool factor” but they belong in a race engine. Ti doesn’t have a long lifespan. It get hard and brittle. Yes, there are coatings, but coatings never last forever. I’d go with hollow stem stainless intake valves (weighs 98 grams vs. 88 grams Ti), and put a new set of pm guides in the heads. It works on every other GM engine just fine, for hundreds of thousands of miles. That’s what I have in my LS7 heads, and I expect a long life out of it. Stainless or inconel for the exhaust as well.
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Rich2342 (02-11-2023)
09-07-2018, 11:25 AM
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Thanks for the responses so far. Just to keep the responses on point, this really is not about which type of guide is superior. I have decided I am not going to replace a worn low mileage bronze guide with another bronze guide regardless of the cause of the wear. Also, I am not going to be replacing the light weight factory Ti intake valve with any type of stainless intake valve. However, I will replace the current solid stem stainless exhaust valve with a hollow stem stainless exhaust valve.
I guess to be more specific as to what I need help with is, does the process TSP uses fix more potential issues than the more traditional process it appears AHP uses? If so, there are a lot of positive testimonials on CF re: AHP's work "fixing" LS7 heads while I don't see a lot of feedback on TSP's work on factory heads.
After hours of searching, I did find a blurb on pg 23 of the Corvette Action Center's LS7 article: "Obviously, from a seat run-out perspective, there is a significant advantage in having a service vendor such as Texas Speed and Performance, which uses Newen machines, doing the heads for your modified LS7 engine."
I guess to be more specific as to what I need help with is, does the process TSP uses fix more potential issues than the more traditional process it appears AHP uses? If so, there are a lot of positive testimonials on CF re: AHP's work "fixing" LS7 heads while I don't see a lot of feedback on TSP's work on factory heads.
After hours of searching, I did find a blurb on pg 23 of the Corvette Action Center's LS7 article: "Obviously, from a seat run-out perspective, there is a significant advantage in having a service vendor such as Texas Speed and Performance, which uses Newen machines, doing the heads for your modified LS7 engine."
Last edited by Formula8; 09-07-2018 at 05:16 PM.
09-07-2018, 11:34 AM
#11
Exotic performance **** and typically long OEM service life don't go together. This is a perfect example. Che70velle's suggestion is probably closest but that extra 11% mass in the valve will start to matter as the RPMs really crank as the stress curve doesn't increase in a linear fashion. It's shocking that GMs design has as much headroom as it does.
09-07-2018, 01:00 PM
#12
You may want to consider our TFS 260 heads. We found the geometry issue in the stock heads and putting new guides in the old location is a temporary fix. The geometry on our heads is revised so you won't have any more issues.
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09-07-2018, 01:02 PM
#13
@Che70velle, that's the best one I heard of !!!!!!!!!!!!!!!!!!! I have the valves and the thought of guides is Ever present even with using a shaft mounted rocker. PM guides and Hollow stem valves. Gone head on @Che70velle with your bad azz.
Texas Speed has been posting that they CNC the guide out. This allows them to place the guide at the correct angle and possibly re-position it as well (which may fix the issue with LS7 heads where the guide is located the incorrect distance from the rocker mount)
Last edited by Patron; 09-07-2018 at 01:13 PM.
09-07-2018, 02:21 PM
#15
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@Che70velle, that's the best one I heard of !!!!!!!!!!!!!!!!!!! I have the valves and the thought of guides is Ever present even with using a shaft mounted rocker. PM guides and Hollow stem valves. Gone head on @Che70velle with your bad azz.
09-07-2018, 03:13 PM
#16
TECH Senior Member
Hey, it's Patron... are any of us ever really sure of what he is saying???
09-07-2018, 03:49 PM
#17
@Che70velle, that's the best one I heard of !!!!!!!!!!!!!!!!!!! I have the valves and the thought of guides, is Ever present even with using a shaft mounted rocker. *PM guides and *Hollow stem valves. Gone head on @Che70velle with your bad azz.
My opinion, and I have an engine building background, is to just say no to bronze guides on any engine that you expect to last very long. The benefit of bronze along with heat dissipation, and natural lubricity properties, is that it’s easily machined, because it’s soft. Personally I like stainless valves and pm guides. It just works. Titanium valves are lightweight, and full of “cool factor” but they belong in a race engine. Ti doesn’t have a long lifespan. It get hard and brittle. Yes, there are coatings, but coatings never last forever. I’d go with hollow stem stainless intake valves (weighs 98 grams vs. 88 grams Ti), and put a new set of pm guides in the heads. It works on every other GM engine just fine, for hundreds of thousands of miles. That’s what I have in my LS7 heads, and I expect a long life out of it. Stainless or inconel for the exhaust as well.
09-07-2018, 05:15 PM
#18
Teching In
Thread Starter
Thanks for the response. I did look up the TFS GenX for LS7s. Looks like $2750 for the heads. So I spend about $1200 more, get solid stainless valves and have to use headers. I am sure those are great heads that may work for other applications but a deal breaker for me.
09-07-2018, 09:18 PM
#19
I think it is wise to make your decision with the thought that reworking GM LS7 heads only resets the clock until the next time the same job is needed. Especially if you have a cam with decent lift.
You don't have to be right or wrong.... just take action assuming the risk exists and whether you can accept it or not.
You don't have to be right or wrong.... just take action assuming the risk exists and whether you can accept it or not.
09-07-2018, 10:17 PM
#20
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Thread Starter
I think it is wise to make your decision with the thought that reworking GM LS7 heads only resets the clock until the next time the same job is needed. Especially if you have a cam with decent lift.
You don't have to be right or wrong.... just take action assuming the risk exists and whether you can accept it or not.
You don't have to be right or wrong.... just take action assuming the risk exists and whether you can accept it or not.
As TFS responded, they found the geometry "error", and corrected it. Simply replacing the guide is not likely a long term fix which is probably why many have the opinion it cannot be fixed. If you are going to just replace the guides, I think there probably are some improved materials like AHP's Moldstar or spiral bronze guides or finishes like Del West applies to the current LT4's valves that would provide increased life. That said, if you don't address the angle and just stick an unpolished Ti valve in a standard bronze guide then put stuck rockers on it, I would not be shocked to be replacing the guides again in short order as I am looking at doing.
