hi

how much power should this hemi make ?

10.5 -1 comp

511 cu in 4.250 bore 4.5 stroke 7.100 rods

cam is a roller 236 / 244 @50 solid

mopar peform heads alu

2 625 e brock avs carbs inline stock intake

2" headers


thank you !

I've built similar motors that made above 600 HP after sorting out the aftermarket carbs. All the ones I built and dyno tested for customers that had the original street hemi carbs with similar parts all made above 600 HP with stock jetting
Is your intake manifold stock? If so make sure and replace the right rear secondary jet(rear carb) with a .075 I.D or smaller tp start with, do NOT leave the stock jet in that carb It will flood #8 cylinder, those intakes had similar jetting on all the stock street hemi carbs from the factory 1966 to 1971, they had either .065 or .063 in them stock

Should make decent torque, not a ton of power with stock intake and a 236/244 cam. Bet it runs really nice on the street though.

Had a similar engine years ago, but with more cam. Only made 480hp to the wheels. Your missing 100hp with that cam and heads. But it will be well mannered and very drivable. Just won't be an angry monster when you step on it. I ran a hyd cam like that in a 340. +.030......Ran 12.0 with one 750 on it.

I have those heads on my Hemi. MCH ported them a few years ago. My combo is 540", 250* FTS, Indy dual plane, 1050 Dom.

Made over 650HP during break-in. Made a few more ponies with the single plane, but the throttle response and torque was so much better with the DP.

www.facebook.com/SRTeric/posts/1239617192750960

Your cam and headers are on the small side which will hold the numbers down some, but will make for a very streetable combo.

Its my understanding Hemi's are less prone to detonation. I would put more compression in it and then if you ever go to a larger cam in the future, you will have the compression for it. Compression can be your friend.

I ordered my reciprocating assembly and cam from Ray Barton. Spoke to him directly when ordering and I had wanted more comp, too. He said that Hemis do respond well to additional compression. But for a street car, finding the right gasoline is getting to be more and more of an issue. He suggested 10.25 for mine as it is primarily street. The lower comp ratio does leave some power on the table, but if I wanted more power, he suggested finding it somewhere else such as throwing some more displacement at it. Again, this is for a primarily street driven car.

I run 91 pump swill with no problems even on the hottest days. It might be happy with even less octane, but 91 is readily available most everywhere I go, so I run it. The only concession I make to gas is that I only run Top-Tier rated gasoline.

https://toptiergas.com/licensed-brands/

The MP 528 crate hemi was rated at 610hp, and that was with more cam and a single plane intake.
I don’t see why the hp/ci would be much different between the two........ so I’ll call it a little under 600hp.

That would assume the heads are unported.

Barton knows way more than I, but i would have put that at 11.25:1 on Michigan pump gas. I ran a 408@11.25:1 on 93 on the street and the track and now a 511@12.5:1 with 1 can of 110/113 Dragon and 2 cans 93 Sunoco mixed makes about 101 octane and works real nice. When the 511 was 11.25:1(200psi cranking) i also ran it on 93 pump gas(175 cranking) without an issues, so was just making a suggestion, but i understand where your at with that. Piece of mind is worth alot.

I ran right at 11:1 on my al head 499 wedge. Did okay on 93 most of the time. But it didn't like anything but 93 and in hot weather with some heat soak it would hit the starter when cranking.

I built a 540 rather than a 572. I went with the dual plane rather than the single. I stayed with the 1050 even though it was starting to pull some vac. I went with a flat tappet rather than a roller. I went with the MP Eddy heads rather than some other 'better' heads that would have been more expensive in this situation.

What I am trying to say is that I completely agreed with Barton that if I wanted more power, there were a ton of other ways to get it. I don't know if you have ever been in a position of searching for a particular gasoline that your engine will run on when out cruising, but I have. And it can be a real pain. All those compromises that I made were in the search for driveability while keeping up a reasonable level of performance that is expected for a Hemi.

As it is, even with Cal-Tracs and MT drag radials, traction is always an issue. More power would only be able to be used in fewer situations than I can use now. With a street car, there has to be a compromise between just enjoying driving the car and all-out, every pony possible performance.

made above 6000 HP?

