Bret unfortunatly the motor is at a shop in Ill and I live in WI. I did ask them to take a picture but haven't got one as of yet. I think I will be going there myself on Weds to drop off my catback and look at this with my own eyes. I just got off the phone with Trick Flow and they have yet to hear about this issue apparantly with LT1 castings. This leads me to think it is not the heads. TFS was going to contact speed inc and try and figure this out for me. I would like to see what happens without guide plates also. I have a hunch that the pushrod is bouncing off the pushrod tube and throwing all geometry off. TFS was asking what size cam I had, what length valves are in it etc. This is really fustrating not knowing what the heck is wrong with this combo. I did suggest going to a 1.5 rr and seeing if that pulled the pushrod slightly away from the head. There was a article in a magazine where a similar engine 9.0 383 TFS heads non lt1 though lost 40hp going to a 1.6 rocker over a 1.5. They traced the issue to the pushrod deflecting off the pushrod tube after the 1.6 rocker located it closer to the head. TFS did not seem to think the guideplates were the issue. He thought my GMPP would be fine but I did order the TFS anyway and Speed Inc should have them thursday.

 

I don't have much experience with the TFS heads, but just wanted to say how impressed I am with Speed Inc and the thoroughness that they have on all the work they do. They have found a lot of problems with my car and aren't satisfied until they are all fixed. I have them building me a 383 with RGR stage II ported TFS right now, I should pick it up in a couple of weeks.

 

I know they are an excellent shop. I have heard nothing but good things about them and the work that they do. I am sure they will sort out this issue and I am very happy they are the ones who noticed it and not me. If it is a issue with the heads then I definitly would rather have them telling it to TFS as they are alot more credible then I am. They have been very straight forward with me and a pleasure to work with. I would recommend them and I have been to anyone needing any serious work done.

 

Sounds like a good shop with the customers best intrests in mind. Keep on reccomending them to whomever you can, it's hard to find a high quality shop that doesnt just care about the quick buck.

 

I definitely will do that. There are only a handful of fast LT1s in my neck of the woods and with them setting up and tuning this combo it should be a good attention getter for the LT1 crowd up here. 2 decals on my car period....Speed INC and CMS. Maybe only Speed since CMS seems to have dropped off the map lately.

 

Our LT1 heads use the GM "Phase 6" Bowtie valve spacing. This is why a standard SBC guideplate will not work.
Use either a set of our guideplates (TFS-30400623-8) or the GM # 14011051 (For aluminum "bowtie" heads, Will have a the numbers "05" stamped on it).
The Phase 6 valve spacing has the exhaust valve moved an additional .050" away from the bore centerline over a "standard" SBC head.
If you try to use any guideplates other than what I listed above (or the previously mentioned Isky adjustable...), You will never be able to come up with correct rocker arm geometry.

 

I am almost 100% positive that is the guide plate we are using and I gave them with the heads/shortblock. If that doesn't fix the issue what else could it be but a defect in the casting. I looked up the GMPP guideplates last night and I am almost positive that the part # you listed is a match to what I ordered. I ordered those to fix the issue I was having with the comp guide plates after doing some research here. Either way Speed inc will have the correct TFS guideplates by tomorrow to see one way or another.

 

Same here.

I hope the TFS guide plate fix your problem but guide plates dont change the horizonal alignment of the rockers, especially if the roller tip is already over top of the valve. They will only locate the rockers over the valve not latterally align them.

I just dont see guide plates fixing the problem although I hope they do for you.

Can you take pics of them?

 

I am sorry I cannot take a pic of them as I am out of state. I did request that Speed Inc. post one so we can all see what is going on. Hopefully tomorrow we will get it up.

 

ah, I finally found this post.

I did not know the GM 14011051 guide plates were the same. Hmm, good to know.

man, it seems like the studs and valves are not in line with each other for what ever reason. Maybe try to loosen the studs on the misaligning ones and and spin 180 degrees to see if that changed anything (bent studs).

If not, I guess the studs/guides would have to have been machined at different angles.

I have never seen a problem with any head like this but I am just trying to put into words what could cause this.

Lloyd

 

Problem is he said all of them are affected. So that leaves us with either the guide bore's or rocker pad/stud holes being mis-machined.

I haven't seen that before either

It's very easy to find out where the problem is depending on what tooling you have availible.

 

I have had to weld up and redrill the stud holes in SBC heads before but it was one head and all the holes. A way to get out of that kind of work is put shaft rockers on it with the mounting holes tweaked to fit the misaligned stud holes.
Crane makes a pretty good set for a reasonable price

 

I would think Trevor would have found the "cant" if the guides were goffy when he did the VJ, so I don't think it's that. I would run the Isky guideplates and if that doesn't fix it then we need pictures.

Bret

 

Depends on which stage of the machining that the error occured. If the guide holes were bored off a miscut deck, then the seat and guide machine would show the guides as being level side to side becuase the deck angle would match the guide angle. But I dont know how many op's and setups they use to fininsh machine the castings so that is questionable. But yes, if the deck is true - then a set of canted guides would show up when leveling for the VJ. If the rocker pads are mis-cut, then it should show up as decreasing pad height across the cylinder head.

There are a lot of different possible causes and it depends on how TFS finish machines the heads, if they are located off a finished deck or if they use a 4th axis roll-over fixture off the accessory holes.

 

I haven't heard back from speed inc or TFS on this issue..HopefullyI will be able to let you guys know the issue soon.