What will bigger runners do for me?

[Edmond]

Assuming that I hog them out along with the hogged out plenum and a hogged out intake manifold?

What I'm looking for is low end power.

Will this move the power curve further up than what I would be using for most street driving?

Used runners are $200 and new ones are $400. It's not a big choice but if I didn't need to spend that money, I could use it on something else like 1.6 roller rockers.

 

[vetteboy86]

From what I believe, the length of the runners is what gives us the massive torque we have. I dont think this will necessarily hurt the low end grunt.

Edmond, I have to tell you that I love the new setup I have. I have ported plenum, runners, and big mouth manifold.

 

[Edmond]

Edmond, I have to tell you that I love the new setup I have. I have ported plenum, runners, and big mouth manifold.

Did you get that manifold new or used? Honestly, the idea of shelling out $400 for a manifold isn't really going well with me. That's why I'm going to find out what I can do with the stock manifold. I know it was originally designed for the 305. But it's not going to see the track and I'm not feeding the cubic inches that you are.

I think that if I can port it, I can get just a bit more out of it and be satisfied. I'm only shooting for 325 horsepower and 380 torque. I think that won't be too difficult to achieve.

I can port the plenum myself.

In fact, I even thought about porting the cylinder heads myself but I'm not that confident in doing the short side radius port or the combustion chamber area. However, I think I could port the area where the intake manifold goes into the heads. It looks like that could be done by matching the gasket.

 

[tigmaned]

the ported runners and plenum is that a good time to also go for the bigger T/B right. so doing all this what kind of horse power increase do our L98 get from it? the idea of this sounds better then dealing with the headaches i think come form the other aftermarket big rams.

 

[Edmond]

I've got new injectors on the way via UPS so my next step are looking at what to do with the heads and what to do with the intake/runners. I've already decided that a ported plenum will suffice.

When Moonunit gets back to me on the heads, that'll give me a clear idea of where I want to go with that.

Unless I really need to, I won't buy an intake. But if I had to, I would probably get the Edelbrock intake and runner set. New, I think the set was in the $700 range but I'll try to find used first.

I don't see a problem with buying something like that used.

 

[milehigreg]

Edmond. I bought and have read Lingenfelter's book on modifying the small block Chevy. It was refernced here on the forum. I thought you said you had a copy. There is an excellent discussion on the TBI in the book. Basically, short,fat runners make good top end HP and limit low end torque. Long thin runners make low end torgue at the expense of top end HP. Give it a read.

 

[Moonunit 451]

the ported runners and plenum is that a good time to also go for the bigger T/B right.

Negative on the TB! The 48 will be fine. I'll be working on the head thing today as I get time Edmond. Lot's of folks "siamese" port the original runners with good results, and you can do it yourself. The intake I'm not sure on, but I bet you can get some additional performance doing your own work as well.

 

[vetteboy86]

I will try to post some pics of what I bought. I bought all the stuff used from a member here. Basically, the new manifold is supposed to handle the more cubes. I guess, I dont really know much about it. However any time you can get more air into the engine, the better off you are.


Edmond, are you going to redo the bottom end?

 

[Edmond]

Edmond, are you going to redo the bottom end?

Not as of now. With 102,000 on the clock and no problems, I'm not going to tear the motor apart. There is some minor seepage on the oil pan and valve cover gaskets that will be taken care of. There is also a power steering fluid leak (which C4 doesn't have that problem? :L:L:L) But I'm just going to do the top and when the time comes to do the bottom, I'll do that. But at the rate I'm driving at, that won't be for a long time.

And with what I want to do, which is keeping it a street machine, I won't need something radical.

 

[89ZZ4]

Edmond, the offer of either of the two pairs of 113 Dport Heads I have stands as we have discussed. My original set off my 89 has less than 10K miles on them and the ZZ4 heads, hot cam springs, ARP studs,1204 gasket matching and less than 6K on them are available. I'll consider taking your old heads in trade if they are 113 Dports if bottom line $ is an issue. I can throw in the ZZ4 cam for later. This way you can have them inspected by the local speed shop but it's probably cheaper than a valve job and new springs which I personally would replace at 100K miles. In addition if you want to start porting early you can use any of my plenum, manifold, runners I took off my 89 and swap them out when you pull yours off if they are in good shape. Personally if you have the intake and heads off you might as well swap cams and put on roller rockers.

 

[Mad-Mic]

probably 30 rwhp with the bigger aftermarket runners and ported plenum/base. shift at 5300 rpm. torque curve will come up but you should get a few extra pounds of it also.

 

[Edmond]

What I really want is more torque. I don't need HP at 5000 RPM's because with my driving, my car will rarely see those revs.