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Discussion Starter · #1 ·
Howdy Folks,

OK, a little back ground: I have a 1973 FB with a 1967 YT code block. When I installed the engine, I was still driving the car to work. (I no longer do that). In fact - I haven't driven or even started the car for about 6 years. Since at the time she was my daily driver, I installed 4X-7H (Screw in stud) heads, an Edelbrock performer intake with a Q-jet (don't recall it's lineage- it does need help), an MSD 6A ignition (hidden in the trunk), long branch cast iron headers, it has a TH350 (Stock for a 2bbl 350- that had 2.73 rear gears). The car now has a 12 bolt with 3.55's. I am running 255R60's all around on 15" honeycombs.

OK, now my question.... I want more performance out of my engine. Nothing crazy (I do not race). Should I stick with the 4X heads (If so - how to improve performance with them) - or switch to either the 670 or #62 heads that I also have - ? Any other thoughts-? (Should I look for 6X-4's - ?)

At the moment I plan on picking up a new Q-Jet from SMI. From here -- any advice is greatly appreciated.

Thanks,
Wolf
 

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"... I want more performance out of my engine. Nothing crazy (I do not race). Should I stick with the 4X heads (If so - how to improve performance with them) ..."

Most online info shows those heads to have 98cc chambers. So, if you have flat top pistons, you should have just under 8:1 static compression.

To increase performance you need to increase compression. The cheapest help I know of is to install a small Voodoo cam. These were designed to increase cylinder pressure in low comp engines. This is called increasing dynamic compression.

The 256 would probably be best for a stock converter. With a 2400-2600 stall converter, the 262 would make a little more power, and feel a lot stronger.

https://www.lunatipower.com/Product.aspx?id=1774&gid=287

https://www.lunatipower.com/Product.aspx?id=1775&gid=287

Another way to increase comp is to use thin Cometic brand head gaskets. But, they are about $100 each. Also, I'm just assuming that your shortblock is in good enuff shape to stand more compression. I think I'd try the cam & SMI carb you mentioned,1st. That may give you all the extra power you want. :yes

"...or switch to either the 670 or #62 heads that I also have - ?..."

With flat top pistons, these heads have too much compression for pump gas. I would not use 'em without dish pistons, to reduce comp to 9.5:1 or less. :no

"...Should I look for 6X-4's..."

The 6x-4's have about '93-94cc chambers. So, unless you have 'em cut down to below 90cc, they will not give you a significant power increase. However, if you plan to have a good set of heads built. I would definitely recommend using the 6x-4's.

"...Any other thoughts-?..."

Don't know what your budget is. But, the easiest way to get lots more power is to use your 400 block to build a stroker shortblock. Then the 4x heads will work well. But, it'll take nearly $3000 to build a stroker shortblock, using your block. :(

http://lenwilliamsautomachine.com/455_Short_Block.html

http://www.sandovalperformance.com/#!product/prd12/2017678915/budget-series-shortblocks-starting-%40
 

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Discussion Starter · #3 ·
Thank you, Don!!

This is certainly food for thought.

So, looks like I will check out: A TCI Breakaway converter and the Lunati 262 cam with a new SMI Q-jet.

As I will stick with the 4X heads. Don't really want to go the stroker route. Just looking for respectable power for the street.

Thanks again!!

Wolf
 

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Discussion Starter · #5 ·
I had a bad experience with TCI products. And I've read that a lot of others have, as well. You can buy cheaper converters, on Ebay, that will probably work just as good, or better.

I've read that the best street converter is a Continental. But it's also among the highest. :(

Wow, thanks for the heads up Don. I thought TCI was a very good brand. After being out of this hobby for so darn long -- I've not kept up with stuff. With this info - I'll look at the Jeg's unit.

Wolf
 
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