- Where do you have the initial timing and total timing set ??
- You verified the throttle is coming all the way open ?
- what did each cylinder record on the compression test ?
- What was the spark plug coloring ?
Big Block seems to slow
- Thread starter 360Duster75
- Start date
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Looks like not bad spec's better that a 360, add like stealth heads decent cam and be a great platform, add 3.75 stroke for a better 408, the only problem like all smaller V8 is larger one's are readily available.
618 hp 361 with a 3.75 stroke.
Mopar 412 Big-Block - Popular Hot Rodding Magazine
PRH
Well-Known Member
There are no fundamental design flaws with a 361 BB Mopar that would make it unresponsive to the normal hot rod treatment.
Compared to most other engines of similar displacement it has heads with bigger intake valves and ports, and a bigger bore.
As long at the basic engine is mechanically “good”, (no broken rings, heads aren’t trashed, etc), a well thought out combo should easily be able to equal(or slightly exceeed) the power output of a stock HP 383(335hp).
However, if the basic long block is pretty tired and will need refreshing, at that point it might be worth considering starting with more cubes to begin with(from a hp/$$$ spent standpoint).
A lot would depend on what your capabilities are, and the resources readily available to you........ along with what the actual condition of the engine is.
I can tell you this, in the 80’s I re-ringed several “very well used” BBM’s that ran really well afterward, especially considering what I started with.
I guess in my mind the make or break point for a 361 would be whether it needed pistons or not.
If the pistons and bores were so bad a re-ring wouldn’t be feasible, then I’d start with something else.
Edit- I just did a search and see that a place called Falcon Performance sells coated cast flat tops in a .040 oversize for just over $400.
So apparently there is some demand for them.
Other than that, all I saw were silvolite dished truck pistons which would have rather low compression and take an odd ring pack.
Customs could be made, but for less money........I could likely find a 440 core.
Compared to most other engines of similar displacement it has heads with bigger intake valves and ports, and a bigger bore.
As long at the basic engine is mechanically “good”, (no broken rings, heads aren’t trashed, etc), a well thought out combo should easily be able to equal(or slightly exceeed) the power output of a stock HP 383(335hp).
However, if the basic long block is pretty tired and will need refreshing, at that point it might be worth considering starting with more cubes to begin with(from a hp/$$$ spent standpoint).
A lot would depend on what your capabilities are, and the resources readily available to you........ along with what the actual condition of the engine is.
I can tell you this, in the 80’s I re-ringed several “very well used” BBM’s that ran really well afterward, especially considering what I started with.
I guess in my mind the make or break point for a 361 would be whether it needed pistons or not.
If the pistons and bores were so bad a re-ring wouldn’t be feasible, then I’d start with something else.
Edit- I just did a search and see that a place called Falcon Performance sells coated cast flat tops in a .040 oversize for just over $400.
So apparently there is some demand for them.
Other than that, all I saw were silvolite dished truck pistons which would have rather low compression and take an odd ring pack.
Customs could be made, but for less money........I could likely find a 440 core.
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PRH
Well-Known Member
When I was in the Air Force, stationed out in Sacramento, Ca I bought a 69 Charger.
This was in 1980.
I really didn’t know anything about anything, but I did learn to look at the VIN to see what engine was in the car.
This car was an “H”, so a 383.
It had a 4bbl on it...... so I “assumed” it was as appeared.
It was all stock....... and was a bit of a dog.
I tuned it up, and drove it to Sacramento raceway to see what it had.
After a few passes....... it was in the 15.60’s as its best.
That seemed kinda slow to me, so I checked the rear gears........ 3.23’s.
Okay, not terrible.
For some reason I was suspicious of the engine.
I looked on the block where the serial # was supposed to be and nothing was there.
Then I cleaned some greasy stuff off by the distributor housing..... and there it was........”C361”.
I guess the 383 had died, and some bone yard ‘66 361 was installed in its place, and they put the 383 intake & carb on it.
That satisfactorily explained the uninspiring performance to me....... and I started looking for a 440 core to build to replace it.
There’s a ton more easily accessed info now than there was 42 years ago(and I know a tad more than I did then).
Depending on what the goals for the car are........ I wouldn’t necessarily rule out the 361 as quick as I did in 1980.
This was in 1980.
I really didn’t know anything about anything, but I did learn to look at the VIN to see what engine was in the car.
This car was an “H”, so a 383.
It had a 4bbl on it...... so I “assumed” it was as appeared.
