Okay guys, I've done quite a bit a research on this conversion and I'm not coming up with a lot information. It looks as if there's not a whole lotta interest in doing this anymore with the holly stelth ram now available. A lot of the links that would normally give me the information I need to know are no longer active or accessible. I did however find out enough information that tells me the conversion is possible and worth the effort.
I think the subject deserves A little updating.
From what I understand there are several things need to be done To accomplish this Conversion. I'm not interested in being persuaded out of the idea of using an lt1 intake and I would like to focus on the process involved to complete a successful conversion.
It seems as if you can pick up an lt1 manifold complete with rails regulator injectors and sensors for under 100 dollars, and for me that makes it worth it!
Well guys let's hear it , what do you guys know?
I know you guys have pictures, a completed reworked manifold would be great to see!
I intend to share my progress and supply you folks with pictures as I go, a little help here from the experianced would be awesome!
Also forgot to mention I'm running a tpi L98 so I already have the computer wiring harness ready

 

Somebody's gotta know something.

 

its sorta a PITA and one reason I went with the HSR.

I got the manifold and rails for like 50 bucks. You need to fill in the bolt holes and re-drill. For some reason I had to redrill most of them to bolt to the heads. I used quiksteel epoxy putty to cover the old holes and then redrilled new ones



You have to fab block off plates for the EGR and such




There are several spots where there are big casting bosses left over that need cut out and ground down to allow bolt hole modifications



I plugged the stock MAP sensor location hole since I had MAF sensor

 

Drill and tap for MAT sensor on the one port side of the intake



Drill and tap or just epoxy in 5/8" hose barbs for the coolant ports at the rear of the intake. Some guys have done front, but i chose to do rear

Also see the distributor hole drilled and the spacer ring epoxied in. The ring was custom machined froma member on this site a long while back. Its at the right angle for the sbc, its not a flat ring! Alignment is pretty critical here so engine mock up is necessary.
Also need a distributor hole down threaded hole. I chose to epoxy a nut to the base and thread thru that, but epoxy isnt strong enough by itself. Really should weld it on.



In this pic below, look carefully at the corners of the intake where the manifold meets the head. Also in the middle around the EGR port. The waterjackets need material built up around the passage in the manifold to seal on the head. If not, you will never get this to work. I again used epoxy putty since I cant weld aluminum and I am not sure I'd trust epoxy putty. Its best to have someone weld a few strips of metal around those ports. Also along the EGR port!! What you cant see is under neath the manifold you need material built up too, not just the top of the port.

 

You will need the remote mount thermostat housing for this as well.



Then run lines to the rear of the intake and to the heater core water valve if still using that.

3 ports on it for that so theres enough.

Fuel lines I was able to get from Pure Choice motosports. Its got the snap fit connections for the LT1 rails and then run the standard metric adapters on the TPI hardlines on the body. Should work out just fine.

 

that's exactly what I was looking for! What'd you do about your throttle body?
Are you running a stock LT1 fuel pressure regulator and injectors?

 

Gotta know where to look
http://www.eecis.udel.edu/~davis/z28...ke_conversion/
http://www.lt1engine.com/tech/lt1-to...-bolt-pattern/
http://www.popularhotrodding.com/tec...ls1/index.html
http://www.s10wildside.com/wildside/lt1induction.htm
Good reading
http://forums.corvetteforum.com/c4-t...or-an-l98.html

L98 TB and cable bolts straight up
Need 92-93 throttle cable bracket
Later LT1 with 4L60E don't have TV cable mount


Depends on engine mods , LT1 injectors are 24 vs 22lb for L98

Alternative fitting if making your own s/s lines
http://www.summitracing.com/parts/RUS-641300/

 

I was going to use a stock TPI throttle body and bought the LT1 throttle cable bracket but i never did complete the swap.

I was planning to run the stock regulator too, and reuse the L98 injectors but I never completed this, I just sold what I had and bought the HSR

 

Same here.
HSR came along at the right price so went that way

 

Yep. I found an HSR for a good price.

Last I heard, a guy from the Vette forum bought my LT1 intake, overseas somewhere in Europe. He put it on a 383 and it worked out well. Cars an animal but I"m not sure if he modded the intake at all. May have replaced the epoxy work with real metal weld but apparently the conversion worked out.

 

This is all great information guys really appreciate it!
Those are some darn good links with lots of information.
I plan on using this lt 1 intake on a 400 small block with a pair of camel hump heads and
a decent cam. Eventually I would like to go with a set of AFR heads with larger ports.
Is the Stock throttle body on the lt1 intake larger than the stock tpi body?

 

I think they are the same size, 48mm twin i believe.

 

Since I'm putting this setup on a 400 I'm hoping that the stock throttle body will provide enouph flow for 6200 rpm's. What size injectors to use is in question.

 

You may want to look into porting that setup out to hit 6200 rpms. LT1 intakes respond well to porting on higher rpm setups. With a set of camel hump heads, you likely arent going to be turning alot of rpm anyway.

 

Actually 6500 is my goal.
2500 to 6500 is my cam selection 280xfi comp cam
I do intend to port the camel humps for sure.
I will eventually get some afr 220 cc heads.

