Best iron head choice, 516 or 452

[Garys1969RR]

I want to go to a closed chamber head on my 451, so I can get a good tight squish/quench dimension. Deck clearance is .017", so with a .020 shim gasket, it will put me at .037" piston to head clearance. But the only heads I have right now are 516s, and several sets of 452s. From what I've read the 516s have about the lowest flow numbers of any head tested. I would install the larger 1.74 ex valve, and use the Mopar porting templates to improve flow. So my question is: Would these heads in ported form work well on a street/strip 451 engine? Or should I just port some 452s and forget about the benefits of a tight squish dimension. Am also considering going to 2.14/1.81 valve sizes on the 516, along with home porting work. Currently running 906 heads with some bowl blending done, and gasket matching. This has been good for 13.74 @ 103 MPH at 5400 feet in a 69 Road Runner. Thanks for any suggestions.

 

[Cranky]

If it were me, I'd go with the 516's but doubt I'd go with the bigger valves but would put the 1.74 exhaust valve into them at least and do a good pocket port and get rid of the hump in the exhaust exit....but....what's the rest of your combo? Cam, compression etc. If you already have some decent 906 heads, no use wasting money on the 452's because they won't benefit you much if any. Also, how heavy is your car?

 

[Garys1969RR]

I am using the Mopar 509 hydraulic cam. C/R is 12.5 to 1. 3.91 gears in a 3850 lb car. 727 with 11" converter. Leaves the starting line well with a 700 dbl pump Holley, and a Holley Street Dominator intake. Also have a TM-6 Eddy intake I could try out. Thinking is to use the TM-6 and a 3310 Holley 780 with the 516 heads.

 

[Beekeeper]

The 915 head is really what you need flows like 906 and has closed chamber
And the big valves

 

[Cranky]

Yeah, the 915's would be a much better head....and @ 103, you should be running low low 13's. What is gear ratio, converter and tires? You have street gears, converter and tire? Sure sounds that way. A buddy and I have a 72 Demon (his car but a lot of parts are mine lol) with a 318, some work done on the 360 heads (360 heads lower compression to around 7.8), 480 cam, Torker intake, headers, stock converter but it has 4.88 gears and that puppy runs 13.50 @ 102! It's a dog off the line with a 2.2 60 foot. Tires are 29"....

 

[Garys1969RR]

Car has 3.91 sure grip, 16" street tires, Stock HP ex manifolds. Mufflers un hooked. 60 foot times are right at 2.1 seconds or less. And at your elevation of what 2500 feet MSL or less, I'm sure this would run low 13s to high 12s, if it would hook up. I am losing traction at starting line. You wouldn't believe how much power you lose above 4000 feet. And Bandimere 1/4 mile drag strip where I race is at 5400 feet. Right against the mountains.

 

[Garys1969RR]

And yes, I would prefer to start with the 915 head if I can find some. Anyone have any for sale or trade?

 

[Cranky]

I am using the Mopar 509 hydraulic cam. C/R is 12.5 to 1. 3.91 gears in a 3850 lb car. 727 with 11" converter. Leaves the starting line well with a 700 dbl pump Holley, and a Holley Street Dominator intake. Also have a TM-6 Eddy intake I could try out. Thinking is to use the TM-6 and a 3310 Holley 780 with the 516 heads.

Does it make a difference if your mufflers are dropped? The HP manifolds are ok but headers are much better imo. Every time I installed headers, I saw an improvement on all of the cars I did that to. You say here that it leaves the line well then you say "if it would hook up"....kinda hard to get an idea what's it's doing on the launch. Anyways, the TM-6 was a decent intake for a mild 383-400 but I think it's kinda small for a 451 build but it's worth a try. I've never tried one on a larger cube engine. I also think your carb choice is kinda on the small side too. I ran a 750 DP on a very mild 383 years ago and it did fine but the 3310 may do the job better than the 700. Also worth a try. They were always a great carb too and is the only vac secondary Holley that I would consider over the other types of Holley secondary carbs. What converter are you running?

 

[RustyRatRod]

Gary, the 516s will be fine. They will work great. Use what you have, it will save you money. I am going to run 516's on my 383 build. Doesn't bother me at all.

