C4 + LS1 + T-56 = Good times!

[subtlez28]

Matt, come on over, the smell is driving me nuts!



Yeah, if I wasn't clear, the engine sits on those braces. There were diaginal square tubing braces stock. They welded on the braces and gussets.

So, they support the weight of the engine and trans, and contain it's torque. Probably why it is separating.

I have a duplicate thread on CF and a couple others. I have received good and different info on different sites.

[Bow Tie 67]

How was the LT1 originally bolted it? What were the square tubings original function?

I would suggest round tubing to replace it and a strong gussetted plate attached to it.

[subtlez28]

Its an 84, it had an old SBC (Crossfire). They cut off the engine stands. They used C5 stands because it was done in like 01, before aftermarket mount adapters were out.

The square tubing is just structural brace.

[WS6]

Duuuuuuuuude! That's some serious bubba engineering. I still haven't looked at the pics you sent me but I'm guessing they're similar. You have a lot of stuff that is just plain dangerous going on in that car. The good news is that it can be fixed easily since you're not trying to just bolt this in and go.

LT1 C4s held the engine in a similar manner as those people were trying to replicate. Build stronger braces and you can mount the engine in a similar but correct manner. Here's Chris MacDonald's home page. He did an LS2 into a C4 in a similar manner to how you'll need to do your setup. http://mcspeed.homestead.com/ Chris is also a member here. Good info on his page that should help you out.

Your engine is not offset to the passenger side that's for sure. To be certain you have it in there correctly, measure the location of the pinion on the diff since you have everything apart. Then make sure the crank snout is the same distance off center. I think I measured 1.5" when I measured for you. If you need those pictures I sent before again, I should still have them and can send them.

I can't say for certain the headers will clear the bracing you need to build to hold the engine. I didn't design them around anything like that. You may want to get the headers before you build the supports. I'd get them uncoated at this point.

Keep the return style fuel rail since you have it. That will be easier for you than trying to install the C5 FPR. If you need the sending unit that hopefully is still in the tank, let me know. I have a couple sources for salvaged C4s and can pass the numbers on to you. The rear end and fuel tank need to come out to get the fuel lines up in there. You may be able to snake the ends up into the fuel tank area though. The rest of it simply connects up from the bottom if the rear end is out of the way. You should be able to use an L98 fuel filter on the fuel lines. Earl's makes adapters that will screw into those fuel filters and convert to AN for you.

The factory front crossover brake line was attached to the diagonals that were on the car originally. The bracing they put in place of them to hold the engine up probably caused them to alter those brake lines so terribly. Go with stock replacements and see what you can do to work around them or alter them in a better manner. Those lines are really pushed around.

Let me know if you need anything else Shaun and I'll try to get back to you quickly. School is killing me right now but I'll do my best.

Oh, our little cam and pocket ported 5.3 put out 350rwhp/338ftlbs to the wheels through the tremec TKO. Had a very flat torque curve. Very fun to drive what little I did drive it. 100 times better than a TPI engine especially the one that was in our car.

Good luck. It'll be so worth it.

[WS6]

To give you an idea of how far off the engine is from correct, a stock C5 power steering pulley will fit and clear the frame ears for the upper control arm no problem.

[subtlez28]

Thanks Trey!

I will likely move the engine over to the passenger side. I removed the HVAC, so room is plentiful over there. It was a B!+# to gen the driver's side shorty header out, so I'm worried about long tubes.

[subtlez28]

Decisions, decisions... My 1st plan was to leave the engine together so I could focus time and energy on the other areas of the swap. Then go through the engine next winter.

But, with all the 1/2-@$$ stuff I'm finding, I wonder how much could be wrong with the engine. I noticed the rear of the engine is abnormally oil covered (was an auto car) and the rear cover is missing a bolt... Also, the driver's valve cover is missing a bolt...


I picked up:
LS6 heads
LS6 cam (and springs)
Ported Oil Pump and TB (by Drag Werks)
LS6 Intake
Katech rod bolts
and I'm considering an Improved Racing F-Body Trap-Door Race Baffle (oil pan baffle)

So I'm strongly considering going through the engine now, rather than gamble. Not to mention more power is a beautiful thing!

Tomorrow I'll clean this thing off and ponder...


Input is welcome here.

Also, does anyone have an extra rear cover or 98 Valve cover bolt?

[WS6]

Actually, the driver's side header goes in from the top or the bottom. It's very close to the firewall right where it juts out from the wiper motor area to the brake booster flat. The passenger side header comes in from underneath. It's not bad at all really.Like I said though, I didn't design them for use with cross brace type stands. Supposedly some guys with LT1 cars that have gutted and converted them are using the headers no problem. Those cars simply use C5 stands and some other mounts to position the engine.

[subtlez28]

So, LT1 cars have different engine mount set ups? I wonder if I could convert to those. Do you have more info or pics on the LT1 style mounts?

[WS6]

No I don't unfortunately. Basically, the LT1 used stands just like the C5 did to hold the engine up. These stands mounted onto the Kbraces(the diagonals that are under the engine in these cars). The Kbraces for an LT1 car are a little different than the early L98 cars in size, shape, and connecting points. However, the idea will work the same for you. Just build some nice diagonals that are strong enough to handle the weight of the engine which isn't much. Keep the diagonals as short as possible so that don't intrude into the engine bay too much.

A search on CF in the photo gallery should produce some pictures for you. They have 1000s of pictures typically.

[subtlez28]

Trey, I haven't located pics of the LT1 C4 set up yet, but..

A member of another board who is doing a similar project suggested fliping the C5 stands.

Flipping the stands moves the contact spot ahead ~4.5". The bushing lines up with the bosses on the block, so flipping to the front mounting bosses is easy to calculate even without C5 stands.

