Topic: new motor
in Forum: C3 Engines
Already a Member?
Click Here to Login
Not yet a Member?
Click Here to Register for Free!
SPONSOR AD:: (Our Sponsors help support C3VR)

Hot Springs, AR - USA
Joined: 4/24/2004
Posts: 3236
Vette(s): 69 Conv #'s match 427, TKO-600/.64, 3.36HD-Posi, HT, T/T, PS, PB, PW, SP, Leather, Comp XE264HR & Roller Rockers & Lifters, Air-Gap RPM intake, Holley St Av 770 VS, MSD 6AL+Dist+Blaster SS, K&N, Jet-Hot Hooker Side-Pipes, Steeroids, Al Rad, Spal Fans
you need to figure out what is actually wrong with the engine before you make that choice..
can you describe the symtoms in more detail...
this could be something as simple as fouled plugs..
can you describe the symtoms in more detail...
this could be something as simple as fouled plugs..
Former Member
Send PM
DOWNINGTOWN, PA - USA
Joined: 11/24/2001
Posts: 962
Vette(s): 1969 Monza Red Black Conv / Black Vinal hardtop
454/480 Tremec 5 Speed 308 Posi.Black Leather Interior, PS, PW, Air cond., tilt/tele,AM/FM Cass.-5 Pack CD, Hurst Shifter, side pipes
2004 Yellow convertible with black top and black interior
Definately look at all the simple stuff first, then get nervous !
You most likely have the same problem I do, you lose a lot of diagnostic ablily cause you can not hear anything over the sound of the side pipes.
Hope your compression test comes out good.
You most likely have the same problem I do, you lose a lot of diagnostic ablily cause you can not hear anything over the sound of the side pipes.
Hope your compression test comes out good.
Former Member
Send PM
Portland, TN - USA
Joined: 4/29/2003
Posts: 805
Vette(s): 1972 Coupe
Anything, but Stock and more mods to come!
SSBC Force 10 Brakes, 3.73, TH350, 355 CID, Rack and Pinion, Vette Brakes suspension front and rear.
I'll take a shot at the worse case scenario. If you are running that big supercharger, then you might have rolled a piston ring with too much boost being pushed into the cylinders. Do you know anything about the engine and what was put into it? But I would certainly start with the small suggestions first until they are exhausted then worry about tearing into the engine.

just finished the compression test all cyl between 175-180.
Now at least I know it is not the rings. Is the comp high or is it because it is a blower motor??
What I need to know now is how do I check the integrity of the head, I guess specifically the valves and the valve guides??
All suggestions appreciated
Now at least I know it is not the rings. Is the comp high or is it because it is a blower motor??
What I need to know now is how do I check the integrity of the head, I guess specifically the valves and the valve guides??
All suggestions appreciated

Former Member
Send PM
Newark, CA - USA
Joined: 4/29/2004
Posts: 350
Vette(s): 1969 Corvette 4-speed ZZ-4 crate
Monza Red
What did the plugs look like when you pulled them?
This will tell you alot.
This will tell you alot.
all the plugs were black, one or two were slightly wet but did not seem like a gas smell.
I know the car had been running rich, but my understanding with a blower you would rather have a richer than leaner mixture.
How do I check the valve guides to make sure oil is not getting down into the cylinders??
I know the car had been running rich, but my understanding with a blower you would rather have a richer than leaner mixture.
How do I check the valve guides to make sure oil is not getting down into the cylinders??


