Personally I'd pick the casting you like and make it aluminum, buy the stealth heads. Since you're going to need to match up the springs to your camshaft. No sense paying for someone else's build when some of the parts may not work.
906 or 915 ?
- Thread starter 44o gts dart
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No sir. There are two distinctly different 915 big block castings. Only one is the 67HP casting and that's the one with the 1.74 exhaust valves and better ports. I've had both in my hands before as well as the 516s. I'm very familiar with them.
33IMP
Well-Known Member
I paid $900 to freshen a pair of iron heads a while back, and I certainly would NOT have done that, except they were professionally ported 286 max heads. I would assume, getting a set of 906s to the same point (reconditioned, but not ported) would run almost the same. I would NOT spend that on 906s.
My guess is the PORTED 915s are pretty good. I'm also guessing that if they are going on an M code A-body, they'll have to be iron. I might be tempted to offer half of what a pair of stealths run, but I think $750 is not bad. You CERTAINLY can't get equivalent performance from your 906 for anywhere near that price. If the previous owner was running a roller, you can expect to have to change the valvesprings.
Only thing I'd worry about is too much compression, depending on your pistons.
My guess is the PORTED 915s are pretty good. I'm also guessing that if they are going on an M code A-body, they'll have to be iron. I might be tempted to offer half of what a pair of stealths run, but I think $750 is not bad. You CERTAINLY can't get equivalent performance from your 906 for anywhere near that price. If the previous owner was running a roller, you can expect to have to change the valvesprings.
Only thing I'd worry about is too much compression, depending on your pistons.
IIRC the 915 was a 67 only 440 head, I can't remember if it had larger intake or exhaust valves or both. Although, I have a 426 wedge that appears to be a virgin, that has 915's on it, may have been swapped
If your plan is for a daily driver, I'd get unleaded valve seats installed in the 906's, or get a lead substitute to help cushion the valves
If your plan is for a daily driver, I'd get unleaded valve seats installed in the 906's, or get a lead substitute to help cushion the valves
MopaR&D
Nerd Member
FYI Stealths have that name because externally they look just like a factory iron head. Paint them and you'd have a hard time telling the difference on an assembled engine. Losing ~60 lbs off the top of the engine would be beneficial in an A-body.
But if the choice is only between the 906s and 915s you mentioned I'd go 915, as long as your buddy is trustworthy and you can inspect them reasonably closely before buying. I'd be bringing my valve spring compressor and popping out a few valves to check the guides and seats.
But if the choice is only between the 906s and 915s you mentioned I'd go 915, as long as your buddy is trustworthy and you can inspect them reasonably closely before buying. I'd be bringing my valve spring compressor and popping out a few valves to check the guides and seats.
44o gts dart
Well-Known Member
But would the 915’s be that advantageous if your going to have the block decked, squared and new piston’s that bring compression to about 10.1 or 10.5 ?
MopaR&D
Nerd Member
Yes because then you could take advantage of the closed chambers and have some squish. All the more reason to have the block square-decked. If you're using open-chamber heads there isn't as much benefit to blueprinting the short block like that.
The 915s are good for quench, but I still believe the 906s will have the edge for flow.
I'd use the 915 and put the piston on top.
The 906 will see a benefit from installing a larger exhaust valve. It greatly improves the short side of the port coming off the valve. The Trick Flow has such a better exhaust port than the 906 it can use a smaller valve effectively. We did a dyno test on a 8:1 compression 440 where we all we did was install a larger exhaust valve in the factory iron head and got a significant increase in horse power. With 2.25/1.81 valves in 906 heads on a 451 we just missed 700HP on 91 octane pump gas by 6HP. For those math challenged the 451 made 694HP. Basically the same engine with ported 2.25/1.81 RPM heads made 787HP.
If you do not reshape the throat after installing a larger valve you will probably reduce airflow through the cylinder head.
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Was that the run on that crappy green Duster with the red fender? lol
Wow, that's amazing. Thank you for your reply!
I believe that was a Demon.
Hey! Tetanus was a '72 DEMON with '70 Duster front fenders. And remember it is famous. It got the Popular Hot Rodding unofficial award for the 'Ugliest car at Mopars At The Strip' some 10 years back. The YouTube video was with the 500"/440 and that was 696 RWHP. We did use the same cam in the 694HP 451. I believe that cam is still on the shelf around here somewhere.
That's funny. It's just the kinda car I'd cruise the wheels slam off of.
Boy I'd sure like to but it sits w/o an engine right now. I gotsta build a 440 for Cody's Mopurban and then one for the '73 Charger and then we'll have one for Tetanus and it'll be back on the road.
Send it to me I'll put some miles on it. LOL
In your case I'd probably have a set of Stealths prepped and use them. Never run any aftermarket head right out of the box. If you must use stock iron you'll probably have the same money in them as prepped Stealths. Design the engine for whichever heads, compression ratio and fuel you decide to use. Design this baby completely on paper before buying parts and starting building.
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33IMP
Well-Known Member
Not virgin 906s compared to (I assume) heavily ported 915s.
What's the letter mean?
Have you had a chance to work over any trickflow 240s ?
Like installing 2.250 and 1.81 valves.
Not many will you. It's a 'Flintstone' model right now.
No, not yet. Though there is a virgin set on the shelf here.
Well that ought to be interesting to see what you can do with them for sure. I'll be eating popcorn for that thread if you do one.
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