Not nice to make fun of old people....LOL
I oughtta know.

Joe

Actually I am also. Lol

Corrected now

Yep, i absolutely know what your saying. I liked shell premium and it was getting hard to find in my area and now no where to be found close by. Sunoco is getting hard to find now too. Mobil is one i used to use in a pinch and can find it most any where.

It sounds like a stump puller, probably be alot of fun to drive and should have good street manners.

hi all

yes it is very well mannered , only drove it once around the block last year to test the rev limiter .

hope to get it out next summer for some good drives and a trip or three to the track .

not a fuel dragster but what would you do with that much power , the street will only allow so much to be used,

running any brand fuel is a plus for street cruseing for me. i want to drive it to some shows that are 100 + miles one way .

thank you !

[i][/i] I think Barton gave you sound advice on the compression. Hemis love compression but you have to be realistic about the availability of good fuel.

All engines like HC

And let's face it, an extra point of compression in this situation would be worth, what.......15hp, 20hp? Any more than that? Is that really worth the extra difficulty finding the right fuel not to mention the expense?

Well, i can't say what it's worth in HP, but my increase from 11.25 to 12.50 was worth 4 tenths and 4 mph. I will be honest and say i also ported the intake plenum and added an electric water pump as well, so not apples to apples, but the hp gain is much more than some may think. I try not to leave anything on the table anymore with my street/strip set up.

I'd guess 550ish. You could do better. The most mismatched part is the cam. That cam should be in a motorhome, not a street Hemi. I'd swap in something with 10 - 15 more degrees duration, and let'er rip!

I agree. I have that cam in my fathers 400 small block chevy. Works great and can be driven any where, but your leaving a lot on the table with that cam with a 511 cube street motor.

I agree, at least with the not being apples to apples part. Four MPH from a single point of compression is more that a little hard to believe.

Wallace Calculators gives a 600HP engine less than 5 additional horsepower when going from 11.25 to 12.5. Just one example, and not for a Hemi. But probably much closer to reality than the horsepower it takes to get another 4MPH. Which Wallace says would take about 17 more horsepower for each MPH.

http://www.wallaceracing.com/hp-cr-chg.php
http://www.wallaceracing.com/hp-mph-increase.php

Yep and thats what everyone else thought as well. I did the calculators and they were not showing much increase either, but i have the time slips to prove it. My 511 loved it and i think it might like some more.

You can’t attribute that whole gain to just the ratio.

You mention porting work and the addition of an electric water pump.

Glad it went faster though.

Yes, but the ratio was the biggest part of the gain. IMO that gain was worth 2 tenths. Well worth bumping compression up. Street car or race car, i leave nothing on the table, its there, use it.

That kind of gain isn't happening just by bumping compression up a hair over a point.
I suspect your gain was more because everything you had was too “ big” for the compression you had( in other words an under performing combo) and the bump in compression helped make the combo “ fit” better. In other words run more like its supposed to.
The shop doing my new engine, was taking to them about gains. Going from10 to 1 to 12.5 compression. 360 to 418 cubic inches. Cleaned up heads to mildly ported heads, dual plane to single plane. Same cam( too big on 360) to “ about right” on 418.
We are hoping for about an 80 horse gain from all of that. Seems pretty reasonable.
When you see the kind of gains you saw with that compression bump, it's more fixing an issue you had, than it is a +-3% gain from a little more than a point in compression would net 4 tenths and 4 mph.
Otherwise everybody on here would be milling heads a little and or changing to thinner head gaskets tomorrow to reap such gains

Not sure you remember at the time i was talking about bumping it up, most on here said it wouldn't gain much if anything. I can agree with that. I was talking to Wilsons one day and they told me any time the air slows down in the intake port, the fuel can fall out of suspension. Compression can speed things up on both intake and exhaust. My theory was at the time that my MW victors had lazy ports and more compression might be the fix and i believe it was. Helped the border line cam as well. so, maybe 1 point compression wont help everyone in every situation, but from this point i will always have at least 12.0:1 compression in every motor i build and just run good gas. They just seem to be happier with more compression.