 

What gaskets are the afr heads using?

 

AFR 220's will be like a 1206 but not exactly 1206. The 195's I have are close to 1205 felpro size, but arent exactly 1205 size AFR uses slightly different shapes.

XFI cam may go to 6500, its not much different than the cam i use in my 400 and it only turns to about 6000 at the moment but there may be other issues with it that are causing the short power band.

280 is a good cam tho. My friend uses it in his n/a 360" motor I tuned. Runs good and would turn 6500 easily in that setup if it wasnt for the valvesprings.

You need good stiff springs for those XFI cams with 1.6 rockers.

 

That brings up another question. The lift on that cam is over .500 , 550 I believe. I've read max lift on stock heads is about .500 so its iffy if it will work.

 

Max lift on flow or max lift on stock springs?
Online info shows stock LT1 heads ,210 cfm @.500 and not getting any better with higher lift.
But just because the head is maxed out at that lift does not mean intake is also

 

The stock TB's are the same size.

tranz zm--If you need any top end LT1 parts, let me know. I have an entire engine.

 

Sounds good. Any 28 - 30 pound injectors?

 

Nope, just the stock 24lb. injectors.

 

The 280xfi is .576/.570 with 1.6 rockers, .540/.534 with 1.5 rockers.

To get that to work on stock heads you may need to have the valve guide bosses milled down a good bit

 

That shouldn't be too hard to do. your just talking about where the valve stem seal goes on correct? Hopefully I won't have coil bind. I will buy the springs that match the cam.
Also I was curious if the lt1 injectors are the same type as the ones used on the tpi. I have heard there 2 different styles of injectors. Right now the engine that is in the vehicle is using 22 pound injectors on a 350 I was thinking that 24 pound injectors my give it a little bit more power Until I complete the 400.
It's a stock programed chip on a L98.

 

The problem on stock heads is that the valve retainers will hit the guide boss where the stem seal is at around .470 lift, plus or minus alittle, it all depends. You can run .100 valves and setup for a larger install height to get the extra lift capacity, or you can just trim the guide boss down.

For a cam like that, and the springs that are required to reliably run that cam, I'd have the heads reworked at the machine shop. One reason, to cut the valveguides down for the lift. The other reason, to install threaded screw in rocker studs. The pressures on springs for that cam, which are near 400 lbs open, will require a solid valvetrain setup. I dont think press in stock studs would hold it.

Now you can try another lobe design too, but screw in studs are good idea with any higher rpm build with good springs. XE 230/236 offers similar duration with lower lift and may be abit easier to control. There are other lazier lobes out there that work good too. The old comp magnum lobes do well, you can find them on the cc306 grind, 230/244. With stock heads, the 306 would be a better choice

 

The camel hump heads I have, have been rebuilt and screw in studs already installed so I'm good there. I was going to run a different cam ,a magnum 286sam

 

The camel hump heads I have, have been rebuilt and screw in studs already installed so I'm good there. I was going to run a different cam ,a 286h magnum it has a .490 lift but also a 110 lobe separation which I hear is not enough for efi systems to work well , that is unless I am not informed correctly. Currently I am using a mass air flow type set up. I'm going to switch to speed density in the near future.

I already have the 286h cam and matching springs of 380 pounds.

 

I'm sorry, I think I am getting confused... are you running flat tappet or retrofit roller?

If flat tappet then dont worry about spring pressures that I mentioned. Thats too much for a flat tappet.

YOu can run the flat tappet xfi 280 just fine with a good flat tappet spring.

If you plan on going to much better/larger heads like afr 220's it would be wise to look into a roller cam swap to gain the lift to get the most out of the heads.

You can run 110 lsa just fine, just takes abit more effort, and you kinda have to ignore idle blm's in closed loop. Higher overlap gives o2 sensors abit of a hard time but they do work. You could always run open loop too. MAF is more forgiving than SD and easier to tune IMO. You dont have to swap just yet.

 

Sweet! Since I already have that cam, I might as well use it then.
Yes its just flat tappet. The Hydraulic roller conversion is too expensive for me at the moment.

I've been thinking about converting to the ebl flash ecm and it looks like its only for sd. The ecm I'm currently using with my L98 is a stock chip but I know it needs adjusting do to exhaust mods, 4.56 gears, etc.

Burnin a chip every time I ajust something on the engine does not appeal to me. I would rather be able to adjust things with a desktop.
What are you using?

 

i have recently started this conversion. The info here is true but one thing I noticed that I havent heard talk about is the intake bolt hole angles. sb gen1 heads have the bolts holes drilled square to the cylinder head intake surface. lt1 heads do not. For this reason all bolt holes in an lt1 intake must be filled and redrilled. After that the the new holes in the intake will be square to the intake to cylinder head surface, but the intake to cylinder head surface and the contact surface under the head of the bolt is not parrellel to each other. this will require the use of leveling washers (wedge washers) to be corrected. This info is based on a 90 corvette. i believe iron heads (87-92) may have been drilled on 72degree angles on the 4 center intake bolt holes.

 

That's correct.

I use wedge washers