[CK7684]

OK, I've got my headers installed but havent had it wet yet. I am just wondering what kind of performance gains I should expect from them. This is basically the same engine as mine, except that I had logs n snails before...headers are Bassett twisties with baffles. I have a Berk "F" pump with an "A" impeller

http://popularhotrodding.automotive.com/45404/0707phr-big-block-chevy/index.html

 

[SmokinLowriderSS]

OK, I've got my headers installed but havent had it wet yet. I am just wondering what kind of performance gains I should expect from them. This is basically the same engine as mine, except that I had logs n snails before...headers are Bassett twisties with baffles. I have a Berk "F" pump with an "A" impeller

http://popularhotrodding.automotive.com/45404/0707phr-big-block-chevy/index.html

My experince:
Yours may vary.

I put Lightning Thru-Transom Headers on my 454.
Before the headers, the stock engine was re-built, the stock 700CFM Holley sat atop an Edelbrock Performer RPM Air Gap manifold, Hydraulic flat cam specing .565" lift, 280* total duration, stock large oval port heads with the small factory valves (casting 353049), and logs with snails.

4,800RPM on a Berk A impeller before.
5,000RPM after, no other changes. That charts out to be 50HP.

The logs are choking yours likely a good deal worse than they were mine.

When I (last mod) had my heads ported and larger valves installed and port-matched the intake up again, I put another 400RPM on, 100HP.

 

[CK7684]

Thanks...I was running about 4800 RPM before also. My snails had a 90* exit into some rubber mufflers which took another 90* turn to the exhaust tips. I'm guessing that really choked the engine down quite a bit...

 

[H20MOFO]

Watch your jetting...

 

[jetboatperformance]

This can be worth 10% to 20% increase as long as you have intake, carb etc to support the "modifications" just be aware Jets take a significant HP increase for a small mph gain IMO

 

[SmokinLowriderSS]

Thanks...I was running about 4800 RPM before also. My snails had a 90* exit into some rubber mufflers which took another 90* turn to the exhaust tips. I'm guessing that really choked the engine down quite a bit...

At least my logs fed straight to 2 7/16" trumpets on the stern.

I DID go up one size in jetting all arround.

Went up 3, was fat as hell, slobbering all over itself, dropped 2, and very happy.

 

[CK7684]

I guess I will be finding out soon!! I am hoping that these let the engine breath, as the rest of the engine was built a bit more stout than the logs were capable of. Thanks for the reminder on checking the jetting...

 

[Squirtcha?]

This was from personal experience and other individual's results may vary. Three different boats of each genus species (Ford, Chevy and Olds). Each boat made the switch from logs to headers and each gained an honest 200 rpm. No other changes.

It seems to be pretty consistent.

Post up some results when you get them. I'll be curious if this holds true.

 

[CK7684]

Just pulled it out of the water. Looks like I gained about 100-150 RPM. I am still being plauged by my oil pressure drop issue :|err so I didnt push my luck...

 

[Tahiti428]

What kind of additional speed will that 200RPMs give you?

 

[CK7684]

Hopefully i will find that out soon also. I didnt really stay in it due to my oil pressure drop. That and the "lake" I tested on is only about 1/2 mile long or so...

gonna try a mechanical gauge next. I'm hoping thats all it is...

 

[CK7684]

Actually, it looks like I gained 200rpm (checked my notes)...looking at my plugs and they have a touch of black to them instead of a nice tan color. I'm thinking the headers could be flowing well enough to pull more gas into the cylinders...?

 

[H20MOFO]

Unless I'm 180* off here they should look leaner with a less restrictive exaust. Seems like last year when I just threw my baffles in, the plugs looked darker.

 

[watergun4u]

Unless I'm 180* off here they should look leaner with a less restrictive exaust. Seems like last year when I just threw my baffles in, the plugs looked darker.

Baffles in the headers with chock down your motor and make it run fat!!! I would drop a jet size or two!

 

[Squirtcha?]

What kind of additional speed will that 200RPMs
give you?

Unfortunately I can't tell you what the speed was before or after. None of
us had a gps back in those days.

Probably around a 5 mph gain though (guess). All I know for sure is the owners
were all real happy with the results.

 

[CK7684]

5 mph gain would be perfect for me ...I'm currently learning how to properly read my plugs so I can make sure the tune is "on"
As far as the baffles, they should still breath better than my log set-up. I'm guessing that they arent scavenging well enough to pull in more fuel though.

I'm still learning...