Sure, you can get a "better" head, but why go to all the extra trouble and expense if all you want to do is have a good strong street engine. Any of the big block iron heads can be made to flow around 600HP. That comes straight from a source that's DONE it.

I'd venture to say the difference between the 516s and whichever other iron head flows best (either the 906 or 915) all things equal would be less than 20%. Perhaps even less than that.

Go for the 915s if you want. But if I were you I would use the 516s since that's what I had......because that's what I AM gonna do.

 

[Garys1969RR]

Thanks, Rusty. Thats what I plan to do this winter, then I can take it to the track next spring and see if it made much difference. Are you going to use the porting templates to port your 516s? I plan to do that and go with some bigger ex valves.

 

[Garys1969RR]

Yea Cranky, was running a best of 14.24 at 100MPH through the mufflers. So the muffler removal was good for about a half second and 3 MPH. I put some 29" by 10" wide slicks on it, and could only get around 13.90 at 100MPH. So my fastest times so far are with the 16" (wheel size) by about 8" wide street tires. The car hooks up pretty good, but sometimes it spins the tires a little then they grab. I expected the slicks to E T better, and was surprised when it slowed down!

 

[Garys1969RR]

I am running an 11" converter that was modified by a local trans guy for a higher stall speed.

 

[RustyRatRod]

Thanks, Rusty. Thats what I plan to do this winter, then I can take it to the track next spring and see if it made much difference. Are you going to use the porting templates to port your 516s? I plan to do that and go with some bigger ex valves.

No sir. We have access to a great local porter with almost 40 years of experience.

http://killiansportingservice.com/index.html

That's Jerry Killian. He's kinda a local legend around here far as porting. He did my slant six head. If you go to his "automotive heads" page at the top, then scroll almost all the way down, my slant head is there on the left. He does some awesome work. I know he's taken some big block heads that were ported off the templates and surpassed them pretty good.

 

[Cranky]

How tall are your street tires vs the 29" slicks? One the Demon I mentioned, we had 27" ET Streets on it and they were not holding the car on the 1-2 shift plus it was topping out rpm wise at around 900 feet out so we put the 29x9" slicks on it and it ran all the way through and no more tire spin on the shift. ET dropped from 13.73 to the 13.50. Yeah, the combo is all wrong but we were just having some fun with the old 318 and threw some parts at it that were laying around. Some things were bought new because they will fit the 340 that's going in someday. The 360 heads....the only thing done to them was a good pocket port job. The factory under cut really sucks and you will make a lot of difference just doing that and then blend it into the rest of the port. And a 14.24 should have you right around 96 mph so you're making some power. 100 mph should have you around 13.75's if everything is right. And I don't use the templates either. I have a friend that did head porting for several local shops (sort of a contractor for them lol) and he showed me where to grind and where not to.

 

[Cranky]

This is a shot of the intake pocket (or bowl) of a Eddy RPM head. Compare it with a stock pocket and you'll see why stock heads flow kinda crappy

Exhaust side. These are out of the box so they could be touched up...

 

[Garys1969RR]

Yea those are some awesome looking ports! If I can afford some after market Alum heads closed chamber, I may buy them.

 

[Cranky]

Yea those are some awesome looking ports! If I can afford some after market Alum heads closed chamber, I may buy them.

If you can't do at least some of your own work on your heads, the Eddys are not a bad buy but, do you really need them? I had a 68 road runner that went 10.60's using 906's. They flowed the same as the Eddys but the Eddys had a better design and in the real world, they would make the car go faster. Flow numbers are not gospel. Taking some weight off of you car would also make it go faster. There's more than one way to skin a skunk

 

[Garys1969RR]

Wow thats really fast! What cam were you using? Or better yet, what was your set up? C/R, Gears, Intake, Carb etc.

 

[RustyRatRod]

You have to scroll to find them, but flow numbers are here:

http://users.erols.com/srweiss/tablehdc.htm

 

[benno440]

http://www.moparmusclemagazine.com/images/mopp_0608_mopar_cylinder_heads/viewall.html

very useful thread,
452 head is best supposedly, but aftermarket aluminium they reckon are better