It was all stock....... and was a bit of a dog.
I tuned it up, and drove it to Sacramento raceway to see what it had.
After a few passes....... it was in the 15.60’s as its best.
That seemed kinda slow to me, so I checked the rear gears........ 3.23’s.
Okay, not terrible.
For some reason I was suspicious of the engine.
I looked on the block where the serial # was supposed to be and nothing was there.
Then I cleaned some greasy stuff off by the distributor housing..... and there it was........”C361”.
I guess the 383 had died, and some bone yard ‘66 361 was installed in its place, and they put the 383 intake & carb on it.
That satisfactorily explained the uninspiring performance to me....... and I started looking for a 440 core to build to replace it.
There’s a ton more easily accessed info now than there was 42 years ago(and I know a tad more than I did then).
Depending on what the goals for the car are........ I wouldn’t necessarily rule out the 361 as quick as I did in 1980.
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Here's another thought to why it's not running correctly. Does it have the correct spark plugs in it? Recently a guy running a BB Mopar at the track was having a poor performing car. He ended up having the wrong reach spark plugs in it. He changed to the Autolite 85 plugs I recommended and the car picked up 3/10 of a second in the 1/8 mile. Lots of little simple things can get in the way of good performance.
Tom
Tom
512Stroker
We are all here because we are not all there.
If you plan on keeping it the first thing you need to do is run a compression test on all 8 cylinders. Post the numbers here that will give us an idea of what you are dealing with.
Pull the coil wire off at both ends
Take all 8 spark plugs out
Wire the throttle wide open
Run the test with a good compression gauge. If you dont have one the local auto parts store will lend one out to you.
Good luck
1968rt
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516 heads are 84ccs from the factory. Small exhaust valve, but that can be fixed. 915s are 79ccs. Also that single plane manifold with log exhaust manifolds aren't helping.
Ok, maybe I was thinkin about the 915s. Still though, the 516s can achieve some quench with the right piston. The bore size is a popular one, so that's a good thing. Still might have to be a custom pin height though.
Sounds like a drop in 361 with the 383 intake/carb. 15.60's in a B-body with 3.23's isn't all that dead if the rest of the engine was stock. The OP has his in a Duster, so I would assume lower 15's if he has similar gearing, and that's a far cry from the 18 seconds he says it feels like.
OldmanRick
Well-Known Member
To the OP for future quick reference...
Pic from a FCBO post.
Pic from a FCBO post.
Bakerlite
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Well then you should have said you'd tuned it...
That would prevent a bunch of people telling you to tune it.. Logic right?
You didn't check it's compression..before you quoted my post..
Did you shorten the timing curve and advance your initial timing?
Because if you haven't done that, then you haven't seriously tuned it..
Can you tell us what you did to tune it? Initial and total timing? WHAT RPM the total is? The more info you give, the more you'll get. If we keep having to pull teeth, I'm outta here. I wanna help though.
Bakerlite
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If it seems to slow, then lower your expectations....
360Duster75
Well-Known Member
When you come from a mid 9 second daily driven hellcat everything seems slow just not this slow.
PRH
Well-Known Member
Check over all the basics....... and then take it to the track and put a few passes on it to get a baseline.
360Duster75
Well-Known Member
Rebuilt the carb (found sticking rear blades not opening), retimed again set to 12* initial and 36* total (probably off from ideal due to where the timing marks are hidden under the water pump but seems to be the best I can get for now), new kick down cable, and readjusted shift linkage pretty much fixed the issue. Car now runs and drives like it has a small big block in it has no issues other than still needing fine tuning on the kickdown linkage. Does a one wheel peel with ease now so going from not doing that even when it was wet is night and day.
Nice.
and to think some goofy dude in post 3 recommended checking for WOT. I tell ya....
You gotta be a little careful when the advice comes from a guy that looks like a trailer park boy... (Bubbles...)
and to think some goofy dude in post 3 recommended checking for WOT. I tell ya....
Who also does comedy... And looks like both of you...
The comedy guy is pretty good and also refers to himself as a trailer park boy if you take the time to watch the whole thing, instead of the part where I bookmarked here for a good joke...
360Duster75
Well-Known Member
First track results was a 14.4 @ 96 the thing is a pig off the line bogs hard unless I slow roll into the throttle. But once off the line it picks up great. The 2.94 gears ain’t helping at all so guess that and going to a dual plane RPM intake vs the huge single plane I have on it.
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