Hot Rod Forum banner
1 - 20 of 43 Posts

·
Registered
Joined
·
393 Posts
Discussion Starter · #1 ·
So I was wondering if cutting 2 feet off my pipes would do anything for me in terms of power? Or would it just be a waste of my time? They're 2.5 inch straight pipes about 6ft long with 1.5 inch primary shorty headers..
Also my headers glow red hot. They're wrapped in DEI heat wrap. Is that because of the heat wrap? Or could it be because the primaries are so small?
Unfortunately this is all I can do for exhaust because an SBC in a 1950 chevy with stock steering doesn't really leave me much room.

Thanks guys. I appreciate all the input.

-Chris
 

·
Registered
Joined
·
17,613 Posts
So I was wondering if cutting 2 feet off my pipes would do anything for me in terms of power? Or would it just be a waste of my time? They're 2.5 inch straight pipes about 6ft long with 1.5 inch primary shorty headers..
Also my headers glow red hot. They're wrapped in DEI heat wrap. Is that because of the heat wrap? Or could it be because the primaries are so small?
Unfortunately this is all I can do for exhaust because an SBC in a 1950 chevy with stock steering doesn't really leave me much room.
Cutting 2 feet off the pipes will lighten the car by about a half pound, make the exhaust note more raucous and dull a perfectly good hacksaw blade.

I wouldn't blame the red hot header pipes on the wrap. I'd blame it on a far-too-lean fuel/air mixture and/or very late ignition timing which will allows the burn to continue out into the pipes.

As far as headers, call Doug Thorley Headers and ask about their D358 headers. Not sure they will fit, but they would be about as close as anything you'll come across in the aftermarket....
800-347-8664
 

·
Registered
Joined
·
393 Posts
Discussion Starter · #3 ·
Hmm. That's odd.. because my ignition timing is at 18° initial and 36° total.. and according to my plugs i'm running a little rich. And thanks for the header info, I'll give them a look. Right now I'm running the Sanderson headers, which are specifically made for the 49-54 chevy cars with stock steering and an SBC swap.. I'd really like 1 5/8in primary 3in collector mid-length headers.. I found some by flowtech, but idk if they'll hug the block enough to squeeze under the car and between the frame rails.
 

·
Banned
Joined
·
2,474 Posts
Hmm. That's odd.. because my ignition timing is at 18° initial and 36° total.. and according to my plugs i'm running a little rich. And thanks for the header info, I'll give them a look. Right now I'm running the Sanderson headers, which are specifically made for the 49-54 chevy cars with stock steering and an SBC swap.. I'd really like 1 5/8in primary 3in collector mid-length headers.. I found some by flowtech, but idk if they'll hug the block enough to squeeze under the car and between the frame rails.
ARE you sure.. did you check for true top dead center? or going by the timing marks on the balancer?? and hoping the outer ring hasn't moved
 

·
Registered
Joined
·
393 Posts
Discussion Starter · #6 ·
Yeah they're probably not accurate haha.. even though they are both brand new aftermarket parts (balancer and timing tab), but I've learned to never assume that just because it's new that it's right.. and i have considered them. I really like the fenderwell headers.. the only thing is idk if it'll interfere with my front tires due to the lowered ride height.
 

·
Registered
Joined
·
393 Posts
Discussion Starter · #7 ·
And even if the timing marks aren't accurate, the motor sounds really good by ear. With the throttle blades adjusted properly for the the transfer slots, and the idle mixture set to max vacuum with the "18°" of initial, it idles at 1300 in park and 950 in drive. And the plugs don't look fried, just a little rich if anything.
 

·
Registered
Joined
·
270 Posts
The heat wrap is probably to band-aid lean fuel or retarded timing that's causing the red headers. Personally I'd leave the exhaust pipes alone, keep the shorty headers, and look for power else where.

Ignition timing and mechanical curve should be checked. If your dist. isn't very good or pretty old and crusty id get a new one or put some new guts in it. Fresh plugs and a tune up would probably go a long way. I'd verify tdc with a piston stop and ensure your mark is accurate.

