Nilak

Hello,
Hello,
I have the engine purchased from Smeding Performance mounted on the car now (1991 corvette L98version) but we are dealing with some challenges:
- I have a set of intake manifold gaskets but they are way too small. The plan is to find larger gaskets and try to port match the manifold
-the old clutch set (aluminum fidanza) doesn’t fit the flywheel that came with the new engine that has a shallower center cavity, so I understand I need a clutch set compatible with my transmission and the new flywheel . Alternatively I could install my Fidanza flywheel but I don’t know about balancing if the flywheel that came with the engine balanced with the engine? I’m waiting for answer from the seller. my aluminum flywheel was balanced by me using a position sensor made from a laser rpm meter, an accelerometer mounted below the flywheel on the bell housing and a oscilloscope, and it worked well. so I could do the balance again but it would interfere with the engine breaking in procedure.
the long block is basically designed for hot rods with perimeter valve cover holes, but aluminum heads.
If anyone can have useful advice please leave a comment.
thank you.

cadmaniac

383 Engines can be Internally or Externally balanced. That's the first thing to find out. Lower priced 383's usually have a larger balancer on the front. If that's the case, you will need to get a counterweight and install it on the Flywheel. With an internally balanced assembly, you need to make sure you don't have the counterweight installed. I would use the original flywheel you have it. The one he sent out with the engine might not be correct for a C4 Corvette ZF pull type clutch. You could check (measure) the depth from the crank to the clutch surface and of course the surface diameter for the clutch to engage as well. Some will recommend having the chosen flywheel and clutch assembly balanced together prior to installation. I've never done that (more of a C5 and up thing maybe).

There are several Fel-pro gaskets for chevy intakes. 1204, 1205, 1206 come to mind, They even have different thicknesses in case the heads were milled a bit. Measure the Cylinder Head port size, and the intake port size. Go with the Cylinder head size if it's a bit larger than the intake. Some will port match the intake to the cylinder head for better flow, which is a great idea, but a bit time consuming.

There are many on this forum that know a lot more than me, but at least this might be a start.

Nilak

thank you
The new flywheel has much a shorter distance between clutch surface and mounting surface. I like the fidanza that is much lighter. I will match balance it with the new one.
for the manifold, the gaskets specified by the engine builder is felpro 1205s3. Now I’m looking at the tpis manifold which I think would be a better choice for the ported heads and more aggressive cam.

yakmastermax

You need to get the following information from the engine builder:

What cylider heads were put on there
What flywheel was put on there
What crankshaft balance configuration it was set up as.

It sounds like it has aftermarket aluminum cylinder heads if they are specified to match a 1205 gasket.
You did not specify, but it sounds like you were originally planning on reusing your stock 1991 L98 TPI intake manifold setup on this motor? If so, that will not be a good match the the cylinder head intake ports, and more problematic, it will severely restrict anything but the most mild 383 in terms of power output. If you have the budget, I suggest an upgraded intake manifold setup. There are many options, Miniram, Superram, FIRST, ported stock TPI and Arizona Speed Runners, used upgraded TPI base and Arizona Speed Marine runners etc...You also need a new tune.

You did not specify, but I assume you have a ZF6 car and setup? If the motor was set up by the builder as a GM factory roller one piece rear main seal compatible setup... I believe that it should have a neutral balance front harmonic damper on it, and then the flywheel that came installed on the motor should have weights installed such that the setup is rear externally balanced. If that is the case, then any factory GM ZF6 dual mass flywheel meant for 1989-1996 cars that still has its original weights attached, OR any aftermarket ZF6 flywheel, solid steel single mass, fidanza Aluminum etc, that has already had weights added/set to balance the flywheel for a GM factory spec external rear balance setup, should work and should result in adequate balance. That being the case, just bolting on a GM factory balance spec ZF6 flywheel I do not believe will necessarily result in the best balance possible. It might, but most likely it would just result in adequate balance, but if you plan to race or spin this motor high and hard...you might want more peace of mind.

Good luck!

Nilak

I have finished measuring the necessary weight and position for the Fidanza flywheel- static balancing. It already has a steel weight bolted on that I trimmed for the stock engine and needs 19g more. I’ll put some red RTV (density is near 1) which I think is the easiest to add a little more weight on this. I did the same way for the old engine (14g in a different position).
the engine has harmonic balancer at the front, internal balance front and external rear, I’ve chosen this because for 5700rpm redline may not be worth going for fully balanced motor. requires a little more work and time though. The transmission is a ZF6.
Now looking for manifold options
the TPI manifold has 45 mm in height ports and the smeding has 55mm. width is nearly identical. But the problem is that the overlap at the top is reduced and may compromise sealing. Doesn’t seem to be enough material in the base for match porting.

another issue I think can be the stock exhaust at higher rpm like 4500-5500- because with a short runner and large ports it will produce an higher airflow.

thank you
awesome community,

Nilak

I would go for the tpis but it’s a long waiting, till then I would try port matching.
-if anyone knows, does this base have more material to mill from at the top of the intake ports?

Edelbrock 3860 High-Flow T.P.I. Baseplate

there is also the debatable coolant restrictor at the rear. I could find an equivalent felpro 1205s3 gasket with restriction so I can bolt two small 1.5mm aluminum plates and stainless steel bolts.
To me, that the restriction would make more coolant flow at the front of the heads so if I remove it the thermostat being at the front would tell if the water is too hot but some say it traps more coolant to cool down the back of the heads. water should flow from the driver’s side block then up the heads with slightly less flow towards no8. it heats up from the block slightly which is good for preventing thermal shocks then through the manifold cools down slightly then to the left side heads. at no 7 the flow is a bit lower and water is hotter than at 8. then down the block. the restriction at the rear would create a much lower water flux at the rear imo, but maybe there are different explanations

AZSP33D

You can get a clutch friction disc that doesn’t have the spring hub center, but solid instead, and that will provide the clearance. Downside is noise from torsional vibration.

Nilak

thank you, for now I’ll be using the fidanza flywheel (match balanced) and store the steel flywheel as backup.
as for the manifold, I’ve decided to buy a ported elderbrock base and asm runners, initially wanted the miniram but it’s more work and diverges from stock appearance, needs work even to give it a factory look and hard to find. I’ve bought it already ported to 1205.
update: could’t find ASM runners and just bougth a ser of elderbrock runners.

Nilak

I've ordered the TPIS gaskets for the Elderbrock runners but it could take a long time and I can't wait too much. Until the base and runners come I was trying to draw the gaskets myself so I can laser cut them from gasket paper but looks like the stock gaskets don't match with neighter Edelbrock nor TPIS. The 8mm bolts on the stock need to be adjusted to the left for TPIS and to the right to match Edelbrock so the only way is to make them using the real base and runners. the stock gasket is scanned and the tpis and edelbrock are from online pictures. The pink outline is the stock gasket