Woody35
Active Member
S engine is rated at 185 hp and 360 torque. feels like a stock 350 on steriods.
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Highest HP ever out of a 6.5
- Thread starter 6.5quest
- Start date
bobbywalter
New Member
Acesneights1
New Member
Yea I think the 6.2s were more in the 165hp range. Maybe even lower.
randomid25
Rattle-Trap Cap'n
6.2s are 130 to 160 depending on the version you have. Mine has a dyno tag on it from jasper when it was rebuilt says 150hp. It has a little more than that now.
turbovanman
I has boost, :O)
Late to the party. My 2 cents, why doesn't anyone port the head properly, not just extrode hone them? That has to be worth some serious hp and maybe put bigger valves in? Doing that and a bigger turbo will work wonders, or should.
chevyinlinesix
Eyre Flow Headers
Peninsular Diesel does offer properly ported cylinder heads. $900 each when I called them a few months ago. Also any shop that has worked on performance engines, have a flow bench, coupled with experience should be able to do a good job as well.
You certainly can put in bigger valves too, Manley will happily make you a set, you just have to give them all the dimensions and material you would like to use. Then have your heads machined out to accept the larger valves
You certainly can put in bigger valves too, Manley will happily make you a set, you just have to give them all the dimensions and material you would like to use. Then have your heads machined out to accept the larger valves
turbovanman
I has boost, :O)
Peninsular Diesel does offer properly ported cylinder heads. $900 each when I called them a few months ago. Also any shop that has worked on performance engines, have a flow bench, coupled with experience should be able to do a good job as well.
You certainly can put in bigger valves too, Manley will happily make you a set, you just have to give them all the dimensions and material you would like to use. Then have your heads machined out to accept the larger valves
I know about custom stuff,
Just curious why no one does it?
Everyone goes bigger this, more of that but never porting the heads? 
NVW
Well-Known Member
It has been mentioned that with a turbo it isn't likely to have the same benefit as a N/A engine
Leo
Leo
SmithvilleD
Active Member
GM induction hardened the valve area of the heads instead of conventional valve seat inserts. It's not unheard of to get cracks thru that seat area. When GM first started building the 6.2, they had larger valve diameters. As time went on, GM stepped down valve sizes a bit, supposedly to lessen potential cracking issues btwn the valves.
If keeping the stock 6.5 sized valves, there is enough material in the seat area to machine out the opening & install hardened valve seats. My cyl head shop said they were very leary of trying to go w/ the earlier, bigger valves & hardened seats because there wasn't sufficient material left after machining to fit the larger valve seats.
Ian can possibly confirm, but I believe the articles on Heath's Bonneville engine said they fitted the larger valves & just machined the larger seats into the cast iron - recognizing that some of the new, larger valve seat area being machined into the head gets outside the induction hardened area. So it probably wouldn't have the wear resistance for OEM longterm durability levels.
On my 6.5 heads, the area just below the valve seats would benefit from smoothing/blending into the valve bowls. Also, the exh port's match w/ the exhaust manifold was consistently poor - actually the worst I've seen on a modern engine. I think these two areas can be improved by most folks as long as they're cautious not to nick the valve seats, envision which direction the air is flowing, & keep conservative in only removing material where you can see a clear benefit.
If keeping the stock 6.5 sized valves, there is enough material in the seat area to machine out the opening & install hardened valve seats. My cyl head shop said they were very leary of trying to go w/ the earlier, bigger valves & hardened seats because there wasn't sufficient material left after machining to fit the larger valve seats.
Ian can possibly confirm, but I believe the articles on Heath's Bonneville engine said they fitted the larger valves & just machined the larger seats into the cast iron - recognizing that some of the new, larger valve seat area being machined into the head gets outside the induction hardened area. So it probably wouldn't have the wear resistance for OEM longterm durability levels.
On my 6.5 heads, the area just below the valve seats would benefit from smoothing/blending into the valve bowls. Also, the exh port's match w/ the exhaust manifold was consistently poor - actually the worst I've seen on a modern engine. I think these two areas can be improved by most folks as long as they're cautious not to nick the valve seats, envision which direction the air is flowing, & keep conservative in only removing material where you can see a clear benefit.
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turbovanman
I has boost, :O)
That is very wrong. Turbo's can mask alot of intake/cylinder head inefficency's but porting and better flowing everything reduces exhaust backpressure, helps fill the cylinders easier and generally will make more power at less boost.
I haven't really played with our heads yet, good info. I wonder if the new casting heads have more meat per say?
Mikey von
Member
You mean something like this (6.2 HD unshourded vavles). The intake seats are hardened steel, while the exhausts are a high temp nickel alloy designed for use with the stellite faced exhaust valves.;
(I am a certified pic whore!
)
turbovanman
I has boost, :O)
^^^^^^^^^Very cool, :thumbsup:
What did you up the size to on the valves? Any flow testing? porting?
What did you up the size to on the valves? Any flow testing? porting?
SmithvilleD
Active Member
Yes.
The circular cut below the valve seat ledges takes care of a fair bit of what I meant about blending just below the seat, smoothly into the bowls. I would expect the edges below that circular cut were blended later by hand.
Would be interesting to know how much the unshrouding chamfer cut helps flow. Looks like it ought to help the important low/early lift flow. Particularly on the engine, where the bore itself is a shrouding factor.
Has the shop or guy that did this work run a 6.2/6.5 turbo head w/ that unshrouding cut before?
Playing devil's advocate, is there any concern about the valve edges being more exposed to heat? Perhaps they're also an aftermarket valve of better materials?
The circular cut below the valve seat ledges takes care of a fair bit of what I meant about blending just below the seat, smoothly into the bowls. I would expect the edges below that circular cut were blended later by hand.
Would be interesting to know how much the unshrouding chamfer cut helps flow. Looks like it ought to help the important low/early lift flow. Particularly on the engine, where the bore itself is a shrouding factor.
Has the shop or guy that did this work run a 6.2/6.5 turbo head w/ that unshrouding cut before?
Playing devil's advocate, is there any concern about the valve edges being more exposed to heat? Perhaps they're also an aftermarket valve of better materials?
Veg_Out
Walking J Designs
I am beginning to have motor envy!
turbovanman
I has boost, :O)
I don't see how that could happen, if you use the right material, it will last. Also remember, diesels don't run that hot, look at gas engines running huge valves,
:thumbsup:
Matt Bachand
Depends on the 6.5
I don't see how that could happen, if you use the right material, it will last. Also remember, diesels don't run that hot, look at gas engines running huge valves,
Not sure what hot is, but diesel combustion chamber temps can reach upwards of 3,000 df...
Not sure how that compares with gassers, but sounds hot to me
turbovanman
I has boost, :O)
Not sure what hot is, but diesel combustion chamber temps can reach upwards of 3,000 df...
Not sure how that compares with gassers, but sounds hot to me
They can get pretty hot in their too, but diesel EGT's are much lower which equates to easier life on the exhaust valves. Gasser's are much hotter, my EGT's on my minivan hover around 15-1700 at WOT,
Woody35
Active Member
a few people have. its been talked about a little somewhere in these threads
ak diesel driver
6.5 driver
Hank 1948 ported his