For making more power I'd look at the intake and carb combo, cam, maybe heads or have your heads gone through (valve job, bowl blend), stuff like that. First make your engine run right, then make some meaningful mechanical changes. I'd bet your leaving some power on the table as it sits now.
 

·
Registered
Joined
·
393 Posts
Discussion Starter · #9 ·
Thanks ben. Yeah i don't doubt it. I really need to get the tune dialed in. Im just chasing carb tuning and timing right now. I'm having trouble finding the right jetting and getting the accelerator pump cam i want. But in regards to ignition timing... wouldn't the motor sound and run like crap if i had retarded timing? Not to mention wouldn't it have a sloppy low idle?
 

·
Premium Member
Joined
·
6,623 Posts
18 degrees is a lot of initial, why so much?

Whats the specs on you carb, jet sizes, pump cam, vac sec or double pumper etc?

Shortening you exhaust pipe is a waste of time, why would you think this would help?

Getting TDC dialed in so you can make basic timing adjustments should be where you start as well as a tune up, the header wrap just cracks your headers sooner in my opinion...works as intended but cooks mild steel into a brittle mess.
 

·
Registered
Joined
·
393 Posts
Discussion Starter · #11 ·
Initial timing is so high because of my cam specs. 236° @ .050" and gross lift of .528".. and I have a holley 670 with vacuum secondary. 68 primaries and 76 secondaries.. and I the blue cam on position 2. And after i posted that exhaust question i second guessed posting it because i figured it was a dumb question.. but why not ask? I thought maybe that shorter distance would MAYBE help the motor to squeeze the exhaust out.. however i look back and realize that it probably wouldnt do a damn thing.
 

·
Premium Member
Joined
·
6,623 Posts
14-16 degrees is more typical and usually plenty, the rest of a total 34-36 degrees all in by 3600 rpm is quite common. Cam does not have much to do with it, its the chamber that dictates timing.

Once you have the timing calibrated to TDC and properly dialed in you can address the jetting, usually the brown cam works the best when everything else is correct.

Unless your running really low compression your probably detonating it off the line and not know it, you need to check your plugs with a loupe to see little aluminum balls to know for sure...you cant just throw more initial at it until you get the best vacuum...thats a recipe for disaster and burnt valves or collapsed ring lands or worse.
 

·
Registered
Joined
·
393 Posts
Discussion Starter · #15 ·
And I didn't adjust the timing to max vacuum.. just the carb idle mixture. I set timing with a light and was recommended by multiple people on here to run 18-22 initial.. but thag has always seemed a little excessive to me.
 

·
Premium Member
Joined
·
6,623 Posts
Torque off the line will appear better with more initial but then you need to restrict the timing curve to slow the ramp up as rpm builds, typically what happens is the excess timing heats the chamber which causes a brief period of detonation which you likely wont hear.

Its a poor approach to proper tuning and is hard on the engine, unless your egt temps show otherwise. Your glowing headers would be an indication if you ask me.

I've never seen this approach work on a four stroke but it works sometimes on a two stroke with a lot of reversion which richens the mixture in that rpm range.

Typically you would lengthen the intake port length to reduce reversion instead of cranking up the timing to cover up the issue.

Stick to basics, set up your distrib curve to be all in by 3600rpm and start at 10-12 initial and creep up on intial timing until you witness aluminum on the plugs and back off 2 degrees from there.

This is a safe methodology with any engine, of course this all assume proper TDC knowledge and no scatter or crossfire in the ignition.

Don't just set these things according to a recommendation, you need to experiment to find the sweet spot...and thats done with a stopwatch and patience while you sneak up on the right combo.

Carb is another issue that complicates the setup, once you get one right you may need to tweak the other to get an optimal tune. In all cases your plugs tell the story and need to be read to know what to do next.
 
  • Like
Reactions: HeavyChevyDeluxe

·
Registered
Joined
·
393 Posts
Discussion Starter · #17 ·
Thanks a lot chuck. I really just need to tinker. I'll try backing the timing off and screwing with the plugs and ensuring that tdc is actually tdc. Your help is greatly appreciated. This timing has been giving me **** for a while.
 
1 - 20 of 43 Posts
Top