I wasn't sure where to post.. but I figured 13b would best be known by the 2nd gen people..

I'm looking to discover the best N/A 13b out there..
is it the S5 because of high compression?

I want to get an aggressive street ported 13b and I'll carb it for my 1st gen..
But what block do I start with? (are there good seals for N/A power and whatnot?)

I dont know about engine building, but I imagine lots of you do

thanks!

 

P-port 3 rotor with RX8 rotors

or a P-Port 2 rotor with RX8 rotors with tall velocity stacks perched on top.. and balanced to rev out to 11,000 rpm

:p

 

well.. I can dream lol..
I'd like something a little more practical, that wont cost an arm and a leg to build..
It's my DD in the summer, and a P-port will burn a hole through my wallet just in gas i'm sure..
Something that can be build out of a S4 or S5 13b?

 

If you are running a carb, then both the S4 and S5 NA engine will be running well below it's potential. The S5 especially considering most of it's power gain over the S4 is due to the VDI intake manifold. The S4 has a slightly less advanced intake manifold but it still contributes a significant amount (about 10HP over the 13B in the GSL-SE) to the overall total power.

If you want to carb something, your best bet is to build a 4 port 13B with S5 NA rotors. Port appropriately depending on your goals. If you intend on building with 6 port irons, then you are going to have a massive torque loss down low.

 

the difference between the s4 and s5 rotors is that the s5's are light and give you .3 more compression and for the housing on a N/A you have to grind out the baffles in the exhaust ports or just change them for turbo ons . so start with that, then for seals just get a seal kit with steel 2 piece apex seal and for the carb its up to you what you like. i am doing the exact same but fuel injecting it.

 

you're saying if I took the S5 N/A engine.. street port and big weber..will have significantly less power than stock intake??

 

You'll make more power, but probably less torque through the powerband. The power increase would be due to the steet port.

Running any 6 port engine with the aux ports open below 4K will result in a large loss of torque.

 

OK i have a question after reading all this.

On my 87 I had, We wired the ports open. I didnt think it had lost that much power. What is a guess at the amount of lost torque (is that even a fair question?)?

Was i just that wrong on what I should have expected the torque to be? at the time I also had an F150 with a 302 so I may have been expecting less due to having a V8 also.


Thanks

Paul

 

I've run my S5 engine with the ports on and off below 4K on the dyno, the graph will easily show lower power when the ports are open, rather than closed. Forgot how much lower it was though.

 

Hmm, you guys know alot more than me..
I'd like to go carb..
So what would be a good balance between tq and powerband.. 6 port or 4?
I still want a powerband, but i dont want to be gutless sub 4k

 

Aaron is right! My last motor was an s5 w/ a 4 barrel Holley 600 in an FB. We got it to run beautifully and wow did she pull strong.........so I thought, until I got behind the wheel of an stock F.I s5 and the difference was tremendous.

 

I suggest then building a 4 port engine with a street port.

 

well if your comparing a stock s4 vs a stock s5 then the s5 would be the best bet i beleve they have 165hp and 150ish trq and they redline at 8000rpm opposed to 7000rpm

 

This question really depends on your budget and intended use for the car.

For a street car, a streetported n/a in an FB can be a ton of fun. A buddy of mine ported a S4 and put it in his 79 running S4 electronics (carb bad) and it was a hoot. You could break the rear end loose in the first three gears. It ran a 13.8 in the 1/4 mile too. The whole swap cost less than $1000 (remember to use a gslse front cover to make it easy).

Josh

 

To give you some perspective I just built a 4 port engine for a customer that put out 216bhp @ 7000 rpm.

Specs are as follows:

'89 4 port irons
86-88 High Compression rotors (read NA)
One of our largish street ports
"Oval" street exhaust ports

The carb we used was a 48 DCOE SP, with a 45 DCOE 9 we put out 194bhp @ 7000 rpm.

Oh, we had ~141 torque by 3000, peaking at 6000 with 166. This engine had more power to be had with more revs.

 

finally..
What should i go with? considering the hassle of hooking an ECU and EFI into a 1st gen..

Do they both have the same power, but distributed differently?

 

Your going to have a hard time keeping up with Me and this other guy.