Potential of going with larger valves. Questions

[70_Fastback]

70fastback, if you need to do head work, I'd suggest looking for some GT40's before you put time/money into those J code heads.

Just curious - Why? What's the large difference between the 2 ?

 

[70_Fastback]

I wouldn't assume that the valves are damaged. Why would they be? Your 351 is not a Honda 4 cylinder with an interference fit valvetrain.

Hey Dave,

I am anxious to find out if there is any or not. The concensus Is basically a 50/50 split on opinions on this one - if I sustained valve damage or not....

I honestly don't know for sure, as never having experienced this yet - but logistically it seems possible, to me, that if a valve was fully open with the cam stopped that a piston could possible ting it a little though... I just don't know. I would rather be sure than sorry though.

 

[daveSanborn]

I still can't fathom that you've not torn into the engine yet.

I spun a bearing on my 347 last Summer/Fall. The crank and rods were in the trunk of my DD within 24 hours driving around looking for a machine shop. I can't stand it when something is broken.

 

[tarafied1]

I honestly don't know for sure, as never having experienced this yet - but logistically it seems possible, to me, that if a valve was fully open with the cam stopped that a piston could possible ting it a little though...

That's all I'd be worried about, been there and done that... twice, bent at least one valve each time.

I still can't fathom that you've not torn into the engine yet.

me either, drives me nuts to at least figure out what all I need to do to fix it even if I have to wait for funds, I want to KNOW what I'm dealing with right away, but to each his own...

 

[tarafied1]

Having run both, I'm much happier with the 280H (w/Rhoads lifters). It's more happy to wind up to 6k, and I take it there fairly often.

70fastback, if you need to do head work, I'd suggest looking for some GT40's before you put time/money into those J code heads.

I've used those lifters before, I felt like they sucked the life outta my engine compared to when I took them out.

and to answer your question, the GT40 casting is a better design in terms of the ports and the combustion chamber... better flow and more even burning cumbustion (less detonation or hot spots for high compression engines)

 

[70_Fastback]

I still can't fathom that you've not torn into the engine yet.

My schedule just doesn't allow for a lot of car time during the week. Most of my work gets done on the weekends. And this is the weekend for that.

 

[Starfury]

I've used those lifters before, I felt like they sucked the life outta my engine compared to when I took them out.

and to answer your question, the GT40 casting is a better design in terms of the ports and the combustion chamber... better flow and more even burning cumbustion (less detonation or hot spots for high compression engines)

Interesting. After swapping from the XE268H to Rhoads Lifters on a Magnum 280H, I have a lot more usable power between 1500 and 3k, and it seems to want to climb to 6k a little more readily. The lifters let the valves smack down into the seats, making a solid-lifter type racket under the hood, but I love them. FYI: Until the recent switch to a variable timing setup, Viper V10's came from the factory with Rhoads lifters.

As far as the GT40's, they're essentially 351W port casting heads with smaller (64cc?) 302 combustion chambers. The port castings are the major improvement as stock 289/302 head castings are absolutely terrible before '87, and not too much better afterward.

 

[tarafied1]

maybe there was something wrong with my Rhoads lifters. I thought it was a good idea at the time but the engine just wasn't performing as I thought it should with them. When I took them out it came to life. I started with the 268H and swaped to the 280H before yanking them out thinking I just didn't have enough cam. We put the 268H cam in my dad's Mustang without the Rhoads lifters and it was a mild engine. It ran better than mine with the lifters. The concept is great because as I understood the design, it would effectively lower the lift and duration at low RPM's by bleeding down and allow the full cam specs to kick in at higher RPM's with less time to bleed down. Mine must have never pumped up right I guess cause it just didn't work. If and when I build another small block I'm going with HYD roller cam cuz you can ramp up faster and hold the full lift for longer duration. Does Rhoads make roller lifters?

 

[Starfury]

Not sure if they have fsb roller lifters, but I do know they will modify lifters you send to them.

 

[blackford]

My question is...why are you wasting time with OE heads? Even ported, stock head castings suck.

Your right...mine suck plenty...plenty of air that is. Please see sig and keep in mind that my timing was off and I was running a tad lean at time of dyno.

Jeremy, those heads will do much better with new larger valves. Any tulip swirl polish valve will improve things drastically over stock valves. I would go with 1.9/1.6 valves. Unshrouding the valve is a must on stock heads with larger valves.

If you have the whole engine apart, do this: Put head on block and put a bolt on either end of the head and slightly tighten down the bolts. Turn the block over and look into the cylinder. You'll probably see the exposed edge of the chamber on either side. Scribe the edges and take the head off and open up the chamber sides to the scribed line. You want to unshroud the valves AT LEAST this much. The intake may benefit from a little more unshrouding.

 

[Starfury]

Blackford, your 351W heads are a damn sight better than any 289/302 head. GT40 heads use essentially the same port castings, and there's good reason.

 

[Anonymous]

Blackford, your 351W heads are a damn sight better than any 289/302 head. GT40 heads use essentially the same port castings, and there's good reason.

I'm running 1966 iron heads on my 289, 1.84" intake and 1.5" exhaust, ported to the gills. Good enough for 313HP and 295TQ. Nothing wrong with iron heads if you open them up and let em breathe!

 

[Starfury]

Iron heads in general, no. But original 289/302 heads have flat horrible exhaust port castings. They should be opened up even on a bone stock car. A port job helps, but a set of Windsor Jr's will flow better out of the box than a lot of ported OE 289/302 heads. Good aluminum heads will blow them out of the water.

 

[blackford]

Iron heads in general, no. But original 289/302 heads have flat horrible exhaust port castings. They should be opened up even on a bone stock car. A port job helps, but a set of Windsor Jr's will flow better out of the box than a lot of ported OE 289/302 heads. Good aluminum heads will blow them out of the water.

Honestly I think the '65 289 exhaust ports are better than '69 or '70 351w exhaust ports because they didn't have the thermactor hump...both ports suck though. I don't use ford iron because they are better, I use them because that's how I built motors 30 years ago and to me it is more enjoyable to make HP than to buy HP.

 

[Anonymous]

Honestly I think the '65 289 exhaust ports are better than '69 or '70 351w exhaust ports because they didn't have the thermactor hump...both ports suck though. I don't use ford iron because they are better, I use them because that's how I built motors 30 years ago and to me it is more enjoyable to make HP than to buy HP.

Plus it's fun to see the jaw drops and drool from those that think you are running super duper high tech stuff!

 

[Starfury]

Fair enough. I just don't think it's worth it to pay someone to do a valve job, tap for screw-in studs, and port a set of OE heads when superior aftermarket heads are readily available for a couple hundred bucks more. If you can do it yourself, you're in better shape.