Hot Springs, AR - USA
Joined: 4/24/2004
Posts: 3236
Vette(s): 69 Conv #'s match 427, TKO-600/.64, 3.36HD-Posi, HT, T/T, PS, PB, PW, SP, Leather, Comp XE264HR & Roller Rockers & Lifters, Air-Gap RPM intake, Holley St Av 770 VS, MSD 6AL+Dist+Blaster SS, K&N, Jet-Hot Hooker Side-Pipes, Steeroids, Al Rad, Spal Fans
are you sure the smoke is blue?
since you had a good compression test your engine is in pretty good shape overall...
all your valves are closing..
head gaskets are in good shape.
rings are good.
as for stem seals and guides.. that usually isnt an overnight thing..
and usually the manifests itself by seepage when the car is off and a puff of smoke on a cold start.. and doesnt drastically hinder performance suddenly.. also since you have multiple fouled cylinders this means you would have to have a sudden valve guide failure on more than one cyl at the same time..
if your plugs looked fouled but dont smell like fuel.. then i would guess water... since your compression test went fine it would probably be intake manifold gasket leak..
do you know which cylinders are missing and fouled the most ?
do you have any secondary indicators for water.. does the oil look good..
when do you get the smoke?? constantly or just during a start or just cold starts..
is it smoking from both sides ??
take a clean sheet of paper and hold it near your exhaust after warming the car for a few minutes.
(i would say make sure there is a constant outward flow of air.. but we know your valves are closing so it shouldnt suck the paper in. (just for future reference .. if it tries to suck the paper in.. it could be stuck/burnt vavle))
see if there is any moisture of any sort coming out of your exhaust.. it will collect on the paper..
the other thing you can do is take long cotton swabs (like for gun cleaning) and swab around through the plug hole and see what you come up with ..
since you had a good compression test your engine is in pretty good shape overall...
all your valves are closing..
head gaskets are in good shape.
rings are good.
as for stem seals and guides.. that usually isnt an overnight thing..
and usually the manifests itself by seepage when the car is off and a puff of smoke on a cold start.. and doesnt drastically hinder performance suddenly.. also since you have multiple fouled cylinders this means you would have to have a sudden valve guide failure on more than one cyl at the same time..
if your plugs looked fouled but dont smell like fuel.. then i would guess water... since your compression test went fine it would probably be intake manifold gasket leak..
do you know which cylinders are missing and fouled the most ?
do you have any secondary indicators for water.. does the oil look good..
when do you get the smoke?? constantly or just during a start or just cold starts..
is it smoking from both sides ??
take a clean sheet of paper and hold it near your exhaust after warming the car for a few minutes.
(i would say make sure there is a constant outward flow of air.. but we know your valves are closing so it shouldnt suck the paper in. (just for future reference .. if it tries to suck the paper in.. it could be stuck/burnt vavle))
see if there is any moisture of any sort coming out of your exhaust.. it will collect on the paper..
the other thing you can do is take long cotton swabs (like for gun cleaning) and swab around through the plug hole and see what you come up with ..
Former Member
Send PM
Portland, TN - USA
Joined: 4/29/2003
Posts: 805
Vette(s): 1972 Coupe
Anything, but Stock and more mods to come!
SSBC Force 10 Brakes, 3.73, TH350, 355 CID, Rack and Pinion, Vette Brakes suspension front and rear.
You can do a leak down test to see if the valves are holding close or if the guides are bad. I have fuel soaked spark plugs bad enough to cause the engine not to even run or for it to miss.
If you are running rich its probably because your power valves are not closing due to the negative vacuum created by the supercharger. This is very common. You can remedy this several ways. You can outside reference the power valve channel to the lower intake and plug the channel on the throttle plate. Or you can put in power valve plugs and jet up 4 jet sizes. That should cure your rich condition.
If you are running to much compression you can push out the cylinder head gasket between the cylinders. During a compression test you should be able to see this. The best way to avoid this is to take all the plugs out and only do the one cylinder you are working on. This way you won't be catching comp from the other cylinder.
You may never be able to keep a gasket from blowing out if the engine has too much static compression before adding the blower. Static compression should be no more the 8.5:1 and the blower should be making no more the 5 to 7 lbs of boost.
What concerns me is the engine is a 454 stroked to 468. If the builder didn't use the right piston with the chamber on the heads to keep the compression down then it probably is too much compression. Very common error.
To the best of my knowledge you engine is most likely this combination. These figures are typical for off the shelf parts. Problem is there are very few pistons available off the shelf with the correct dish to get the compression down to a safe limit
4.310 or 4.315 bore
9.780 deck – Zero Deck
Possible Cylinder Head Chambers 124cc, 118cc, 110cc
.039 compressed gasket
Using the assumed variable above you need to have one of the following pistons depending on heads to achieve an 8:1 compression. Your total cylinder volume should be 136.94
With 124 cc head – Flat top piston works perfectly
With 118cc head - Piston needs to have a –9cc dish.
With 110cc heads – Piston needs to have a – 17cc dish.
If you decide to pull the heads look at the pistons if it has a dome your probably running way to much compression, unless the piston is setting down in the bore. The only way to tell is to measure the cylinder head volume and where the piston sets in the bore at top dead center.
If you are running rich its probably because your power valves are not closing due to the negative vacuum created by the supercharger. This is very common. You can remedy this several ways. You can outside reference the power valve channel to the lower intake and plug the channel on the throttle plate. Or you can put in power valve plugs and jet up 4 jet sizes. That should cure your rich condition.
If you are running to much compression you can push out the cylinder head gasket between the cylinders. During a compression test you should be able to see this. The best way to avoid this is to take all the plugs out and only do the one cylinder you are working on. This way you won't be catching comp from the other cylinder.
You may never be able to keep a gasket from blowing out if the engine has too much static compression before adding the blower. Static compression should be no more the 8.5:1 and the blower should be making no more the 5 to 7 lbs of boost.
What concerns me is the engine is a 454 stroked to 468. If the builder didn't use the right piston with the chamber on the heads to keep the compression down then it probably is too much compression. Very common error.
To the best of my knowledge you engine is most likely this combination. These figures are typical for off the shelf parts. Problem is there are very few pistons available off the shelf with the correct dish to get the compression down to a safe limit
4.310 or 4.315 bore
9.780 deck – Zero Deck
Possible Cylinder Head Chambers 124cc, 118cc, 110cc
.039 compressed gasket
Using the assumed variable above you need to have one of the following pistons depending on heads to achieve an 8:1 compression. Your total cylinder volume should be 136.94
With 124 cc head – Flat top piston works perfectly
With 118cc head - Piston needs to have a –9cc dish.
With 110cc heads – Piston needs to have a – 17cc dish.
If you decide to pull the heads look at the pistons if it has a dome your probably running way to much compression, unless the piston is setting down in the bore. The only way to tell is to measure the cylinder head volume and where the piston sets in the bore at top dead center.

in Forum: C3 Engines
SPONSOR AD: (Our Sponsors help support C3VR)