490 SBC pumpgas 23* dyno results, need expert "power" advise

[67RS502]

Is a 4.42 stroke .985” piston really long life though? 1.4 rod stroke ratio? Curious how this all works out over time

I don't know, I was going to drive it, run it down the track, and at least pull the pan off to inspect it after a while.

[67RS502]

Is a 4.42 stroke .985” piston really long life though? 1.4 rod stroke ratio? Curious how this all works out over time

Stock 400 SBC has a rod/stroke ratio of 1.48... any many of those have lasted 200k miles.

Compare this 700 horsepower small block to 99.9% of the other 700 hp small blocks... and give me a realistic comparison regarding their expected service lives. Other 700 hp units will rev WAY higher, have a lot more compression, have solid vs. hydraulic lifters, etc, etc.

This is a low maintenance, long service life 700 hp small block. The fact that is was skillfully done with what most would call well outdated 23 degree equipment... instead of the latest, high dollar, CNC, billet, altered valve angle, etc part of the week is especially impressive!

Great build!

Huh, I really didn't think this engine would get any respect here, with all the smart people and professional engine builder.
Especially since it is so odd ball / different with a poor rod ratio.
So thank you, and I'll agree with everything but the "skillfully done" part... I'm just a hack who built it in his garage.

An engine that really impressed me back in the day was Flyin Ryan's 400SB, it made 740 on pumpgas with 23* heads years ago, I'm sure its here on speedtalk somewhere.

[MadBill]

....Also whats acceptable as far as manifold vacuum for a street/strip engine? 1"

Depends on transmission (M or A), torque converter, gearing, willingness to not flat-foot it at 1500 RPM in 4th with a manual, vs. going no deeper than the P-S detent and biggie: how well the carb is set up. (With the same peak power, one shop's 1000 CFM 4150 might take WOT smoothly from 2,000 RPM and another might fall on its face below 3,500.)

That said, power gains and drivability tend to drop off fast below ~1.0" Hg.

[Steve.k]

Not to many sb pump gas motors na running around with your hp so it will be a good ride for sure. Try dommy or two see where she goes.Good luck and stock up on tires.

[67RS502]

Did Jimmy do the original work on those heads?

No I got these from Eric, he used them on his EMC 406.
He said that Self Racing did the heads, the intake ports were already huge, that's why I bought them,
figuring they wouldn't take much work for a big cube SB.
I did some minor short turn work, had the P-rod pinch welded (since I couldn't use offset lifters), I raised the roofs,
and lowered the floors a bit to make up area for that. Opened up the chambers a bunch, unshrouding and to lower compression.
And did a bunch of work to the Exhaust ports, because they were not only small, but had an hourglass profile with
a bad choke point around the guide... which I only discovered after taking some measurements.
Jimmy gave me lots of pointers on the Darts I have on my 420, but not so much on these as he passed away around the time I was working on these.
I think he flowed them the 1st 2 time, the final time was one of the guys at Trumbles shop.

[splitdecision71]

Did Jimmy do the original work on those heads?

No I got these from Eric, he used them on his EMC 406.
He said that Self Racing did the heads, the intake ports were already huge, that's why I bought them,
figuring they wouldn't take much work for a big cube SB.
I did some minor short turn work, had the P-rod pinch welded (since I couldn't use offset lifters), I raised the roofs,
and lowered the floors a bit to make up area for that. Opened up the chambers a bunch, unshrouding and to lower compression.
And did a bunch of work to the Exhaust ports, because they were not only small, but had an hourglass profile with
a bad choke point around the guide... which I only discovered after taking some measurements.
Jimmy gave me lots of pointers on the Darts I have on my 420, but not so much on these as he passed away around the time I was working on these.
I think he flowed them the 1st 2 time, the final time was one of the guys at Trumbles shop.

This is a very interesting thread and very cool build. I love the idea of big cubic inch sbc. Thanks and please post your results as you go please.

[cjperformance]

Since you've stepped up to a solid roller lobe, presumably you've also checked out the number of recent advanced design and/or short travel lifters?

A shop I frequent builds several dozen big Hemis yearly. A few years ago he did up a 572" for a TV show. They wanted 700 streetable HP and preferred hydraulic rollers. With a big aggressive HR cam, it initially dynoed a disappointing low sixes and was short on revs. He spent a couple of hours working over the plenum plus dropped a set of solids onto the same cam with the same springs. That stepped it up to ~760 and added 1,200 RPM to the usable power curve. He figured all but maybe 20 HP was the lifters. (This was before the widespread availability of the 'New Tech' crop of hydraulics.)

Yes a good point Bill, hydro lifter bleed down can obviously have a big effect on how the cam profile looks the the running engine. This would be a good engine to asses with solids or shimmed/short travel hydros before moving forward.

[67RS502]

Since you've stepped up to a solid roller lobe, presumably you've also checked out the number of recent advanced design and/or short travel lifters?

A shop I frequent builds several dozen big Hemis yearly. A few years ago he did up a 572" for a TV show. They wanted 700 streetable HP and preferred hydraulic rollers. With a big aggressive HR cam, it initially dynoed a disappointing low sixes and was short on revs. He spent a couple of hours working over the plenum plus dropped a set of solids onto the same cam with the same springs. That stepped it up to ~760 and added 1,200 RPM to the usable power curve. He figured all but maybe 20 HP was the lifters. (This was before the widespread availability of the 'New Tech' crop of hydraulics.)

