Imco manifolds and reversion.
 

First off. I’m not new here but it’s been a while since been on. I had to register again under a new account. I lost my login info and for some reason and for reasons unknown to me OSO, no matter how many times I tried, didn’t send an email to me to change my password.

Anyway, my question is.
Does anyone know? If I purchase IMCO power flow manifolds with the standard bravo SS risers that allow connection to line up to bravo transom tips on a 454 with a comp cams 11-236-4 (226/236 @.050, 112 lsa .544/.547 lift) will have any reversion issues?
I was talking to Scott at Hardin marine the other day about ordering the manifolds but he brought up the issue of possible reversion. We’ve both been trying to contact IMCO to ask about this with no success at all in reaching them. Possibly their phone lines are down. No reply from emails either.
This is all a new build in putting together so I’m trying to get manifolds ordered and be ahead of the game when the engine is ready.

I used the same standard "A" risers on my 502 and also the 454 mag in my last boat. No issues with reversion with either motor. However, both motors were/are bone stock. I don't know much about your cam, but I assume it's a bit more than stock, and the reason why the Hardin guy asked about it. You can get IMCO risers that are 3" and 6" taller in height and are cut to mount to stock Bravo location. If you have to room to go taller, it would probably help also.

Are you calling the California shop? 909-592-6162? If you can't reach them, call the Nevada shop and see what the problem is. They are usually very good about answering questions. Also, they used to have cardboard templates they would send you. If they still do that, have them send you a set and once you measure from the manifolds back, they will build the risers custom to your template. I will say that some boats exhaust tips are cut truer and others. First boat I did, I had to have the risers custom built so they would match up. Current boat was almost perfect with the standard risers. Personally, I would order the manifolds first and wait on the risers till you have the motor in the boat to get the right measurements. Once they get your order, they usually have them done and shipped in 2-3 days.

I was calling the cali number you posted. I wasn’t aware of another location to call. I’ll try that out. Thanks.

I could fit the +3” risers in the engine cover but my transom won’t allow it because of the swim platform being built into the hull. From the prints showing the dimensions of the manifolds with risers the +3” is simply that, 3” higher all the way. It still has the same 16 degree pitch down to the transom. With the standard A bravo risers they’ll fit right to the top of my transom. Something like a HP style riser would work the way they loop up then back down and kick back up again to line up to the tips. Problem with those like in the GIL replacements for HP series is they’re border line too tall to fit in my engine cover. I didn’t see any HP series risers on IMCO’s website.

What's the advertised duration?

Asking to be able to figure out overlap.

Advertised duration is 270/286

Finally got in touch with someone at IMCO. He said border line was 235 @ .050” and the standard height “A” riser.
They seem more focused on the duration than the LSA.
I’m new to building a marine engine but I thought more focus was towards the LSA when it came to reversion. 🤷‍♂️
I may have to scrap this whole cam and chose another but now I’ll have to find one that’ll work with my pistons. 454, 120cc chamber with 18cc domed pistons.
Any cam recommendations for that CR? (About 9.4:1) I can’t change pistons now because the rotating assembly is out being balanced as we speak.

As stated, they can custom fit the risers for you. The additional cost in nominal, if I remember correctly. I would post pics of the template they sent me, but OSO says I can't. Say you need at least 10 posts and I have over 200, but still can't. Pm your number and I will text them to you, if interested. You can make your own templates out of a large cardboard box to get the measurements. I still have the IMCO instruction sheet that tells you how to make your own template and how to measure.

Overlap is 54 degrees. I don’t think it’ll be an issue really.

Im sure if you ask the mods they could fix your old account if you provide them the screen name, Griff, Speedgirl, Cashbar are all mods