[traveler]

Does a 350 SBC use an internally balanced type dampener and a 400 SBC use an externally balanced type dampener?

If I need a dampener for a 383 and that engine has a 400 crank then it's important that I use a 400 dampener, correct?

For a Blue Print 383 engine Summit recommended the BPP400L dampener. When it arrived I see that it has no permanent TDC inscribed. The TDC mark is lightly painted on. The main finish on the dampener is extremely thin as well and shipping motion in the box has worn the finish down to bare metal which is going to rust. And the worst area is right where the superficial timing marks are painted on. There's no practical way I can spray a decent finish to stop rusting without losing the painted on TDC mark.

I am looking for any suggestions up to and including using a different a balancer with an actual deep scribe mark for the TDC. Or, might it be better not to trust the painted on TDC anyway - just paint the BPP400L and use a piston stop to find TDC and mark it myself as best I can? Maybe I'm over thinking this?

 

[BillK]

Basically everything you said is correct. Only "maybe" is do you know for a fact that your engine is external balance ? The fact that it has a "400" crankshaft doesnt mean anything. Somebody might have internally balanced it.

Personally I would NEVER trust Summit as far as tech advice. If you have a Blueprint Engine then call them and ask them which damper to use.

 

[mark f]

I have a Blueprint 383. I used a Summit SUM-161400. Its a pretty nice piece. Has engraved timing marks.

 

[traveler]

All I know Is that the engine is a Blue Print 383 which is spec'd as externally balanced. Summit told me that Blue Print recommends their BPP400L dampener for this engine. The BPP400L does have a large weight fastened inside. I'm just not too thrilled about the lightly painted on lines and a finish so thin it rubbed off on the box and will rust unless I paint it over the timing marks.

I am getting enthused about the SUM-161400 that mark f is using - thanks! Reading the reviews it looks like the only complaint is that the engraving isn't too deep. But at least it's there and reviewers like the overall finish on it. mark f, did you find the SUM-161400 perfectly suitable for installation just as it came or did you need to paint it? What color was it on arrival? Thanks for the responses.

 

[snow427]

That damper should have laser engraved markings that are pretty clear and easy to read. If I had to guess the dry silica packet broke open and that is what caused the finish to get damaged, I have seen that on those style dampers before. Summit should swap it out for you.

 

[traveler]

That damper should have laser engraved markings that are pretty clear and easy to read. If I had to guess the dry silica packet broke open and that is what caused the finish to get damaged, I have seen that on those style dampers before. Summit should swap it out for you.

I wish it did have actual engraving of the timing marks but it looks very much like a painted on "lick and a promise" after-thought for the markings. There was no silica packet. Once paint rubs through to where there is bare metal you are able to tell it was never very thick to start with especially when the cause of it is just rubbing on a cardboard box while in transit.

 

[snow427]

That is surprising, they may have changed where they are getting them, they used to be laser etched. Any 400 style external balance damper should work. The only odd thing I have seen with some after market crate engines is if it a one piece rear seal it will a lot of time use the standard imbalance from those engines which is external on the flywheel side and neutral on the damper side. But I don't think that is the case with the blueprints.

 

[BillK]

All I know Is that the engine is a Blue Print 383 which is spec'd as externally balanced.

If that is the case then I would use the Blueprint damper even with the lousy finish.

The reason I say that is having balanced engines for almost 30 years now I have found that if you buy 5 "400" dampers from different manufacturers and spin them on the balancing machine they will all be different amounts of "unbalance". Some significantly more than others, especially the less expensive ones. Its scary.

More than likely Blueprint used their own damper when they balanced the assembly so your chances of not having vibration issues will be much better with their damper.

Just my opinion,

 

[mark f]

It is perfectly suitable. I used a yellow crayon to highlight the timing mark worked great.

 

[2/75NastyNewbs]

Powerbond makes a very nice damper at a good price.

 

[DZAUTO]

A lot of good information here, and I especially agree with Bill above.
TYPICALLY, a "built" SB400, or derivative, including a 383 engines (engines with a 400 stroke crank), are USUALLY EXternally balanced. Which means they have a 400 style balancer as well as an UNbalanced flywheel (or flexplate). Over the years I've torn down multiple SB400s (I really like them) and saved the balancers and flexplates (why I save flexplates is a mystery to me because I despise auto trannys). When I build a 400, 383, whatever, I go through my stash of 400 balancers, select a good one (how do you know if it is "good"?) and then send everything to my machinist. Typically, the weight on a balancer and flywheel for a 400 is not changed. Balancing is done by removing (or adding) weight from the crank journals. I don't know if that is how Bill does balancing on EXternal balance assemblies, but that is how my machinist does it and I've been using him for over 35yrs-------------NEVER an issue with any engine he has done for me.

Now, with all that said, I'll add one exception. The 389 in my 51 Chevy has a NEUTRAL balance flywheel which I took to my machinist. for balancing, he drilled some big holes into one side of the flywheel to make it UNbalanced. Worked great!

 

[traveler]

If that is the case then I would use the Blueprint damper even with the lousy finish.

The reason I say that is having balanced engines for almost 30 years now I have found that if you buy 5 "400" dampers from different manufacturers and spin them on the balancing machine they will all be different amounts of "unbalance". Some significantly more than others, especially the less expensive ones. Its scary.

More than likely Blueprint used their own damper when they balanced the assembly so your chances of not having vibration issues will be much better with their damper.

Just my opinion,

Sounds entirely believable to me. I will call BP and verify that the damper and flexplate Summit wants me to use is correct for their 383. I would rather the engine run smooth and long rather than look pretty. Maybe I'll also ask their tech dept. if they think it'll make much difference which brand of external damper I use, just to see what they say.

 

[600renegade]

My BP dampener that I got with my 383 Blueprint engine has all timing marks laser engraved up to about 40. This unit looks just like a 400 with the section cut out of the dampener.

I did use the external balance SFI rated flexplate from TCI.

 

[traveler]

My BP dampener that I got with my 383 Blueprint engine has all timing marks laser engraved up to about 40. This unit looks just like a 400 with the section cut out of the dampener.

I did use the external balance SFI rated flexplate from TCI.

I believe a decent balancer should at least have a section cut out to permanently mark TDC. I didn't like the fact that the Blue Print BPP400L is perfectly smooth and all marks are thinly painted on. Then you get to the fact it'll soon rust on account of the wearing off of the extremely thin black base coat. So I'm sending it back. I did call Blue Print Tech Dept. to ask if it mattered whether I used one of their dampeners or not. I was told that as long as I used an externally balanced type dampener it wouldn't matter whose it was. Reason being, they said, (and I think I understand this) is because the off-the-shelf BPP400L that I was going to use was never included when the crank was balanced. The BP38315CTC1 engine that I plan to use does not normally come with a balancer. I don't know anything about the possibility of another 383 version that comes with a balancer and if that balancer might have been included when the crankshaft balance job was done.