Funny thing is there is no letter after the 1-043, casting is just flat. Is this because it is a Merc application?

I'm also looking at a pair of pro topline aluminum 320 heads, but I've heard they had lots of issues. Would you go for the toplines over the Merlin's in a freshwater boat?

I have never heard of a Merlin cylinder head being used by Mercury.

the 320 pro topline was the same head design as the EQ 320, and RHS 320. I believe when RHS was bought out by comp cams, they had no interest in the iron versions, so engine quest picked them up. Outside of marine and truck pulling classes, theres very little market for bbc iron heads in the automotive world.

The 525 EFI heads by Edelbrock, I think were a 320 runner ?? then later on I think Dart made some 525 Merc. heads.....

i think dart made some 525 replacement heads, but dont think they came from factory on 525s, otherwise theyd prob been 550s lol

engine build
 

I'm with Phragle... run AK heads :hitit:

Ok I'm looking at the aluminum heads, can I just turn down the boat by not over driving the blower to try and keep the the HP down if I do heads and a roller?

Thats my plan.......

The stock 525SC pulley is a 3.25" upper and 6.5" lower if I recall correctly. I know it is 2:1 overdriven and stock boost is 5.5#.
Nobody ever made a larger upper pulley than stock that I'm aware of. Not sure what size you have?? I'm guessing 3.12" ??
The splined pulley is NLA so you would have to find a used one or have your blower shaft changed to keyed one.

Im keyed... :cool-smiley-011:

Yeah I got a 7" lower with a 2.875" upper, if I go to 3.25" upper or a 6.5" lower that's put me about 2.09:1 to 2.15:1. And with my supper chiller boost reduction, I think I'd lucky to make 5lbs with that set up.

P.S. I'm looking for a automotive style keyed front shaft if someone has one laying around ( Blower is apart rebuilt and waiting to go back together :).

They may have been 3.5" and 7" stock. I can't remember for sure, and thinking back, I think they were.
Either way, you are more than 2.15 overdriven.
Divide bottom diameter by top diameter and you are at 2.43:1

i believe eve there were 2 different ratio / pulley combos a standard and a high altitude

The high altitude was supposedly just a smaller upper pulley.
I've heard Merc had them but never seen it listed in any parts lists.

Ok doing the alighn-hone and need to know what main cap bolts to run, stock or ARP?

What's the max HP stock GM 4-bolt main bolts should be ran up to with a blower?

Thanks

for the price of them...I would run arp...that's what I'm doing with mine...went with the bolts instead of the studs...extra insurance never hurts imo

Ok need to figure out windage tray options.

​​​​​​I plan on getting a "offshore" style 8 to 10qt oil pan, is it better to run a oem style windage tray bolted to the main caps or get a pan with a windage tray in it and eliminate the oem style one?

You don't need anything more than the stock setup.

"Stock set up" is good to how much HP?

Stock are 8qt pans and should be fine to 650-700 as long as you have a good oil cooler.
Same pan is used on the 700sci
Genuine Mercury & Mercruiser parts. 845668T PAN ASSY-OIL Genuine OEM Mercury Marine-Mercruiser part

that makes me feel a lot better!! saves me some loot thanks griff!!

Good info, thank you.

Over 700hp what do you recommend on size and windage screen set up (in pan on caps)?

Ok came across a set of rods and Pistons, that I can use but the rods are 6.358"not the original 6.135" and the Piston compression height is 1.365" not the original 1.645"

​​​​​​What would be the positives and negatives of running the shorter compression height (top ring land is .400 down so top ring is not a concern) with the longer rod vs the stock set up.?

What changes to the power curve & engine longevity would this set up make?

And would I need to change any of the machining, clearances etc if I go this route?

Ok we'll see if this gets any traction :sport009:

​​​​​​Finalising the rods and Pistons so I need to decide on how I'm setting up the heads and static compression ratio. I'm heavily leaning towards the EQ320 and with the 177 spun at 2.44:1 and a super chiller which eats 2lbs boost. (According the the weiand chart that puts me at 9.4lbs -2 for chiller = 7.4lbs boost =effective of 12.5:1), SO based on piston & rod selection I'm going to be .010 in the hole and 8.51:1 static.

If I'm going with iron heads is this a little high to run on pump 89 gas?

I was thinking of running a .060 mls instead of a .040 with the taller quench to help stop detonation...OR is it better to try and get the compression ratio down to 8.0:1 or 8.25:1 with piston selection rather than running a taller quench?


.

Get it lower with the pistons or by enlarging the chambers on the heads.
Increasing the quench beyond about .060 will actually increase the risk of detonation.
Adverse effects of too much quench? - Yellow Bullet Forums

Thanks Griff, I understand quench and it basic effects, I have a high HP 2 stroke and it's squish and squish band in that head, which is the basic equivalent to quench in this car motor.

From what I've read the top end of pump 91 (which is max I can get in suck-a-fornia), is 12.0:1 ??

If I wanted to run 89, what effective compression ratio is about the max i could run with a flat top with 2-3cc valve reliefs, .010 below the deck, and a .038 compressed MLS, with non ported EQ320 heads?

Thanks

If youre using a flat top, a .040 gasket, and a 119cc chamber head with the piston .010 below, you should end up at 8.25 or so, maybe even lower.

i wouldnt worry about the quench issue on a blower motor. Guys are running with pistons way further down the hole these days.

being 89 octane, id prob keep the boost to about 5-6lbs max, and have a good timing curve , and not locked timing. Jmo.

I've ran the numbers here Compression Ratio Calculator | Tools | Diamond Racing Pistons and it comes out to 8.51:1 with the 6.385 and the 1.395 comp height.

... So what's about the max effective compression ratio to run 89?

are you entering plus 2 or 3cc, or minus 2 or 3cc for the valve relief in the calculator

You're right MT, I misplaced the decimal on the head gasket bore diameter and now that I've corrected it I'm at 8.0:1, so with 7.0-7.5lbs boost post chiller that puts me right at 12.0:1 effective or just a hair under.

So what's the upper compression limit on 89 octane?

I was assuming you were running a head gasket with a 4.370 bore. https://cimg7.ibsrv.net/gimg/www.off...4268d7cfc8.jpg

Hey Griff,
This ad for the EQ 320's is gone, do you know who was selling them, assembled I assume?

Thanks

No, I don't remember for sure. Maybe Ateco??

Competition products also sells them assembled. I am pretty sure they will put whatever valves and springs in them you want also.

I'll check competition & Ateco on the heads, thanks for the tip.

Griff.........crane 168731 or 168741...have to replace mine this fall.