Yes a good point Bill, hydro lifter bleed down can obviously have a big effect on how the cam profile looks the the running engine. This would be a good engine to asses with solids or shimmed/short travel hydros before moving forward.

I disagree, my 420 makes peak power at 6800-6900, and shift it at 7200-7300, Morel lifters, similar spring pressures and solid roller lobes.
490 has Johnson lifters, very quiet, milder lobes, but heavier valves. It should still be good to upper 6000 range I believe.
I just don't have all the issues that other seem to have with HR valve trains, but I do pay att. to the setup.
Good lifters, right spring pressure, tree trunk P-rods will do on most setups pretty well.
I don't believe that my engines lack of rpm is caused by the HR lifter, if it was, retarding the cam wouldn't have worked.

[67RS502]

Did Jimmy do the original work on those heads?

No I got these from Eric, he used them on his EMC 406.
He said that Self Racing did the heads, the intake ports were already huge, that's why I bought them,
figuring they wouldn't take much work for a big cube SB.
I did some minor short turn work, had the P-rod pinch welded (since I couldn't use offset lifters), I raised the roofs,
and lowered the floors a bit to make up area for that. Opened up the chambers a bunch, unshrouding and to lower compression.
And did a bunch of work to the Exhaust ports, because they were not only small, but had an hourglass profile with
a bad choke point around the guide... which I only discovered after taking some measurements.
Jimmy gave me lots of pointers on the Darts I have on my 420, but not so much on these as he passed away around the time I was working on these.
I think he flowed them the 1st 2 time, the final time was one of the guys at Trumbles shop.

This is a very interesting thread and very cool build. I love the idea of big cubic inch sbc. Thanks and please post your results as you go please.

Glad some find it interesting.
I will, but it will not happen anytime soon.
First I need to decide on the changes to be made.
Make the changes,
and set up a time with Larry for the dyno.
Plus I just do this as a hobby, so its in my spare time... I'm slow.

[cjperformance]

Since you've stepped up to a solid roller lobe, presumably you've also checked out the number of recent advanced design and/or short travel lifters?

A shop I frequent builds several dozen big Hemis yearly. A few years ago he did up a 572" for a TV show. They wanted 700 streetable HP and preferred hydraulic rollers. With a big aggressive HR cam, it initially dynoed a disappointing low sixes and was short on revs. He spent a couple of hours working over the plenum plus dropped a set of solids onto the same cam with the same springs. That stepped it up to ~760 and added 1,200 RPM to the usable power curve. He figured all but maybe 20 HP was the lifters. (This was before the widespread availability of the 'New Tech' crop of hydraulics.)

Yes a good point Bill, hydro lifter bleed down can obviously have a big effect on how the cam profile looks the the running engine. This would be a good engine to asses with solids or shimmed/short travel hydros before moving forward.

I disagree, my 420 makes peak power at 6800-6900, and shift it at 7200-7300, Morel lifters, similar spring pressures and solid roller lobes.
490 has Johnson lifters, very quiet, milder lobes, but heavier valves. It should still be good to upper 6000 range I believe.
I just don't have all the issues that other seem to have with HR valve trains, but I do pay att. to the setup.
Good lifters, right spring pressure, tree trunk P-rods will do on most setups pretty well.
I don't believe that my engines lack of rpm is caused by the HR lifter, if it was, retarding the cam wouldn't have worked.

Theres only one way to find out! And its always interesting to test.
But really, its not performing way short of expectations and what small shortfall is there is easily expalined so it probably does not have any issue here. I just think that all avenues are always worth throwing out there and thinking about.

[jarmoyp]

1.6" exhaust valve, is it big enough?

[econo racer]

Is your cam tunnel raised up and have bearings? I would love to build something like your sbc and then try to make it look stock You might have a good power tour motor and add maybe 100 hp nitrous

[rustbucket79]

Cool build, pretty exotic for a first gen 265 sbc build if you ask me.

My thoughts, it has a huge arm, needs to be (somewhat) streetable, and has smallish heads and cam for its displacement. (If max hp was the ultimate goal) looking at what you have, I would be tempted to try a dominator since it is a stroker 454 which should be a nice gain up top. The rest I would leave alone because a few hp either way won't be noticed on the street.

It would be very interesting to see what a set of solid rollers would do to see if there is any losses from the squishy lifters.

I can tell you what lack of spring pressure looks like on the dyno and it ain't what you see. The graph takes a big dip when that happens, not unlike hitting the rev limiter.

[CGT]

This is what hydraulic roller "troubles" sound and look like on the dyno. Along with a dyno operator that I didn't realize was virtually deaf and blind prior to this.

He was a split second from being tackled.

https://www.youtube.com/watch?v=_eBdSp4ah-E


Keep an eye on the horsepower display on the monitor. The engine was clean to 7000, this was an attempt at 7500. That little "oversight" didn't do that engine any favors.

[PRH]

Looked like it was down about 250hp before he let off...........nice.