calling all 6cyl 250 gurus - Team Camaro Tech
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post #1 of 13 (permalink) Old Mar 8th, 03, 02:17 PM Thread Starter
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Hey everyone,

I am looking to squeeze every nanospec of power out of my straight 6.
I am a bit of a rookie when it comes to performance building so I am looking for some assistance. I got questions, lots of questions!

Right now I have a 1 bbl Rochester carb, it is not original for the Camaro. Somewhere down the line before I got the car someone slapped a carb from a 67 Nova on it. Anyway, my first of many questions is: is there some sort of adapter plate or something that would allow me to upgrade my carb to a 2 or a 4 bbl?? On cliffordperformanceshop.com they sell an intake manifold that you can have dual 2 or 4bbl carbs. What is the advantage of having 2? How does that help? Are there noticeable performance changes? Is it worth the $300 for the intake and then another $500+ for 2 carbs?
I guy I work with told me that his uncle has this same engine (250) and that he put a camshaft from the 292 engine in it and it made a big difference? Will that really work?? Is he just blowing smoke up someone's...??
Last question (for right now anyway): Is it advantageous to upgrade to a HEI distributor? I need to replace my distribtor and if I am going to replace it I might as well do it right. Should I go with an HEI? Are they better?

Man that was long. Thanks in advance.

Heath
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post #2 of 13 (permalink) Old Mar 8th, 03, 03:13 PM
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Heath;

The Clifford single 4 bbl intake (water heated) is what you need. Don't bother with a dual quad. You have to build a very radical engine to justify that.

As for exhaust, use the Clifford header. It fits & it works.

I just bought a Pertronix ignitor. That will give me a stock looking ignition but a lot better than points. Th HEI is also a good choice, & possibly cheaper if you get one from a bone yard.

There is a great book about Chev 6 cylinder performance by Leo Santucci. I picked mine up from a book vendor at a car show. Get one & read it. If you want increased performance from a 6, that book is what you need.

Glad to see another 6 cyl Camaro in the works. I think there are very few left out there.

Paul [img]graemlins/beers.gif[/img]

'69 Camaro, 250 inline 6, EFI Turbo rebuild is running!!
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post #3 of 13 (permalink) Old Mar 8th, 03, 04:11 PM
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Go with an HEI a real performance increase for little money. Headers on 6s are a real problem when it gets cold. The carb will freeze without the exhaust heat to keep it warm. the Clifford set up is better than nothing but using a stock exhaust and an Offy manifold that will work like a stocker is a better idea, A 292 cam won't work in a 250 they physically aren't the same.
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post #4 of 13 (permalink) Old Mar 8th, 03, 04:26 PM
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If you seperate the manifold pieces be sure to clean the the flow chamber around the mounting base for the carb. I had a 250 in a 1967 Chevrolet truck. I had to take the manifold off once and I took it apart. There was scale and rust built up in the chamber so the warm air flow through that area was not good. I live in Missouri and the winters get cold. If the carb doesn't have any heat then frost will build up in the throat of single barrels and 2 barrels. Then, if the carb has an automatic choke, it will come on causing the engine to run bad.


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post #5 of 13 (permalink) Old Mar 8th, 03, 09:41 PM Thread Starter
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Where could I get an HEI distributor?
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post #6 of 13 (permalink) Old Mar 10th, 03, 06:17 PM
 
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Here you go www.cliffordperformance.com

What about a turbo or some other type of forced induction? Did you know that the 250ci shares the same bore and stroke as that of the 307ci? That opens up some options. Good luck.
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post #7 of 13 (permalink) Old Mar 11th, 03, 01:55 AM
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250 I6 = bore 3.875", stroke 3.53"

230 I6 = bore 3.875", stroke 3.25"

307 V8 = bore 3.875", stroke 3.25"
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post #8 of 13 (permalink) Old Mar 11th, 03, 03:28 PM
 
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Eric,

You forgot the one that I always wanted to play with and it is the little 4-banger, 153 motor!

The one before the Iron Duke came out!

I always wanted to install one of the Dukes cross flow heads on it and hop it up a schosh more just for grins... pdq67



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post #9 of 13 (permalink) Old Mar 11th, 03, 03:32 PM
 
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Back again, ditch your engine and go hunt up a Pontiac Sprint SOHC straight 6-banger.

It came stock with a four barrel, Q-Jet and a split exhaust manifold as well as the single belt driven overhead cam...

Something like 225hp or more but I don't remember for sure???

pdq67



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post #10 of 13 (permalink) Old Mar 11th, 03, 05:42 PM
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I thought about that but everything is Pontiac and sticking one in an early Nova isn't worth the trouble. In a Camaro I bet it would be much easier if there wasn't any serious oil pan problems.
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post #11 of 13 (permalink) Old Mar 12th, 03, 04:41 AM
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Also, how about finding a 194 head and having it worked up? Increases CR some. I've heard of this but never did it.
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post #12 of 13 (permalink) Old Mar 12th, 03, 09:43 AM
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. . . and I thought you could stroke a 250 using a 292 crank and rods (truck engine I think). That would raise compression too. and I think the old I6 blocks are thick wall and can take like a 1/8" overbore like the old 396 BBC castings. If I recall a 1/8" over bore and 292 crank will make it a 292! Doh! now that I think of it, if you find a block with a good 292 crank, you might as well build the 292.

The one nice thing about the I6 head is that it uses a 1.7 or 1.75 big block style rocker arm which helps get some extra lift out of your cam. That will help if you do some porting on the head and get some good high lift flow numbers out of it.

I know a guy (my machinist) who is a 300 I6 Ford fanatic --- he spent a lot of off-hours porting the I6 Ford head. He showed me his flow-bench data where he got about 225cfm out of the intake with 1.94"I 1.50"E valves. He runs it in a 4100 lb truck and got 14.1's out of it in the 1/4 mile. Might not sound like much but with tall tires, 3.73 gears, a stock cam, and a stock converter 14.1 is screeeeaaaamin' in a 4100 LB truck.

One not-so-good thing is that the I6 Chev, conn rods use small bolts and a stock crank will not have a good balance --- you need to get the absolute best bolts you can, maybe shot peen and polish the beams too. A good balance job on the crank is a must if you are going to rev over 5,000!

Can you tell I've been thinking about this

[ 03-12-2003, 12:04 PM: Message edited by: Eric68 ]
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post #13 of 13 (permalink) Old Mar 12th, 03, 12:51 PM
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The deck heigth is different on a 292. You can use the crank but it will require custom pistons.
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