The bad news is on the passenger side the stand interferes with the C5 A/C bracket. The good news on that is the part of the A/C bracket it contacts doesn't seem necessary. It is that furthest back ear, I don't yet know why it couldn't be ground off, or even what it is for...

That far left hole is just kind of floating back there.
Not an issue for me, as I do not intend to run A/C.

Now, moving my mounting location ahead 4.5" puts me just behind the flat surface of the cross-member. This would be an easy location to add a plate.



Only down side it the flat surface of the crossmember is 2.5-3" higher than the current mount location. I want to raise the engine, but not quite that much. Although I would think using something other than the C5 bushings would solve that.

The C5 stands bushing location is about even with the top of the pan. My f-body pan hangs ~5.5" below (a C5 pan ~5" according to the conversion pan sticky). The C5 bushings are ~3". So if the cross member hangs 2.5" below the bushing, I'm set.

More good news is that by moving the mount back 4.5", I can run flat between the 3" bushings and not hit the pan (no cut out required).

[subtlez28]

Wow, time has flown. Not much progress over the winter except some parts gathering.
I picked up 4 17x11s and 315/35/17 Kumhos from DTD. I will run these on all four. The 36 mm offset is close, but it looks like I will need to run a small spacer. I went with the Kumhos as I intend to run street tire class.


I also picked up some other cool and surprisingly expensive parts like LS1 ARP head bolts, crank bolt and flywheel bolts. A road race oil pan baffle from Improved Racing. A Fel-pro gasket set. Clutch hydraulics. A used T56 bell housing and mini starter. New water pump, tension pulley, and idler pulley for the C5 accessory drive.


Over the last couple days I finished grinding off the old mount system (this was an early LS1 conversion). I plan to make new mounts from angle iron coming off the crossmember, and C5 stands flipped forward. This will be similar to LT1 mounts, and have been successfully used by other swappers. I cannot use the speed hound conversion mounts as my original mounts were cut off during the previous swap.

The old cut off mounts were plated welded to the cross braces and frame:

It took more time and effort to grind these off than I expected...



I also dug the Liberty Face-plated T-56 out of its crate. Face-plating is a process where the syncros are removed (except for 5th and 6th). This will allow for extremely fast upshifts (think motorcycle or Jerico trans).

I bolted on a stock f-body hurst shifter. Then I mounted the C-beam adapter bracket... This was no easy feat. I had to batter it into position. I tried using a rubber mallet but eventually resorted to beating it into place with a BFH... So much for the pretty powder coating. Once in place I had to use this C-clamp to torque it into a position where the 3 bolt holes lined up.


Hopefully I will make more progress as in the next couple days.

[brrymnvette]

Awesome build. I see a 96 vette everyday and wish I still had mine more and more to do this exact swap with.

[73lt4]

Here is a pic of a C4 frame that had an LT1.

[CruizinKev]

sweet! looking good!!

[andrewb70]

Nice to see you working on this project Shaun. I know that trans!!! :-)

The torque arm mount looks scary. I am not worried about the mount itself, but more about the integrity of the tailshaft housing. I am sure the Tremec engineers never intended the tailshaft housing to experience such loads in a cyclical fashion. Every time you get on and off the throttle, the tailshaft housing will be stressed. This may not be a huge issue given the length if the torque arm, but it's something to think about.

Andrew

[subtlez28]

Nice to see you working on this project Shawn. I know that trans!!! :-)

The torque arm mount looks scary. I am not worried about the mount itself, but more about the integrity of the tailshaft housing. I am sure the Tremec engineers never intended the tailshaft housing to experience such loads in a cyclical fashion. Every time you get on and off the throttle, the tailshaft housing will be stressed. This may not be a huge issue given the length if the torque arm, but it's something to think about.

Andrew

Hmm, thanks a lot Andrew! Now I can worry about another breakage point!

Actually, I hear what you are saying. However, 3rd and 4th gen f-bodies mount torque arms to the trans. And the original 700R-4s and 4+3s that came in the C4s shouldn't me a ton stronger... right?

Seriously, what do you think?

-Shaun-

[andrewb70]

Hmm, thanks a lot Andrew! Now I can worry about another breakage point!

Actually, I hear what you are saying. However, 3rd and 4th gen f-bodies mount torque arms to the trans. And the original 700R-4s and 4+3s that came in the C4s shouldn't me a ton stronger... right?

Seriously, what do you think?

-Shaun-

Given all that, I am sure it will be fine. This swap has been done before, so if there were problems, people would have discovered them already. Ignore me...carry on...

Andrew

[subtlez28]

Given all that, I am sure it will be fine. This swap has been done before, so if there were problems, people would have discovered them already. Ignore me...carry on...

Andrew

I think you have a valid concern Andrew. Come to think of it the f-bodies at least have a trans cross member to spread the load.

I wonder if the bridge/truss design of the aluminum C-beam works to soften the impact of shock...

Although the stock trans set ups have lived, I do intend to put more power through it than any stock C4 engine. Plus my road race plans, and face plated trans should be kind of punishing...

I think I will pose a question on a vette forum for some explanation, and hopefully comforting information.

But don't worry Andrew, thanks to sleep deprivation and an 11 hour day at work, I still slept fine last night. I didn't dwell to much.

-Shaun-

[John Wright]

I also dug the Liberty Face-plated T-56 out of its crate. Face-plating is a process where the syncros are removed (except for 5th and 6th). This will allow for extremely fast upshifts (think motorcycle or Jerico trans).

hey...how come we didn't get a picture of you standing there holding that tranny up on your shoulder?...and what's with it rolling around on those dollies?...Bwhahaha.