FurthermoreHe's got 454's I believe, so ARP or Permatex thread sealer on threads. ARP's lune on washers and underhead of bolts.

in my opinion that’s a bit light for 5500+ rpm. Rather see at least 420-450 open.

Edit: i misread.

His cam lift is just .550” vs the .610” to .632” or more we typically see on bbc builds. So maybe that makes the open look lower than normal ? Time for some math for a look see.

“To calculate a valve spring rate, subtract the seat pressure from the open pressure, then divide by the lift.”

So, plugging in the provided #’s:
340lb (open) - 155 lbs (seat) = 185lbs
1.92” seat - 1.370” open = .550” lift
185lbs/.550in = 336.4 lbs/in spring rate

Did i do math right ? 336 rate is low. As example The popularly used Isky 8005A is 400lbs/in.

https://media.giphy.com/media/xT9IgG...prBC/giphy.gif


Sorry, couldn't help myself

If you would like to have my head guy look at them for you just let me know. Valako just finished up my 302 and might have some time between the 496's he's rebuilding. He's local.

https://www.racingsprings.com/index....ing-11334.html

Install height = 194lb
Spring rate is 469lb/in (PAC website)
469*.550 = 258lb
258lb + 194lb = 452lbs open
Those are close to the Comp 933's I run.

i missed the pac # then. What is it ?

edit in: Okay, from your link PAC-1940.

Actually subtract 20lbs. AFR install is 176lbs. Still reasonable.

"PAC Racing #1940 1.550” OD Hydraulic Roller Dual Valve Spring, 175 lbs. on seat, .725” maximum lift, Max RPM 6500-6700"

I thought someone talked to pac and they said not to use the hot rod series for marine endurance ?

I paged Tim, there used to be a guy on here that used to tell all his customers that his heads were built by AFR to his specs including larger clearances but he was a liar, stock heads stock clearances, he cost a lot of people a lot of money.
Also any place that assembled all that and didn`t mention this I would definitely not go back to. Find a reputable builder that knows marine.
I had a guy build me motors , set the piston to wall clerance too tight and they lasted 2 months.
The story I heard from BBWWT about your dyno place is pretty bad.

https://cimg7.ibsrv.net/gimg/www.off...38b963d7bc.jpg
https://cimg8.ibsrv.net/gimg/www.off...bf2fab1e60.jpg

Also sorry man but theres something to be said about stock engines.

Ok no bashing bs here but here's the facts, no head is bolt on ready for marine use, always always always build them for your application, had I listened to that advice from a buddy and not someone else a world of hell would have never happened, my afr had .0010-0012 clearances, with a lot of metal transfer bronze to valve, I will look for a pic, that combined with a slightly tight lifter bore (another clearance I asked about and was told was fine) created a very expensive failure in less then a hour. I took care of them issues and had new cams ground, along with proper upgrades springs... my supplies springs were upgraded for marine, yet when o personally talked to pac they were a "street car hot rod spring" I might even have that email still..

take or don't take my info but many guys here can say this was my situation, some hate me for posting the culprit so save that bs that's years ago...

that being said after them issues fixed the engines are currently still going rock solid after my boat and sold them to a guy in a 38 scarab for 6 seasons now

curious, whats your beef with them? dealt with them dozens of times for almost 40 years, never had a problem and always more than helpful. they built my current 557's and they have been flawless for 4 years.

Ahhhh memories lol 🤦🏽🤦🏽🤦🏽 simply, build own heads call it a day. https://cimg8.ibsrv.net/gimg/www.off...5cc60290a9.png
https://cimg9.ibsrv.net/gimg/www.off...40974969b.jpeg
https://cimg0.ibsrv.net/gimg/www.off...8f84e3faa.jpeg
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Good morning everyone, So I'm not sure I was clear about this and maybe BBYSTWY misunderstood too. Performance Engineering in Jenison only performed the dyno and final tuning for me. They did NOT build the engines. I spoke with them yesterday and he said that they always check clearances in the heads before install. My original guy did not. Could be because I supplied everything, I don't know and at this point it's water under the bridge. I am not going back there. Moving on.
Whether Performance Engineering feels bad for me or maybe it's regular pricing, he gave me a number I can live with to straighten out the heads. I believe that the "consensus" is .002 clearance on the valve guides(?) and then up the spring pressure to low to mid 400's? With the springs, I don't want to be the guy that "trips over a dime to pick up a nickel" but is this "pressure" something that can be achieved with a shim? Maybe a shim moves the "bind" number? There was a lot of math earlier in this post and I think the existing open ht pressure of 340 was just barely acceptable in my application? I think it figured out to be 336 required? The website says out of the box their springs are good for a bigger cam than I currently am using.

Are these clearance problems only associated with aluminum heads? Only with AFR heads? I went aluminum because they are supposed to make more power, obviously the weight reduction is a good thing and well the "cool factor". ICDEDPPL, you mentioned that there's something to be said for stock power. I agree however stock sucks. Of course this dilemma I'm in sucks too but... I never looked at buying stock marine engines at all. The prices from Mercury are ridiculous. Maybe I could \ should have looked around but clearly I'm the guy who puts the cart in front of the horse. I always thought Mercury just bought a bunch of truck engines complete, swapped the water pump out and sent them out the door. Does Mercury just order parts and marinize and assemble their engines? I believe that 100% on the big stuff but 7.4's?

