How much difference in power could you expect going from a TPI to a different manifold like a single 4 barrel or modified tunnel ram with no other changes other than tuning for the new maniold. Has anyone dynoed one with a single 4 barrel? And not a simulation a real dyno pull..LOL..

 

Lots of people have done it, If you change nothing but the intake over to carb you will see a small increase in high rpm power, say 20-30 hp. The real benefit from going carb is that heads/cam combos will be more effective. A carb is like a short runner intake and would move the power band to a higher rpm, kinda like LT1 intakes.

 

Nothing wrong with a carb setup, just make it fits under the hood. I'm running a 750 with a dual-plane right now, but I'm gonna be moving down to a 650 double pumper since the 750 is bogging and has a blown power valve.

I changed the cam with the carb install, mostly for the reason demonic stated - the intake changes the powerband to higher RPMs. Now my car pulls hard from 3k to 6k, only limited because my intake wasn't designed to flow much after 5500.

Stock cam + 650 holley + low profile dual-plane = nearly identical torque without the TPI wall of 4500 RPM. Let me put it this way, torque and HP are equal at 5252 RPM but, if you stop making power before that(TPI), you won't make the sheer HP that a carb setup can.

 

The late L98 with 113 heads is essentially the same motor as the GMPP ZZ4 crate engine which makes 335Hp with a bigger cam (208 /221 .474 .510)
Potential is there.
I would suggest that if you were going to the trouble of a carb swap then a cam change to suit the carb would be recommended.Stock L98 cams are pretty wimpy and not really suited to the extra revs available from a carb setup.

 

Actually looking to build an intake from a holley tunnel ram with efi and the l98 throttle body runner length will be about the same as a single plae 4 brl..
On the GMPP website they have a couple of combinations you can put together and only allow building a couple of different versions that they have no doubt tested the winner seems to be the ZZ4 cam with the GM fastburn heads. I used a 750 carb and open plenum manifold in the couple of diffenent tests. Made more torque at 1800 than the TPI ever makes LOL what is the point of TPI again? Basically come up with a very flat torque curve of about 400 ft pounds from 3000 to 5500and 400 hp.. The LT4 cam made a little more power up top but paid for it big time in the midrange. It looks like for 2500 to 3000 a pretty simple winter project. I really don't want to spin it over 5500 to 5800 to be honest so a good combination from what I can see. The only thing I wanted to add and could not was 1.6 rockers over the 1.5 ones, thinking they might have picked up more as well. This thing is definately not going to nose over like a TPI with + 150 ftlbs at 5000..LOL

On the manifold height from follow threads here it looks like 9 inches from the china rail is max height, correct?

Second how do you get the damper off in an L98 with the engine in the car with a crossmember right in front of it. Really not looking to remove the engine to change the cam..sigh...

 

https://gmspecialservicetools.spx.com/SearchTools.aspx

Check this out, your FSM will have your part number. Yours probably isn't the one with the picture, but one of the others above it. You have to remove the tube part of the power steering reservoir? or whatever that is on the crossmemeber (my FSM is at home, so I don't have the proper term for it).

 

I think the ZZ4 is a very under rated cam.Many here bag it stating you need bigger.It was factory designed for the 113 heads making 355Hp (w/ carb ).Stepping up to the much superior Fastburn heads as in your sim only picks up 30Hp and loses 50ft/lb

With the dist out you can pull the engine mount bolts and jack engine to give a little more working room.
Also makes it easier to drop front of oil pan to remove timing cover

 

Just ran the simulations again and while not a dyno by any means. looked like i lost 13 ft pounds at peak 405 vs 418 less in other places but filled it in all through the curve especially past 4500 50 6000 and picked up 50 hp up top Either one should be fun to drive on the street and keeping the stock heads is still + 100 hp over stock and a ton cheaper as well. I guess I would have to ask myself if 1500 bucks is worth the 50 hp...