Mystery BBC please help
 

Recently Purchased a 1992 IMP Europa 240 that had a BBC and Bravo 1 swapped into it sometime around 2006. I am trying to get an idea of what kind of horsepower numbers I should expect from the engine. This is what I know about the engine:

Block Casting number #10114182, 1991 and up gen V 454 CI 4 bolt main standard deck block. Mercruiser 454 Magnum Long block, Forged pistons, rods, and crankshaft. Early 90's 454 mag pistons. Gm std. # 14097021. 13.8cc dome 8.8:1 Compression ratio.Cylinder Head Casting #14097088, cast iron 118cc open chamber rectangular port heads. Largest as cast GM production iron head ports (325CC intake runners). Retrofit hydraulic roller camshaft (unknown cam specs) with Crane Gold roller rockers. Weiand Single plane aluminum intake manifold (port matched to heads). Holley #9022 4150 style 800CFM double pumper w/ mechanical secondaries.

What kind of HP numbers should I be expecting out of this set up?

401.6 ?

That’s an oddly specific number. Not sure I understand your response.

I would agree 400 is in the neighborhood.

I didn’t mention it in my previous post but there is a very noticeable lope at idle, so I am fairly certain there is a larger cam than the stock 454 mag cam. Not sure how much of a difference it will make. I would assume the limiting factor on my setup is the 8.8:1 compression ratio?

The limiter in your setup is the 088 heads.

The 365 mag hp rating I believe is at the prop. The GM marine forged BBC offerings were pretty much identical. They were rared at 390hp @5200 at the flywheel. Important to compare the apples to apples.

This would have been with cast exh manifolds. Manifold upgrade would likely net some better peak tq and HP #s.

As mentioned, the 088 heads have maybe the worst exh port GM made. Flows 165cfm at 0.400" lift. That is SBC territory. Intake ports are not bad for flow at 240cfm ish at 0.400" intake lift. That is great for a SBC with a 195cc port. Prett lazy on a 320cc port.

These heads were on the 800SC 420 blown engines, so they can make power, but that exh port is requiring a lot of gross energy to pump out.

My 088 heads have been machine in from the factory so there is very little to no venturi taper underneath the seat. The only real way to fox that is to put larger valves in and rework the seat, so the valve port diameter is 90% of the valve size.

These engines cam with a single pattern cam 224/224 @ 0.510" lift. Hyd FT. 115.5° LSA.

The L29 BBC Vortec heads flow better for a 450hp marine application.

Without knowing what cam you have in the engine, difficult to determine where you are HP wise.

Single plane intakes here are not as efficient as a good dual plane. You don't get as good of a signal to your carb, and you're likey not turning enough rpm to benefit from them.

A good dual plane rec port style intake and a good flowing exh. system, would wake it up.

If you prop for higher rpm 5500 to 6000, with proper cam and springs, the heads will flow, and you'll make more HP.

088 heads are great for what they are, but not worth putting any paid port work into them etc.

boat weights about 4200lbs with gear and fuel, I’ve got a 24p bravo 1 prop. Hoping for mid 60s. Is this too optimistic?

Hard to say. If the cam has been done, it's going to want to breathe above 5000, vs the 4600-5000rpm suggested by Merc. Something like that.

You don't know if the cam's been done, or what valve springs you have in there.

What exhaust have you got?

Post some photos.

4200 lbs isn't super heavy, but getting to 60mph is your first goal.

What drive do you have?

Assuming you have a 1.5 drive reduction.

24p prop
5000rpm
12%slip ish

Gives you 67mph.

Depending how it runs with the 24p, dropping down a bit may be beneficial, if you can't hit at least 5000rpm.

can has def been done. Boat has a very noticeable Chop at idle. Retrofit comp roller lifters are in it as well as crane roller rockers and aftermarket valve springs. Seems like someone built it to turn some RPM. I’m hoping boat is lite enough to tolerate the 24p prop.

Here is a short video of the idle

https://youtube.com/shorts/cVviyM_rl3g?si=cVD-HiOijsyPdTgu

No link....


Roller link-bar lifters in the Gen V...gtg.

TThse are my stock 088 heads with 25 hrs of use. They just hogged in, then put a seat in for the intake valve. No venrturi under the valve. This really hurts flow. Aluminum, you could weld it up and shape it. Iron...all you can do is put 2.300 valves in and see if the throat is small enough at 90%.
https://cimg5.ibsrv.net/gimg/www.off...35fecf85ba.jpg

But the 088 heads will flow with some cam and rpm. You should have inconel exh valves as well...if stock.

Let us know how it runs when you get it wet.

What is the issue with link bar lifters and the gen v block?

Need to hit 10 posts to be able to post url found out…

video of the idle, let me know what you all think?

Sounds good to me. Here's what this cam spec sounds like Bullet 244/250 112 .664/.663:

Sounds good, can definitely hear the Cam in yours! based upon what I can hear in mine at idle, it definitely does not sound like a stock cam. But not super aggressive either. Curious what the general consensus is about it?

No issue..GTG = Good to Go. My back for using it.

Thr mentioned intent was that you obviously also have a non-stock cam if you have roller lifters from a Flat Tappet.

I gotcha, I read it as got to go lol. Where you able to view the video link I posted. I’d like to know your thoughts on if you can glean anything from the idle sound?

I can make regular cams sound pretty lopey at idle and I can make pretty big cams idle pretty smoothly. So I don’t get it. A cam in a bbc can be 0-10-50-100hp or so difference with nothing else changed.

does it matter if it is 300 or 600 hp? it is going to do what it does so you are going to prop it to run where it is happy. if it only turns 4000 then prop it down, if it turns 6000 then prop it up. you will feel when it seems to run the best so stop worrying about hp numbers or speed and just let it do the best it can and enjoy it.

sounds like you have a 3/4 race cam in it.

Excuse my ignorance. Can you elaborate what exactly a 3/4 race cam is? Manufacturer/part number? Would be super interested in seeing the cam specs.

Full race = 1 (4/4)
3/4 race = 3/4
Some call it a stage III :)

To guess hp off of idle lope is impossible.

Sutphen 30 is throwing out an old drag race term from the 70's..........humor..........:lolhit:.......where is KS are you ?

I did some google research and bright myself up to speed lol. I’m in the kck area around the speedway. You?

Im just down the road from the speedway in Basehor

actually I think that is from the '50's. did have a guy at a car show ask me once if my engine had a 3/4 cam, I said "no, I put the whole cam in there". he did not seem amused.

sent you a dm

it’s always fun to learn about yesterdays terminology!

It's normally on the shelf next to the RV cams.

If it doesn't have aftermarket exhaust, then chances are the cam is nothing much over stock. You can't run a cam that is much bigger than stock without aftermarket exhaust or you'll get water reversion.
Probably making 400hp or so. Low to mid 60's sounds about right.