Can you modify L31 Vortec heads to work on an second-gen LT1?
05-18-2018, 11:42 AM
#43
Village Troll 
iTrader: (2)
Really? That rumor has been around since the inception of the LS platform. As far as the L98/LT1, if one can take advantage of the long runner intake of a L98 it will produce far more torque at lower RPM than the mini-ram style LT1 intake. If the OP wants to operate a street car at less than 4500rpm for stop light to stop light then more torque to him...
05-18-2018, 01:16 PM
#44
Really? That rumor has been around since the inception of the LS platform. As far as the L98/LT1, if one can take advantage of the long runner intake of a L98 it will produce far more torque at lower RPM than the mini-ram style LT1 intake. If the OP wants to operate a street car at less than 4500rpm for stop light to stop light then more torque to him...
05-20-2018, 08:02 PM
#45
I personally would not touch the F-car cam. I have put it in numerous L31s and it wakes them up compared to the B-car grind they came with that was installed 5° advanced in them. The factory L31 cam is unimpressive in the lower rpm range you are talking about as well. My Express van had a LT4 cam with 1.6 rockers about 8 years ago. It made enough torque down in the 1,200-1,500 rpm range it would pull the van around town and uphill in overdrive with the converter locked as low as 40 mph. I have also had the 395' Marine cam in the same van. In the lower rpm ranges between those 3 cams you honestly cannot feel or tell a difference. However once the tach climbs. The factory Vortec cam is a dog, the marine cam is a bit stronger, but the LT4 cam pulled like a freight train.
I have also had both a Vortec truck intake manifold and a TPI intake on the same engine. The TPI intake and Vortec intake with ports the length of the TPI base plate both felt about the same off-idle up to about 2,500. From 2,500-4,000 the TPI made a bit more umph. From 4,000-redline for all practical purposes they felt exactly the same. The runner length of a TPI resonates strongest around 3,200 rpm and in other areas of the powerband the runners can actually cause torque loss. A dual plane intake makes more torque under 2,500 than a TPI for example. You could consider converting a dual plane LT1 intake to port fuel injection similiar to the Mercruiser MPI intake that is basically a performer rpm with injector bosses added. But bottem line your not going to get the torque you want without adding stroke and thus cubic inches. 6" rod 396 would be the best bet!
I have also had both a Vortec truck intake manifold and a TPI intake on the same engine. The TPI intake and Vortec intake with ports the length of the TPI base plate both felt about the same off-idle up to about 2,500. From 2,500-4,000 the TPI made a bit more umph. From 4,000-redline for all practical purposes they felt exactly the same. The runner length of a TPI resonates strongest around 3,200 rpm and in other areas of the powerband the runners can actually cause torque loss. A dual plane intake makes more torque under 2,500 than a TPI for example. You could consider converting a dual plane LT1 intake to port fuel injection similiar to the Mercruiser MPI intake that is basically a performer rpm with injector bosses added. But bottem line your not going to get the torque you want without adding stroke and thus cubic inches. 6" rod 396 would be the best bet!
Fast355, I am torn on the camshaft. I remember a post by SS RRR suggesting the mild port with 1.6 RRs for my stock cam and that helping to give me what I want. However, then my mind starts applying that to the B-body camshaft and I wonder what that would yield. I don't want a build or camshaft that is going to eat into my city mileage, which is why I am teeter-tottering on boundary to keep the car pretty stock or to cam it with something that will yield the most torque production, surpassing the B-Body camshaft but not being so extreme that my daily driving experience and mileage will suffer from the given power production.
With regards to the TPI intake, I am researching, thinking, soul searching, and asking myself if it is what I want. I have too many conflicting comments with regards to burning more fuel below 2000 RPM from pumping losses and not being able to tune for this, although less airflow at that RPM band, I would think, would lend itself to better fuel economy over my LT1 intake which yields marginally more power off idle to 2000 RPM. Then, the suggestions to use the FIRST TPI intake, although I don't know if it is necessary, flow wise, for my very mild engine build...