I set clearances at .002, zero issues after, every marine head should be custom built to your specifications that also goes for valve springs. You can't just use a general pressure you need to get with the cam manufacturer and use what they tell you and set up that way.

After 420 hp many things change in marine engines...

FULL FORCE, thanks for the info. I am checking with Comp Cams to see if I have the right springs for my cam. AFR's site says yes but I am experiencing a problem at and above 5300rpm so we will see. Obviously by my posts, I should have gone to a marine engine shop. The guy who built them knew they were for a boat but there's a difference between circle track engines etc. and the marine environment. The entire package I ordered was with the help of a phone operator at Summit and stuff I saw on the internet. There is crapload of stuff I am unfortunately now just finding out that pertains to marine engines. I don't have deep pockets and now am wondering if I have built a couple engines that are going to require way more maintenance (constant parts replacement) than I am accustomed to. Thanks again.

As you know, peeps are here to help you.
Think of all the money you SAVED by not installing these engines in your boat!
You will have these engines dialed in, drinking a beer on the water in no time, enjoying the fruits of your labor.

dykstra, Thank you. I'm pretty sure there would have been at least one catastrophic and that would have put me (financially) out of the game for quite a while.

Like I said before good you caught it now. The solution really shouldn't be that bad since the engines are still out. And when done at that HP level they should be pretty reliable.

Thanks wildman. I really hope so. I also hope the boat runs clean and doesn't try to kill me. :D

Not hard to build them reliable, just have to know what to do. Do you by chance know main and rod clearances? L if too tight that's another huge issue waiting to go boom, probably the biggest failure I ever see in marine engines are guys running clearance is too tight and then they blame the oil for being a problem

Piston to wall would be good to know as well.
General rule of thumb, car guys build car engines. Marine guys build marine engines. There are plenty who do both (Tyler and Jack Boyd and myself come to mind) but never ever ever ever let a car only guy build your marine engine. There are SO many things car guys (road toads) can get away with that we cant. Shelf stock heads are just one example. Hot Rod guys actually think Eagle makes a decent rod. It goes downhill from there.
An other good rule of thumb for engine program success. Stay with one shop. Don't let one guy short block it, another dress it and another dyno it. It's just a bad plan and a recipe for failure.

PQ 290, where are you located ? there might be someone on here willing to lend you a hand if you need help redoing these engines, I would but think Im a ways from you

Thanks F-2. I am in West Michigan. I called the 2nd builder who up to date has only performed the dyno sessions and asked him some questions based on what I've learned and he had the right answers. Taking them back for the repairs. Same guy SABER28 has used for apparently many years with no problems so I believe I am in good hands now. Thanks again

The 1st key to building a reliable engine is having a stable and reliable valvetrain. Spend the time(and money) to research/buy high quality valvetrain products and have someone reputable with marine experience set everything up.

to quote an article we did for engine builder magazine
..."there are no adequate preassembled heads for the marine environment. You MUST buy a bare casting and do your own setup...."

.....

Thanks everyone who asked about piston clearance. I thought I would take a look and now I am pissed at the original builder. He knew these engines were for a boat. He installed KB hypereutectic pistons and the card clearly states for N/A Marine the the piston to wall clearance should be .0035 - .0050 for what looks like a 4.100" bore and up. Mine are .002 - .0025.
https://cimg0.ibsrv.net/gimg/www.off...93c4ceedda.jpg
Might as well get all of this out there. The ring end gap for the 1st ring on my build sheet is: .021 the 2nd ring: .022 and the oil ring is: .025
So now comes the question, Would you go back to this builder, with the new information, and demand that he make it right on HIS dime? He absolutely didn't follow the recommendations from the piston company. I suppose I would / should pay to the have the valve guides done but this has just turned into a complete redo short of parts of course. The obvious problem is that would he do the job correctly or be pissed and not?

No, I would find a reputable marine builder to take them down and start over. I also question why, since you went overbore and had to replace the pistons, the decision to go with hypereutectic over forged. I went forged on my otherwise stock 496 MAG after it bent a rod due to hydro-locking a cylinder. Cheap insurance to help out in case you run into detonation for whatever reason.

So to reach my goal of 500hp using the parts I bought, boring the cylinders was not required and because the bores were in good shape I was able to maintain the standard bore so just a hone. The guy said at my level, forged pistons weren't required. Forged are apparently also heavier(?) and again, just not necessary at my hp level. That was the story.

So, how about them Bears ?
(if your not old, sorry, it’s an old saying)

PQ290,

Just an opinion... There is no such thing as "too strong". I would opt for forged ANYTHING over cast. Just sayin'.....

Thanks. Brad.
(937)545-8991

hypereutectic pistons...? All due respect, you need a new engine builder. That's fine in a stock marine small block and a very stock big block. 500hp? Nah. Car stuff man. Boats are in 4th gear going up hill all day. No shifting, no coasting.

SB, LOL!!!! I am old and How bout those Lions!!!!