So which heads will get my 358 in the high 10's

[econo racer]

I would put the 8 inch converter in it 1st.

[6.50camaro]

I would put the 8 inch converter in it 1st.

I can attest to that fact, when I went from a 3500 stall 10" converter to a 8" 5300 stall my street/strip 383 was .3 quicker in the 1/8th mile and dropping the full exhaust for 12" collector extensions dropped it another .15 to .2 . went from a mid to high 7.40's car to a high 6.90's car. Dan

[1980RS]

I would put the 8 inch converter in it 1st.

That's the plan, along with my ported Vic Jr. I wanted to put in the Coan 9" converter I got from a friend last year but I will test this 8" first.

[steve cowan]

I would put the 8 inch converter in it 1st.

That's the plan, along with my ported Vic Jr. I wanted to put in the Coan 9" converter I got from a friend last year but I will test this 8" first.

I have done alot of passes testing between my 2 x converters.
9 " 4200
8 " 5600
I have run 383 combos from 400hp - 550 hp
The 8" converter wins every time and it's all in the 60ft.
My 383 with 500" lift cam that I shifted at 6000 rpm ran the best with the 8" converter.
If you have a well built converter they drive just as good as a smaller converter.

[skinny z]

We found big gains going from our off the shelf TCI 10" to a spec'd 9.5" Yank convertor.
The most noticeable difference was the split in shift RPMs. Especially with the 700R4/4L60 1st to 2nd gear change.
The TCI, when shifting at 6500 would fall back to to less than 4000 going into 2nd. Then it's a long haul up the rev range to the next shift.
With the Yank, data logs show the revs never went below 5500 (+/-). Much improved ETs. If memory serves, it meant have been a few tenths. Maybe four with some of that coming from an improved 60'.

[lefty o]

We found big gains going from our off the shelf TCI 10" to a spec'd 9.5" Yank convertor.
The most noticeable difference was the split in shift RPMs. Especially with the 700R4/4L60 1st to 2nd gear change.
The TCI, when shifting at 6500 would fall back to to less than 4000 going into 2nd. Then it's a long haul up the rev range to the next shift.
With the Yank, data logs show the revs never went below 5500 (+/-). Much improved ETs. If memory serves, it meant have been a few tenths. Maybe four with some of that coming from an improved 60'.

a TCI turd, not surprised.

[skinny z]

We found big gains going from our off the shelf TCI 10" to a spec'd 9.5" Yank convertor.
The most noticeable difference was the split in shift RPMs. Especially with the 700R4/4L60 1st to 2nd gear change.
The TCI, when shifting at 6500 would fall back to to less than 4000 going into 2nd. Then it's a long haul up the rev range to the next shift.
With the Yank, data logs show the revs never went below 5500 (+/-). Much improved ETs. If memory serves, it meant have been a few tenths. Maybe four with some of that coming from an improved 60'.

a TCI turd, not surprised.

They're certainly not on par with any of the big boys. At least not from what I've experienced or come across internet-wise.
But I can say, for an average guy looking for a step up in street performance, they've worked very well for the more pedestrian applications.
That said, I doubt very much this thread is about anything pedestrian.
Following with interest.

[1980RS]

I think the difference in converters is what's driving in front of a converter. When I ran another 12:1 355 I had the same 10" converter in the car I run now and that sbc ran 11.70's@115mph. I swapped in the 8" I bought new and the car ran after a bit of tuning 11.40@118mph so that was quite a gain with converter only. Several years later I ran that same 8" converter with my 454 12:1 roller cam BBC and engine just blew through the converter and most likely hut my ET. I think the same thing happened with this 8" when I ran my 12:1 406 last year. Before I run that engine again I will get a new convert that's right for that SBC.

[skinny z]

Somewhat similar to what you're describing, I'm hoping this current 10" will come into it's own with a stronger engine in front of it. It's an off the shelf piece so hardly optimized but it's effective when compared to something stock. And more effective is what I'm expecting.
Then maybe another Yank or similar once the combination is sorted.