05-24-2018, 10:22 PM
#46
TECH Resident
I have since been persuaded not to go about this endeavor. The LT1 cylinder heads are unique to the engine and it is best that I keep them so, for compression reasons as well as to not mess with the cast coolant passages. I was seduced by the thermal properties of iron for the combustion process, however, I can have my aluminum heads coated to behave the same way while enjoying the benefits of aluminum and it's weight savings. I was talked into a mild porting job for my daily driving "fun" needs, which this was suggested from the start a long time ago by SS RRR. So thank you, it comes full circle to where I need to go with regards to my cylinder heads.
Fast355, I am torn on the camshaft. I remember a post by SS RRR suggesting the mild port with 1.6 RRs for my stock cam and that helping to give me what I want. However, then my mind starts applying that to the B-body camshaft and I wonder what that would yield. I don't want a build or camshaft that is going to eat into my city mileage, which is why I am teeter-tottering on boundary to keep the car pretty stock or to cam it with something that will yield the most torque production, surpassing the B-Body camshaft but not being so extreme that my daily driving experience and mileage will suffer from the given power production.
With regards to the TPI intake, I am researching, thinking, soul searching, and asking myself if it is what I want. I have too many conflicting comments with regards to burning more fuel below 2000 RPM from pumping losses and not being able to tune for this, although less airflow at that RPM band, I would think, would lend itself to better fuel economy over my LT1 intake which yields marginally more power off idle to 2000 RPM. Then, the suggestions to use the FIRST TPI intake, although I don't know if it is necessary, flow wise, for my very mild engine build...
Fast355, I am torn on the camshaft. I remember a post by SS RRR suggesting the mild port with 1.6 RRs for my stock cam and that helping to give me what I want. However, then my mind starts applying that to the B-body camshaft and I wonder what that would yield. I don't want a build or camshaft that is going to eat into my city mileage, which is why I am teeter-tottering on boundary to keep the car pretty stock or to cam it with something that will yield the most torque production, surpassing the B-Body camshaft but not being so extreme that my daily driving experience and mileage will suffer from the given power production.
With regards to the TPI intake, I am researching, thinking, soul searching, and asking myself if it is what I want. I have too many conflicting comments with regards to burning more fuel below 2000 RPM from pumping losses and not being able to tune for this, although less airflow at that RPM band, I would think, would lend itself to better fuel economy over my LT1 intake which yields marginally more power off idle to 2000 RPM. Then, the suggestions to use the FIRST TPI intake, although I don't know if it is necessary, flow wise, for my very mild engine build...
05-25-2018, 09:52 AM
#48
Village Troll
iTrader: (2)
Car dynoed 310/310 after the heads, rockers and Edelbrock shorty headers which went into the stock y-pipe. Ran a best of 13.2 @ 106 and it behaved just like stock. You wouldn't know a thing was done to it. The torque and HP curve characteristics were identical to stock. This would be your easiest solution to what you want. If you want more, then put your B-body cam in or a shorter duration cam with high lift and it should do you an even better service, all the while giving you excellent MPG.
05-25-2018, 10:35 AM
#49
TECH Resident
Car dynoed 310/310 after the heads, rockers and Edelbrock shorty headers which went into the stock y-pipe. Ran a best of 13.2 @ 106 and it behaved just like stock. You wouldn't know a thing was done to it. The torque and HP curve characteristics were identical to stock. This would be your easiest solution to what you want. If you want more, then put your B-body cam in or a shorter duration cam with high lift and it should do you an even better service, all the while giving you excellent MPG.
That being said if one was intent on going to a smaller cam in a F-car the 395' cam is what I would consider. It has slightly more lift and duration than the B-car cam, has a 2° tighter LSA and is advanced 3°. It can also be bought from GM for less than $200.