View Full Version : My Combo - Dart Pro 1 345cc Heads
Guys,
I've just got a lead on some Dart Pro1 Heads. They are brand new according to the seller. $1300 for the pair. That seems like a great deal. Should I jump on them based on my motor combo needs?
Here's my Combo and what I want out of it. I'm not sure about the cam specs as I purchased the motor blown up. I did measure the lift on intake and exhaust. Haven't checked the duration. (Had dropped a valve)
500-600 HP Desired Naturally Aspirated
Bowtie 502 Block
Steel 7/16 GM Rods 6.135
4.00 Steel GM Crank
Hyd Flat Tap Cam: Int 502, Exh 544 (Any Advice here appreciated)
Pistons SRP (looks to be forged Part No 212139)
Comp Ratio = 10.2 with 118 cc heads (Darts are 119)
GM Dual Plane Rect Port Intake (Any Advice here?)
850 Quadrajet - Edelbrock Modified Performer RPM Carb - they don't make them anymore #1910
Just curious if the Dart Heads would be overkill in your opinions. I think it's a great deal though, but I realize it doesn't mean they are right for me.
Joe
Pass on them.
Cross sectional area is too large for your cubes, intended rpm range, and etc.
cstraub
10-19-2006, 08:33 AM
Pass on them.
Cross sectional area is too large for your cubes, intended rpm range, and etc.
I agree with Scott. Way to big for a 502. If you plan on turning this thing in the mid to high 5000 rpm range a good head between 280 to 310 will work the best.
Yeah, I don't really want to go much over 5000. And, these heads probably don't start really working until 6-7 right? Thanks for keeping me in check. I appreciate your input.
Below is a photo of some 14096188's that came off this particular motor. Not sure what happened but the head of the exhaust valve seems to have popped off. I found it in the exhaust manifold. Any ideas what might have caused this?
Head Damage
http://www.***boat.com/image_center/data/500/3562Head_Damage.JPG
Pretty much ruined #1 cyl. I've gotta have it sleeved because there's a 2 inch axial crack up the side of the cylinder (see red arrow).
Cylinder Damage
http://www.***boat.com/image_center/data/500/3562Crack.jpg
I know the 188's are 317cc, and you mentioned not to go over 310. Even though they are on the max, would they be better suited if they are still good. I've not had them pressure tested for cracks yet. Here's some flow specs I found on Car Craft's Head database for stock 188's.
Flow Numbers (courtesy Car Craft.com)
http://www.***boat.com/image_center/data/500/3562Iron_188_-_specs.jpg
I've also got a set of 1973 049 oval ports that are completely stock 2.06/1.72's Would I be better off with them vs. the 188 rectangular ports. They probably won't breath like their rectangular port brothers. I know, I know, I should be looking for torque. Gotta get to 5000 rpm somehow.
I really appreciate the advice.
Oh yeah,...
Here's the specs on an 049. Look like they are on the small range at 253cc.
http://www.***boat.com/image_center/data/500/3562Iron_049.jpg
Thanks again,
Joe
SmokinLowriderSS
10-19-2006, 11:06 AM
Pass on them.
Cross sectional area is too large for your cubes, intended rpm range, and etc.
I'm in agreement here. Unles you plan to spin 6-large, those heads will give you mid-RPM flow trouble on a 502, be better on a 572. I'd try to stay close to your stock heads as far as intake port spec goes. While I love my '049's on a 454, I think, unless ported to about stage 1, they will choke the 502 a bit. Too small a ports. They will bennefit a lot from a mild porting on a 454 as well.
Go for 2.19"/1.88" valves, I personally go Manley Pro Flow, Severe Duty Intake, Extreme Duty Exhaust (their marine advice).
Cam, I personally think more lift, over .550" lift or you're wasting effort. Keep the duration under 290* (seat-seat) for a boat personally, my opinion, jet or prop, prop especially.
Intake, go aftermarket, ports to match whatever heads you get. Dual-plane like the Performer RPM series (my fav but other good ones are out there).
cstraub
10-19-2006, 11:43 AM
JoeB,
I just did cams for a twin 572CID BBC (500 Bulldogs that came down due to a cracked cylinder). We used the OEM 188's ported and with hyd roller cams the engines made 680HP @ 6000 rpm and 655#/ft @ 4900. So the heads you have are capable of making some excellent power.
If the damaged head checks good I would just repair it and run them. The popped exhaust valve is common. The valves get to bouncing on the seat do to low spring pressure. Contact with the seat allows the valves to transfer heat and cool itself...if the valve is bouncing it does not have enough contact time to cool and gets over heated and its yield strength is surpassed and it breaks!!!!!!
Wow those are good numbers, then I will stick with the 188's definitely. I would like to do some bowl blending and a mild port match before taking them to the machine shop and having seat work done. Is there a way for me to pressure test them myself for cracks before spending a lot of time only to find out later from the machine shop that they are cracked? I'm assuming I just need to pressure test the water jackets in the heads right.
Interesting analysis on the broken valve. I could see that happening, but the springs look new on the heads. However, if it were over-revved that would cause the same condition.
The machine shop dude here in KY said that his experience has been with the guides allowing some water to seep in on top of the valve. I could see how that would cause quenching at extreme temperatures lowering the ductile properties of the valve. Becomes brittle in other words. Regardless, I will check spring pressure to see that I have enough.
