Hey guys,

So after a disappointing summer I am tearing into my sbc's again. Had a gimbal bearing go bad, and pregnant wife so, the water time was almost non existant.

I have sbc's with RHS 180runner 64cc cumbustion chamber aluminum heads, 1.5 full roller rockers, edelbrock rpm air gap intakes and edelbrock 1410 carbs, DUI ignition. I was not to happy with the cams that I put in so I am looking to do the retro roller conversion. Didnt do it last time as I kept factory exhaust($$$ issue).

I am looking at a cam specd as follows:
278/ 286 duration

225/ 233 duration@050

.525 /.530 lift with 1.5 rockers

110 LSA

If you guys think I can get a little more agressive with the cam let me know!

My exhaust choices are limited as I need a six inch riser spacer to work with the thru hull set up(no way around it), also tall rocker covers. I have been looking at the IMCO Powerflow, Stainless Marine and HI-TEK. I looked at Lightning, but he said he does not offer anything taller then factory mercruiser. That sux because I really like the lightnings.
I talked the owner of HI-TEK, and he will give me a great deal, basically matching the cost of the IMCO's or Stainless. The Hi_Teks have a cool design and internally are similar to CMI's. I really like the fact that tere are NO gaskets!

Both IMCO and Stainless have great reps and proven performance and I wont have reversion worries. So any thoughts are appreciated.

What is the static / dynamic compression ratio of your combo now and what weren't you happy about with the performance of the existing cam?

If you are happy with the heads I suggest moving to a pair of Quick Fuel 750 Double Pumpers to make consistent power with that Cam.

I think the Edelbrock will starve your overall throttle response and starve those motors in the mid range while you are accelerating up and down between 3000 and 4500...you really do need that active secondary to fill in the voids left by a vacuum secondary carb. I'm talking about real world "Driving the Boat" feel...not just Dyno numbers.

Best calculation I have is approx 10.3 to 1 CR. the motors just feel weak, the current cams are single pattern 465lift 114 lsa flat tappet. I know the cam is the weak spot but I wanted to stay safe running factory manifolds/risers. I know stepping up to roller is a good gain, plus the added lift/duration and the 110 CL will help out big time in the power department. Plus I would like to squeak a few hundred more rpms out of the motors when going all out. Right now 5200 is tops, 54-5600 would be great.

I agree with Sprink, that being said, I would start with the 750 dbl pumpers first. May be a tad much for that cam, but you would probably see them come alive.
I only owned one Edelbrock carb, and I felt the same way you do now!
They're good for daily drivers, thats about it for me.

I agree on upgrading to a 750 DP carb design of your choice over the Edelbrock. I ran a 355ci in summer 07. Cam was a 226/230 .528/.511 112+4 hyd roller, AFR 190 heads, RPM airgap, HP 750, GLM alum manifolds, Imco performance risers with 16" extensions to keep it from reverting water at idle. It ran great and pulled hard to 5700-5800rpms. Idled N @ 750-800rpms. Boat ran low 70's GPS all day with that combo.

With whatever exhaust choice you choose, go with the longest risers you can get to avoid reverting water.

Running a 377 stroker with a Crower 221/230 & .525/.545 on a 114 LSA hyd roller and 1.5 rockers with a Merc EFI MP system. GLM exhaust with stock Merc stainless risers to thru-hull and no reversion noted to date.

Looks like I am going with the imco powerflows, for exhaust. I am still undecided on the cam though, they can make or break a motor.

I'm a big fan of hyd roller cams. I think it would go well with what you intend to do. LSAs of 112-114 in the higher duration cams can help mitigate reversion issues in most cases.

Been running a set of polished Imco powerflows on my small block for a decade.

You will like them. The long riser is a good idea.

I run a pretty hot cammed 406 that idles pretty choppy and have never had a reversion issue.

How many cubic inches do you have?


Uncle Dave