Is anyone running an xe274h comp cam on their sbc ? - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board
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Old 03-21-2013, 07:12 PM
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I have loooked at a number of low cost options for headers with a variety of names, none of which mean anything. I have seen some that claim to have good thickness flanges but I am always concerned when you are buying based on a picture that may not even be the part your buying.

I noted that you are apparently tight at the distributor with your conversion, and curious if that was dictated by front end clearance. I am still working on my frame but hope to be in a position to locate the engine and weld in the engine mounts in the near future. I went with the short water pump in hopes to gain as much room as I could on the front end but the distributor I picked up is huge so now I am neveous about having enough fore/aft space.

Sorry for the ramble, just good to touch base with someone that has already been there so to speak.

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Old 03-21-2013, 07:18 PM
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Quote:
Originally Posted by WICruiser View Post
I have loooked at a number of low cost options for headers with a variety of names, none of which mean anything. I have seen some that claim to have good thickness flanges but I am always concerned when you are buying based on a picture that may not even be the part your buying.

I noted that you are apparently tight at the distributor with your conversion, and curious if that was dictated by front end clearance. I am still working on my frame but hope to be in a position to locate the engine and weld in the engine mounts in the near future. I went with the short water pump in hopes to gain as much room as I could on the front end but the distributor I picked up is huge so now I am neveous about having enough fore/aft space.

Sorry for the ramble, just good to touch base with someone that has already been there so to speak.
trust me there is a lot of space bro, once you put it in you'll realize it's actually smaller than the straight 6

I just have a slight, very slight clearance issue, don't worry about it

and for the headers ? trust me pull the trigger i've seen block huggers go for north of 350$ plus shipping, that's a freaking rip off

for the past 3 years these 100$ ebay headers have been amazing
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Old 03-22-2013, 02:09 AM
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Hi,
I run that cam in my 383 SBC and found I had to do exactly what F-Bird says

Originally I ran an MSD6AL box and Twin point distributor with no vacuum and little mechanical advance adjustment. It would only idle at 1000rpm (i experimented and wound the distributor round and idle improved, this told me it needed much more advance than this distributor could provide).
And then you couldnt really adjust the carb down and it would stumble when put into D.

Recently I fitted the MSD Pro Billet and set it exactly as F-Bird said.
Lots of initial and 34 all in. It has transformed the tickover. 800rpm, carb adjusted right down off transfer slot etc and doesn't die in gear.

I think the gist of it is that if you can't give enough idle you compensate by opening the carb past transfer slots. !?

Cheers
Jim
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Old 03-22-2013, 07:24 AM
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Carburated engine need to "WARM UP". This is the nature of a carbed motor.

In the Winter when it is colder...it takes longer for the motor to warm up.
This is why you use a choke on the carb and employ a heated plenum
intake manifold ( exhaust heat, water heat, electric heat) to aid cold weather warm up and driving in cold weather.
While the cold engine is warming up use the choke and fast idle carb linkage
to aid warm up. Give it some choke and some more idle rpm during warm up.

This is the nature of all carbed motors. Let it warm up in the winter.

And fix the distributor timing curve for that cam.
24 to 26deg base initial at idle.

16 is not enough.
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Old 03-22-2013, 08:03 AM
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Originally Posted by F-BIRD'88 View Post
Carburated engine need to "WARM UP". This is the nature of a carbed motor.

In the Winter when it is colder...it takes longer for the motor to warm up.
This is why you use a choke on the carb and employ a heated plenum
intake manifold ( exhaust heat, water heat, electric heat) to aid cold weather warm up and driving in cold weather.
While the cold engine is warming up use the choke and fast idle carb linkage
to aid warm up. Give it some choke and some more idle rpm during warm up.

This is the nature of all carbed motors. Let it warm up in the winter.

And fix the distributor timing curve for that cam.
24 to 26deg base initial at idle.

16 is not enough.
alright guess i'll have to do some more tuning

i'm no stranger to a carb in the winter, the thing was that the engine would die even after 6+ minute warm up period due to the power steering pump and I suspect the heavy tires just being too much for the erratic sun 800rpm idle

thanks everyone(mostly f-bird)
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Old 03-22-2013, 10:30 AM
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The engine is stalling when you turn the wheel (power steering) because the rpm is dropping and the timing is dropping off too.
The modified distributor curve with a consistant stable 24 to 26deg initial base timing will correct this.
( and the power valve must stay closed at idle too.)

When its cold out , let it warm up. With no choke and or a non heated intake manifold it is going to take longer.
Do not allow the engine to idle slow when it is cold. 1500+rpm idle speed when cold.
Give it time to warm up.
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Old 03-23-2013, 09:44 PM
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So i played with my timing today, the idle dropped to around 875 rpm or so, the thing is I didn't even touch the carb, the idle just dropped on its own

The engine feels amazing, more power at lower rpm and better throttle response, should i be worried about the idle dropping without me touching the carb ?
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Old 03-24-2013, 09:42 AM
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You say you are going cruising around in the vehicle or plan to. Ask yourself if the vehicles engines combustion event needs a variable timing map for load? If you have ever use a gas analyzer you will see increases. Being the products of incomplete combustion without the vacuum advance hooked, while testing on the rollers.

If you are cruising at 45, or accelerating threw 45, the engine has totally different requirement for a complete combustion event. The better the engine is fed , the better it will perform when driving around.

Now I said need, and does it truly NEED it? Well no, but it would be well worth a little research.
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