Thanks for the replies,
Joe
A few hundred more you can get new Dart Iron Eagle 308's or World Products Merlin 315's. Cast iron and no Canfield or AFR, but who really cares, your not planning on going over 5000rpm.
You sure you didn't detonate that motor with the 10.2:1 compression (I didn't look up piston - just going buy what you said) and relatively short camshaft ?
Actually, that crack in the cylinder letting water thru could have busted your exhaust valve (exhaust valves will break when they are super hot and cold water keeps hitting them) and then took out piston.
cstraub
10-19-2006, 12:54 PM
Actually, that crack in the cylinder letting water thru could have busted your exhaust valve (exhaust valves will break when they are super hot and cold water keeps hitting them) and then took out piston.
Good call on that Scott..
Joe B,
Didn't see your location.. I grew up on Wolf Creek in the Summer time above Alligator 2 Dock. I worked for Bob's Marine there in Eli for a few summers while going to WKU.
Is the machine shop you using Cornetts? I have got a good customer in Glasgow if you need another option.
SmokinLowriderSS
10-19-2006, 04:07 PM
Interesting analysis on the broken valve. I could see that happening, but the springs look new on the heads. However, if it were over-revved that would cause the same condition.
Thanks for the replies,
Joe
If I recall what I've seen on here, the 502's are a bit notoroius for weak valve springs, brand new. Likely allowing high-RPM bounce, not a problem on an auto as the revs are not sustained long, boats, different story, and not necisarally from being over-revd past spec, just past what the springs can keep up with.
Good call on that Scott..
Joe B,
Didn't see your location.. I grew up on Wolf Creek in the Summer time above Alligator 2 Dock. I worked for Bob's Marine there in Eli for a few summers while going to WKU.
Is the machine shop you using Cornetts? I have got a good customer in Glasgow if you need another option.
Chris,
Wow, so you're really familiar with the Lake Cumberland area. I grew up here as well. Actually, moved all over the country and then back. No place like home.
Actually, this wasn't Cornett's, although they are pretty famous around here as you know. I've had them do some work for me in the past, but I would like to have some other options.
I've heard some good things about another guy that's just started a business in Somerset I'm thinking about trying. He was the fellow I had been talking with. Although, if you have a good lead in Glasgow, I would be willing to consider them too. It never hurts to have plenty of options.
Joe
Actually, that crack in the cylinder letting water thru could have busted your exhaust valve (exhaust valves will break when they are super hot and cold water keeps hitting them) and then took out piston.
Scott,
I bought the boat with the motor blown. I don't know what happened. Compression seems a little steep to me too. I would rather be down in the 9's.
The previous owner did say he had been running the motor really hard for a while 20-30 mins. I'm suspecting the cylinder crack too, but I don't guess I'll ever know which came first.
Joe
If I recall what I've seen on here, the 502's are a bit notoroius for weak valve springs, brand new. Likely allowing high-RPM bounce, not a problem on an auto as the revs are not sustained long, boats, different story, and not necisarally from being over-revd past spec, just past what the springs can keep up with.
Makes sense. I haven't heard that, but I will measure all spring pressures to verify that all is well. How's a good way to guage this type of condition once the motor is running down the lake at 5500? A lot of exhaust popping?
Joe
cstraub
10-20-2006, 05:27 AM
Chris,
Wow, so you're really familiar with the Lake Cumberland area. I grew up here as well. Actually, moved all over the country and then back. No place like home.
Actually, this wasn't Cornett's, although they are pretty famous around here as you know. I've had them do some work for me in the past, but I would like to have some other options.
I've heard some good things about another guy that's just started a business in Somerset I'm thinking about trying. He was the fellow I had been talking with. Although, if you have a good lead in Glasgow, I would be willing to consider them too. It never hurts to have plenty of options.
Joe
I PM'd the name of the shop to you. Ask for Jeremy.
LynnsJet
10-20-2006, 08:35 AM
Was your boat running OT exhaust when it dropped the valve?
I had reversion and dropped my valve. I will not run wet OT's again for that reason.
L J
cstraub
10-20-2006, 08:38 AM
Thanks for the tip!
PM Jbone on the board. I did a custom cam based on your combo with bowl ported heads. Cam is very mild. He ran it maybe 10 hours or so before he leaned the engine out in testing and spoked some pistons. He bought a ZZ502 to put in the boat. He said the old 502 with the heads and my cam pulled harder then the ZZ and my cam was smaller then the ZZ. He may give you a good deal on the cam. I would use a new set of Morel hyd Marine lifters on the cam though.
Chris
SmokinLowriderSS
10-20-2006, 11:58 AM
Makes sense. I haven't heard that, but I will measure all spring pressures to verify that all is well. How's a good way to guage this type of condition once the motor is running down the lake at 5500? A lot of exhaust popping?
Joe
I'm not sure. I think the popping would be more indicative of valve float (different but similar to "bounce" as they just wouldn't be getting closed.
I THINK an acceptable closed spring pressure will be something arround 120 pounds and up (I'm running 130#), then spring tension as compressed is a matter too (If I recall right, my springs are 300#/inch). I'm running balpark 290# wide open, hydraulic, no problems at all. I ran lighter for break-in (left inner spring of 3-piece spring set out) was still no trouble there, was under 4,800 RPM. 5500 RPM, I think you're going to need springs similar to mine.
cstraub knows cams like few others (more than I for sure), give his advice some weight. :)
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions Inc. All rights reserved.