I'll say one thing though, I don't have it in me to experiment as much as you do. I'm at the point in this "hobby" where I'd like to be one and done. Maybe twice.

[bpenrod]

Great thread 1980RS. Real world results with using what you have and trying to improve on your combo.Keep it going and keep posting the results. And thanks to everyone else also for posting their combos and results.

[steve cowan]

Somewhat similar to what you're describing, I'm hoping this current 10" will come into it's own with a stronger engine in front of it. It's an off the shelf piece so hardly optimized but it's effective when compared to something stock. And more effective is what I'm expecting.
Then maybe another Yank or similar once the combination is sorted.

I'll say one thing though, I don't have it in me to experiment as much as you do. I'm at the point in this "hobby" where I'd like to be one and done. Maybe twice.

Kevin,
I understand about budget and doing a one off type deal but I strongly recommend getting a custom converter for your application first time.
When you change converter only and pick up 3 tenths in the 60ft it's worth the money in my opinion.
Took a friend for a cruise the other week and he was amazed with how well my car drove with the 8" converter, he asked me 3 times what size converter it was as I don't think he believes me lol.

[skinny z]

Somewhat similar to what you're describing, I'm hoping this current 10" will come into it's own with a stronger engine in front of it. It's an off the shelf piece so hardly optimized but it's effective when compared to something stock. And more effective is what I'm expecting.
Then maybe another Yank or similar once the combination is sorted.

I'll say one thing though, I don't have it in me to experiment as much as you do. I'm at the point in this "hobby" where I'd like to be one and done. Maybe twice.

Kevin,
I understand about budget and doing a one off type deal but I strongly recommend getting a custom converter for your application first time.
When you change converter only and pick up 3 tenths in the 60ft it's worth the money in my opinion.
Took a friend for a cruise the other week and he was amazed with how well my car drove with the 8" converter, he asked me 3 times what size converter it was as I don't think he believes me lol.

I can appreciate all of that Steve and have little doubt that something spec'd would be better. The example I posted earlier is testimony to that. That said, I've had dozens of iterations of this same car since for 20+ years since I got back into the sport a 2nd time. (The first being in the late seventies, early eighties.) What I haven't done is experimented with this convertor with this transmission and this engine. I'd like to see the results. It'll take me 50 CHP over my last pass to see an 11 second time slip. I'm going to be there in spades. The rest of the car should be up to it. If not, I'll address it then.

[1980RS]

Great thread 1980RS. Real world results with using what you have and trying to improve on your combo.Keep it going and keep posting the results. And thanks to everyone else also for posting their combos and results.

I got really excited after I ran the one 406 in the high 10's with Vortec heads in 2019. After that I had a lot of enthusiasm to work even harder testing stuff. Wife always asks "when will you stop this stuff?" I just tell her, "when it goes 9.99 N/A and they toss me out of the track"

[1980RS]

So today was moving day (cars that is) and in the afternoon I pulled the engine to swap the in the 8" converter and while the engine was on the ground I put the ported Vic Jr. on the 358. Would have used the S/V but I looked and matched that for my Dart 215's on last years 406, so when I try that engine out again I will pull off the 300-25 and put the S/V on for a test. The 350 is in the car now and I should have it running later this week.

[steve cowan]

So today was moving day (cars that is) and in the afternoon I pulled the engine to swap the in the 8" converter and while the engine was on the ground I put the ported Vic Jr. on the 358. Would have used the S/V but I looked and matched that for my Dart 215's on last years 406, so when I try that engine out again I will pull off the 300-25 and put the S/V on for a test. The 350 is in the car now and I should have it running later this week.

Looking forward to your results there Bob,
I am testing again this Saturday, wet weather is going to clear apparently.
I put my trustee 950 hp (750) back together, last years combination with that carb pulled 1" vacuum through the stripe so I suspect it will do the same.was going to run open headers but don't want to change to much at the moment.